Severe Weather Thread (April 2, 2012 - April 4, 2012)

[David Reimer]

Still quite a bit of model disagreement on the overall setup, but Monday certainly does have the potential to feature a rather active severe weather day. We'll see what happens...

ORE SUBSTANTIAL SEVERE THREAT APPEARS LIKELY TO EXIST DAY 5...AS

THE UPPER TROUGH EMERGES INTO THE PLAINS...AND A COLD FRONT SWEEPS

EWD ACROSS THE PLAINS EARLY IN THE DAY...AND REACHES A POSITION FROM

ROUGHLY THE UPPER MS VALLEY SSWWD ACROSS MO AND INTO E TX. WHILE

SOME THREAT WILL LIKELY EXIST AS FAR N AS THE UPPER MIDWEST/UPPER

GREAT LAKES REGION...GREATEST POTENTIAL APPEARS LIKELY FROM THE

OZARKS SWD/SEWD TO THE WRN AND CENTRAL GULF COAST REGION.

HERE...STRONG SHEAR AND AMPLE INSTABILITY SUGGEST FAIRLY WIDESPREAD

SEVERE POTENTIAL...WITH SUPERCELL ORGANIZATION LIKELY AND ASSOCIATED

THREATS FOR WIND/HAIL AND POSSIBLY ISOLATED TORNADOES. THREAT WILL

SPREAD EWD WITH TIME...POSSIBLY REACHING THE TN VALLEY AND AL DURING

THE EVENING/OVERNIGHT.

THE SURFACE FRONT ASSOCIATED WITH THIS SYSTEM IS PROGGED SHIFT EWD

ACROSS THE ERN U.S. DAY 6...AND WILL LIKELY HAVE MOVED TO/OFF THE

ATLANTIC COAST BY THE END OF THE DAY 6 PERIOD...WITH THE UPPER

TROUGH AXIS FOLLOWING SHORTLY THEREAFTER. AGAIN HOWEVER...WITH

MINOR DEVIATIONS IN MODEL SOLUTION EXPANDING DAY 6...WILL NOT

AREALLY HIGHLIGHT ANY THREAT AREAS WHICH MAY BE EVENTUALLY ADDED

NEAR/E OF THE APPALACHIANS. WITH LARGE-SCALE/PERSISTENT RIDGING

FORECAST ACROSS THE CENTRAL U.S. IN THE WAKE OF THIS SYSTEM...A LULL

IN CONVECTIVE THREAT ACROSS THE MAJORITY OF THE COUNTRY APPEARS

LIKELY -- AND THUS PRIMARY SEVERE WEATHER CONCERNS APPEAR CONFINED

TO THE FIRST HALF OF THE PERIOD.

..GOSS.. 03/29/2012

[Ellinwood]

It could be a bigger day if the GFS/secondary low solution plays out versus the more progressive Euro solution. GFS creates the secondary low along the cold front by nearly cutting off an upper-level vort. max over the southern Plains and lower MS valley, whereas the Euro doesn't dig/separate the upper-level energy as much.

[tornadotony]

It could be a bigger day if the GFS/secondary low solution plays out versus the more progressive Euro solution. GFS creates the secondary low along the cold front by nearly cutting off an upper-level vort. max over the southern Plains and lower MS valley, whereas the Euro doesn't dig/separate the upper-level energy as much.

If the GFS is right, you'll be lucky to have 20kt of wind at the jet level.

[Stebo]

If the GFS is right, you'll be lucky to have 20kt of wind at the jet level.

Yeah I think the bigger potential would be with the Euro. GFS has 0 upper jet winds with the split flow.

I am not hard buying into the split flow with this just yet, especially with the Euro coming back to the previous solution.

[Chinook]

reposted from the other thread:

Tthe GFS partially cuts off the low in Oklahoma and Arkansas, but the ECMWF keeps it north, with no cutoff, and the vort max in Nebraska. That's a pretty big difference.

[Ellinwood]

If the GFS is right, you'll be lucky to have 20kt of wind at the jet level.

Yeah I think the bigger potential would be with the Euro. GFS has 0 upper jet winds with the split flow.

I am not hard buying into the split flow with this just yet, especially with the Euro coming back to the previous solution.

Further north, I'd agree RE: Euro being better severe potential. Stronger flow aloft and you don't have the more extreme backing in the upper-levels like the GFS solution.

In the SPC's highlighted risk area, I'd rather have the GFS' stronger vort. max and better low-level directional shear.

I should add that I'm looking at the tornado potential more than general severe at this point... in terms of non-tornadic severe, I'd take the Euro over the GFS.

[tornadotony]

Further north, I'd agree RE: Euro being better severe potential. Stronger flow aloft and you don't have the more extreme backing in the upper-levels like the GFS solution.

In the SPC's highlighted risk area, I'd rather have the GFS' stronger vort. max and better low-level directional shear.

I should add that I'm looking at the tornado potential more than general severe at this point... in terms of non-tornadic severe, I'd take the Euro over the GFS.

But you won't have upper-level support to keep updrafts from raining into themselves, which often chokes a lot of tornadic potential from a system. Also, though you have low-level turning, you don't actually have very much speed shear and thus you don't actually have a ton of shear at all.

[Ellinwood]

But you won't have upper-level support to keep updrafts from raining into themselves, which often chokes a lot of tornadic potential from a system. Also, though you have low-level turning, you don't actually have very much speed shear and thus you don't actually have a ton of shear at all.

At this range, I'm not as worried about getting the details of the actual wind speeds so much as making sure there's going to be rotation in the atmosphere for tornado development. Getting stronger winds aloft won't matter much to the tornado potential if the wind profile is unidirectional.

That being said, I do agree that the storm as presently modeled would not carry that strong of a tornado threat. What I'm looking at is the moderate/strong vort. max, a surface low backing the surface winds and creating a more veered wind profile, plenty of instability and a pronounced frontal boundary. The only thing missing is good speed shear.

EDIT to add... I mean hell, you've got a tornado warning in TX right now and they don't have that much speed shear to work with, either. Not the most critical ingredient out there.

[brettjrob]

Honestly, I have a difficult time envisioning this system presenting a high-end severe threat on either Sunday or Monday, regardless of location. Neither the GFS nor EC look very menacing, different as they are. The huge blocking high centered over the Midwest will lay waste to the potential associated with this trough, which would have had have unseasonably-rich moisture to work with. Interestingly, this is a more extreme version of the same problem that plagued the 18-19 Mar event. Really hoping this doesn't become a chronic problem over the next several weeks/months.

[Radtechwxman]

Honestly, I have a difficult time envisioning this system presenting a high-end severe threat on either Sunday or Monday, regardless of location. Neither the GFS nor EC look very menacing, different as they are. The huge blocking high centered over the Midwest will lay waste to the potential associated with this trough, which would have had have unseasonably-rich moisture to work with. Interestingly, this is a more extreme version of the same problem that plagued the 18-19 Mar event. Really hoping this doesn't become a chronic problem over the next several weeks/months.

I am really feeling the same way at this time. The trough seems to be shearing out as it progresses east and pushes against the high. if that high could just nudge a little more to the east than it would be so much better. but we are still several days out and models can tend to lose systems for a while so just hoping we can see a turn around. not getting my hopes up though. Gary Lezak, not sure if thats how you spell it, that created the LRC seems to think mid April will be the prime time for a major severe weather outbreak

[baroclinic_instability]

Honestly, I have a difficult time envisioning this system presenting a high-end severe threat on either Sunday or Monday, regardless of location. Neither the GFS nor EC look very menacing, different as they are. The huge blocking high centered over the Midwest will lay waste to the potential associated with this trough, which would have had have unseasonably-rich moisture to work with. Interestingly, this is a more extreme version of the same problem that plagued the 18-19 Mar event. Really hoping this doesn't become a chronic problem over the next several weeks/months.

I am really feeling the same way at this time. The trough seems to be shearing out as it progresses east and pushes against the high. if that high could just nudge a little more to the east than it would be so much better. but we are still several days out and models can tend to lose systems for a while so just hoping we can see a turn around. not getting my hopes up though. Gary Lezak, not sure if thats how you spell it, that created the LRC seems to think mid April will be the prime time for a major severe weather outbreak

Agreed, it is all about the position/intensity of that high. It also isn't subtropical in nature, so there will be no enhanced STJ and/or Polar Jet/STJ interactions. GFS has cruddy jet level flow as mentioned above (as well as cruddy mid level flow). EC is dominated by the high as well even though the solutions are highly disparate. Both solutions would fall victim to that high...and there likely won't be a better middle ground given the fact all guidance now progs that Pacific wave to occlude offshore... not conducive to strong baroclinic development inland.

[Radtechwxman]

Agreed, it is all about the position/intensity of that high. It also isn't subtropical in nature, so there will be no enhanced STJ and/or Polar Jet/STJ interactions. GFS has cruddy jet level flow as mentioned above (as well as cruddy mid level flow). EC is dominated by the high as well even though the solutions are highly disparate. Both solutions would fall victim to that high...and there likely won't be a better middle ground given the fact all guidance now progs that Pacific wave to occlude offshore... not conducive to strong baroclinic development inland.

I am totally with you on that one. GFS had a fantasy storm a few days ago and EC didnt look half bad either but all of a sudden the upper level support has went to crud. I am not really sure what the SPC is seeing that we arent. this high poses major issues with the progression and strength of the system. it almost looks like all the upper dynamics may go north and the instability will stay south. really tricky forecast in the coming days

[andyhb]

Honestly, I have a difficult time envisioning this system presenting a high-end severe threat on either Sunday or Monday, regardless of location. Neither the GFS nor EC look very menacing, different as they are. The huge blocking high centered over the Midwest will lay waste to the potential associated with this trough, which would have had have unseasonably-rich moisture to work with. Interestingly, this is a more extreme version of the same problem that plagued the 18-19 Mar event. Really hoping this doesn't become a chronic problem over the next several weeks/months.

I wouldn't be surprised, in all honesty.

[tornadotony]

I wouldn't be surprised, in all honesty.

There's really no way to know that this'll be a problem beyond the mid-range.

[andyhb]

There's really no way to know that this'll be a problem beyond the mid-range.

Well yes, although the majority of the mid range ensembles/models keep that ridge as the dominant feature across the CONUS at least into the 8-10 day period.

[baroclinic_instability]

The EC has been unusually inconsistent and poor with this system the past 4 days, but the 0Z is much more inline with the rest of the global guidance. Blocking high dominates and the northern stream remains displaced well to the N.

[baroclinic_instability]

Might as well cancel any sig severe threats for the next 10-15 days. Blocky global pattern with all the cold air dumping into the regions it has all winter...Europe and the west Pacific. Torchfest 2012 is in full swing.

[andyhb]

Might as well cancel any sig severe threats for the next 10-15 days. Blocky global pattern with all the cold air dumping into the regions it has all winter...Europe and the west Pacific. Torchfest 2012 is in full swing.

Yikes. Bringing back bad memories of the 600 dm death ridge last summer.

This pattern, for lack of a better word, sucks for any interesting weather across much of the US...

[thewxmann]

LOL @ the 0Z ECMWF. I don't think anything's even had a slightest handle on this system.

As for whether this is a chronic pattern, can't be sure. But it's hard to shift the severe wx south after it's shifted consistently north, and death ridges are hard to break down (especially this year since it feels like the jet stream's been less energetic than it has in recent years). Second year Nina climo also argues against a busy severe wx season. So although we can't say anything for sure, the odds are not in our favor.

Now granted, I've had to eat crow before. And we will surely still see some legitimate severe weather threats between Apr-May.

[Ed Lizard]

I remain glass quarter full optimistic on some impressive hail, if we can get any discrete cells at all Monday on the dry line. Deep layer shear stills looks more than a little marginal, but seems a tad better on the 12Z GFS than the 0Z GFS, and we have fat and juicy mid level instability. Awfully light on the low level winds for much of a tornado threat, LFC isn't very low, but again, silver lining optimist, I'd say the tornado threat isn't non-zero because some preceding clouds/rain mean its cool enough for decent LCLs, and who knows what meso/microscale features might enhance low level shear.

[Hoosier]

Regarding tornadoes (and accounting for some reduction in March prelim reports), things are ahead of last year at this point, although we'll probably fall off the pace soon as it will be hard to have anything like last April.

[brettjrob]

While I still don't expect a major event, it has been fun to watch the havoc this system has wrought on NWP the past week or so. The consensus now favors the southern stream energy cutting off over NM/W TX, which will allow for moderate to high instability across much of TX and OK on Monday. As is typical with cut-off lows, the vertical wind profiles over the warm sector will be quite a mess. Low-level shear still looks relatively anemic, and to compound problems in terms of classic supercells, flow above H5 will be backed and weakening with height. Messy supercells and/or an eventual MCS will be the things to watch for Monday into Monday night.

EDIT: Some of the NAM fcst soundings near the triple point Monday evening are intriguing for their uniqueness... fairly supportive of tornadic supercells below 3-4 km AGL, then the flow goes to complete crap above that. It's one thing to have subtle veer-back-veer issues that mess with classic supercell structures (we see that fairly often), but this is an extreme case, with strong backing and very weak flow in the 200-300 mb layer. Note the 10 km storm-relative flow is easterly at 30 kts on this example, whereas the 0-6 km shear vector is more classic: southwesterly at 43 kts. There's virtually no difference between the storm-relative inflow at the ground and the storm-relative wind at anvil level.

[Minnesota Meso]

I just posted this on the Minnesota Forecaster site....... It's what the ECMWF and UKMET have been advertising .....For Monday things looks very interesting for MSP and points south and east. The Euro forecast sounding for Monday night 7pm at Rochester shows Surface based CAPE close to 1100 , with a lifted index value of -5. The winds at the surface should be out of the SE but at the 500mb level they should be out of w/sw, so directional sheer is strong. But the speed shear weakens at the mid levels, in other words the winds at 500mb are not great as far as speed. (they do get stronger above that level). If this holds true I think that the SPC will put us in a slight risk for Monday. Currently my AMATEUR eyes are thinking this, severe hail is a possibility but it should stay around a inch in diameter, strong winds and a possible weak tornado is not out of the question. Stay tuned to you favorite weather outlet for more detailed info. The US models do not show this at this time. We will see what they show with tonight's runs. Stay tuned!!!!

[Srain]

DAY 2 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1230 PM CDT SUN APR 01 2012

VALID 021200Z - 031200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE SRN AND

CNTRL PLAINS...

...SRN AND CNTRL PLAINS...

AN UPPER-LEVEL LOW WILL MOVE SLOWLY SEWD INTO THE SRN ROCKIES ON

MONDAY. TO THE EAST OF THE SYSTEM...A LOW-LEVEL JET WILL REMAIN IN

PLACE ACROSS THE SRN PLAINS WHERE AN AXIS OF STRONG INSTABILITY IS

FORECAST FROM SW TX NWD INTO WCNTRL OK. A CAPPING INVERSION WILL

ALSO EXIST ACROSS THE SRN PLAINS THROUGHOUT MUCH OF THE DAY BUT A

WEAKENING CAP DURING THE LATE AFTERNOON SHOULD ALLOW FOR THE

INITIATION OF THUNDERSTORMS ALONG A DISTINCT DRYLINE IN WCNTRL TX

EXTENDING NWD TO A COLD FRONT IN WRN OK. THUNDERSTORM DEVELOPMENT

SHOULD ALSO TAKE PLACE ALONG THE COLD FRONT FROM NW OK EXTENDING

NEWD INTO SRN KS.

FORECAST SOUNDINGS ALONG AND JUST EAST OF THE DRYLINE NEAR ABILENE

AND BRADY TX AT 00Z SHOW IMPRESSIVE THERMODYNAMICS WITH MLCAPE OF

3000 TO 4500 J/KG AND 850 TO 500 MB LAPSE RATES OF 8.0 TO 8.5 C/KM.

THIS ALONG WITH 30 TO 35 KT OF DEEP LAYER SHEAR SHOULD EASILY

SUPPORT SUPERCELLS WITH LARGE HAIL. HAIL GREATER THAN 2 INCHES IN

DIAMETER WILL BE POSSIBLE WITH THE MORE DOMINANT STORMS. AN ISOLATED

THREAT FOR TORNADOES AND WIND DAMAGE MAY ALSO DEVELOP ESPECIALLY AS

STORM COVERAGE INCREASES DURING THE EVENING.

FURTHER TO THE NORTH ALONG THE COLD FRONT IN NWRN OK AND SRN

KS...FORECAST SOUNDINGS AT 00Z SHOW STRONG INSTABILITY AND MODERATE

DEEP LAYER SHEAR SUGGESTING A SEVERE THREAT WILL ALSO EXIST THERE

MONDAY EVENING. LAPSE RATES ARE NOT FORECAST TO BE AS STEEP AS TO

THE SOUTH BUT THE STRONG INSTABILITY SHOULD BE FAVORABLE FOR

EFFICIENT HAIL PRODUCTION. THE ENHANCED LOW-LEVEL CONVERGENCE ALONG

THE FRONT SHOULD HELP ORGANIZE THE STORMS INTO A LINE. THIS FACTOR

COMBINED WITH STEEP LOW-LEVEL LAPSE RATES MAY RESULT IN A GREATER

WIND DAMAGE THREAT THERE THAN IN AREAS FURTHER TO THE SOUTH.

...WRN GREAT LAKES/UPPER MS VALLEY...

AN UPPER-LEVEL RIDGE WILL MOVE EWD ACROSS THE UPPER MS VALLEY MONDAY

AS AN AXIS OF MODERATE INSTABILITY DEVELOPS FROM ERN MO NEWD INTO

ERN IA. THUNDERSTORM DEVELOPMENT IS FORECAST MONDAY AFTERNOON NORTH

OF THE STRONGER INSTABILITY NEAR AN INVERTED TROUGH AND ALONG THE

AXIS OF A LOW-LEVEL JET IN ERN MN AND WRN WI. THE STORMS SHOULD

EXPAND IN COVERAGE AND MOVE SEWD ACROSS WI AND NRN IL MONDAY

EVENING. FORECAST SOUNDINGS MONDAY EVENING ALONG THIS CORRIDOR SHOW

MUCAPE IN THE 1000 TO 2000 J/KG RANGE WITH EFFECTIVE SHEAR OF AROUND

30 KT. THIS COMBINED WITH STEEP MID-LEVEL LAPSE RATES SHOULD SUPPORT

A MARGINAL THREAT FOR LARGE HAIL BUT THE ELEVATED NATURE OF THE

CONVECTION SHOULD LIMIT THE WIND DAMAGE THREAT.

..BROYLES.. 04/01/2012

[Minnesota Meso]

ok the 01/12z run of the Euro stops the 60° dews at the MN/IA border instead of bringing them into the MSP area. I think strong convection is still possible up here, but any severe should be isolated, so I think the SPC will keep us in a general t-storm/see text area as the severe threat doesn't seem to be as wide spread, thus precluding a slight risk area as aerial threat will not be large enough.

[Chinook]

I just posted this on the Minnesota Forecaster site....... It's what the ECMWF and UKMET have been advertising .....For Monday things looks very interesting for MSP and points south and east. The Euro forecast sounding for Monday night 7pm at Rochester shows Surface based CAPE close to 1100 , with a lifted index value of -5. The winds at the surface should be out of the SE but at the 500mb level they should be out of w/sw, so directional sheer is strong. But the speed shear weakens at the mid levels, in other words the winds at 500mb are not great as far as speed. (they do get stronger above that level). If this holds true I think that the SPC will put us in a slight risk for Monday. Currently my AMATEUR eyes are thinking this, severe hail is a possibility but it should stay around a inch in diameter, strong winds and a possible weak tornado is not out of the question. Stay tuned to you favorite weather outlet for more detailed info. The US models do not show this at this time. We will see what they show with tonight's runs. Stay tuned!!!!

looks like SREF supercell composite values are 3-6 up by Minneapolis and 3-9 in south Texas. I think Minnesota has a shot at severe weather.

[Minnesota Meso]

looks like SREF supercell composite values are 3-6 up by Minneapolis and 3-9 in south Texas. I think Minnesota has a shot at severe weather.

Interesting

silly me forgot to check the SREF

[David Reimer]

Tomorrow is getting more interesting along the dryline in Texas, especially if the GFS verifies. I'll be chasing tomorrow with a helmet and a baseball bat!

[MnWeatherman]

ok the 01/12z run of the Euro stops the 60° dews at the MN/IA border instead of bringing them into the MSP area. I think strong convection is still possible up here, but any severe should be isolated, so I think the SPC will keep us in a general t-storm/see text area as the severe threat doesn't seem to be as wide spread, thus precluding a slight risk area as aerial threat will not be large enough.

Where do you find ECMWF soundings?

[Minnesota Meso]

Where do you find ECMWF soundings?

They can be found in 6 hour increments on the ACCU pro site...there is a free 30 day option available if you want to check it out. It also has 6hr min and max temps, cape, dews, lapse rates etc. If you do choose to try it, the soundings are under the main model page, under ECMWF, scroll down to where it says Skew T, you will probably have to enter the LONG/LATT of the site you want to see. Other than that play around with the animator, cool feature. The monthly fee is $25.00 and worth every penny for their model output, but keep in mind posting any ECMWF map onto the net is strictly prohibited, that's why I don't show them or any where else.