Tennessee Weather Forum

Weather Forecasting and Discussion => Severe Weather => Topic started by: StormNine on April 02, 2017, 08:15:54 AM

Title: April 5th Severe Weather Threat
Post by: StormNine on April 02, 2017, 08:15:54 AM
We are watching for a strong system for Wednesday. At this time the greatest threat is probably just to our south, but there is a highlighted threat for much of TN as well. 
Title: Re: April 5th Severe Weather Threat
Post by: BRUCE on April 02, 2017, 08:23:58 AM
talking bout a scary afd sort of... BMX birmingham al... saying if euro is face value... be strong to viloent torndaoes for them late wed...  guess this may be shaping up for another big daddy miss for midsouth... but its going to be fun still watching this play out to how much tennessee gets invovled in ::coffee::
Title: Re: April 5th Severe Weather Threat
Post by: JTM1988 on April 03, 2017, 06:45:51 AM
Latest GFS and NAM makes it seem like it could get interesting around BNA early afternoon Wednesday. Cape shoots up with development to the west and plenty of shear. (https://uploads.tapatalk-cdn.com/20170403/f65047991139544382494de30bb325fa.png)


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Title: Re: April 5th Severe Weather Threat
Post by: Vols1 on April 03, 2017, 07:54:02 AM
Hmm that appears to be a line of possible super cells to me 😳
Title: Re: April 5th Severe Weather Threat
Post by: StormNine on April 03, 2017, 01:45:36 PM
Latest GFS and NAM makes it seem like it could get interesting around BNA early afternoon Wednesday. Cape shoots up with development to the west and plenty of shear. (https://uploads.tapatalk-cdn.com/20170403/f65047991139544382494de30bb325fa.png)



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That output looks very 3/28/2009 ish. The setup on Wednesday has some 3/28/2009 similarities and even a little bit of last Thursday.

1) The potential for Gulf Coast/Deep South storm action which could prevent inflow of sufficient moisture return.

2) The potential for a narrow corridor of instability and relatively sufficient moisture return into KY/TN.

The question then remains, will there be enough clearing to our south to allow for a brief period of more unstable air to advance into our area. If there is then hail (locally quite large), damaging winds, and even tornadoes are all in the cards with a situation similar to that NAM output. If it does not then it is a repeat of last Thursday.
Title: Re: April 5th Severe Weather Threat
Post by: JTM1988 on April 03, 2017, 05:41:53 PM
Seems like there is a gradual shift west in the models and a POTENTIAL threat Wednesday afternoon with a lot of uncertainty. However it seems like the ceiling on the event could be very high as well which leads to a forecasting nightmare I assume. Just looking at these helicity tracks we are too close to comfort to a substantial event. I do not envy the forecasters after seeing model trends today.


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Title: Re: April 5th Severe Weather Threat
Post by: JTM1988 on April 03, 2017, 05:43:35 PM
Forgot to include the graphic (https://uploads.tapatalk-cdn.com/20170403/e79d18d7a159cb4b69d9a65d2a4782d0.png)


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Title: Re: April 5th Severe Weather Threat
Post by: BRUCE on April 03, 2017, 06:48:39 PM
Seems like there is a gradual shift west in the models and a POTENTIAL threat Wednesday afternoon with a lot of uncertainty. However it seems like the ceiling on the event could be very high as well which leads to a forecasting nightmare I assume. Just looking at these helicity tracks we are too close to comfort to a substantial event. I do not envy the forecasters after seeing model trends today.


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agree 100 percent... never understood the SPC putting the risk so far east begin with... got slp nw of us and drops in pressure as it moves ne of us... look for SPC to make some adjustments ... SPC has had a bad start to this year to be honest with you... :)
Title: Re: April 5th Severe Weather Threat
Post by: Crockett on April 03, 2017, 06:56:52 PM
agree 100 percent... never understood the SPC putting the risk so far east begin with... got slp nw of us and drops in pressure as it moves ne of us... look for SPC to make some adjustments ... SPC has had a bad start to this year to be honest with you... :)

It's very simple, actually. SPC doesn't have the luxury of wish-casting.
Title: Re: April 5th Severe Weather Threat
Post by: BRUCE on April 03, 2017, 06:59:04 PM
It's very simple, actually. SPC doesn't have the luxury of wish-casting.
think they actually go over board on some things...
Title: Re: April 5th Severe Weather Threat
Post by: JTM1988 on April 03, 2017, 07:27:12 PM
It's very simple, actually. SPC doesn't have the luxury of wish-casting.

I'll give them some credit. By the time they released the day 3 all of the cape values at the time of storm initiation were all plateau and east on most models. The trend west really ramped up with 6z and on which would have impacted another day 3. Based on what they knew at the time it was a pretty good call. I'm VERY interested in the next day two.


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Title: Re: April 5th Severe Weather Threat
Post by: StormNine on April 03, 2017, 09:29:53 PM
Several times the Day 3 by the SPC looks quite a bit different than the eventual Day 1. A lot especially on the mesoscale can change between that Day 3 outlook and the day in question. 11/15/2005 and 12/23/2015 were originally 15% slight risk days on the Day 3 outlook and we have also had some Day 3 MDT risk busts as well. The SPC deserves some leadway because in most cases there is still uncertainty or unknowns at the time when they release the Day 3 outlook.
Title: Re: April 5th Severe Weather Threat
Post by: JTM1988 on April 03, 2017, 09:55:24 PM
Don't think the 0z run of the nam trended to less ominous solution from southern IL to northern Bama


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Title: Re: April 5th Severe Weather Threat
Post by: justinmundie on April 04, 2017, 06:26:23 AM
SPC update

(http://i63.tinypic.com/28iudfq.gif)
Title: Re: April 5th Severe Weather Threat
Post by: Eric on April 04, 2017, 07:52:49 AM
This one has legs, boys and girls.  Tremendous amount of moisture feeding into this thing with mid 60 Tds as far north as the Ohio River.  Pockets of 70F Tds across the MDT risk.  Last time I remember seeing Tds that high across the Deep South prior to a severe event was 4/27.  LCLs will be very low with only a small dew point depression. 

6z NAM skew for BNA:

(http://i63.tinypic.com/5x1tvt.png)

 ::wow::
Title: Re: April 5th Severe Weather Threat
Post by: justinmundie on April 04, 2017, 08:34:52 AM
This one has legs, boys and girls.  Tremendous amount of moisture feeding into this thing with mid 60 Tds as far north as the Ohio River.  Pockets of 70F Tds across the MDT risk.  Last time I remember seeing Tds that high across the Deep South prior to a severe event was 4/27.  LCLs will be very low with only a small dew point depression. 

6z NAM skew for BNA:

(http://i63.tinypic.com/5x1tvt.png)

 ::wow::

Nice little cap there. How much will it take to bust that thing?
Title: Re: April 5th Severe Weather Threat
Post by: Eric on April 04, 2017, 08:39:45 AM
Nice little cap there. How much will it take to bust that thing?

Convective temp is 75F, but the cap will limit any burdensome crapvection during the day.  Once we hit lunchtime, storms will likely explode near I-65.  Need to see if further model runs support this notion.
Title: Re: April 5th Severe Weather Threat
Post by: lyngo on April 04, 2017, 08:48:43 AM
Wondering if we get to moderate risk with this one?  Today's runs will be interesting.

Title: Re: April 5th Severe Weather Threat
Post by: Eric on April 04, 2017, 08:51:18 AM
Wondering if we get to moderate risk with this one?  Today's runs will be interesting.

Doubtful.  I bet the MDT shifts N some overtaking some of HUNs counties, but I think we stay ENH.
Title: Re: April 5th Severe Weather Threat
Post by: StormNine on April 04, 2017, 09:02:57 AM
During the Day 1, I could see a Moderate Risk being added to parts of southern IN and central KY closer to the Low Pressure system. There is too much uncertainty about moisture return and any lingering convection down in ALto warrant that at this time.
Title: Re: April 5th Severe Weather Threat
Post by: Matthew on April 04, 2017, 09:03:34 AM
Will there be a round of severe storms in morning?
Title: Re: April 5th Severe Weather Threat
Post by: Eric on April 04, 2017, 09:05:12 AM
Will there be a round of severe storms in morning?

Negative. 
Title: Re: April 5th Severe Weather Threat
Post by: Matthew on April 04, 2017, 09:15:09 AM
The 30% hatched is nothing to dismiss that is for sure.
Title: Re: April 5th Severe Weather Threat
Post by: JayCee on April 04, 2017, 10:20:48 AM
Welcome to April.  It's usually the month we get some of our worst severe outbreaks.  Looks like this one could be the real deal.

Time to batten down the hatches. 

BTW--is that what the hatched zone is all about?   ::pondering::
Title: Re: April 5th Severe Weather Threat
Post by: Dyersburg Weather on April 04, 2017, 10:47:21 AM
Looks like some are expecting a High to be issued for parts of Georgia. We shall see.
Title: Re: April 5th Severe Weather Threat
Post by: Matthew on April 04, 2017, 11:25:10 AM
Eric.  Could being close to the low pressure (triple point) be a concern for this area?
Title: Re: April 5th Severe Weather Threat
Post by: StormNine on April 04, 2017, 11:28:33 AM
We mention lingering southern convection being a limiting factor for severe weather and that is true, but it could also leave a boundary down say in the SE AL/SW GA area that could provide even more of a focus for strong to violent tornadoes. That would focus most of the severe weather to the southern/southeastern end of the risk, but really up the ante (not Annie lol) on the tornado threat. That is something I can see as a potential option as well. 

For us at home, it really depends on the coverage of the storms down in AL/est FL Panhandle and how fast they can clear out. If morning storms backbuild to say southern Mississippi or any type of mesolow forms in that area during the morning hours then we will likely repeat last Thursday in KY/TN/N AL. If the storms clear out of the S MS/S AL/West FL Panhandle area by the morning and we get sufficient moisture return then we will become involved in the events of tomorrow with all severe weather hazards on the table.

Post Merge: April 04, 2017, 11:31:45 AM
Eric.  Could being close to the low pressure (triple point) be a concern for this area?

If sufficient moisture return occurs and is not blocked by lingering convection then there is a localized greater hail/tornado threat on the triple point. That is why I mentioned that a secondary greater threat (which could even require a Day 1 MDT during the 13 or 1630Z outlook depending on that moisture return)  across southern Indiana and central Kentucky. Those storms would backbuild potentially and spread into TN and N AL as well.
Title: Re: April 5th Severe Weather Threat
Post by: justinmundie on April 04, 2017, 11:38:16 AM
Am I seeing the 3k NAM right on my phone? Looks like 76/66? That's frightening.
Title: Re: April 5th Severe Weather Threat
Post by: Eric on April 04, 2017, 12:01:28 PM
Eric.  Could being close to the low pressure (triple point) be a concern for this area?

Not really.  The triple point is where the warm front and cold front occlude.

(http://www.theweatherprediction.com/habyhints2/530/triplepoint.jpg)

I think we're going to be too far south. 

Post Merge: April 04, 2017, 12:03:27 PM
Am I seeing the 3k NAM right on my phone? Looks like 76/66? That's frightening.

It appears so.  There's only a small window for strong/severe across Mid TN, but anything that goes up in that type of parameter space is going to be wicked.

Post Merge: April 04, 2017, 12:36:49 PM
New SPC Day 2, for OH/TN Valleys...

Quote
THE NORTHWARD ADVANCE OF LOW-LEVEL MOISTURE WILL BE MORE LIMITED 
ACROSS THE OH/TN VALLEYS WEDNESDAY, BUT WILL STILL BE MORE THAN 
SUFFICIENT TO SUPPORT SURFACE-BASED CONVECTION. A BAND OF SUPERCELLS 
APPEAR LIKELY PER LATEST MODEL GUIDANCE GIVEN THE STRENGTH OF LOW 
AND MID-LEVEL WINDS COUPLED WITH WEAK TO LOCALLY MODERATE 
INSTABILITY. LARGE TO VERY LARGE HAIL AND DAMAGING WINDS APPEAR TO 
BE THE MAIN THREATS, WITH A FEW TORNADOES ALSO POSSIBLE. GIVEN THE 
FORECAST COVERAGE OF CONVECTION, IT IS NOT OUT OF THE QUESTION THAT 
HIGHER SEVERE PROBABILITIES MAY NEED TO BE CONSIDERED IN A LATER 
OUTLOOK UPDATE. 
Title: Re: April 5th Severe Weather Threat
Post by: SuperCell on April 04, 2017, 12:58:32 PM
I have been getting rumblings from some people blowing off this threat. They are saying things like "the last few storms didn't happen, this one won't either". Guess it's some kind of psychological trick to make them feel better or something. I don't get it.  ::twocents::
Title: Re: April 5th Severe Weather Threat
Post by: Thundersnow on April 04, 2017, 01:38:01 PM
MDT risk area is expanded a bit on the new Day 2 to include Birmingham and near Huntsville and more of north GA. Slightly more of TN is in the ENH risk now (western boundary of the area has been nudged westward).

Quote
   ...SUMMARY...
   An outbreak of severe thunderstorms is likely Wednesday across much
   of the Southeast, continuing northward along and west of the
   Appalachians into the Tennessee and Ohio Valleys.  This will include
   supercell development with a risk for tornadoes, some of which will
   be strong and long-lived, particularly across the Southeast. Large
   to very large hail and damaging straight-line winds also appear
   likely.
Title: Re: April 5th Severe Weather Threat
Post by: StormNine on April 04, 2017, 02:25:54 PM
I am going to take a shot at a forecast for this event.

- Everyone in or around the Enhanced and Moderate Risk areas needs to make tomorrow a weather alert day. It only takes one storm to make for a bad day for your community. Make sure you have multiple weather sources, have plans for if you go under a warning, etc..

- I think everyone in the risk area has a chance at severe with large hail (some very large), damaging winds, and a few tornadoes, but I think there are two areas of maximum threat especially with tornadoes.

1) East-central and southeastern Alabama into much of central and southwestern Georgia: This area features great instability, the low-level jet and good wind shear, and the potential for outflow boundaries that can further enhance storm development. This area has the potential for strong to violent tornadoes and the introduction of a High Risk by the 06 or 13Z outlook if things go as planned.

2)  Southern Indiana: With a nice deep low-pressure system there is always concern about the triple point and the warm front. Usually, moisture return takes care of its self when you have a deep low-pressure system, assuming that there are no MCS complexes blocking that moisture return. The atmosphere will not be a rich and quite as unstable as the first highlighted area, but being in the triple point area gives you backed winds and favorable jet dynamics. This can allow for any supercell to produce tornadoes and if there isn't any contamination down south in AL, I would not rule out a significant tornado or two in this area tomorrow.


This puts middle/east TN, south-central KY, and north AL in the middle of what I think will be the two maximums. The main threat for us is large hail, but there is potential for tornadoes in the strongest storms. If the discrete storms can line up and form an MCS or QLCS then brief MCS spinups can occur along with damaging winds.
Title: Re: April 5th Severe Weather Threat
Post by: JTM1988 on April 04, 2017, 03:10:17 PM
Small detail but the latest run of the nam is even further west with the instability axis at 18z tomorrow.


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Title: Re: April 5th Severe Weather Threat
Post by: Matthew on April 04, 2017, 04:16:29 PM
I will say.  Some of the latest short range models is quiet concerning.  Plus DP in mid 60's & Justin pointed out.  I see what Eric means by any storm that does develop will be wicked.  This could get ugly from TN river east.  Even if not tornadoes the wind & hail damage could be substantial.
Title: Re: April 5th Severe Weather Threat
Post by: EastTNWX on April 04, 2017, 04:39:19 PM
There seems to be a healthy winter threat coming from this storm as well, a consummate April special!
Title: Re: April 5th Severe Weather Threat
Post by: cgauxknox on April 04, 2017, 04:41:34 PM
Here's the very interesting Special Weather Statement on this system for East TN.  Severe storms followed by blowing snow in the higher elevations:

Quote
... An enhanced risk of severe weather exists for east Tennessee,
southwest Virginia and southwest North Carolina for Wednesday
afternoon and evening...

... Wintry conditions with significant snowfall expected across the
higher elevations of southwest Virginia and far east Tennessee for
Thursday and Thursday night...

A strong upper level storm system will across the Tennessee
Valley and southern Appalachians for Wednesday and Thursday.
Scattered showers and thunderstorms are expected in the morning,
and then redevelop during the afternoon and evening hours.

The thunderstorms during the afternoon and evening could be
severe with the main risk being damaging winds and large hail up
to golfball size. There is also a risk of tornadoes, especially
across southeast Tennessee and southwest North Carolina.

A strong cold front will move across area Wednesday night with
colder air spilling into the southern Appalachians. The cold air
will allow the rain showers to change to snow across the higher
elevations Thursday morning. Snow accumulations of 3 to 6 inches
are possible at elevations at or above 4000 feet, and 1 to 4
inches between 2500 and 4000 feet, by Thursday evening. Heavier
amounts possible across the highest elevations.

Besides the snow, windy and colder conditions are expected area-
wide. The windy and snowy conditions will produce blowing and
drifting of the snow across the higher terrain.

Please stay tuned to NOAA Weather Radio and other local media for
further details or updates.
Title: Re: April 5th Severe Weather Threat
Post by: SKEW-TIM on April 04, 2017, 05:18:25 PM
Hey from North Carolina.

Greeting it's been over a year since I moved back home to NC.  I wish I could say that my post was a pleasant one but , I am a little worried about tomorrow.
I live in WNC but work in Upstate SC.. just outside the MDT risk zone. 
I have lots of friends and family I am worried about ,, plus I work in SC just east of Greenville.

Would love to hear your input about dynamics and timing of this. 
This system is legit.. and I want to have my facts straight

worried in CAROLINA .
Title: Re: April 5th Severe Weather Threat
Post by: Charles L. on April 04, 2017, 05:56:06 PM
IF the 3 km NAM is to be believed and taken at face value. I could easily see the SPC issue a High risk for eastern AL/western GA and then they expand the MDT risk northward as far as Murfressboro, IMO.
Title: Re: April 5th Severe Weather Threat
Post by: StormNine on April 04, 2017, 06:11:33 PM
The concerning trend in the short term model runs is that there isn't that lingering MCS or convection over MS/AL that is one of our most common reasons for a busted severe weather event. If that verifies that will allow for us to get in on that more unstable airmass.
Title: Re: April 5th Severe Weather Threat
Post by: Charles L. on April 04, 2017, 06:19:18 PM
The concerning trend in the short term model runs is that there isn't that lingering MCS or convection over MS/AL that is one of our most common reasons for a busted severe weather event. If that verifies that will allow for us to get in on that more unstable airmass.

It is looking more and more likely we won't have any lingering moisture to our south to impede that flow northward.
Title: Re: April 5th Severe Weather Threat
Post by: Matthew on April 04, 2017, 06:21:15 PM
Wo[attachimg=1]
If even close to being right.  Ugly.
Title: Re: April 5th Severe Weather Threat
Post by: BRUCE on April 04, 2017, 06:44:38 PM
Wo (Attachment Link)
If even close to being right.  Ugly.
looks like a very potent triple point setting up there also


Post Merge: April 04, 2017, 06:46:23 PM
nasty stuff im seeing on latest models... makes me wonder if SPC will break out the black crayon tomorrow... ::pondering::
Title: Re: April 5th Severe Weather Threat
Post by: Dyersburg Weather on April 04, 2017, 07:11:03 PM
Alabama governor has declared state of emergency.
Title: Re: April 5th Severe Weather Threat
Post by: StormNine on April 04, 2017, 08:00:24 PM
If we see this trend of no lingering MCS's in the Alabama region then I suspect that the MDT risk will have to be pulled into at least the southern half of TN and that one will need to be added for Indiana for the triple point. They could just go MDT from central/southern Indiana down through KY/TN to the deep south as well. 
Title: Re: April 5th Severe Weather Threat
Post by: BRUCE on April 04, 2017, 08:14:18 PM
looks as if the nam is trying to slow this thing down. bit more even... interesting
Title: Re: April 5th Severe Weather Threat
Post by: Eric on April 04, 2017, 08:27:14 PM
23z HRRR for BNA... 74/62F w/1900 SBCAPE. 
Title: Re: April 5th Severe Weather Threat
Post by: StormNine on April 04, 2017, 08:52:15 PM
The latest HRRR launches storms along and just east of US 45 in both states. US Highway 45 or from Martin to Jackson TN is probably the western edge of the threat.
Title: Re: April 5th Severe Weather Threat
Post by: Dyersburg Weather on April 04, 2017, 09:01:47 PM
23z HRRR for BNA... 74/62F w/1900 SBCAPE.
Has storms firing along Tn river on what looks to be dry line
Title: Re: April 5th Severe Weather Threat
Post by: Eric on April 04, 2017, 09:16:06 PM
0z NAM parameters are crazy...65-66F Tds and SBCAPE over 2800 across S Mid TN.
Title: Re: April 5th Severe Weather Threat
Post by: StormNine on April 04, 2017, 09:25:56 PM
The NAM 3K is supercell city from Indianapolis all the way down to Montgomery.
Title: Re: April 5th Severe Weather Threat
Post by: Eric on April 04, 2017, 09:44:47 PM
The NAM 3K is supercell city from Indianapolis all the way down to Montgomery.

Isn't that a tad bit worrisome...
Title: Re: April 5th Severe Weather Threat
Post by: Charles L. on April 04, 2017, 09:46:57 PM
I am praying the NAM is wrong. If not, then we are in for a very rough day tomorrow afternoon...
Title: Re: April 5th Severe Weather Threat
Post by: StormNine on April 04, 2017, 09:47:24 PM
The latest HRRR shows mid 60 dewpoints into Middle TN at 1pm. Chattanooga has 66F and southern Middle TN has 63-66F.
Title: Re: April 5th Severe Weather Threat
Post by: WXRocker on April 04, 2017, 10:13:18 PM
Isn't that a tad bit worrisome...
Just a touch.... ::bagoverhead::
Title: Re: April 5th Severe Weather Threat
Post by: SuperCell on April 04, 2017, 11:05:39 PM
Skinny line of storms forming along the gulf coast. Anything to that? Think that's the warm front...

Title: Re: April 5th Severe Weather Threat
Post by: skillsweather on April 05, 2017, 01:18:26 AM
And we have Moderate risk in Tennessee! Wilson county included yay! Hopefully we get some good storms. 
http://www.spc.noaa.gov/products/outlook/day1otlk_1200_prt.html
http://www.spc.noaa.gov/products/outlook/day1otlk.html
Quote
..Tennessee through Ohio Valley...

   A relatively narrow corridor of dewpoints in the upper 50s near 60 F
   will advect north into the TN Valley in advance of the approaching
   cold front and vigorous shortwave trough contributing to moderate
   instability (1500 J/kg MLCAPE) as the boundary layer warms during
   the afternoon. A secondary branch of the low-level jet will
   strengthen within exit region of approaching mid-level jet, and
   storms are expected to develop along and just ahead of the front by
   mid afternoon from the OH valley southward into the middle part of
   the TN valley. Discrete supercells will likely be the initial mode,
   and these storms will be capable of producing very large hail and
   tornadoes as they develop east and mature. An eventual upscale
   growth into mixed modes with line segments may occur during the
   evening as activity approaches the Appalachians. 
Title: Re: April 5th Severe Weather Threat
Post by: SuperCell on April 05, 2017, 01:43:35 AM
Really don't think that's something to be proud of I am afraid.
Title: Re: April 5th Severe Weather Threat
Post by: StormStalker on April 05, 2017, 02:36:32 AM
I love me some severe weather more than anybody, but I think I'll have to pass on the baseball-sized hail, thank you very much. I'd prefer to not have my vehicles and home smashed to bits.
Title: Re: April 5th Severe Weather Threat
Post by: Thundersnow on April 05, 2017, 05:33:52 AM
Tornado probabilistic map

(http://www.spc.noaa.gov/products/outlook/archive/2017/day1probotlk_20170405_1200_torn_prt.gif)


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Title: Re: April 5th Severe Weather Threat
Post by: Matthew on April 05, 2017, 06:26:51 AM
Tornado probabilistic map

(http://www.spc.noaa.gov/products/outlook/archive/2017/day1probotlk_20170405_1200_torn_prt.gif)


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Even hatched.  That stinks.
Title: Re: April 5th Severe Weather Threat
Post by: Charles L. on April 05, 2017, 06:30:08 AM
The Huntsville NWS office is saying the HRRR is "useless" in the short term today. They are leaning towards the NMM and the ARW.
Title: Re: April 5th Severe Weather Threat
Post by: justinmundie on April 05, 2017, 06:34:03 AM
Anyone notice the 06z 3k NAM pushes things well east of i65 before it really kicks off organized storms? Very different from 0z. I'm waiting until 12z before I start really sounding the warning bells for friends and family.
Title: Re: April 5th Severe Weather Threat
Post by: Thundersnow on April 05, 2017, 06:36:04 AM
Quite a risk "gradient" on the map across the state. There's little to no risk from Jackson westward. The west edge of the moderate risk is basically I-65. I'm guessing we see initialization of cells west of I-65 and then things really intensify east of I-65. Anywhere between Nashville, Knoxville, and Chattanooga- watch out today.

Post Merge: April 05, 2017, 06:39:43 AM
Anyone notice the 06z 3k NAM pushes things well east of i65 before it really kicks off organized storms? Very different from 0z. I'm waiting until 12z before I start really sounding the warning bells for friends and family.

I'm thinking this is targeting the Plateau later, though Nashville is not out of the woods. It's a little weird to be on the western edge of the risk area with more threat east of Nashville, but that is the zone of some pretty infamous outbreaks (i.e. 1974 and 2011... not in magnitude but in areas affected).
Title: Re: April 5th Severe Weather Threat
Post by: joemomma on April 05, 2017, 07:04:03 AM
Do I need to be sounding the alarm for family yet?  What is our timing looking like?
Title: Re: April 5th Severe Weather Threat
Post by: Matthew on April 05, 2017, 07:05:47 AM
All about temp & dp will be telling.
Title: Re: April 5th Severe Weather Threat
Post by: Dyersburg Weather on April 05, 2017, 07:37:10 AM
Everyone be safe today. A cool 59 /50 here this morning.
Title: Re: April 5th Severe Weather Threat
Post by: RobD on April 05, 2017, 07:57:52 AM
My oldest just moved to Atlanta last month. She just texted me that they're all in the lobby in downtown; under a tornado warning till 9am ET.
Title: Re: April 5th Severe Weather Threat
Post by: Eric on April 05, 2017, 08:00:48 AM
My oldest just moved to Atlanta last month. She just texted me that they're all in the lobby in downtown; under a tornado watch till 9am ET.

Warning?
Title: Re: April 5th Severe Weather Threat
Post by: RobD on April 05, 2017, 08:05:02 AM
Ugh. Yes. Warning. Just edited my post. Having my first caffeine :(
Title: Re: April 5th Severe Weather Threat
Post by: Eric on April 05, 2017, 08:07:06 AM
MDT shifted E some with the latest SPC update. 
Title: Re: April 5th Severe Weather Threat
Post by: JayCee on April 05, 2017, 08:07:35 AM
Hope everyone stays safe today . . .

Looks like the first round of storms in AL & GA may actually clip parts of east TN now.  Already clouding up here in advance.

Quote
Area Forecast Discussion
National Weather Service Morristown TN
721 AM EDT Wed Apr 5 2017

.AVIATION...
Storms to our south look like they have a better chance of making
it towards the KCHA/KTYS terminals this morning. These storms
could bring strong winds and hail.
The main story is still the
storms in the afternoon along and ahead of the front moving in
from the west. High resolution models have handled precipitation
thus far extremely poorly so forecast confidence on the timing of
the storms this evening is very low. Have best forecast in the
TAFs but this may very well be altered with later forecast
issuances.

Title: Re: April 5th Severe Weather Threat
Post by: justinmundie on April 05, 2017, 08:25:06 AM
MDT shifted E some with the latest SPC update.

Looks to me like SPC is leaning hard on the 3k NAM. I am waiting with baited breath to see what happens on the 12z run. the 6z seemed to be an outlier for storm initiation compared to the prior 24 hours of runs.
Title: Re: April 5th Severe Weather Threat
Post by: Eric on April 05, 2017, 08:26:42 AM
Looks to me like SPC is leaning hard on the 3k NAM. I am waiting with baited breath to see what happens on the 12z run. the 6z seemed to be an outlier for storm initiation compared to the prior 24 hours of runs.

May have been a bad initialization somewhere.  I know the previous run of the HRRR was ::poo:: . 
Title: Re: April 5th Severe Weather Threat
Post by: Matthew on April 05, 2017, 08:32:04 AM
May have been a bad initialization somewhere.  I know the previous run of the HRRR was ::poo:: .

I thought I read the HRRR had been doing great up until this event & the 3K Nam was awful.  Go figure.
Title: Re: April 5th Severe Weather Threat
Post by: justinmundie on April 05, 2017, 08:43:29 AM
Matthew - the HRRR has not been initializing well for this event. NWS Huntsville said in their last AFD that it will be "useless". I don't know that I would go that far, but its not the preferred model right now for whatever reason.

Just looking at the soundings for the 6z NAM.... Nashville proper still gets like 3 hours of PDS Tor soundings. The issue it seems is just initialization. Storms could easily miss the I65 corridor all together if initialization is delayed at all, and I65 could easily get a serious event if they initialize 25-50 miles further west than the latest round of models think.

Honestly, I'm surprised they pulled the moderate further east just from a pragmatic standpoint. A lot of times they will be overly cautious and keep major metros in the highest risk just because the risk of loss of life and property are so much higher in densely populated areas.

t minus 15 minutes until the 12z NAM  ::coffee::
Title: Re: April 5th Severe Weather Threat
Post by: Chipper31 on April 05, 2017, 08:47:46 AM
Looks to me like SPC is leaning hard on the 3k NAM. I am waiting with baited breath to see what happens on the 12z run. the 6z seemed to be an outlier for storm initiation compared to the prior 24 hours of runs.

SPC leans hardest on the SREF, which shows a rapid increase in the probability of supercells between 21z and 00z.  New outlook lines up almost perfectly with the 03z SREF.
Title: Re: April 5th Severe Weather Threat
Post by: dwagner88 on April 05, 2017, 09:02:17 AM
Had to go to Ducktown for work this morning. When I left it was 45 and raining. Not exactly what you'd expect given the ominous forecast for today. Much warmer down here in the valley though, and I suspect that the storms coming through now will bring the warm front with them. They aren't moving very fast. We may get some flash flooding issues from them before they clear out this afternoon.
Title: Re: April 5th Severe Weather Threat
Post by: justinmundie on April 05, 2017, 09:03:24 AM
SPC leans hardest on the SREF, which shows a rapid increase in the probability of supercells between 21z and 00z.  New outlook lines up almost perfectly with the 03z SREF.

SREF members are weighted heavily towards the NAM though, correct?
Title: Re: April 5th Severe Weather Threat
Post by: JTM1988 on April 05, 2017, 09:06:44 AM
The latest 3K nam definitely just got things organized further west than previous runs


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Title: Re: April 5th Severe Weather Threat
Post by: JayCee on April 05, 2017, 09:14:38 AM
Had to go to Ducktown for work this morning. When I left it was 45 and raining. Not exactly what you'd expect given the ominous forecast for today. Much warmer down here in the valley though, and I suspect that the storms coming through now will bring the warm front with them. They aren't moving very fast. We may get some flash flooding issues from them before they clear out this afternoon.

I've noticed the slow movement as well.  It was clear this morning, but now it's completely cloudy where I sit--and very cool.  I'm wondering with rain and storms moving in later this morning, will it clear soon enough to build enough heat and instability for any severe later?
Title: Re: April 5th Severe Weather Threat
Post by: Chipper31 on April 05, 2017, 09:17:33 AM
SREF members are weighted heavily towards the NAM though, correct?

WRF more than NAM, but it's all shades of gray when you're talking about 26 different members...
Title: Re: April 5th Severe Weather Threat
Post by: justinmundie on April 05, 2017, 09:31:46 AM
I've noticed the slow movement as well.  It was clear this morning, but now it's completely cloudy where I sit--and very cool.  I'm wondering with rain and storms moving in later this morning, will it clear soon enough to build enough heat and instability for any severe later?

Those storms are along a warm front. The warm front should pass through Tennessee later this morning.
Title: Re: April 5th Severe Weather Threat
Post by: Thundersnow on April 05, 2017, 09:52:23 AM
From the SPC: they may pull the trigger on a High risk for portions of AL/GA/SC.

http://www.spc.noaa.gov/products/md/md0440.html
Title: Re: April 5th Severe Weather Threat
Post by: JTM1988 on April 05, 2017, 10:08:55 AM
Interesting....(https://uploads.tapatalk-cdn.com/20170405/8750bb69f9863d85fd4580f6cde1ba37.png)


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Title: Re: April 5th Severe Weather Threat
Post by: Vols1 on April 05, 2017, 10:10:32 AM
Holy crap. I hope that isn't right.
Title: Re: April 5th Severe Weather Threat
Post by: SuperCell on April 05, 2017, 10:11:56 AM
Holy crap. I hope that isn't right.

Supercell City right there.
Title: Re: April 5th Severe Weather Threat
Post by: JayCee on April 05, 2017, 10:21:10 AM
Rain/storms having a hard time making it up into the central East TN Valley out of AL/GA.  It is very cloudy--and the dense clouds are keeping it cool and stable over this way. 
Title: Re: April 5th Severe Weather Threat
Post by: Eric on April 05, 2017, 10:23:19 AM
Rutherford Co EMA says schools closing 2 hrs early.  Awaiting confirmation.
Title: Re: April 5th Severe Weather Threat
Post by: Matthew on April 05, 2017, 10:23:26 AM
Interesting....(https://uploads.tapatalk-cdn.com/20170405/8750bb69f9863d85fd4580f6cde1ba37.png)

That pic right there would not be a good for anyone in the way of those supercells.


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Post Merge: April 05, 2017, 10:25:50 AM
Rutherford Co EMA says schools closing 2 hrs early.  Awaiting confirmation.

City or county?
Title: Re: April 5th Severe Weather Threat
Post by: joemomma on April 05, 2017, 10:36:59 AM
Putnam Country schools releasing at 130.
Title: Re: April 5th Severe Weather Threat
Post by: dwagner88 on April 05, 2017, 10:39:35 AM
Hamilton and I think also Bradley announced an early dismissal yesterday. Not taking any chances. The warm front must be moving through now. It's still cloudy but the rain has stopped and it is getting very muggy.
Title: Re: April 5th Severe Weather Threat
Post by: Heath22 on April 05, 2017, 10:43:50 AM
Rutherford Co EMA says schools closing 2 hrs early.  Awaiting confirmation.

Yep, my son just called they are getting out early.
Title: Re: April 5th Severe Weather Threat
Post by: flipman2013 on April 05, 2017, 10:46:00 AM
Hamilton and I think also Bradley announced an early dismissal yesterday. Not taking any chances. The warm front must be moving through now. It's still cloudy but the rain has stopped and it is getting very muggy.

Cleveland is also opening storm shelters at 4pm or earlier if warnings start getting issued.
Personally I'm hoping they aren't really needed today.
Title: Re: April 5th Severe Weather Threat
Post by: StormNine on April 05, 2017, 10:48:30 AM
Now that most of the significant storm action has cleared at least the western part of Alabama, this should  allow for more rapid and significant moisture return into Tennessee.
Title: Re: April 5th Severe Weather Threat
Post by: Eric on April 05, 2017, 10:48:51 AM

Post Merge: April 05, 2017, 10:25:50 AM
City or county?

County.  No news on City yet.
Title: Re: April 5th Severe Weather Threat
Post by: Coach B on April 05, 2017, 10:49:03 AM
Heard that the latest numerical guidance is exhibiting a dry bias across the southeast.  Anybody want to translate what that means?
Title: Re: April 5th Severe Weather Threat
Post by: Eric on April 05, 2017, 10:49:37 AM
Heard that the latest numerical guidance is exhibiting a dry bias across the southeast.  Anybody want to translate what that means?

Increasing tornado threat.
Title: Re: April 5th Severe Weather Threat
Post by: Matthew on April 05, 2017, 10:49:50 AM
County.  No news on City yet.

Thanks Eric.  My wife teaches.
Title: Re: April 5th Severe Weather Threat
Post by: StormNine on April 05, 2017, 10:53:01 AM
Heard that the latest numerical guidance is exhibiting a dry bias across the southeast.  Anybody want to translate what that means?


From the SPC, could get a High Risk in 1630Z for portions of SE AL, GA, and perhaps even adjacent parts of SC.

Quote
"GPS PW data are exhibiting a low bias by at least 0.5
   inch from parts of AL into GA, which has influenced initialization
   of the latest numerical weather prediction guidance.  Per
   coordination with the Weather Prediction Center, it appears that
   related initialization is causing substantial dry biases in model
   guidance -- extended through the Day 1 forecast period.  With an
   inland influx of rich moisture feeding ongoing intense supercells in
   southern AL (with dewpoints into the middle 70s), and the
   around-16.6-g/kg mean mixing ratio per LIX 12Z sounding, and around
   1.5-inch PW per Atlanta and Birmingham 12Z soundings, it is evident
   that rich moisture and related strong buoyancy does indeed extend
   inland"
Title: Re: April 5th Severe Weather Threat
Post by: Eric on April 05, 2017, 11:06:53 AM
MCS two hours early.
Title: Re: April 5th Severe Weather Threat
Post by: skillsweather on April 05, 2017, 11:36:26 AM
Im still in the Moderate risk but on the far western side. Outside it feels like its going to storm for sure. its really warm but not to warm and kind of humid but not really like humid humid. its actually really nice out with the wind. To bad im going to be at work during all of this. Yet again (missed last weeks storm too)..

I guess like everyone is saying the biggest question for Middle Tennessee is when initiation happens. The air is ripe for us all pretty much but if it takes longer to start up we could dodge a bullet but if it starts up sooner I-65 is more in the action.

High risk is out now
Title: Re: April 5th Severe Weather Threat
Post by: SuperCell on April 05, 2017, 11:39:34 AM
Tornado Emergency now in Southwest GA.
Title: Re: April 5th Severe Weather Threat
Post by: JayCee on April 05, 2017, 11:56:24 AM
Looking worrisome. . . per MRX:

Quote
National Weather Service Morristown TN
1116 AM EDT Wed Apr 5 2017

.DISCUSSION...A very active day is in store with a strong upper
level trough of low pressure moving from Missouri/Arkansas toward
the lower Ohio Valley. Satellite shows a double jet structure
across the Tennessee/Mississippi Valleys which will enhance the
lift over the Region Today into the this evening. The strong jet
forcing will enhance the fronto-genetic forcing across middle
Tennessee Alabama by mid/late afternoon.

Ahead of this activity, a warm frontal boundary is moving slowly
north across northeast Alabama/northern Georgia. Models are doing
a poor job in analyzing this activity thus confidence with this
convection is low. However, as pressure falls increase ahead of
the strong upper trough over the Tennessee Valley this boundary
will likely move slowly northward. This boundary may enhance the
tornado threat across southeast Tennessee/southwest North Carolina
later Today.

Giving increasing shear and instability later today along with
synoptic forcing, threat for severe storms will increase. Strong
potential long-track tornadoes are possible, especially over the
southern Plateau and southeast Tennessee given the warm frontal
boundary.

Besides the tornado threat, strong winds aloft, lowering freezing
level, and increasing HAIL CAPES will likely produce some damaging
winds and large hail up to Golfball size.

Title: Re: April 5th Severe Weather Threat
Post by: dwagner88 on April 05, 2017, 12:33:05 PM
The cell approaching Columbia SC looks really bad. Huge hook echo and a 75 dbz hail core.
Title: Re: April 5th Severe Weather Threat
Post by: JTM1988 on April 05, 2017, 12:43:05 PM
Gotta wonder when they will issue a watch for the area based on the new short term high res models


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Title: Re: April 5th Severe Weather Threat
Post by: SuperCell on April 05, 2017, 12:47:10 PM
https://weather.msfc.nasa.gov/cgi-bin/get-goes?satellite=GOES-E%20CONUS&lat=35.59&lon=-87.37&zoom=1&width=1000&height=800&map=county&info=vis&numframes=7&quality=100&type=Animation (https://weather.msfc.nasa.gov/cgi-bin/get-goes?satellite=GOES-E%20CONUS&lat=35.59&lon=-87.37&zoom=1&width=1000&height=800&map=county&info=vis&numframes=7&quality=100&type=Animation)

Look at the cloud streaks south and west of Nashville. I think I remember those were talked about before the April 27, 2011 event started.
Title: Re: April 5th Severe Weather Threat
Post by: JayCee on April 05, 2017, 12:47:40 PM
The cell approaching Columbia SC looks really bad. Huge hook echo and a 75 dbz hail core.

Been watching that one.  Sister lives in Irmo, just to the north of Columbia.  Hoping it passes south of her. 

Cloud canopy has all but disappeared here.  Won't have trouble getting some instability going now. . .
Title: Re: April 5th Severe Weather Threat
Post by: WXHD on April 05, 2017, 12:55:45 PM
The Masters begin tomorrow in Augusta. I wonder what the course will look like by then. You don't just set it all up in the morning.
Title: Re: April 5th Severe Weather Threat
Post by: mamMATTus on April 05, 2017, 12:58:07 PM
Chat room link?
Title: Re: April 5th Severe Weather Threat
Post by: NismoWx on April 05, 2017, 01:02:05 PM
OHX launched a balloon a few minutes ago...

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Title: Re: April 5th Severe Weather Threat
Post by: Thundersnow on April 05, 2017, 01:07:22 PM
Watch coming... http://www.spc.noaa.gov/products/md/md0442.html
Title: Re: April 5th Severe Weather Threat
Post by: Vols1 on April 05, 2017, 01:11:24 PM
How long till the balloon data comes in
Title: Re: April 5th Severe Weather Threat
Post by: collinsk on April 05, 2017, 01:12:14 PM
What is it looking like for the Chattanooga area? Development? Timing?
Title: Re: April 5th Severe Weather Threat
Post by: StormNine on April 05, 2017, 01:19:54 PM
I'm skeptical of the tornado threat from I-40 north unless trends rapdily change in the next 1-3 hours. There seems to be too much mixing going on and I'm not so sure the 60F dewpoints will even reach into KY. I do think N AL and S/SE TN have a shot at a better tornado threat due to better moisture and possible boundary interaction. We have instability developing and steep lapse rates so hail is going to be a potentially big threat.
Title: Re: April 5th Severe Weather Threat
Post by: Dyersburg Weather on April 05, 2017, 01:20:41 PM
This was in discussion about forthcoming watch.
" Tornadoes are expected, and significant tornadoes
   will be possible -- especially as supercells mature "
Title: Re: April 5th Severe Weather Threat
Post by: Thundersnow on April 05, 2017, 01:26:00 PM
Starting to see some returns on radar in western Middle TN- could be the beginnings of initialization.


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Title: Re: April 5th Severe Weather Threat
Post by: Coach B on April 05, 2017, 01:27:48 PM
Watch coming... http://www.spc.noaa.gov/products/md/md0442.html

Quote
NWS Storm Prediction Center Norman OK
   0102 PM CDT Wed Apr 05 2017

   Areas affected...Portions of central KY...middle
   TN...northern/central AL...extreme northwest GA

   Concerning...Severe potential...Tornado Watch likely

   Valid 051802Z - 052030Z

   Probability of Watch Issuance...95 percent

   SUMMARY...The risk for significantly severe storms capable of
   producing very large hail and tornadoes, along with damaging winds,
   is expected to increase around and after 19Z. The issuance of a
   Tornado Watch is expected soon.

19Z is 2:00 CDT
Title: Re: April 5th Severe Weather Threat
Post by: NismoWx on April 05, 2017, 01:37:19 PM
Starting to see some returns on radar in western Middle TN- could be the beginnings of initialization.


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West of 65, to boot. I'd say the next 30-45min are going to be telling.

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Title: Re: April 5th Severe Weather Threat
Post by: NismoWx on April 05, 2017, 01:40:47 PM
How long till the balloon data comes in
Should be any time now.

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Title: Re: April 5th Severe Weather Threat
Post by: dwagner88 on April 05, 2017, 01:40:59 PM
What is it looking like for the Chattanooga area? Development? Timing?

On paper, this looks like the most credible tornado/hail threat Chattanooga has had in quite a while. As always, exact storm tracks are impossible to predict accurately. As far as timing, I would expect convection to start firing over the western TN valley any time now and rapidly strengthen as it moves east of I-65. I think the peak for us should be right around 6-9 PM.
Title: Re: April 5th Severe Weather Threat
Post by: spanarkle08 on April 05, 2017, 01:52:25 PM
How far west will this thing blow up?
Title: Re: April 5th Severe Weather Threat
Post by: ServoCrow on April 05, 2017, 01:59:01 PM
(https://pbs.twimg.com/media/C8q6hAVXsAE8HN1.jpg)
Title: Re: April 5th Severe Weather Threat
Post by: SuperCell on April 05, 2017, 03:10:50 PM
Storms really popping on I24 corridor now.

Title: Re: April 5th Severe Weather Threat
Post by: StormNine on April 05, 2017, 03:56:58 PM
http://www.spc.noaa.gov/products/md/md0448.html

Best tornado threat is in SE Middle TN and SE TN into NE AL/NW GA where a boundary and better moisture is located at.
Title: Re: April 5th Severe Weather Threat
Post by: Clay on April 05, 2017, 04:01:17 PM
I'm guessing the SVR threat for the 65 corridor in TN is quickly diminishing.
Title: Re: April 5th Severe Weather Threat
Post by: kristin on April 05, 2017, 04:01:29 PM
Sorry to ask but I am on my work PC and I can't find the chat button.  Thank you!
Title: Re: April 5th Severe Weather Threat
Post by: dwagner88 on April 05, 2017, 04:04:45 PM
Wow. Big time activity along I-65 now.
Title: Re: April 5th Severe Weather Threat
Post by: JayCee on April 05, 2017, 04:10:16 PM
Very interesting to see how quickly the air mass and conditions changed here today.  For a big part of the day we've had stratiform clouds overhead (altostratus-cirrostratus).  Now, within a matter of about two hours, the sky is filled with towering cumulus.  They seemed to develop out of nowhere.  I've also noticed an abrupt increase in the humidity as well. 
Title: Re: April 5th Severe Weather Threat
Post by: Thundersnow on April 05, 2017, 04:17:36 PM
I'll call it- I think I-65 corridor and west are in the clear. The axis of development has definitely set up east of I-65.
Title: Re: April 5th Severe Weather Threat
Post by: SuperCell on April 05, 2017, 04:18:08 PM
Rotation showing up on that Tullahoma cell.


http://www.spc.noaa.gov/products/md/md0448.html

Post Merge: April 05, 2017, 04:23:49 PM
Tornado Warning for Coffee County. Strong rotation on radar.

Damage reported in Shelbyville & Tullahoma.
Title: Re: April 5th Severe Weather Threat
Post by: Clay on April 05, 2017, 04:35:16 PM
Coffee co TOR  looks like it tracked very close to Bonnaroo campsite.
Title: Re: April 5th Severe Weather Threat
Post by: SuperCell on April 05, 2017, 04:38:12 PM
Tornado reported on ground between Mile marker 113 and 118 on I24 in Coffee County.
Title: Re: April 5th Severe Weather Threat
Post by: dwagner88 on April 05, 2017, 04:44:40 PM
Something is inhibiting storm development in central AL. As a result, not much is happening downstream of KCHA. It's still early, but we may dodge a bullet with this one.
Title: Re: April 5th Severe Weather Threat
Post by: Susan on April 05, 2017, 05:00:29 PM
Oh! McMinnville to Spencer looks BAD. 


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Title: Re: April 5th Severe Weather Threat
Post by: Matthew on April 05, 2017, 05:08:12 PM
Really surprised we did not even get any rain today.  Surprised in a hatched area it did not have more storms or warnings.  Really dodged a bullet.  Forecasting is a tough business.
Title: Re: April 5th Severe Weather Threat
Post by: vanster67 on April 05, 2017, 05:21:00 PM
Tornado sirens going off repeatedly here in Monterey!  Sun peeking through clouds!
Title: Re: April 5th Severe Weather Threat
Post by: Hank W on April 05, 2017, 05:27:28 PM
I know we've discussed before, but man I wish every market could have a James Spann. Watching his coverage and then switching to other markets...The difference is unreal. He is great to say the least.
Title: Re: April 5th Severe Weather Threat
Post by: Thundersnow on April 05, 2017, 05:56:46 PM
DP is 51 in Nashville. I guess the dry line has passed.


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Title: Re: April 5th Severe Weather Threat
Post by: mamMATTus on April 05, 2017, 06:13:05 PM
I'm not going to be the one to say the word, but this did not at all live up to the hype
Title: Re: April 5th Severe Weather Threat
Post by: justinmundie on April 05, 2017, 06:14:26 PM
I'm not going to be the one to say the word, but this did not at all live up to the hype

#bust

Most definitely. SPC is having a bad year.
Title: Re: April 5th Severe Weather Threat
Post by: BRUCE on April 05, 2017, 06:32:12 PM
#bust

Most definitely. SPC is having a bad year.
without a doubt.... ::)
Title: Re: April 5th Severe Weather Threat
Post by: JayCee on April 05, 2017, 06:33:27 PM
We can always shift gears back to Winter and discuss the snow situation.   ;D

Quote
WINTER WEATHER ADVISORY IN EFFECT FROM 8 AM THURSDAY TO 8 AM
EDT FRIDAY...

The National Weather Service in Morristown has issued a Winter
Weather Advisory for snow, which is in effect from 8 AM Thursday
to 8 AM EDT Friday.

* EVENT...Rain will change to snow across the higher elevations
  Thursday. Snow accumulations of 3 to 6 inches are expected for
  elevations at or above 4000 feet, and 1 to 3 inches for
  elevations between 2500 and 4000 feet.

  The snow and windy conditions will produce some blowing and
  drifting. Occasional white-out conditions are possible.

* TIMING...Rain showers changing to snow showers Thursday morning
  continuing through early Friday morning.

* IMPACTS...Snow and ice covered roadways are expected across the
  highest terrain. The wind and snow combined may produce white-
  out conditions at times. Some blowing and drifting are also
  expected. Anyone planning on venturing out across the higher
  terrain need to be prepared for wintry conditions. Hazardous
  conditions are likely.

Title: Re: April 5th Severe Weather Threat
Post by: Thundersnow on April 05, 2017, 06:33:40 PM
For some reason, I never really felt it with this one anyway.


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Title: Re: April 5th Severe Weather Threat
Post by: harlequin on April 05, 2017, 06:36:43 PM
All 3 High "busts" (if today ends up being one) happened at relatively low lines of latitude.

And I guess January 23 may not be a bust. Significant EF3 killed 5 and the outbreak sequence killed 20, but the High did underperform.
Title: Re: April 5th Severe Weather Threat
Post by: wfrogge on April 05, 2017, 06:45:58 PM
I don't get all this talk about "busts".  The potential was there for tornadoes to rake across the area so the high was warranted.
Title: Re: April 5th Severe Weather Threat
Post by: WXHD on April 05, 2017, 06:51:12 PM
I don't get all this talk about "busts".  The potential was there for tornadoes to rake across the area so the high was warranted.

Agreed.
Title: Re: April 5th Severe Weather Threat
Post by: JayCee on April 05, 2017, 07:16:59 PM
On paper, this looks like the most credible tornado/hail threat Chattanooga has had in quite a while.

Used this quote to voice a thought.  As he said, everything did look credible on paper for a significant outbreak of severe weather.   If I worked at the SPC, I would feel negligent if I didn't issue the proper outlooks and watches.  If it doesn't happen, then perhaps we don't yet know every equation and factor that causes one system to produce an outbreak, while another "busts." 
Title: Re: April 5th Severe Weather Threat
Post by: SuperCell on April 05, 2017, 07:19:51 PM
As far as I am concerned *BUST* = good.
Title: Re: April 5th Severe Weather Threat
Post by: justinmundie on April 05, 2017, 07:45:07 PM
I don't get all this talk about "busts".  The potential was there for tornadoes to rake across the area so the high was warranted.

Verification is important. If you just always warn of potential, and then what happens is decidedly not as severe, the public stops paying attention. We're not just saying there's a potential for severe storms, we're giving probabilities and those probabilities are without a doubt, super incorrect.

Fact of the matter is, modeling crapped the bed again. As it has repeatedly recently. It seems like maybe some additional conservatism is in order. If you don't go high risk with a hatched area, and then the extreme storms start happening, it's a lot easier to start warning than it is to stop the hype train.
Title: Re: April 5th Severe Weather Threat
Post by: JayCee on April 05, 2017, 07:54:48 PM
Lightning visible to the west now as the line of potent storms approach.  Only warned storm is in the far southern valley for now.  Nevertheless, the storms approaching Knoxville look like they pack a punch. 
Title: Re: April 5th Severe Weather Threat
Post by: wfrogge on April 05, 2017, 08:10:45 PM
Verification is important. If you just always warn of potential, and then what happens is decidedly not as severe, the public stops paying attention. We're not just saying there's a potential for severe storms, we're giving probabilities and those probabilities are without a doubt, super incorrect.

Fact of the matter is, modeling crapped the bed again. As it has repeatedly recently. It seems like maybe some additional conservatism is in order. If you don't go high risk with a hatched area, and then the extreme storms start happening, it's a lot easier to start warning than it is to stop the hype train.

The probabilities were correct given the data we had with 24 hours to go.  If you know different there is a job at the SPC with your name on it :)
Title: Re: April 5th Severe Weather Threat
Post by: WXHD on April 05, 2017, 08:11:09 PM
Verification is important. If you just always warn of potential, and then what happens is decidedly not as severe, the public stops paying attention. We're not just saying there's a potential for severe storms, we're giving probabilities and those probabilities are without a doubt, super incorrect.

Fact of the matter is, modeling crapped the bed again. As it has repeatedly recently. It seems like maybe some additional conservatism is in order. If you don't go high risk with a hatched area, and then the extreme storms start happening, it's a lot easier to start warning than it is to stop the hype train.

I have to respectfully disagree.

I think you and I are privy to the nuances of forecasting, model hugging and wish-casting that eludes the vast majority of people. For you and I and most everyone else on this forum, weather is at the least a hobby and likely a passion.

Forecasters did not tell us that there was a 100% chance of tornadoes happening. The forecast and maps showed a a smaller chance of such horror happening. To that end, the forecast was nearly perfect. How individuals chose to interpret that is no fault of the people responsible for giving their best effort to alert the public to the potential for significant weather. We are very fortunate that nothing extreme panned out. However, you and I were both watching the models, radar and reports until the last moment. We both know that had things positioned themselves just a few miles in a south west direction things could have brought a very different outcome. Everyone I know was aware of the weather and the potential for tornadoes. To that end, I feel like the forecasters did their job exceptionally.

I'm mobile so there's likely some errors, sentiment remains. As does my respect for you and your ability to read and interpret models Justin.
Title: Re: April 5th Severe Weather Threat
Post by: cgauxknox on April 05, 2017, 08:12:17 PM
Lightning visible to the west now as the line of potent storms approach.  Only warned storm is in the far southern valley for now.  Nevertheless, the storms approaching Knoxville look like they pack a punch.

We've had plenty of thunder and some rain here in West Knoxville over the last 30 minutes or so but nothing severe yet.  I don't know we'll have any excitement but am grateful for the rain.
Title: Re: April 5th Severe Weather Threat
Post by: dwagner88 on April 05, 2017, 08:19:19 PM
I thought for sure I was going to see some hail as the line came through (nearly 70 DBZ returns). It was all torrential rain. Got 1.1" in about 15 minutes. Nothing severe verified here thankfully.
Title: Re: April 5th Severe Weather Threat
Post by: StormNine on April 05, 2017, 08:43:45 PM
The southern IN through KY/TN portion of the threat didn't do that bad as far as verification goes especially considering that the HRRR and the NAM overestimated the dewpoints by 5 to 8 degrees. Not sure what happened down in GA but overall the threat underperformed pretty significantly although there were some tornadoes down that way. With this coming off the heels of last Thursday and a somewhat underperforming High Risk back on the 2nd, the SPC will feel the criticism. I am more concerned about the continued failure of radars during severe weather events and the fact that our computer models are not making the progress that they should than I am about the SPC's risk areas.

With that being said it appears that the SPC is in a rough patch similar to where it was during the spring of 2005 and 2009 where it kept making forecast errors due to complex systems. A lot of the underperforming events of those years were due to gulf convection allowing for the blockage of sufficient moisture return. Spring 2005 was an extreme example that saw one of the biggest High Risk busts ever and several Moderate Risk busts.
Title: Re: April 5th Severe Weather Threat
Post by: Dyersburg Weather on April 05, 2017, 08:47:07 PM
I interrupt this discussion to say it's colder than ****. Carry on.
Title: Re: April 5th Severe Weather Threat
Post by: andyhb on April 05, 2017, 09:32:57 PM
Verification is important. If you just always warn of potential, and then what happens is decidedly not as severe, the public stops paying attention. We're not just saying there's a potential for severe storms, we're giving probabilities and those probabilities are without a doubt, super incorrect.

Fact of the matter is, modeling crapped the bed again. As it has repeatedly recently. It seems like maybe some additional conservatism is in order. If you don't go high risk with a hatched area, and then the extreme storms start happening, it's a lot easier to start warning than it is to stop the hype train.

Eh, I'll respectively disagree with the bolded. It's hard to get people's attention at the last minute when they have already made prior plans/etc. since they didn't expect a high magnitude event. They are basically equally tricky situations.

A multitude of things today, primarily as a result of the southern stream vort max that passed through the warm sector this morning, prevented a larger scale event from a seemingly favorable synoptic setup. Without going too far into detail, the lack of stronger low level flow through much of the afternoon was the #1 cause of the underperformance. For starters, it meant that the cold pool laid out by the morning storms basically saw no modification over E AL/GA.

This weak flow was a result of the aforementioned vort max leading to the primary low level jet axis being shifted into GA/etc. (in response to localized pressure falls). Here, bulk shear was comparatively weaker, the column was more saturated leading to HP/outflow-dominant storms and surface winds grew increasingly veered with time. Moisture return further north was hampered by the lack of stronger low level flow, as was hodograph curvature (lack of turning between 850 and 500 mb was also an issue further south into AL). Once the storms in E AL and TN reached the backed low level flow near the boundary, they had very little residence time before reaching stable air.

Post Merge: April 05, 2017, 09:41:23 PM
without a doubt.... ::)

Bruce, if half of the events you called for a week out verified, most of this forum would probably be in the ground with engraved blocks of granite sitting atop them.
Title: Re: April 5th Severe Weather Threat
Post by: BRUCE on April 05, 2017, 10:59:08 PM
well... its time to dig into the models n see when we have a next chance of opportunity... you have a great night andy... ;)
Title: Re: April 5th Severe Weather Threat
Post by: skillsweather on April 06, 2017, 12:51:08 AM
Man bummed to not got any storms here. It really felt like it would storm today earlier. The air felt perfect for storms but guess other things messed it up.. I miss spring days with back to back storms like one each week at least.
Title: Re: April 5th Severe Weather Threat
Post by: justinmundie on April 06, 2017, 06:42:48 AM
Eh, I'll respectively disagree with the bolded. It's hard to get people's attention at the last minute when they have already made prior plans/etc. since they didn't expect a high magnitude event. They are basically equally tricky situations.

A multitude of things today, primarily as a result of the southern stream vort max that passed through the warm sector this morning, prevented a larger scale event from a seemingly favorable synoptic setup. Without going too far into detail, the lack of stronger low level flow through much of the afternoon was the #1 cause of the underperformance. For starters, it meant that the cold pool laid out by the morning storms basically saw no modification over E AL/GA.

This weak flow was a result of the aforementioned vort max leading to the primary low level jet axis being shifted into GA/etc. (in response to localized pressure falls). Here, bulk shear was comparatively weaker, the column was more saturated leading to HP/outflow-dominant storms and surface winds grew increasingly veered with time. Moisture return further north was hampered by the lack of stronger low level flow, as was hodograph curvature (lack of turning between 850 and 500 mb was also an issue further south into AL). Once the storms in E AL and TN reached the backed low level flow near the boundary, they had very little residence time before reaching stable air.

Post Merge: April 05, 2017, 09:41:23 PM
Bruce, if half of the events you called for a week out verified, most of this forum would probably be in the ground with engraved blocks of granite sitting atop them.

Maybe I'm a bit hyperbolic... but I spent most of my evening trying to explain to people who were critiquing the weather service and local mets how difficult forecasting is, which is frustrating. But it's hard to justify when you can't even lean on the probabilities being even close to right. I also haven't seen anyone mention how models were essentially useless yesterday.

I realize I'm alone, but even when we have an enhanced risk, people are paying attention. I feel like we're going to have a much greater problem in the future when people start ignoring moderate and high risk events, and that's certainly going to happen the more often those events turn into nothingburgers.
Title: Re: April 5th Severe Weather Threat
Post by: Thundersnow on April 06, 2017, 08:26:40 AM
At the risk of beating a dead horse about the current risk scale... people, in general, don't really understand it.

"Enhanced" sounds worse than "moderate." If I didn't know better, I would think the same.

I heard someone on the radio yesterday actually confuse the two. The news person said something about an "enhanced risk" around Chattanooga, but "moderate" everywhere else.  I think a numeric "category" scale might actually make more sense... most people seem to understand the 1-5 scale (in terms of severity) with regard to tornadoes and hurricanes. Why not do something similar for severe risks?
Title: Re: April 5th Severe Weather Threat
Post by: StormNine on April 06, 2017, 09:22:24 AM
At the risk of beating a dead horse about the current risk scale... people, in general, don't really understand it.

"Enhanced" sounds worse than "moderate." If I didn't know better, I would think the same.

I heard someone on the radio yesterday actually confuse the two. The news person said something about an "enhanced risk" around Chattanooga, but "moderate" everywhere else.  I think a numeric "category" scale might actually make more sense... most people seem to understand the 1-5 scale (in terms of severity) with regard to tornadoes and hurricanes. Why not do something similar for severe risks?

I use the numbers when I discuss severe weather threats and I'm noticing more news outlets and even the NWS start to get on board with calling it a Level 3 risk instead of an Enhanced. I usually put the category name in parathesis so those used to seeing understand better. I think it is time to shed those sometimes confusing names and go numbers (using High Risk for a Level 5 would still make sense though). This is why the Tor Con works so well with the public is because it is a simple 1 to 10 measurement.

The non-weather caring public operates on the KISS principle. The simpler and more concise the weather information is the better. At the end of the day, all they want to know is how concerned they should be about seeing severe weather at their precise location. Unless it is a bar filled with Earth Science/Meteorologist fanatics, you don't have to worry about a full on bar brawl being started over whether Georgia should be in a Moderate or High Risk.

Title: Re: April 5th Severe Weather Threat
Post by: BRUCE on April 06, 2017, 09:33:10 AM
Maybe I'm a bit hyperbolic... but I spent most of my evening trying to explain to people who were critiquing the weather service and local mets how difficult forecasting is, which is frustrating. But it's hard to justify when you can't even lean on the probabilities being even close to right. I also haven't seen anyone mention how models were essentially useless yesterday.

I realize I'm alone, but even when we have an enhanced risk, people are paying attention. I feel like we're going to have a much greater problem in the future when people start ignoring moderate and high risk events, and that's certainly going to happen the more often those events turn into nothingburgers.
truth is think we all have a bit of hyperbolic in us... if we didnt, we wouldnt all be in this forum posting about weather... its a passion we all have... weather it be winter storms or severe weather... no one wishes devastation or destruction on no one... but seeing a violent long track tornado is such a adrenaline rush cant explain...
Title: Re: April 5th Severe Weather Threat
Post by: Curt on April 06, 2017, 10:16:11 AM
One thing I'm learning from severe weather events is how much the warm front or morning convection plays a huge role in making or breaking the event. I know in April 2011, the morning MCS played a huge role in tipping the event into epic proportions. However, the same MCS or convection event yesterday IMO played a role to lessen the event. In north GA, it actually created a huge cool pool for much the Atlanta metro north, thus instability was almost zero by the time the event could have gone gangbusters. This was WELL forecast 24 hours in advance by CAPE modeling on the short term NAM and HRR- and most offices did not account or at least believe this in those areas. I'm not sure if the rest of the event was lessened overall by its impact of lack of recovery time for instability as a whole over the region or lack of recovery time for moisture- who knows. It appears to the green person that I am- that these pre event thunderstorm clusters might be the key to the overall puzzle.
Title: Re: April 5th Severe Weather Threat
Post by: BRUCE on April 06, 2017, 11:28:27 AM
One thing I'm learning from severe weather events is how much the warm front or morning convection plays a huge role in making or breaking the event. I know in April 2011, the morning MCS played a huge role in tipping the event into epic proportions. However, the same MCS or convection event yesterday IMO played a role to lessen the event. In north GA, it actually created a huge cool pool for much the Atlanta metro north, thus instability was almost zero by the time the event could have gone gangbusters. This was WELL forecast 24 hours in advance by CAPE modeling on the short term NAM and HRR- and most offices did not account or at least believe this in those areas. I'm not sure if the rest of the event was lessened overall by its impact of lack of recovery time for instability as a whole over the region or lack of recovery time for moisture- who knows. It appears to the green person that I am- that these pre event thunderstorm clusters might be the key to the overall puzzle.
100 percent agree... great post
Title: Re: April 5th Severe Weather Threat
Post by: wfrogge on April 06, 2017, 12:04:54 PM
I interrupt this discussion to say it's colder than ****. Carry on.

Take that nonsense to the winter forum!   (I kid, I kid...)
Title: Re: April 5th Severe Weather Threat
Post by: NismoWx on April 06, 2017, 06:28:14 PM
How about that anticyclonic EF1 tornado in Bedford County? I'm going to drive out there Saturday on my way to Tullahoma to see what I can see.

Also confirmed EF1 in Warren County south of McMinnville.
Title: Re: April 5th Severe Weather Threat
Post by: StormNine on April 06, 2017, 06:50:20 PM
With the two tornadoes in TN and several likely tornadoes in KY the threat in KY/TN actually did decently relative to the risk level assigned. That is with dewpoints that were 5-7 degrees lower than what was expected according to the HRRR and NAM.
Title: Re: April 5th Severe Weather Threat
Post by: Eric on April 06, 2017, 08:03:20 PM
Told this to numerous folks yesterday in regards to SPC risk areas.  They outline and delineate what COULD happen, not necessarily what WILL happen.  More people need to understand this.
Title: Re: April 5th Severe Weather Threat
Post by: JHart on April 07, 2017, 04:38:04 PM
I thought this was interesting information from NWS...

Quote
... NWS damage survey for April 5, 2017 tornado event - update #2...

.Tornado #2/Bedford County EF-1 anticyclonic landspout tornado...

Rating:                   EF-1
estimated peak wind:      95 mph
path length /statute/:    5.4 miles
path width /maximum/:     150 yards
fatalities:               0
injuries:                 0

Start date:               April 5, 2017
start time:               347 PM
start location:           5 miles south southwest of Shelbyville
start lat/lon:            35.4120, -86.5069

End date:                 April 5, 2017
end time:                 353 PM
end location:             1.5 miles southeast of Shelbyville
end_lat/lon:              35.4715, -86.4380

Survey summary:
a rare and unique anticyclonic landspout tornado touched down in southern
Bedford County off a left splitting supercell and an anticyclonic rear flank
downdraft coupled with strong southwesterly surface flow. The damage path
started off of Charlie Russell Road consisting of uprooted and snapped trees
as well as a barn sustaining significant damage from rear flank downdraft
winds.  The path continued northeast uprooting and snapping dozens of
Hardwood and softwood trees. Off of Highway 412, several homes sustained
roof damage as well as loss of underpinning off of a couple of Mobile homes. 
Additional barn damage was observed on Womack Road along with several more
trees uprooted and snapped. Significant tree damage occurred off of Narrows
Lane including a 4ft wide Oak Tree snapped at the base.  The tornado then
weakened and continued northeast lifting near Tennessee Highway 130.