* User

Welcome, Guest. Please login or register.

Login with username, password and session length

Advertisement


Author Topic: Memorial Day Weekend Storms  (Read 26868 times)

0 Members and 1 Guest are viewing this topic.

Offline mempho

  • Tornado
  • ******
  • Posts: 3,711
  • Location: Collierville
  • Liked:
  • Likes Given: 1
Re: Memorial Day Weekend Storms
« Reply #105 on: May 29, 2017, 09:17:31 PM »
Still 113,000 out, myself included.

Here's a pic of blowdown in North Memphis at Hwy 51 and Watkins. This is probably 3-5 miles NW of Midtown in Frayser. Populated areas begin near here.
That is near the pocket of 120+ that was showing up on WREG radar -  it was so high that they looked for rotation and found none.  They makes it look like it actually could have been a pocket of Cat 3 winds. 

Sent from my SM-G900R7 using Tapatalk



Put on my big snow boots and
I boarded the plane
Touched down in the land of the Delta Blues
In the middle of the freezing rain

Snow up high
Won't you pour down over me
Yeah, I got some accretion
But I'm as blue as a boy can be

Offline mempho

  • Tornado
  • ******
  • Posts: 3,711
  • Location: Collierville
  • Liked:
  • Likes Given: 1
Re: Memorial Day Weekend Storms
« Reply #106 on: May 29, 2017, 10:05:39 PM »
Is that a down burst probably? Because thats very very isolated yet very intense.. Its like a down burst look of damage in a small area.. Almost looks non nature related because of the isolation of it.
It was a small pocket on radar-  the TV guys at first suspected the high velocities over a small area was due to rotation but they found none-  obviously, it was just straight line and probably an early microburst

Sent from my SM-G900R7 using Tapatalk



Put on my big snow boots and
I boarded the plane
Touched down in the land of the Delta Blues
In the middle of the freezing rain

Snow up high
Won't you pour down over me
Yeah, I got some accretion
But I'm as blue as a boy can be

Offline bugalou

  • Administrator
  • Derecho
  • ******
  • Posts: 2,131
  • Location: Southaven, MS
  • Twitter:
  • Liked:
  • Likes Given: 97
Re: Memorial Day Weekend Storms
« Reply #107 on: May 30, 2017, 05:04:49 PM »
It was a small pocket on radar-  the TV guys at first suspected the high velocities over a small area was due to rotation but they found none-  obviously, it was just straight line and probably an early microburst

Sent from my SM-G900R7 using Tapatalk

Look at my TMEM loop from above.  The way those OFBs are perpendicular and intersect would almost certainly create some rotation, I am almost certain there were high rotational velocities.  I didn't get a capture of it, but as I watched the storm on radar scope I got several TVS indications, but a quick flip between RV and BV on the radars and you could see it was not a tornado. 

I think when all it said in done we will see this was not a pure derecho straight line wind event driven by a rear inflow jet from a well established MSC, but this was moderately strong outflow boundaries from several different cells that interacted in a way that sheared on the the boundaries and greatly increased it's speed though conservation of angular momentum.  The path with the most damage aligns quite nicely with that vector.

Here is a terrible drawing to try and explain better than above.



Also note I am not a professional.  I am sure NWS/MEG will have a lot more data than me.  This is just are my thoughts as I watched the event unfold and looked at radar data.
« Last Edit: May 30, 2017, 05:07:43 PM by bugalou »

Offline harlequin

  • Derecho
  • ******
  • Posts: 2,173
  • Location: San Francisco, sometimes Midtown Memphis
  • Liked:
  • Likes Given: 528
Re: Memorial Day Weekend Storms
« Reply #108 on: May 30, 2017, 09:45:38 PM »
About to pass the three day mark. Hopeful about tomorrow.

Also, great posts above.

Offline mempho

  • Tornado
  • ******
  • Posts: 3,711
  • Location: Collierville
  • Liked:
  • Likes Given: 1
Re: Memorial Day Weekend Storms
« Reply #109 on: May 30, 2017, 10:04:27 PM »


Look at my TMEM loop from above.  The way those OFBs are perpendicular and intersect would almost certainly create some rotation, I am almost certain there were high rotational velocities.  I didn't get a capture of it, but as I watched the storm on radar scope I got several TVS indications, but a quick flip between RV and BV on the radars and you could see it was not a tornado. 

I think when all it said in done we will see this was not a pure derecho straight line wind event driven by a rear inflow jet from a well established MSC, but this was moderately strong outflow boundaries from several different cells that interacted in a way that sheared on the the boundaries and greatly increased it's speed though conservation of angular momentum.  The path with the most damage aligns quite nicely with that vector.

Here is a terrible drawing to try and explain better than above.



Also note I am not a professional.  I am sure NWS/MEG will have a lot more data than me.  This is just are my thoughts as I watched the event unfold and looked at radar data.

Wow, awesome post.  When they said rotation, the TV guys did was look at doppler velocities with the red/green directional overlay.  While there may have been some rotation and there may have been a TVS signature, they couldn't find winds moving in opposite directions in that radar scan-  I believe they were focusing on near-surface winds (which makes sense since there was no rotation).

Sent from my SM-G900R7 using Tapatalk



Put on my big snow boots and
I boarded the plane
Touched down in the land of the Delta Blues
In the middle of the freezing rain

Snow up high
Won't you pour down over me
Yeah, I got some accretion
But I'm as blue as a boy can be

Offline bugalou

  • Administrator
  • Derecho
  • ******
  • Posts: 2,131
  • Location: Southaven, MS
  • Twitter:
  • Liked:
  • Likes Given: 97
Re: Memorial Day Weekend Storms
« Reply #110 on: May 30, 2017, 10:18:29 PM »

Wow, awesome post.  When they said rotation, the TV guys did was look at doppler velocities with the red/green directional overlay.  While there may have been some rotation and there may have been a TVS signature, they couldn't find winds moving in opposite directions in that radar scan-  I believe they were focusing on near-surface winds (which makes sense since there was no rotation).

Sent from my SM-G900R7 using Tapatalk
I think it was the close proximity to the radar combined with the hybrid nature of the thunderstorms (being something like a bow echo/derecho with near by cellular storms) caused some measureble Eddies.  Def nothing mesocyclonic or even derecho head tornadic caused any of this.  The partially veering from the opposing winds definitely played into the strength though.

Sent from my P027 using Tapatalk


Offline bugalou

  • Administrator
  • Derecho
  • ******
  • Posts: 2,131
  • Location: Southaven, MS
  • Twitter:
  • Liked:
  • Likes Given: 97
Re: Memorial Day Weekend Storms
« Reply #111 on: May 30, 2017, 10:24:33 PM »
About to pass the three day mark. Hopeful about tomorrow.

Also, great posts above.
I got a generator you are welcome to borrow if things look like they will drag out over the weekend.

Sent from my P027 using Tapatalk


Offline Curt

  • Administrator
  • Tornado
  • ******
  • Posts: 7,730
  • Location: Arlington, TN(Memphis suburb)
  • Liked:
  • Likes Given: 0
Re: Memorial Day Weekend Storms
« Reply #112 on: May 30, 2017, 10:31:49 PM »

Offline mempho

  • Tornado
  • ******
  • Posts: 3,711
  • Location: Collierville
  • Liked:
  • Likes Given: 1
Re: Memorial Day Weekend Storms
« Reply #113 on: May 31, 2017, 12:07:26 AM »
https://youtu.be/A9hv1_r-QiM

Nice vid W Frogge
City, what kind of wind wind speed are we looking at there?

Sent from my SM-G900R7 using Tapatalk



Put on my big snow boots and
I boarded the plane
Touched down in the land of the Delta Blues
In the middle of the freezing rain

Snow up high
Won't you pour down over me
Yeah, I got some accretion
But I'm as blue as a boy can be

Online NashRugger

  • Derecho
  • ******
  • Posts: 1,049
  • Location: Biloxi, MS
  • current US Navy meteorologist & rugby player
  • Liked:
  • Likes Given: 80
Re: Memorial Day Weekend Storms
« Reply #114 on: May 31, 2017, 02:07:04 PM »
City, what kind of wind wind speed are we looking at there?

Sent from my SM-G900R7 using Tapatalk
That easily is a 90-100mph microburst because you have nearly total failure of the entire tree canopy in such a localized area.

Offline @NashSevereWx

  • Severe Thunderstorm
  • ****
  • Posts: 363
  • Location: Davidson & Williamson Counties
    • @NashSevereWx
  • Twitter:
  • Liked:
  • Likes Given: 8
Re: Memorial Day Weekend Storms
« Reply #115 on: May 31, 2017, 02:17:35 PM »
I cosign the OFB explanation in Memphis. The highest BVs were colocated with the OFB moving SW thru Memphis Metro.
Nowcasting Severe Weather
Davidson & Williamson Counties
@NashSevereWx on Twitter
NashSevereWx.com on the web

Offline harlequin

  • Derecho
  • ******
  • Posts: 2,173
  • Location: San Francisco, sometimes Midtown Memphis
  • Liked:
  • Likes Given: 528
Re: Memorial Day Weekend Storms
« Reply #116 on: May 31, 2017, 10:56:16 PM »
96 hours now for me, but I rode down to my parents. Talked to a power crew working on my street, and they explained more about it. Might get it back by morning. They said the houses across the street will be days more. A stretch of Avalon and Dickinson by Lick Creek took quite a hit. Lick Creek and all the alleys in Vollintine-Evergreen are impassable.

MLGW will have over 90 crews here by morning. I think they've done a great job.
« Last Edit: May 31, 2017, 10:59:13 PM by harlequin »

Offline Curt

  • Administrator
  • Tornado
  • ******
  • Posts: 7,730
  • Location: Arlington, TN(Memphis suburb)
  • Liked:
  • Likes Given: 0
Re: Memorial Day Weekend Storms
« Reply #117 on: May 31, 2017, 11:28:14 PM »
City, what kind of wind wind speed are we looking at there?

Sent from my SM-G900R7 using Tapatalk

Nws Memphis

Offline Thundersnow

  • Administrator
  • Tornado
  • ******
  • Posts: 10,824
  • Location: Nolensville
  • Liked:
  • Likes Given: 0
Re: Memorial Day Weekend Storms
« Reply #118 on: June 01, 2017, 06:51:01 AM »
There may have been three separate derechos on Saturday: https://www.facebook.com/NWSSPC/posts/1724297640920525


Sent from my iPhone using Tapatalk

Offline bugalou

  • Administrator
  • Derecho
  • ******
  • Posts: 2,131
  • Location: Southaven, MS
  • Twitter:
  • Liked:
  • Likes Given: 97
Re: Memorial Day Weekend Storms
« Reply #119 on: June 01, 2017, 03:51:50 PM »
I cosign the OFB explanation in Memphis. The highest BVs were colocated with the OFB moving SW thru Memphis Metro.

My final thoughts on the event are basically a moderately strong bowwed segment colliding with a cell based OFB.  This made what would be a moderate damage event into a major damage event and explains the 90-100 MPH+ reports.  The large swath of enhanced winds from this event happened right over the most populated areas.

 

* Recent Posts

Winter 2018-19
by schneitzeit
[Today at 05:54:13 PM]
Climate Change & Cyclical Snowfall Averages
by gcbama
[Today at 01:01:48 PM]
GOAT Snowstorm
by BALLPARK
[Yesterday at 04:49:20 PM]

Advertisement