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Severe Threats Apr. 24-May 1


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I don't know why Geos is primarily noting the Euro to begin with. It's like the last model I would consult with microscale aspects like severe weather. Sure, it's worth a look, but it's certainly not near the top.

 

Agreed the Short Range models and the GFS/NAM are what are the best to look at for situations like this.

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00Z 12km NAM strengthened the little jet max over Iowa tomorrow evening by ~10kts. CAPE also increased coupled with a wide area of 40kts of bulk shear. Still trouble initiating much given a small amount of convergence that will be in place.
 

4km NAM actually spits something out near Galesburg that goes over Peoria where the winds at sfc aren't that terrible veered. There's still ~45° of turning since mid-level flow is out of the west. Bulk shear goes up to 50kts in NW IL at 01Z due to the LLJ kicking in.

Crossovers aren't bad either, neither is the CAPE, though the best low level shear is displaced slightly to the east of the best instability. Storm morphology and amount of convergence will play the largest role tomorrow.

crossover.us_mw.png

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I don't know why Geos is primarily noting the Euro to begin with. It's like the last model I would consult with microscale aspects like severe weather. Sure, it's worth a look, but it's certainly not near the top.

 

Because not everyone has access to it. So I figure I'd put it out there.

The 0z run had a nice squall line on it, 12z not so much.

 

Anywho,

 

4km NAM fired up discrete cells at 0z tomorrow.

 

refcmp.us_mw.png

 

Then forms into a line later.

 

refcmp.us_mw.png

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I think we'll get a Slight Risk at some point for today/Monday if not with the initial day 1 outlook for most of the current Marginal area. I'd personally go with one with the initial d1. Seems like there's enough consensus in convective initiation on southern periphery of midlevel wave moving from eastern IA to IL/WI state line area during late afternoon. The 00z GFS, 03z RAP, 00z RGEM and 00z WRF-ARW & NMM are all in decent agreement in this regard.

Assuming initiation around 21z near the MS River in eastern IA/NW IL, storms will be running into an environment with 40 kt of west to west-northwest shear vectors and good veering from h85 to h5. 00z GFS actually bumped up instability from earlier runs to 1500+ j/kg over eastern IA and northern IL so the ~2000 j/kg being shown on the NAM may not be too far fetched considering decent h7-h5 lapse rates around 7C/km or slightly higher.

If winds can verify closer to SSW than SW, would also mean decent low level veering and a better isolated tor threat, but overall large hail appears to be primary threat and wind as well given steep low level lapse rates. Tor threat even with more veered sfc winds is non zero with lcl's probably manageable given low 60s dewpoints and supercell structures favored at least earlier on.

We'll see what SPC goes with shortly.

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Haven't been all that excited about tor potential all along, but the relative isolated nature of the storms tomorrow along that line should help.  Without any synoptic, or remnant boundaries to help the low-levels, we'll need a storm to become dominant and remain isolated for quite awhile to give it the best chance to produce.  From a chasing standpoint that makes it difficult, as you could pick anywhere from southern WI down to west-central IL for that to happen.  I'll probably shoot east and hang out somewhere between Rochelle and Princeton, and hope to pick the best of what develops.  Chances of scoring a tor tomorrow are pretty low, but I'll just be happy to be out again, and in the presence of powerful convection.  

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Haven't been all that excited about tor potential all along, but the relative isolated nature of the storms tomorrow along that line should help.  Without any synoptic, or remnant boundaries to help the low-levels, we'll need a storm to become dominant and remain isolated for quite awhile to give it the best chance to produce.  From a chasing standpoint that makes it difficult, as you could pick anywhere from southern WI down to west-central IL for that to happen.  I'll probably shoot east and hang out somewhere between Rochelle and Princeton, and hope to pick the best of what develops.  Chances of scoring a tor tomorrow are pretty low, but I'll just be happy to be out again, and in the presence of powerful convection.  

Bit OT, but.. do you have any desire to chase Tuesday? 

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FWIW here's the WRF-NSSL. NAM continues to show that strengthened mid level jet from 00Z runs last night. These would form on the nose of the jet in a good environment despite veered flow near the surface. There's still turning at low levels and conducive amount of 0-1km helicity if storm mode doesn't go messy.

22cf8b5a8aba7c6e9906f448b1372339.jpg

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FWIW here's the WRF-NSSL. NAM continues to show that strengthened mid level jet from 00Z runs last night. These would form on the nose of the jet in a good environment despite veered flow near the surface. There's still turning at low levels and conducive amount of 0-1km helicity if storm mode doesn't go messy.

22cf8b5a8aba7c6e9906f448b1372339.jpg

 

starting to see a good signal that i'm going to split the uprights again

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