Severe WX Severe Weather Event April 13-14, 2019

[andyhb]

0-6 km shear vectors and mid-level winds ahead of the front are looking more SW across MS/AL overnight Saturday into Sunday. That is only going to increase the supercell risk.

That 11/1992 analog is looking pretty good right about now.

 

[Fred Gossage]

That 11/1992 analog is looking pretty good right about now.

Frighteningly so, except shifted east/northeast some overall.

 

[apocalyptic_pleasures]

Where are these 11/92 analogs coming from? CIPS just shows a bunch of March/April analogs which 4/27/11 was #4 earlier but thankfully not even there anymore..

 

[Fred Gossage]

Where are these 11/92 analogs coming from? CIPS just shows a bunch of March/April analogs which 4/27/11 was #4 earlier but thankfully not even there anymore..

Looking at the setup itself and then comparing it to the 1992 setup at a synoptic level.

 

[apocalyptic_pleasures]

Looking at the setup itself and then comparing it to the 1992 setup at a synoptic level.

Wow thats close but isn't mid April actually worse than November due to it being Spring and the Sun?

 

[andyhb]

Where are these 11/92 analogs coming from? CIPS just shows a bunch of March/April analogs which 4/27/11 was #4 earlier but thankfully not even there anymore..

The CIPS analogs are filtered for time of year I believe (i.e. fall events won't show up in spring). Otherwise, I think it might be on there pretty easily.

 

[apocalyptic_pleasures]

Here is why I ask the above-ceiling might be higher in April if Nov 1992 happened in April. Hopefully this all busts and a non event...

 

[jmills]

SPC has issued a Day 2 Moderate risk:

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
0107 AM CDT Fri Apr 12 2019

Valid 131200Z - 141200Z

...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FROM FAR EAST
TEXAS ACROSS NORTHERN LOUISIANA AND SOUTHERN ARKANSAS INTO
WEST-CENTRAL MISSISSIPPI...

...SUMMARY...
Numerous severe thunderstorms are expected across portions of east
Texas, Louisiana, southern Arkansas, Mississippi and surrounding
areas Saturday and Saturday night.

...Synopsis...
As an upper low/trough shifts northeastward across the Great Lakes
into eastern Canada, an evolving trough pivoting around the western
and southern fringe of this system will shift out of the southern
Rockies and across southern Plains Saturday/Saturday night.

In response to this system, a surface low -- initially expected to
reside in the vicinity of the Texas Hill Country -- will strengthen
as it shifts northeastward. By the end of the period Sunday
morning, the low should reside in the vicinity of the confluence of
the Ohio and Mississippi Rivers. Trailing from this low, a cold
front will sweep across east Texas to near the Sabine River by
sunset, and then continue eastward across the lower Mississippi
River into Mississippi and eventually western Alabama. Widespread
thunderstorms -- including potential for a substantial severe
weather event -- are expected.

...east Texas eastward to southwest Tennessee/Mississippi/western
Alabama...
A potentially significant severe weather episode is expected to
evolve across portions of the south central U.S. -- focused from the
Arklatex to the lower Mississippi Valley area, as a seasonably
strong southern-stream storm system advances across the region.

With a moist low-level airmass within an evolving warm sector
undergoing ample daytime heating, mixed-layer CAPE in the 1000 to
2000 J/kg range is expected to evolve by early to mid afternoon.
Increasing ascent associated with the eastward advance of the upper
system should result in an increase in convection by early
afternoon. CAM guidance varies from model to model, but general
consensus appears reasonable -- in that a band of storms will
develop near the front, with some linear/upscale growth with time,
while more cellular convection evolves ahead of the band.

At this time, the banded convection appears likely to evolve across
east Texas, with the more cellular storms affecting northern
Louisiana and southern Arkansas by mid afternoon, and then spreading
across the Mississippi Delta region into western Mississippi by mid
to late afternoon. Given very strong the very strong wind field
accompanying this system, with flow veering/increasing with height
from southeasterly to south-southwesterly, and reaching 60 to 70 kt
at mid levels, well-organized rotating updrafts will likely evolve
within several cells. Along with locally damaging winds and hail,
strong tornadoes may also occur, within a few of the most intense
storms. Convection will continue spreading eastward through the
evening and into the overnight hours. While the pre-frontal,
cellular convection should diminish overnight, a semi-organized band
of storms -- with embedded rotating updrafts and continued
severe/tornado potential -- will cross the central Gulf Coast states
through the end of the period.

...North Carolina/southeast Virginia and vicinity...
Models forecast that the eastern fringe of a warm front associated
with the developing south-central U.S. storm system will lie across
the Carolinas/Virginia vicinity during the day. With some heating
of a moist low-level airmass yielding around 1000 J/kg mixed-layer
CAPE during the afternoon, scattered/diurnally driven thunderstorms
are expected. While not excessive, shear -- aided by 35 kt
mid-level west-southwesterlies -- will be sufficient for storm
organization, and thus risk that a couple of storms reach severe
levels. Hail and gusty/locally damaging winds would be the primary
severe risk, before storms weaken into the evening hours.

...MAXIMUM RISK BY HAZARD...
Tornado: 15% SIG - Moderate
Wind: 45% - Enhanced
Hail: 30% - Enhanced

..Goss.. 04/12/2019

 

[Taylor Campbell]

This is going to be a very dangerous outbreak.

 

[Taylor Campbell]

The threat has really grown for significant severe to continue well into Sunday across many more eastern states. The SPC now has a large enhanced risk from southern Ohio into AL, and GA.

 

[TXTornado]

Lapse rates are still the one thing holding this back.

 

[Argus]

Spann wasn't impressed by the CAPE values for Sunday morning for Bama. The HRRR and Channel 2 just showed rain for us on Sunday.

 

[Darklordsuperstorm]

Bmx to SPC: I see your slight risk and I'll raise you an enhanced risk.

 

[CheeselandSkies]

Wow. Unusual for a local office to openly contradict the SPC.

 

[Richardjacks]

Bmx to SPC: I see your slight risk and I'll raise you an enhanced risk.View attachment 1320

seems a bit bold to me given the questionable CAPE and 48 hours away. I do think the CAPE will be a bit higher than shown, but still. Their morning afd does mention a small temp change would make a big difference in the tall CAPE

 

[CheeselandSkies]

Based off the 06Z NAM, Saturday to me seems rather more dangerous for LA than 4/2/17 (which went high risk). Some of the synoptic scale mitigating factors that were present for that one are also present for this one, but to a lesser degree. Also, the soundings from the areas of greatest EHI are showing several analogs. One thing I noticed that struck me as strange leading up to the 2017 event is that there were all these pretty reds and purples on the EHI/SRH plots, and "PDS TOR" in the soundings yet no "significant" analog matches for a lot of them.

A rather unscientific observation, perhaps, but it stuck out to me before the fact and especially after when the outcome seemed rather underwhelming for the high risk that was issued, although there were numerous tornadoes with a few strong (EF2), there were no jaw-dropping, long-track, unquestionably violent (regardless of whether or not it hit the requisite DIs) tornadoes that I've come to associate with that pink contour on the outlook map.

 

[Kory]

What questionable CAPE? I’m seeing upwards of 1000 J/KG ahead of the main boundary across the models.

 

[Richardjacks]

What questionable CAPE? I’m seeing upwards of 1000 J/KG ahead of the main boundary across the models.
The area of 1000+ CAPE is very narrow and doesn't spread east very far.

 

[Kory]

We don’t need raging 3,000 J/KG for a significant event. The Super Tuesday North AL overnight EF4 was like 200-300 J/KG.

That looks sufficient to me.

 

[Richardjacks]

We don’t need raging 3,000 J/KG for a significant event. The Super Tuesday North AL overnight EF4 was like 200-300 J/KG.

That looks sufficient to me.

Yes, I know...but for April, typically you need higher CAPE vs wintertime events. It could end up being higher than what is shown, but for a mid April event, I just don't find it impressive enough for a Enhanced threat.