May 19 threat in chaser land

[Ed Lizard]

The Euro has been pretty good for me as a quick look, a healthy 850 mb jet, and a good 500 mb low w/reasonable 850 mb temps, and things can become interesting. A couple of days of return flow, the Pacific airmass now pushing into the Gulf should be reasonably well modified by then.

[Thundersnow12]

The two days before also might also hold potential with tues being an upslope play in northeast CO and possibly the eastern TX PH on weds.

[Helicity]

Last Night's Euro Was quite a bit slower than the GFS, having the threat areas further west than the GFS. Either way I believe there will be a severe threat across the plains in this general time frame, but I'm not liking the cool 700 MB temps.

[ZackH]

Typically, you want cool 700 mb temps.

[Amped]

This is a good setup, Cold air over the rockies and wind shear east of the surface low.. Several disturbances should swing around the closed H5 low , and at least one should trigger a severe outbreak.

[Thundersnow12]

weds and thursday are looking like possible good days in the southern plains depending on the speed and location of the trof.

[Helicity]

Typically, you want cool 700 mb temps.

I agree, however that did not work out with the last set up.

[ZackH]

Cool 700 mb temps had nothing to do with why the last setup was a bust.

[Helicity]

Cool 700 mb temps had nothing to do with why the last setup was a bust.

True it wasn't the only reason, what are your thoughts?

[Ellinwood]

Cool 700 mb temps had nothing to do with why the last setup was a bust.

Indeed... it was the midday storms that killed the later stuff. Not enough time behind the storms for enough return flow to trigger storms. Dews were progged to jump into the mid/upper 60s along the dryline, but they were only able to recover into the upper 50s. Add that to a slower-than-expected eastward movement of the low and you've got a big bust.

[Thundersnow12]

The problem with the possible chase days next week IMO is the weaker EML/cooler H7 temps, would like to see a better EML to hold off convection till later in the day, rather than ongoing convection to ruin heating.

[Helicity]

Indeed... it was the midday storms that killed the later stuff. Not enough time behind the storms for enough return flow to trigger storms. Dews were progged to jump into the mid/upper 60s along the dryline, but they were only able to recover into the upper 50s. Add that to a slower-than-expected eastward movement of the low and you've got a big bust.

BUT the mid day storms formed because 700MB tems were too cool and allowed any parcel to pass all the way up to the equilibrium level before the upper level support moved into the area

So there fore the root cause for the convection is because there was enough forcing for ascent and cool enough 700mb temps.

[Helicity]

The problem with the possible chase days next week IMO is the weaker EML/cooler H7 temps, would like to see a better EML to hold off convection till later in the day, rather than ongoing convection to ruin heating.

Bingo.

[k***]

just because the last threat involved early convection doesnt mean people should be rooting for a stout EML...more often than not it's been way too strong if anything

[Ian]

the trough push into the plains looks better than the last event at this range. plus it's during the 3 day window of my free chase option i turned down so it should produce. the closed low over the east is still problematic imo.. not a perfect setup by any means.

[Thundersnow12]

just because the last threat involved early convection doesnt mean people should be rooting for a stout EML...more often than not it's been way too strong if anything

I'm not rooting for a stronger EML, just said based off what the models are showing now, you would want/need a stronger EML /warmer H7 temps.

some days this year the stronger EML has worked nicely, others it hasn't.

[thewxmann]

I'd root for an EML that was just right.

As of right now, the concern that next week's EML is too weak is a valid one. Though last week's setup was ultimately ruined by an ill-timed shortwave, a weak EML allowed it to do the damage it did. A stronger one would've prevented convection from firing in such a widespread and detrimental fashion.

[Thundersnow12]

I'd root for an EML that was just right.

As of right now, the concern that next week's EML is too weak is a valid one. Though last week's setup was ultimately ruined by an ill-timed shortwave, a weak EML allowed it to do the damage it did. A stronger one would've prevented convection from firing in such a widespread and detrimental fashion.

Exactly my thoughts

[brettjrob]

I get the feeling moisture return will be the bane of this entire string of days. It's absolutely ****ing pathetic that we have to worry about getting mid 50s dew points back up to the TX Panhandle after May 15, but it is indeed a concern, given the current wiping of the Gulf. Comparing the NAM and GFS moisture progs at H+84 only bolsters my concern on this front. At this point, I'd go out on a limb and say any meaningful severe convective chances for Wednesday are probably out the window, and I'll be crossing my fingers that the situation improves enough by Thursday afternoon to be worth talking about. You just don't see many notable severe weather days with a multi-contour H5 low parked over TN.

[OceanStWx]

I get the feeling moisture return will be the bane of this entire string of days. It's absolutely ****ing pathetic that we have to worry about getting mid 50s dew points back up to the TX Panhandle after May 15, but it is indeed a concern, given the current wiping of the Gulf. Comparing the NAM and GFS moisture progs at H+84 only bolsters my concern on this front. At this point, I'd go out on a limb and say any meaningful severe convective chances for Wednesday are probably out the window, and I'll be crossing my fingers that the situation improves enough by Thursday afternoon to be worth talking about. You just don't see many notable severe weather days with a multi-contour H5 low parked over TN.

Jet support looks pretty good along the typical dry line areas, so like you said if we can get the requisite moisture return there should be something worthwhile. As it stands now, the 00z Euro has some marginal 0-4km theta-e lapse rates and good jet support (so pretty much the opposite of the last threat forecast thread ).

Also it is 240 hours out, but the last frame the Euro places a 987 mb low in northwest Iowa stretching a warm front east to the southern lakes, with ample low level theta-e lapse rates and a nice jet punching out over the warm sector.

[Helicity]

I get the feeling moisture return will be the bane of this entire string of days. It's absolutely ****ing pathetic that we have to worry about getting mid 50s dew points back up to the TX Panhandle after May 15, but it is indeed a concern, given the current wiping of the Gulf. Comparing the NAM and GFS moisture progs at H+84 only bolsters my concern on this front. At this point, I'd go out on a limb and say any meaningful severe convective chances for Wednesday are probably out the window, and I'll be crossing my fingers that the situation improves enough by Thursday afternoon to be worth talking about. You just don't see many notable severe weather days with a multi-contour H5 low parked over TN.

Starting to see that as well.

GFS has nicer moisture return.

[brettjrob]

Starting to see that as well.

GFS has nicer moisture return.

Surprisingly, the 16/00z NAM actually shows a slight improvement in low-level moisture towards the end of the run. Wednesday is on the cusp of having marginal to moderate chase potential in the eastern TX Panhandle or W OK, but we'll probably need boundary layer dew points to improve a few degrees yet.

Thursday, I must say, looks quite interesting on the NAM, extrapolating its prog at H+84 (for 12z Thu). The trough is significantly slower than on the GFS, meaning morning convection may be less of a concern, and the timing of the best dynamics and kinematics might be fairly favorable. I'd almost go as far as to say Thursday looks like a near-classic setup on the NAM, if you cover up the right half of the image showing a massive ULL over WV with your hand.

[Thundersnow12]

Surprisingly, the 16/00z NAM actually shows a slight improvement in low-level moisture towards the end of the run. Wednesday is on the cusp of having marginal to moderate chase potential in the eastern TX Panhandle or W OK, but we'll probably need boundary layer dew points to improve a few degrees yet.

Thursday, I must say, looks quite interesting on the NAM, extrapolating its prog at H+84 (for 12z Thu). The trough is significantly slower than on the GFS, meaning morning convection may be less of a concern, and the timing of the best dynamics and kinematics might be fairly favorable. I'd almost go as far as to say Thursday looks like a near-classic setup on the NAM, if you cover up the right half of the image showing a massive ULL over WV with your hand.

I also saw the tad better increase in moisture and it actually breaks out discrete precip before 0z wed evening in western OK down to around ABI and the LLJ goes bonkers after 0z. The shear is there for supercells and the tornado threat would improves with the help of the LLJ.

[thewxmann]

Thursday, I must say, looks quite interesting on the NAM, extrapolating its prog at H+84 (for 12z Thu). The trough is significantly slower than on the GFS, meaning morning convection may be less of a concern, and the timing of the best dynamics and kinematics might be fairly favorable. I'd almost go as far as to say Thursday looks like a near-classic setup on the NAM, if you cover up the right half of the image showing a massive ULL over WV with your hand.

Yup, this would be a good setup without the lingering cutoff over the eastern U.S. I think this itself will not be a huge event, but it may open up the door for the jet stream to finally cut into the U.S. - and a more active second half of May.

One positive aspect about this system - with the upper flow so meridional and the low-level flow decently backed, the dryline might not mix as far east as progged (even with the drought conditions). If that ends up being the case the moisture issues won't be quite as bad.

[Ed Lizard]

By Thursday moisture won't be lacking on GFS. I do have a uestion on how Utah U site calculates/displays deep layer shear, but that iis another story.

Friday

Too early to get too hung on forecast skew-Ts, but Thursday 7 pm for OKC looks potentially interesting.

[Helicity]

The 12z NAM is rather slow.

[brettjrob]

The 12z NAM is rather slow.

Which is unquestionably a good thing... no morning convection, and no veering out of the low-level winds. Thursday looks amazing on the NAM for W KS and W OK, with the only flaw I can find being some mixing out of low-level moisture. If it weren't 2011, I'd be pissing myself with excitement right now.

[Helicity]

Which is unquestionably a good thing... no morning convection, and no veering out of the low-level winds. Thursday looks amazing on the NAM for W KS and W OK, with the only flaw I can find being some mixing out of low-level moisture. If it weren't 2011, I'd be pissing myself with excitement right now.

Amen, the hodos look about textbook in between Pratt and Greensburg.

I had concerns about subsidence, but i don't think i need to worry about that now.

[Ed Lizard]

Not sure I like the GFS placing the surface, 700 mb and 500 mb lows so close together.

I figure better shear/helicity action with the lows a little less stacked. There They're not completely stacked, just closer than I like.

[Ian]

im rooting heavily against this one