Svr Wx Event - April 15-17, 2024

[andyhb]

Andy:
Since you do have the advanced credentials and knowledge. Why does the atmosphere or pattern even seem subdued somewhat so far this year on the severe weather aspect? Seems so much underperformance besides one event so far?

IMO it's been partly a result of the active sub-tropical jet, which tends to suppress moisture and lead to more widespread convection (mitigating instability) in the early season. The blocking in the North Atlantic that we saw in later March also tends to suppress moisture, and was the reason for the slow start in years like 2010.

 

[Timhsv]

IMO it's been partly a result of the active sub-tropical jet, which tends to suppress moisture and lead to more widespread convection (mitigating instability) in the early season. The blocking in the North Atlantic that we saw in later March also tends to suppress moisture, and was the reason for the slow start in years like 2010.

Thanks for your insight Andy

 

[tennessee storm chaser]

IMO it's been partly a result of the active sub-tropical jet, which tends to suppress moisture and lead to more widespread convection (mitigating instability) in the early season. The blocking in the North Atlantic that we saw in later March also tends to suppress moisture, and was the reason for the slow start in years like 2010.

Think. We are headed toward a strong Niña later… ? Perhaps lasting through r this winter into next spring ?

 

[MattW]

IMO it's been partly a result of the active sub-tropical jet, which tends to suppress moisture and lead to more widespread convection (mitigating instability) in the early season. The blocking in the North Atlantic that we saw in later March also tends to suppress moisture, and was the reason for the slow start in years like 2010.

I'm barely keeping up with some of this advanced stuff myself. Are there any current forecasts for these things if they're sticking around through April and May?

 

[CheeselandSkies]

SPC seemed to have backed off on the wording a tad for Monday despite keeping the 30%. They note that moisture return/depth will not be particularly robust, whereas previously they explicitly stated they did not expect it to be an issue. The GFS gets a lot of flack, but it's been showing this on forecast soundings for several days, with the moisture going only up to 850mb at best before the dewpoint line jogs sharply to the left.

That said, if a convective cold pool does not completely screw up the warm sector airmass, I would at least a couple of solid tornadic supercells in the Plains states on Monday.

SPC does also note tornado threat might even be a little better into the Midwest on Tuesday, conditional on influence of Monday's activity.

 

[tennessee storm chaser]

SPC seemed to have backed off on the wording a tad for Monday despite keeping the 30%. They note that moisture return/depth will not be particularly robust, whereas previously they explicitly stated they did not expect it to be an issue. The GFS gets a lot of flack, but it's been showing this on forecast soundings for several days, with the moisture going only up to 850mb at best before the dewpoint line jogs sharply to the left.

That said, if a convective cold pool does not completely screw up the warm sector airmass, I would at least a couple of solid tornadic supercells in the Plains states on Monday.

SPC does also note tornado threat might even be a little better into the Midwest on Tuesday, conditional on influence of Monday's activity.

They talk like a 30 percent could be coming later outlook even for Tuesday’s threat

 

[lake.effect]

12z NAM coming in hot...

 

[Scott81]

Could this system possibly reach alabama? I know we have a ridge setting up next week. Didn't know if the ridge would protect alabama or not.

 

[tennessee storm chaser]

Could this system possibly reach alabama? I know we have a ridge setting up next week. Didn't know if the ridge would protect alabama or not.

I could see this affect the north west part the state …. Latest runs starting show signs the severe threat coming bit further east n south ….

 

[keithGA]

dryline_dot_png

 

[andyhb]

SPC seemed to have backed off on the wording a tad for Monday despite keeping the 30%. They note that moisture return/depth will not be particularly robust, whereas previously they explicitly stated they did not expect it to be an issue. The GFS gets a lot of flack, but it's been showing this on forecast soundings for several days, with the moisture going only up to 850mb at best before the dewpoint line jogs sharply to the left.

That said, if a convective cold pool does not completely screw up the warm sector airmass, I would at least a couple of solid tornadic supercells in the Plains states on Monday.

SPC does also note tornado threat might even be a little better into the Midwest on Tuesday, conditional on influence of Monday's activity.

Moisture to 850 mb is fine for most Plains threats. This isn't the SE where profiles are often very moist to nearly 700 mb.

 

[CheeselandSkies]

Moisture to 850 mb is fine for most Plains threats. This isn't the SE where profiles are often very moist to nearly 700 mb.

Thanks, Andy. I suspected as much; I've seen deeper moisture but definitely shallower as well. Should add some of the forecast soundings I've seen over the last couple days showed the moisture dropping off below that level, the 850mb I referenced are the "best" ones. Also, I've mainly been looking at Tuesday in IA/IL/MO and not Monday in the Plains.

 

[TornadoFan]

View attachment 25354

dryline_dot_png

That's quite the dryline

 

[CheeselandSkies]

EHI for Tuesday in the Midwest has come down a good bit from prior runs on the 12Z GFS. SLP has trended a good bit weaker (a couple days ago some runs had it down into the 970s at 21Z Tuesday-00Z Wednesday, 989 mb on this run) and further southwest (over NE KS/SE NE border at 00Z Wednesday, instead of northeast SD).

If nothing else, may have to go further west than I was hoping. Will just have to see how things look as we get closer and higher-resolution models get in range.

 

[lake.effect]

18z NAM ejects the trough quite a bit farther south (and much slower) than the morning runs and slows.
This pushes the tornado threat a little farther west and south. Which is ideal from a chasing perspective (and human impact perspective, these are some sparsely populated areas).

If anything, the ceiling for high-end tornadoes increased with this run, albeit in a slightly different area.

A slower-moving system could also increase the threat of significant severe on Tuesday. Something to watch

 

[andyhb]

18z NAM ejects the trough quite a bit farther south (and much slower) than the morning runs and slows.
This pushes the tornado threat a little farther west and south. Which is ideal from a chasing perspective (and human impact perspective, these are some sparsely populated areas).

If anything, the ceiling for high-end tornadoes increased with this run, albeit in a slightly different area.

A slower-moving system could also increase the threat of significant severe on Tuesday. Something to watch

Yeah the 12z Euro is a significant tornado event on both Monday and Tuesday. Monday over the S High Plains and Tuesday over Missouri and Arkansas.

 

[TornadoFan]

 

[JBishopwx]

 

[CheeselandSkies]

Yeah the 12z Euro is a significant tornado event on both Monday and Tuesday. Monday over the S High Plains and Tuesday over Missouri and Arkansas.

Yech. I'm out if that excludes at least some portions of IA and/or IL.

 

[andyhb]