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Author Topic: Severe Threat, March 19, 2018  (Read 15422 times)

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Offline Eric

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Severe Threat, March 19, 2018
« on: March 18, 2018, 11:09:33 AM »
Been a while since I started a thread.  Here goes.

Potential for a severe weather outbreak over Dixie Alley tomorrow.  Greatest threat for TN is S of I-40 with large hail, winds, and a few strong tornadoes all possible within the ENH risk area.  As always there are caveats with these types of systems - amount of destabilization, ongoing morning convection, cloud cover, etc. - but the threat is there.  I'm afraid, though, that if this thing fires off as expected, and there are remnants of earlier crapvection, this does indeed have the April 10, 2009 feel to it, as Andy intimated.  The EF4 that hit the 'Boro in 2009 was initiated by a rogue outflow boundary left over from morning convection.  Not saying we'll have a redux, but the precedent has been set.

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Offline mamMATTus

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Re: Severe Threat, March 19, 2018
« Reply #1 on: March 18, 2018, 11:22:25 AM »
My biggest concern right now is I think a lot of people are going to be caught off guard. This really seems to have snuck up out of nowhere for the most part and I don't think the public is very aware.

Offline StormNine

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Re: Severe Threat, March 19, 2018
« Reply #2 on: March 18, 2018, 11:31:02 AM »
It should be noted that there are some differences between the NAM and the GFS as far as how far north the strong to severe storm threat gets.  The GFS would feature a severe threat as far north as the KY/TN border, while the NAM and NAM 3k keep much of the instability south of I-40.  The exact low track and presence of morning convection will determine how far north that threat goes. 

The fact that there is some minor capping is a bit of concern as that would prevent additional convection and lead to unstable atmosphere developing, leading to intense convection developing later in the afternoon.  This is what storm chasers like to see in the plains, a cap that is weak enough to break, but strong enough to prevent late morning-midday convection from ruining the greater hail/tornado threat.  Steep lapse rates along with a favorable combination of shear/instability will not only suggest a tornado concern, but also a concern for very large hail. 

Offline BRUCE

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Re: Severe Threat, March 19, 2018
« Reply #3 on: March 18, 2018, 11:50:36 AM »
It should be noted that there are some differences between the NAM and the GFS as far as how far north the strong to severe storm threat gets.  The GFS would feature a severe threat as far north as the KY/TN border, while the NAM and NAM 3k keep much of the instability south of I-40.  The exact low track and presence of morning convection will determine how far north that threat goes. 

The fact that there is some minor capping is a bit of concern as that would prevent additional convection and lead to unstable atmosphere developing, leading to intense convection developing later in the afternoon.  This is what storm chasers like to see in the plains, a cap that is weak enough to break, but strong enough to prevent late morning-midday convection from ruining the greater hail/tornado threat.  Steep lapse rates along with a favorable combination of shear/instability will not only suggest a tornado concern, but also a concern for very large hail.
also... note...  dont count out severe storms late tonight with the passing of the warm front boundary ... though hail will be main threat with these... storms should stay elevated in nature... tomorrow is still big question to me... if the junk can get out n clear in time.... also question how far west can the threat materialize ... something keep eye out. ::coffee::
Come on severe wx season...

Offline Charles L.

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Re: Severe Threat, March 19, 2018
« Reply #4 on: March 18, 2018, 11:57:14 AM »
The triple point will definitely come into play somewhere across middle TN too, maybe even southern KY if the low goes a little further north than forecast.
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Offline mamMATTus

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Re: Severe Threat, March 19, 2018
« Reply #5 on: March 18, 2018, 12:56:55 PM »
James Spann will be doing a FB Live at 8 central tonight about tomorrow's threat. I trust and value anything the man has to say.

Offline SuperCell

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Re: Severe Threat, March 19, 2018
« Reply #6 on: March 18, 2018, 01:22:57 PM »
James Spann will be doing a FB Live at 8 central tonight about tomorrow's threat. I trust and value anything the man has to say.
Same here.
Also looks like large hail is a good possibility. Just what my car needs...
« Last Edit: March 18, 2018, 01:32:31 PM by SuperCell »
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Offline AdamLewis

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Re: Severe Threat, March 19, 2018
« Reply #7 on: March 18, 2018, 01:45:50 PM »
What is the timing on this?

Offline Susan

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Re: Severe Threat, March 19, 2018
« Reply #8 on: March 18, 2018, 01:48:07 PM »
I think 2 - 5p for middle Tennessee
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Offline andyhb

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Re: Spring 2018
« Reply #9 on: March 18, 2018, 02:21:23 PM »
12z CAMs were generally very ominous for tomorrow. It seems almost a certainty that supercells will be the dominant storm mode tomorrow given the low amplitude nature of the shortwave, spotty capping, a pretty obvious pre-frontal trough/pseudo-dryline (yes, whenever these make it east of the MS, there is generally trouble) and shear vectors oriented very favorably to it.

There are still some questions regarding the degree of low level wind response, the resiliency of the wedge front (warm sector extent) and how far into Middle TN sees a threat. Large hail seems almost a certainty, and I can certainly see a scenario that results in a fairly significant tornado outbreak tomorrow given the parameter space and favorable synoptics. GA might have problems after dark tomorrow too.
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Offline BRUCE

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Re: Re: Spring 2018
« Reply #10 on: March 18, 2018, 02:30:25 PM »
12z CAMs were generally very ominous for tomorrow. It seems almost a certainty that supercells will be the dominant storm mode tomorrow given the low amplitude nature of the shortwave, spotty capping, a pretty obvious pre-frontal trough/pseudo-dryline (yes, whenever these make it east of the MS, there is generally trouble) and shear vectors oriented very favorably to it.

There are still some questions regarding the degree of low level wind response, the resiliency of the wedge front (warm sector extent) and how far into Middle TN sees a threat. Large hail seems almost a certainty, and I can certainly see a scenario that results in a fairly significant tornado outbreak tomorrow given the parameter space and favorable synoptics. GA might have problems after dark tomorrow too.
also appears a nice dry line pushing out of east texas towards midsouth could help things also... interesting... 12z euro actually was a up tick in the threat... tomorrow ::coffee::

Post Merge: March 18, 2018, 03:21:33 PM
read on line   4  16  98   was being used for analog tomorrow... ::wow:: not sure bout that...
« Last Edit: March 18, 2018, 03:21:33 PM by BRUCE, Reason: Merged DoublePost »
Come on severe wx season...

Offline DeborahFaye

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Re: Severe Threat, March 19, 2018
« Reply #11 on: March 18, 2018, 04:57:04 PM »
Wonder if schools will dismiss earlier? Probably not but if this starts cranking up some might. If it ends up being clear and sunny tomorrow then thats probably going to mean bigger storms for us potentially since everything else is kind of there.

Several north Alabama schools have already announced they are closing early tomorrow...

Offline mamMATTus

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Re: Severe Threat, March 19, 2018
« Reply #12 on: March 18, 2018, 05:45:48 PM »
I can't believe this thread isn't up to at least 3 pages yet lol.

Online Beth

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Re: Severe Threat, March 19, 2018
« Reply #13 on: March 18, 2018, 05:51:40 PM »
Several north Alabama schools have already announced they are closing early tomorrow...
Yes I just talked to my brother in Hartselle Alabama and he said schools were closing. Some are on spring break this week too.

Offline StormNine

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Re: Severe Threat, March 19, 2018
« Reply #14 on: March 18, 2018, 05:58:18 PM »
http://www.spc.noaa.gov/climo/online/sp3/plot.php?lat=35.293&lon=86.717&zoom=140&mode=0&bdate=19980403/1200&edate=19980404/1200&torflag=1&windflag=1&hailflag=1&t01=0&t02=5&t03=0&t04=9999&t05=0&t06=9999&t07=0&t08=9999&t09=0&t10=9999&h01=0&h02=9999&w01=0&w02=9999&showt=0&legend=1&showh=0&showw=0&cntys=1

^^ That event is an analog to this event^^

More recently, this event reminds me more of 1/10/2008 (with a lot more instability) and 04/10/2009 as far as storm mode is concerned.  There is a lot of similarities with this event to Good Friday 2009, it is almost scary.  The low amplitude nature, storm mode, level of instability, time of day the threat is expected to occur, and even where the storms are expected to initially form. 

With that being said just because there are a lot of big picture similarities to that event and this one, doesn't mean that we are expecting a repeat.  We have to see if any boundaries are left over or if convection is lingering over our area.  It is those mesoscale differences that cause an event to go boom like dynamite or go bust. 

 

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