March 17-18 Severe Weather Event

[eyewall]

It will certainly go down as one of the worst Moderate Risk busts in some time. They seem to struggle when it isn't the Plains or Dixie Alley. None the less here is a pano I took of the tornado warned cell in Alamance County NC:
 

[frazdaddy]

2 hours ago, PackGrad05 said:

Unfortunately, yesterday was a big bust.  No other way to put it.  That just goes to show how complicated the science is.  With that said, both NWS and local mets consistently explained ways that this could end up being less of a big deal..  However, it is tricky because you want people to be prepared in case the ingredients do come together in a Level 3/4 fashion.

Sadly us weather nerds seem to be the only ones that pay attention to the disclaimers in a forecast. 

[NorthHillsWx]

There are a couple of observations I made as to why yesterday failed to produce.

1) lack of strong LLJ. This was apparent from modeling about 24 hours out and very noticeable yesterday. Even when the sun broke out and mixing should have occurred, winds were pretty much calm all afternoon until the outflow from the QLCS came through. On significant severe days, as soon as the sun breaks out and screaming LLJ winds start mixing down, it becomes extremely windy and gusty

2) The meso-low develop in a textbook location from pressure falls along the southern edge of the retreating wedge layer and rode that boundary to a T. This happens so frequently we need to look past other parameters in our area and always remember that these meso scale systems frequently are our main mode for severe weather. The only significant weather yesterday occurred with this feature and it was well outside the area SPC progged for severe weather.ALWAYS watch the wedge front for severe, even if CAPE and other values are not high in those areas

3) as the low crossed the mountains it got strung out. Pressure falls along the coast set up a secondary boundary that became the primary forcing region and led to the formation of a large area of convection near or over the ocean. This was very well modeled within 36 hours. Most CAMs eliminated all convection in the SPC risk area more than a day out. This was very noticeable. Whenever you get a large convective mass on the coast you can pretty much kiss severe threats goodbye. Not only was the LLJ disrupted but a large area of subsidence existed between the pressure falls along the coast and the meso low. This negated the favorable mid level parameters that argued for an outbreak 

4) do not take so much stock in mid level parameters. They definitely determine a severe outbreak, but to be exploited you need storms, lol. This was a situation where the LP got strung out and reformed over the coastal boundary leaving most of NC/SC in a zone of subsidence and no forcing for storm formation. This was actually very well modeled from 24-36 hours out, plenty of time to adjust the severe outlook 

[magpiemaniac]

This woman’s reaction...  

 

[NorthHillsWx]

10 minutes ago, magpiemaniac said:

This woman’s reaction...  

 

Reminds me of that video from Zebulon a while ago on 64

[btownheel]

This woman’s reaction...  

 

No wonder I heard it so clearly. That’s maybe 3 blocks from me. Looks from that like it almost went right down University Dr.

 

 

So yeh, y’all can stuff that bust talk, at least here. Very glad I knew well in advance and had wife, daughter and our cats tucked away.

[NorthHillsWx]

1 hour ago, btownheel said:

No wonder I heard it so clearly. That’s maybe 3 blocks from me. Looks from that like it almost went right down University Dr.

 

 

So yeh, y’all can stuff that bust talk, at least here. Very glad I knew well in advance and had wife, daughter and our cats tucked away.

There wasn’t a single severe report in the level 3/4 threat area. I’m sure there were 2-3 weak spin ups that certainly were scary and damaging under that meso low yesterday but that was outside the threat area. Like issuing a winter storm warning and not getting a flake but a rogue band set up and dropped 1-3 inches outside the warning area

Not downplaying your experience, I’m sure that was harrowing. But this was a bust outside of a very isolated area. If it’d been a level 1 day no one would be calling bust, but it was forecast to be high end. 

[magpiemaniac]

A bust for an 8” snow event is sad and depressing.  I don’t know of anyone who’s sheltered in the basement for flakes.

But a bust for a widespread tornado and severe weather outbreak should be celebrated with ticker tape.  When that NOAA weather radio starts singing and a hook echo is heading towards the house, you better believe I’m praying for a bust.

[landof2rivers]

Amen

[Cheeznado]

I think there is not one shred of a doubt that this this two day event was a colossal bust. (A good thing) This is NOT dissing SPC by any means, although at the time I was somewhat skeptical of the high risk upgrade. On Wednesday from what I can see of the damage reports, there was not one long track or violent tornado, and those were specifically mentioned in the watches and outlooks. Severe forecasting is hard, even for the experts at SPC.

[WhirlingWx]

I'm pretty sure that Wednesday, probability-wise, did verify a high risk in Alabama, now that more late reports have been added in. Can't really say the same for Mississippi though. Plus, did I agree with the addition of the 45% hatched? Not really, and the event did not verify the aggressive wording of "potentially violent" tornadoes either (again, a good thing). I do agree that we still have a lot to figure out in severe wx forecasting.

However, I do want to point out that there was an EF2 tornado in SE Mississippi that crossed into SW Alabama, near or in the southern end of the high risk area, that was on the ground for more than 35 miles and for more than 45 minutes, per a survey by NWS Mobile. There was also an EF1 that tracked over 20 miles in Hale and Tuscaloosa counties in Alabama. IMO, those count as long-tracked. 

Again, was the outlook perfect? No, but we've seen "busts" that are more egregious than Wednesday ever could be. Like Thursday.  (FWIW, pretty sure we did get around 5-10 tornadoes after 12z on Thursday, but they were all weak and outside the highest risk area, which had no severe weather reports). Of course, any time you get hit close to home, it won't feel like a bust for you. All of this discussion is from an objective meteorological perspective, and I think we all agree that people are dealing with losses after this event, which is always tragic. At the same time, it is still pretty miraculous to have had no fatalities.

[jburns]

2 hours ago, TexMexWx said:

Not really, and the event did not verify the aggressive wording of "potentially violent" tornadoes either (again, a good thing).

 

I think the average person would classify any tornado they were caught in as violent.  Sometimes the NWS and SPC shoots themselves in the foot when it comes to informing the general public. The wording of the severe thunderstorm probabilities are a case in point. 

MARGINAL (light green)

SLIGHT  (dark green)

ENHANCED (Yellow)

MODERATE (Red)

HIGH (Magenta)

Moderate is a higher level than enhanced?  Everyone I know knows the difference between marginal and slight.  One means just a little and the other means not much.   Colors don’t help. I’ve never seen a fire engine with flashing magenta lights. Over complicated and just cries out for something simple. I know!!!! Some folks in India invented a system for doing just this almost 2000 years ago that is perfect for this kind of differentation and would not confuse anyone.  

Level 1

Level 2

Level 3

Level 4

Level 5

Everyone I know really does know that 4 is more than 3.

 

[Chinook]

NWS Birmingham

 

information from NWS Mobile (preliminary)   Full text:  https://mesonet.agron.iastate.edu/wx/afos/p.php?pil=PNSMOB&e=202103200352

Quote

Public Information Statement
National Weather Service Mobile AL
1052 PM CDT Fri Mar 19 2021

...NWS Damage Survey For 3/17/21 Long Track Tornado Event...

.OVERVIEW...NWS Survey team started the day at the Wayne/Choctaw 
County line and continued into southern Choctaw and northwest 
Clarke County. It was determined based on a combination of ground
and aerial surveys to be one long track tornado. It should be noted
that a large portion of the tornado track was in very hard to
reach or inaccessible areas. Therefore, additional information will
be analyzed in the coming days and information below will likely
be refined prior to the official publication in Storm Data. 

NWS Mobile would like to thank Wayne County EMA, Choctaw County
EMA, Clarke County EMA, and the Alabama Law Enforcement Agency
for their tremendous help in this survey.

.WAYNE/CHOCTAW/CLARKE TORNADO...

Rating:                 EF-2
Estimated Peak Wind:    125-130 mph
Path Length /statute/:  34.57 miles
Path Width /maximum/:   400 yards
Fatalities:             0
Injuries:               2

Start Date:             Mar 17 2021 
Start Time:             344 PM CDT
Start Location:         9.5 mi E Waynesboro, MS
Start Lat/Lon:          31.6842 / -88.4855

 

[Quincy]

Wednesday wasn’t a colossal bust. Sure, there wasn’t much activity over the western heart of the moderate risk, but several long track supercells produced numerous tornadoes over Alabama.

Thursday was even more fickle.

Remember that SPC produces probabilistic outlooks. Just because the “odds” of a tornado max out at one point does not mean that this is exactly where tornadoes will form. Tornadoes are microscale phenomena and very complex.

[greendave]

On 3/19/2021 at 3:45 PM, btownheel said:

No wonder I heard it so clearly. That’s maybe 3 blocks from me. Looks from that like it almost went right down University Dr.

 

 

So yeh, y’all can stuff that bust talk, at least here. Very glad I knew well in advance and had wife, daughter and our cats tucked away.

So - it started on a NW track out of Whitsett - but turned almost due east once it hit Williamson Ave. It crossed University Dr. but didn't go up it.

This all leads me to the other part of my observation and story. I believe (and yes I know its Preliminary) that the NWS damage survey missed the duration of the tornado. I witnessed the larger broad rotation, and heard it, well east of Williamson Dr. and have groundtruthed damage as far east as Rockwood Dr (near Turrentine Middle School) - i have not looked farther east than that. 

I'm attaching groundtruth points of damage to mostly downed trees - some impacting structures. The damage was strangely sporadic - never a noticeable path of limbs snapped in a line or path. Starting with the flipped daycare van @ Hwy 70 and WIlliamson - it was a tree here or there, some shingle/gutter damage intermittent, then nothing, then another large Oak, then 5 large trees all within a 500yd circumference - then nothing..

I suspect the tornado was on the ground twice as long if not more, than the preliminary report.

For those familiar with Burlington -after crossing Williamson Ave. the tornado turned due east and impacted the areas b/t Hwy 70 (S. Church St.) and Edgewood Ave. My residence is within the blue circle - and witnessed the rotation, intense burst of constant lightning for ~2mins, followed by a white wall of what i feared had turned into a larger wedge tornado. Thankfully the rotation that dropped to the ground was small and fairly weak as indicated by the video taken along S. Church St and passed roughly 0.5mi south of me. Yellow dots are rough locations of groundtruthed damage.

[brianc33710]

Now the AL tornado total from last Wed sits at 24, 6th all time for AL. That's more twisters than the 08 April 1998 High Risk, but obviously without any EF3+ (maybe 1 might still come around) tornadoes like the F5 that hit Pleasant Grove 23 years ago.