Feb 2nd-4th Severe Thread

[andyhb]

Current Day 3 outlook, with a small slight risk across West-Central Texas, although this will likely change per the latest model analysis across this area for Thursday evening/night:

DAY 3 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0229 AM CST TUE JAN 31 2012

VALID 021200Z - 031200Z

...THERE IS A SLGT RISK OF SVR TSTMS WCNTRL TX...

...SRN AND CNTRL PLAINS...

A SOMEWHAT FLATTENED UPPER-LEVEL TROUGH OVER THE GREAT PLAINS

WEDNESDAY NIGHT WILL MOVE EWD ACROSS THE MS VALLEY ON THURSDAY. ON

THE WRN SIDE OF THE RIDGE....MOISTURE ADVECTION WILL TAKE PLACE

ACROSS THE SRN PLAINS AS A 40 TO 50 KT LOW-LEVEL JET STRENGTHENS.

THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE ALONG THE AXIS OF THE

LOW-LEVEL JET IN WEST TX THURSDAY AFTERNOON WITH CONVECTION RAPIDLY

EXPANDING NWD ACROSS NW TX AND WRN OK THURSDAY EVENING. FORECAST

SOUNDINGS THURSDAY EVENING ALONG THIS CORRIDOR FROM 00Z TO 06Z SHOW

MUCAPE VALUES AROUND 1000 J/KG WITH 40 TO 50 KT OF DEEP LAYER SHEAR.

THIS ALONG WITH STEEP MID-LEVEL LAPSE RATES SHOULD BE FAVORABLE FOR

A LARGE HAIL THREAT. A WIND DAMAGE THREAT COULD ALSO DEVELOP

ESPECIALLY IF SFC-BASED STORMS CAN INITIATE. HOWEVER...THE LOCATION

WITH THE GREATEST THREAT IS STILL QUESTIONABLE. THE NAM IS FOCUSING

THE MOST CONVECTION FURTHER TO THE NORTH ACROSS THE ERN TX

PANHANDLE...WRN OK AND SRN KS WHILE THE GFS AND ECMWF KEEP THE

DEVELOPMENT IN WEST AND NORTHWEST TX. AT THIS POINT...AM FAVORING

THE GFS AND ECMWF SOLUTIONS. AS THIS SCENARIO PLAYS OUT...THE SLIGHT

RISK AREA WILL LIKELY NEEDED TO BE MOVED OR CHANGED IN THE DAY 2

OUTLOOK.

However, Friday appears to be an event as well with the strong shortwave and associated vort max moving east, inducing further surface cyclogenesis and advecting a rather moist and potentially buoyant air mass across Central/Eastern Texas into the Arklatex and Southern Oklahoma, along with adequate shear.

Day 4-8 mentioning this potential:

DAY 4-8 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0354 AM CST TUE JAN 31 2012

VALID 031200Z - 081200Z

THE MEDIUM RANGE MODELS BEGIN THE DAY 4 TO 8 PERIOD WITH A

NEGATIVELY-TILTED UPPER-LEVEL TROUGH OVER THE SRN ROCKIES AND AN

EJECTING MID-LEVEL JET ACROSS THE SRN PLAINS. THE MODELS COUPLE THE

LOW AND MID-LEVEL JET ACROSS THE SRN PLAINS ON FRIDAY/DAY 4 AS A

STRONG SYSTEM MOVES INTO THE SRN PLAINS. FOCUSED LARGE-SCALE

ASCENT...ADEQUATE INSTABILITY AND MODERATE TO STRONG DEEP LAYER

SHEAR SHOULD BE SUFFICIENT FOR SEVERE THUNDERSTORMS IN PARTS OF EAST

AND NORTH TX FRIDAY AFTERNOON AND EVENING. FROM HERE UNCERTAINTY

INCREASES AS THE MODELS MOVE THE MOIST SECTOR SEWD INTO THE GULF

COAST STATES. STRONG THUNDERSTORMS WILL BE POSSIBLE ACROSS THE LOWER

TO MID-MS VALLEY EARLY ON SATURDAY/DAY 5 AND IN THE CNTRL GULF COAST

STATES SATURDAY AFTERNOON. ON SUNDAY/DAY 6 AND MONDAY/DAY 7...THE

MODELS MOVE A COLD FRONT ACROSS THE SERN STATES WHERE THUNDERSTORMS

MAY DEVELOP ALONG THE BOUNDARY BUT UNCERTAINTY IS QUITE HIGH BY

EARLY NEXT WEEK. AT THIS POINT...IT APPEARS THAT A SLIGHT RISK AREA

MAY BE NEEDED ACROSS PARTS OF EAST AND NORTH TX ON FRIDAY/DAY 4 BUT

WILL WAIT UNTIL THE DAY 3 OUTLOOK IN ORDER TO GET A BETTER HANDLE ON

THE TIMING OF THE SYSTEM.

Sfc dewpoints at 18z Friday per the 00z NAM:

Similar moisture return on the GFS at the same time period, although it is significantly weaker with the trough itself:

Post from David Reimer's website regarding this threat: http://texasstormcha...hursday-friday/

[tornadotony]

Thursday pretty much a classic recipe for tornadoes in west Texas up into the Caprock region. Yes, I just said that about 2/2. But it's hard to ignore 0-1km SRH up to 400J/kg, CAPE up to 2000J/kg, 40-60kt of bulk shear, a classic dryline, shear vectors perpendicular to the dryline, up to 175 J/kg of 0-3km CAPE, and a nice vort max to induce large-scale lift. And what's scary is that the boundary layer looks to remain coupled to the sfc during the night, allowing for the potential for some tornadoes during the overnight hours in OK and N TX. Don't think it can happen? Research 4/17/70.

[andyhb]

Something tells me the models are underestimating the amount of potential instability with this event as well (although there is plenty already for both days).

April 17th, 1970 had several long-tracked violent tornadoes north of Lubbock.

[tornadotony]

Something tells me the models are underestimating the amount of potential instability with this event as well.

April 17th, 1970 had several long-tracked violent tornadoes north of Lubbock.

It's too early to tell the ceiling for Thursday, but the important thing to gain from looking at 4/17/70 is the time of day (night in that case).

[andyhb]

Yeah, just took a peak at the EHI values for the area you just mentioned, pretty damn impressive at 00z - 06z Thursday night (especially considering this is February we are talking about here). I have a feeling David (and possibly a host of other chasers as well) is going to be all over this.

Edit: Day 2 should be coming out momentarily and based on the latest model analysis, I would say that a 30% area is entirely possible. Changed my initial post to mention the enhanced potential on Thursday night, and it looks like a large portion of Texas could be affected by this event.

03z Thursday night:

06z Thursday night:

[brettjrob]

I'll be surprised if they pull the 30% trigger this early, but no doubt, the ceiling on Thursday is remarkable for mid-winter W of I-35. Needless to say, everything hinges on moisture return. At this point, I'm not that confident it will be sufficient and/or early enough for a significant event. If I'm wrong, however, the forecast hodographs in the LBB-ABI-MAF triangle (and farther N after dark) speak for themselves.

I was looking through John Finch's historical tornado case database earlier today, and judging by his sample set, nocturnal tornado events in W TX look to be favored in the cold season.

[andyhb]

Day 2, no mentioning of tornadoes:

DAY 2 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1253 AM CST WED FEB 01 2012

VALID 021200Z - 031200Z

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

PLAINS...

...SRN PLAINS...

AN UPPER-LEVEL TROUGH WILL MOVE ACROSS THE DESERT SOUTHWEST THURSDAY

AS THE EXIT REGION OF A 65 TO 80 KT MID-LEVEL JET MOVES INTO THE SRN

PLAINS. AHEAD OF THE TROUGH...MOISTURE ADVECTION WILL TAKE PLACE

ACROSS THE SRN PLAINS IN RESPONSE TO A WELL-DEVELOPED 40 TO 55 KT

LOW-LEVEL JET. ALTHOUGH THE AIRMASS SHOULD REMAIN CAPPED FOR MUCH OF

THE DAY...THUNDERSTORM DEVELOPMENT WILL BE LIKELY THURSDAY EVENING

ON THE NOSE OF THE LOW-LEVEL JET OVER THE ERN TX PANHANDLE AND SW OK

SWD INTO THE LOW ROLLING PLAINS. CONVECTIVE COVERAGE SHOULD INCREASE

DURING THE OVERNIGHT PERIOD AS LARGE-SCALE ASCENT INCREASES DUE TO

THE APPROACH OF THE UPPER-LEVEL TROUGH. WEAKER LARGE-SCALE ASCENT

SWD ACROSS WCNTRL TX SHOULD KEEP CONVECTIVE COVERAGE MORE ISOLATED

IN THE SAN ANGELO AREA.

FORECAST SOUNDINGS NEAR ABILENE THURSDAY EVENING SHOW THE BEST

ENVIRONMENT FOR SEVERE STORMS WITH MLCAPE OF 1200 O 1500 J/KG...40

TO 50 KT OF DEEP LAYER SHEAR AND MID-LEVEL LAPSE RATES OF 7.5 C/KM.

THIS ENVIRONMENT SHOULD SUPPORT A THREAT FOR LARGE HAIL AND POSSIBLY

SUPERCELLS. IF THE ACTIVITY CAN BECOME SFC-BASED...THEN A WIND

DAMAGE THREAT COULD ALSO BE PRESENT DURING THE EVENING OR OVERNIGHT

PERIOD. FURTHER TO THE NORTH INTO THE ERN TX PANHANDLE AND SW

OK...THE PRIMARY THREAT SHOULD BE FOR HAIL DUE TO THE ELEVATED

NATURE OF THE CONVECTION.

AT THIS POINT...THE MODELS HAVE COME IN BETTER AGREEMENT BUT THERE

ARE STILL SOME DIFFERENCES. THE ECMWF DEVELOPS STORMS FURTHER TO THE

NORTHWEST AND THE GFS IS FURTHER EAST. HAVE TAKEN A COMPROMISED

SOLUTION BETWEEN THE TWO SOLUTIONS WHICH IS IN CLOSE AGREEMENT WITH

THE NAM. THIS BRINGS THE SLIGHT RISK FURTHER NORTHWEST OF THE

PREVIOUS OUTLOOK AND EXTENDS THE SLIGHT SWD TO NEAR SAN ANGELO WHERE

SFC DEWPOINTS MAY APPROACH 60 F.

..BROYLES.. 02/01/2012

[andyhb]

Day 3:

DAY 3 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0218 AM CST WED FEB 01 2012

VALID 031200Z - 041200Z

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

PLAINS...

...SRN AND CNTRL PLAINS...

AN UPPER-LEVEL LOW IS FORECAST TO MOVE EWD INTO THE CNTRL HIGH

PLAINS FRIDAY AS A 60 TO 75 KT MID-LEVEL JET ROUNDS THE ERN SIDE OF

THE LOW INTO THE SRN AND CNTRL PLAINS. THUNDERSTORMS MAY BE ONGOING

AT THE START OF THE PERIOD ALONG AN AXIS OF INSTABILITY FROM NORTH

TX NWD INTO SRN KS. A MARGINAL HAIL THREAT COULD EXIST WITH STORMS

THAT HAVE ACCESS TO MODERATE INSTABILITY. DURING THE DAY...THE

MODELS MOVE THE CONVECTION EWD ACROSS KS AND INTO ECNTRL OK WITH A

SWD EXPANSION INTO CNTRL AND EAST TX. THE MODELS ARE IN FAIRLY GOOD

AGREEMENT CONCERNING THIS SCENARIO BUT THE MAIN UNCERTAINTIES

INCLUDE TIMING THE EWD PROGRESSION OF THE SYSTEM AND GAGING HOW FAR

NORTH STRONG STORMS WILL DEVELOP.

FORECAST SOUNDINGS FRIDAY AFTERNOON SUGGEST THE BEST ENVIRONMENT FOR

SEVERE STORMS WILL EXIST ACROSS NORTHEAST TX WHERE MLCAPE VALUES ARE

FORECAST IN THE 1200 TO 1500 J/KG RANGE WITH 0-6 KM SHEAR AROUND 50

KT. FORECAST SOUNDINGS AT DALLAS CONVECT USING SFC-BASED PARCELS

SUGGESTING A WIND DAMAGE THREAT MAY EXIST. AN ISOLATED LARGE HAIL

THREAT MAY ALSO BE PRESENT ESPECIALLY IF SUPERCELLS CAN ORGANIZE.

THE HAIL THREAT COULD EXTEND NNWWD ALONG THE INSTABILITY AXIS INTO

NCNTRL OK AND SRN KS WHERE COLD AIR ALOFT IS FORECAST IN THE CORE OF

THE UPPER-LEVEL LOW. HOWEVER...THE HAIL THREAT IN THE CNTRL PLAINS

SHOULD BE KEPT MARGINAL DUE TO WEAK INSTABILITY AND ONGOING

PRECIPITATION THROUGHOUT THE DAY. FURTHER TO THE SOUTH...CONVECTIVE

COVERAGE SHOULD DECREASE WITH SWD EXTENT IN AREAS SOUTH OF DALLAS

WHERE LARGE-SCALE ASCENT IS FORECAST TO THE LIMITED.

06z NAM still has impressive parameters in place Thursday night across Western into North Central TX and SW OK, sort of in a similar area to the Nov. 7th, 2011 event, and perhaps shifting towards the Wichita Falls or even the DFW area with time.

[brettjrob]

Moisture return for Thursday is actually looking a bit better this morning. If we do see surface-based supercells persist after dark, as Tony mentioned, it could get dicey over NW TX, possibly into the SE Panhandle and SW OK.

[tornadotony]

Moisture return for Thursday is actually looking a bit better this morning. If we do see surface-based supercells persist after dark, as Tony mentioned, it could get dicey over NW TX, possibly into the SE Panhandle and SW OK.

It's almost gonna be hard not to have the moisture. There's a huge reservoir of 65+ dews over SE TX already, waiting to be tapped.

[brettjrob]

It's almost gonna be hard not to have the moisture. There's a huge reservoir of 65+ dews over SE TX already, waiting to be tapped.

Yeah, if it weren't for that lead wave coming through today then good moisture would be a lock. Even as it is, with moisture getting shunted into SE TX through late this evening, I have a feeling verification tomorrow evening will be a lot closer to the aggressive NAM solution than anything else. That seems to be the bias in this region in recent months.

[tornadotony]

[SouthernNJ]

Looks to be pretty noisy in the Little Rock area at the moment.

[SouthernNJ]

Looks to be pretty noisy in the Little Rock area at the moment.

Did not expect to see this storm move on and pick up a TOR, but it did.

In addition, winds greater than 70 mph were reported and hail from ping

pong ball to golf ball size were also reported. The worst of it is now

east of Stuttgart and just northeast of Pine Bluff AR.

[SouthernNJ]

Stll some rotation after the TOR expired south of Marvell AR at 419 CST loop.

Would not be surprised to see another one issued.

[SouthernNJ]

Stll some rotation after the TOR expired south of Marvell AR at 419 CST loop.

Would not be surprised to see another one issued.

Not sure if this will produce a tornado or not, but the 428 CST loop had

a pretty good inflow notch where the circulation was.

[JoMo]

Not sure if this will produce a tornado or not, but the 428 CST loop had

a pretty good inflow notch where the circulation was.

* AT 439 PM CST...LOCAL LAW ENFORCEMENT REPORTED A TORNADO 15 MILES

SOUTHEAST OF MARVELL MOVING EAST AT 40 MPH. RADAR ALSO INDICATES

STRONG ROTATION IN THIS STORM AS WELL.

[Thundersnow12]

Stuttgart, AR airport gusted to 86mph.

[baroclinic_instability]

Definitely an interesting setup tomorrow. All the guidance eject a slow lead PV anomaly with a favorable and nearly stationary jet max across the TX Panhandle with continuous a slowly deepening hybrid lee low low. Continued moisture return during the evening and after sunset lowers the LCL's...and the boundary layer, according to models, remains mixed. Certainly makes sense given the persistent mass convergence and deepening of the lee low as that PV slowly migrates through the High Plains into the Panhandle. it isn't terribly common to see these slow ejections of the upper anomaly in late winter with strong synoptic storms tapping this much GOM moisture. Usually they are more of the Colorado Low/Tx Panhandle variety with a strong surging cold front into the plains.

[andyhb]

That's....impressive....

[David Reimer]

i haven't had the pleasure of forecasting severe weather in the Lone Star State west of Interstate 35 this early in the year since February 10, 2009. That being said, I have a couple of concerns for tomorrow. The first of which is dewpoint values. It looks like we'll have enough moisture to produce severe weather, but I'm less confident that we'll have high enough values to allow thunderstorms to produce tornadoes. I did notice the 3 KM CAPE values that Tony posted. Those are certainly impressive and if we do get surface based thunderstorms that are able to remain rooted in the boundary layer after sunset, we could have some interesting weather to track tomorrow evening. Looking at the 12Z/18Z data, I'm thinking that I'll end up between Aspermont, TX and Paducah, TX. The primary limitation in a more northward movement will be the lower dewpoint values. Our tornado outbreak last Wednesday in Central/East Texas got the best of me and I honestly thought we wouldn't see more then isolated severe convection, but the instability values were higher then expected and alas, bow echo of death.

I'm waiting until the 0Z NAM comes in before I really get to in-depth with specifics, but there are a lot of pros that would favor severe weather tomorrow. High instability (lasting well past sunset), favorable wind shear, pretty sweet hodographs, not a significant amount of linear forcing. The cons are the possibility of not enough moisture to support tornadogenesis and from a chasing standpoint, this event will be after dark. However, if this event occurs over the higher elevation regions of the Caprock, I could see 55° dewpoints getting the job done, not to mention that is one of the best places to chase after dark since you have little in the way of trees/hills to restrain your visibility.

I am planning on chasing tomorrow in West Texas and assuming I can get this desktop to function correctly in the car (my laptop is being repaired ATM, I didn't think I would be chasing in late January/early February...) I should be streaming live video of an amazing supercell around this time tomorrow evening.

[andyhb]

Good luck, I'll be watching the stream in all likelihood.

00z NAM is out.

This was the STP from the 18z run at 03z Thursday night.

[brettjrob]

I'll likely be out tomorrow, as well. Aiming for an initial target of Dickens to Guthrie by mid-afternoon, with the highest threat zone expanding northward during the evening. If moisture return is just a bit faster than the 00z NAM indicates, I can foresee a significant event unfolding before sunset, provided we get initiation. Of course, the NAM is on the more aggressive side of the current model guidance regarding moisture, so that might be a stretch.

Regardless of daylight activity for us chasers, I do think a notable tornado threat will materalize in the evening hours over NW TX. It's slightly concerning that none of the local WFO's in that area seem to be mentioning it (even in AFD's), though at least the afternoon SWODY2 used the T-word once. Forecast soundings do not show a nocturnal inversion developing during the 03-06z timeframe, and at the same time, a 50-60 kt LLJ will develop just E of the Caprock. If surface-based dryline supercells do indeed initiate during the late afternoon or early evening, and persist into the Red River Valley, there will likely be trouble.

[David Reimer]

I'll likely be out tomorrow, as well. Aiming for an initial target of Dickens to Guthrie by mid-afternoon, with the highest threat zone expanding northward during the evening. If moisture return is just a bit faster than the 00z NAM indicates, I can foresee a significant event unfolding before sunset, provided we get initiation. Of course, the NAM is on the more aggressive side of the current model guidance regarding moisture, so that might be a stretch.

Regardless of daylight activity for us chasers, I do think a notable tornado threat will materalize in the evening hours over NW TX. It's slightly concerning that none of the local WFO's in that area seem to be mentioning it (even in AFD's), though at least the afternoon SWODY2

Lubbock seems to be on the ball right now regarding the potential tomorrow. They're mentioning a few supercells with a possible tornado threat. That being said, we'll see how quickly other offices are able to obtain situational awareness once the event begins to unfold.

[andyhb]

NAM is popping a 2000+ J/kg CAPE area in W. Texas (albeit in a relatively small area), which is impressive considering that it is after dark in February...

[tornadotony]

I'll likely be out tomorrow, as well. Aiming for an initial target of Dickens to Guthrie by mid-afternoon, with the highest threat zone expanding northward during the evening. If moisture return is just a bit faster than the 00z NAM indicates, I can foresee a significant event unfolding before sunset, provided we get initiation. Of course, the NAM is on the more aggressive side of the current model guidance regarding moisture, so that might be a stretch.

Regardless of daylight activity for us chasers, I do think a notable tornado threat will materalize in the evening hours over NW TX. It's slightly concerning that none of the local WFO's in that area seem to be mentioning it (even in AFD's), though at least the afternoon SWODY2 used the T-word once. Forecast soundings do not show a nocturnal inversion developing during the 03-06z timeframe, and at the same time, a 50-60 kt LLJ will develop just E of the Caprock. If surface-based dryline supercells do indeed initiate during the late afternoon or early evening, and persist into the Red River Valley, there will likely be trouble.

I fear this event is going to catch a lot of people off-guard. I'm looking and looking and I don't really see what's going to prevent an overnight potentially significant tornado threat both at a very rare time of year and a very rare time of day for that area. As long as the moisture makes it there (and at this point I don't really see it not making its way there), tomorrow night has the potential to be rather significant.

[tornadotony]

These are clown images. 240J/kg of 0-3km CAPE on the dryline bulge from 9 PM - midnight CST on February 2nd/3rd? Really?

[baroclinic_instability]

00Z NAM/RGEM/GFS all came in in much stronger with the ejecting anomaly. NAM bombs out the synoptic low. Some of the forecast soundings are disgusting. The deeper this bombs the more unlikely an evening inversion develops.

[andyhb]

This seems like the type of setup that could creep up on the SPC as well (at least, going off the rather benign language in the Day 2 outlooks today). That is insane 0-3 km CAPE in that map that Tony just posted.

Either way, it seems the juiced Gulf is really showing its teeth so far this year...

[brettjrob]

I hate to waffle after my post earlier, but as tantalizing as all these NAM images are, I still have creeping doubts about its moisture advection. I know it nailed November 7, but this time, it really doesn't have much support at all from anything else. The SREF mean dew point plots for tomorrow are laughably different from the operational run, with >55 F confined to areas like San Angelo and Midland by 00z. The SigTor ingredients plot has yet to show a 10% contour on any run thus far. The HRRR and RUC also appear not to be quite as aggressive as the NAM, based on extrapolation. I'm not saying I'll be surprised if the NAM scores a coup, but it's hard to ignore how far out in left field it is in model-land, right now.