Severe Weather Threat - May 6, 2024

Ok, now that we've had a nice discussion about nothing that applies to this thread - can we please keep these discussions to other threads please? We have them and you are welcome and encouraged to use them. This thread, however, is about the upcoming severe threat starting May 6th. Thank you.
 
cincywx said:
gotta dust this off for the third time this season:

Ralph Wiggum Danger GIF
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Have we not filled our severe weather quota for the year?
giphy.gif
 
Specifically regarding my chase prospects on Tuesday/Wednesday (aiming to be back in Wisconsin Sunday evening, and back at work Tuesday); models have been wishy-washy about whether favorable conditions will extend into southern Wisconsin or at least northern Illinois close enough for me to do a regional chase in the afternoon. We should be right in the left exit region of the mid-upper level jet, but most runs of the GFS and today's 12Z NAM show the unstable warm sector getting shunted further south by outflow from preceding convection.
 
Fred Gossage said:
With respect to what constitutes a High Risk level outbreak, it is probabilistically driven completely these days, but from the system's inception in the early 80s up through at least the mid 2000s or later, the outlooks (while having probabilities publicly as early as the early 2000s), were still verified on a reports vs square mileage schematic. Under that verification system, per every 50,000 square miles (think roughly Oklahoma without the panhandle), a High Risk's criteria was met if 20 or more tornadoes occurred with a minimum of at least two of them having to be (E)F3 or higher intensity. Since the late 2000s, those outlooks stopped being verified on a hard reports vs aerial coverage schematic and were 100% driven in all aspects by the probabilistic contours. That makes verification a little more subjective. And in terms of issuing a High Risk outlook these days, SPC has gone on record publicly stating that they tend to try to focus on days when they specifically think violent tornadoes (EF4+) are an elevated concern, even though significant tornadoes overall is what is looked at for verification. With all that in mind, however, the system was designed so that those two verification methods wouldn't really clash with each other. That shows that it doesn't take something as widespread violent as a rare once-a-decade outbreak to verify a High Risk. Both April 26th and April 27th last week would've verified High Risk outlooks on their respective days with total tornado count over a regionally concentrated area coupled with number of those being EF3 or greater each day. That's not a hindsight 20/20 criticism of the SPC outlooks that were issued. Both days had question marks on them. However, in terms of verification itself, both days met High Risk criteria. It doesn't take a once-a-decade type outbreak to do that. We need to stop trying to pull talking points out of our intestinal tracts, please.....
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Not “talking points out of our intestinal tracts” LOL!!!!!!

Always glad to have you here @Fred Gossage !
 
Fred Gossage said:
With respect to what constitutes a High Risk level outbreak, it is probabilistically driven completely these days, but from the system's inception in the early 80s up through at least the mid 2000s or later, the outlooks (while having probabilities publicly as early as the early 2000s), were still verified on a reports vs square mileage schematic. Under that verification system, per every 50,000 square miles (think roughly Oklahoma without the panhandle), a High Risk's criteria was met if 20 or more tornadoes occurred with a minimum of at least two of them having to be (E)F3 or higher intensity. Since the late 2000s, those outlooks stopped being verified on a hard reports vs aerial coverage schematic and were 100% driven in all aspects by the probabilistic contours. That makes verification a little more subjective. And in terms of issuing a High Risk outlook these days, SPC has gone on record publicly stating that they tend to try to focus on days when they specifically think violent tornadoes (EF4+) are an elevated concern, even though significant tornadoes overall is what is looked at for verification. With all that in mind, however, the system was designed so that those two verification methods wouldn't really clash with each other. That shows that it doesn't take something as widespread violent as a rare once-a-decade outbreak to verify a High Risk. Both April 26th and April 27th last week would've verified High Risk outlooks on their respective days with total tornado count over a regionally concentrated area coupled with number of those being EF3 or greater each day. That's not a hindsight 20/20 criticism of the SPC outlooks that were issued. Both days had question marks on them. However, in terms of verification itself, both days met High Risk criteria. It doesn't take a once-a-decade type outbreak to do that. We need to stop trying to pull talking points out of our intestinal tracts, please.....
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Thanks for this Fred! Didn't know that, but it makes perfect sense
 
Strong wording from Wichita, Kansas AFD for Monday
Our attention then turns to the potential for scattered to numerous
thunderstorms Monday afternoon-night across the region, as a
potent/deep shortwave trough and attendant dryline approach from the
west, amidst an increasingly moist/unstable airmass across the
Central and Southern Plains. The anomalous combination of
buoyancy/shear (as highlighted by the NAEFS and EPS) favors severe
thunderstorms, some of which could produce "higher-end" severe
weather in the form of very large hail, damaging winds, and
tornadoes, some of which could be strong.

Latest model trends support the greatest threat for discrete
supercells (and associated greater threat for higher-end severe
weather) across mainly the southern half of KS and into OK, where
mid-upper flow is oriented more perpendicular to the dryline. A
handful of NAM-GFS-ECMWF point forecast soundings up and down the
dryline from mainly the southern half of KS south into OK continue
to indicate a potential kinematic and thermodynamic environment
similar to some past higher-end and even historic severe weather and
tornado events. Further north across mainly the northern half of KS
and into NE, storm mode could be rather messy given stronger
forcing, and a more meridional component to mid-upper flow, which
could tend to limit higher-end severe potential with northward
extent. We will continue to monitor these trends in the upper jet
placement and alignment.

A another piece of uncertainty in the forecast surrounds the extent
of warm/moist sector low clouds throughout the day, owing to rapid
low-level quality moisture return. Too much moisture advection would
tend to keep low clouds locked in through the day, which would limit
insolation and associated peak heating destabilization, especially
with northward extent. This scenario is especially highlighted by
the NAM and RAP. Not enough instability would temper higher-end
severe chances and/or keep these chances further south.

All-in-all, there remains potential for higher-end severe weather
across the region Monday afternoon-night in the form of very large
hail, damaging winds, and tornadoes, some of which could be strong.
We will continue to diagnose the above uncertainty and issue timely
forecast updates.
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Ah yes, the casual 4,000 SBCAPE + 500 1km SRH sounding in central OK at 06Z. Thank you 18Z NAM, very cool.
nam_2024050418_060_35.53--96.94.png
 
Not to mention the 00z Euro for North MS was showing a 50 to 60 kt Bulk shear and dewpoints between 69 to near 75 during the Tuesday thru Thursday timeframe.
 
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