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  • Current Tropical Systems
    Melissa

Severe WX Severe Threat 17-18 March 2021

Kory said:
We had a ton of ascent over the warm sector with a very deep trough practically moving due east instead of the usual glancing by as it’s lifting NE.
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If I'm not mistaken, the original thinking was that the forcing in the warm sector was weak enough that we wouldn't get a huge blowup of convection despite the relatively weak capping, correct?
 
warneagle said:
If I'm not mistaken, the original thinking was that the forcing in the warm sector was weak enough that we wouldn't get a huge blowup of convection despite the relatively weak capping, correct?
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Yeah originally that was I was thinking...more cellular convection and less coverage. But hindsight is 20/20. 4/15/11 was the top analog on CIPS and it was a pretty good match if I must say (should’ve been the first red flag). A large portion of the moderate risk that day was devoid of severe wx and it was all displaced south of the thermal boundary from a mass of convection over North AL.
 
Was definitely thinking 4/15 as it unfolded, pretty much the same areas and pretty much the same flooding issues here
 
Segment from the afternoon AFD by the NWS in Raleigh... updated ~15 mins ago.

"Shear profiles are expected to remain favorable for primarily a
supercellular storm mode; and forecast storm motion vectors around
210-220 degrees will favor long residence times for cells tracking
along the low level frontal zone(s). As such, the risk for all
severe hazards, including the possibility of long-track mesocyclones
capable of producing tornadoes --possibly significant-- will
increase and exist between 19Z-01Z/19th across cntl NC."
 
Mesoscale Discussion 0224
NWS Storm Prediction Center Norman OK
0210 PM CDT Thu Mar 18 2021

Areas affected...northern South Carolina into central North Carolina

Concerning...Tornado Watch 41...

Valid 181910Z - 182145Z

The severe weather threat for Tornado Watch 41 continues.

SUMMARY...Storms will continue to develop east/northeast across the
watch area, and a new watch could be needed into central North
Carolina later this afternoon.

DISCUSSION...A broken line of cells continues to progress east into
northwestern SC, near the surface trough and along and north of the
warm front. Surface analysis shows warming and destabilization
continues south of this front, and this should allow these storms to
persist and perhaps expand in coverage. The greatest severe risk
appears to be along the warm front, where storms will experience
enhanced lift. Strong deep-layer shear as well as effective SRH of
200-300 m2/s2 will favor supercells at times, with a threat of a
brief tornado or damaging gusts. If storm trends continue up over
the next few hours, an additional watch could be needed downstream
into NC.

..Jewell.. 03/18/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...RAH...CAE...GSP...FFC...

LAT...LON 33928101 33918311 35518200 35517986 33928101
 
Matt Grantham said:
Here's video from the first tornado I've ever observed in Alabama. Totally heart pounding trying to chase solo and navigate the roads while having such limited visibility.

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Matt, it's awesome to see that your enthusiasm while chasing hasn't changed one bit! Couple of months ago I found the video of us in Hill City Kansas from back in 2007 with Brett. Watching it made me laugh especially your comments and me freaking out about getting too close.
 
Looking back Tuesday night...the models that kept lowering the Td's Wednesday morning was a sign things were not going exactly as planned. That isn't what happens on the day with a high end event with a EML advecting from the west. And while it wasn't a classic wedge, it had the same impact over NE Alabama. Add to that more rain than was expected and no sunshine, the low level jet wasn't enough to give us clean warm sector.

In hindsight, those Td's were the first sign things were going to be different.
 
akt1985 said:
Brad Travis thinks the reason today wasn't worse than it was was because the upper level low over Missouri never became negatively tilted.
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Fred has previously made a very strong case against the need for a negative tilt. I imagine Brad has his reasons for believing this.
 
The Tornado-Warned storm for the Charlotte area is tracked to basically come just slightly north over where I live. Should be in a good position to see if anything is going on near the ground
 
bwalk said:
Fred has previously made a very strong case against the need for a negative tilt. I imagine Brad has his reasons for believing this.
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What's so funny is that it's Brad Travis back years ago that first keyed me onto the idea of needing to watch positively tilted troughs too. 4/8/1998, 2/5/2008, 5/18/1995, even 4/3/1974 by the afternoon, were all positive tilt troughs. This area of the country has a LONG history of F4-F5 tornado outbreaks with positive tilt and neutral tilt troughs, especially in the spring months. There were other things going on yesterday that lessened the threat (even though it was honestly still a significant tornado outbreak in the Alabama portion of the SPC High Risk area).
 
Richardjacks said:
Looking back Tuesday night...the models that kept lowering the Td's Wednesday morning was a sign things were not going exactly as planned. That isn't what happens on the day with a high end event with a EML advecting from the west. And while it wasn't a classic wedge, it had the same impact over NE Alabama. Add to that more rain than was expected and no sunshine, the low level jet wasn't enough to give us clean warm sector.

In hindsight, those Td's were the first sign things were going to be different.
Click to expand...

That is a good point.
But everyone was so overhyped by Tuesday night that it was easy to miss data like that.
 
bwalk said:
That is a good point.
But everyone was so overhyped by Tuesday night that it was easy to miss data like that.
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And Richard, having worked at NBC 13 during some of our biggest events over the years, will be the first to tell you that you may even see some of those things in real-time ahead of time, but when the conditional potential is so high-end and life-threatening, you have to skew a bit more toward the idea that it can be overcome, simply because of public awareness reasons. You can't afford to send a message that may be incorrectly interpreted as a threat not materializing and then the potential limiting factors end up being overcome after all. Even with the limiting factors that ended up getting into place, immediately on the unstable side of the warm front in central Alabama yesterday, an EF4+ parameter space did get into place and there were cellular tornadic storms that tracked through that parameter space. There were just other factors that kept them from realizing their true potential.
 
Per Jackson NWS: “ Our storm survey team's preliminary reports show that an EF0 tornado occurred yesterday in Lamar County(near the Marion County line) with estimated winds of 80 mph. The damage in southern Marion Co. near Sandy Hook was rated as straight line wind damage at 75mph.”
 
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