Texas/New Mexico/Louisiana/Mexico Obs And Discussion Thread Part 7

[bubba hotep]

Monday could be a sneaky day for the DFW area, there doesn't appear to be any mechanism to provide extra lift and there is probably enough ridging behind the weekend s/w to keep anything from happening. However, if a rouge cell could get off the dryline then it would have some potential. It's the kind of afternoon that Cavanaugh would write up several paragraphs on and then say something like, "however, we don't anticipate any storms initiating this afternoon." Below is form just west of Ft. Worth:

 

 

 

From FWD this afternoon on Monday:

 

SURFACE LEE TROUGHING AHEAD OF THIS SYSTEM WILL

RESULT IN AN INFLUX OF LOW LEVEL MOISTURE ACROSS TEXAS ON MONDAY.

ALTHOUGH MOST OF THE LARGE SCALE LIFT ON MONDAY WILL BE WELL WEST

OF THE REGION...AN APPROACHING DRYLINE AND INCREASING MID LEVEL

INSTABILITY MAY RESULT IN THE DEVELOPMENT OF THUNDERSTORMS. ONE

LIMITING FACTOR FOR STORMS ON MONDAY WILL BE A CAP OF WARM AIR

ABOVE THE SURFACE. HOWEVER...IF THE THE DRYLINE CAN MIX FAR ENOUGH

EAST IT COULD PROVIDE THE NECESSARY FOCUS FOR STORM INITIATION.

[bubba hotep]

Updated graphics from FWD for Tuesday and Wednesday, I'm keeping DFW centric post in our thread and not mucking up the main thread for this event. 

 

 

[NTXYankee]

Euro blows up a nice supercell and moves it over DFW Tuesday followed by line later on. If only we could set that scenerio. Last nights Euro though does favor our area better it seems and along 35 through Oklahoma to Kansas.

[bubba hotep]

Euro blows up a nice supercell and moves it over DFW Tuesday followed by line later on. If only we could set that scenerio. Last nights Euro though does favor our area better it seems and along 35 through Oklahoma to Kansas.

 

The 00z Euro digs the system a bit farther south and is faster with it resulting in a wild looking day across Texas.

[weatherextreme]

Steve McCauley latest update

 

 

 

Latest data continue to suggest a very active weather day coming up late Tuesday afternoon/evening for Texas-Oklahoma-Kansas and points east Tuesday night. As we have been discussing, it all depends on whether the cap will break and allow severe storms to fire.

Unfortunately, the upper-level disturbance that will be moving into the Texas Panhandle appears to be quite large and very strong (i.e., negative tilt), and thus its effects will be felt far and wide.

It does appear sufficiently strong to weaken the cap just enough to allow storms to break through from central Texas to Kansas by late in the day Tuesday and then head northeast Tuesday night.

The highest chance of breaking the cap will be north and west of the immediate DFW area, but with subsequent storm motion to the northeast, it would put the Metroplex in the path of some of the heavier weather.

This, of course, is NOT guaranteed, and it will almost surely change in terms of specifics and exact timing as we get within 24 hours of the event itself. The purpose of these discussions is to keep you updated so you can assess for yourself any positive or negative trends in the forecast.

The good news is that the probability of cap breaking is not 100% anywhere in our area, but admittedly the percentages are a bit higher than I would like to see. A new map will be made tomorrow, and we will see if the chances go up or down.

Of course, there is no cause for alarm. Those of us who have spent years in this area know that this is just a normal aspect of living in this part of the country this time of year. All that is required to be prepared is a rational plan of action and a reasonable sense of awareness.

Stay tuned...

 

 

 

 

[bubba hotep]

FWD has a pretty good discussion on Monday afternoon. If something can get rooted on the other side of the dryline then it would most likely put on a show.

 

From FWD AFD:

 

FOR MONDAY...LOW PRECIPITATION CHANCES WILL CONTINUE AS THE UPPER
AIR PATTERN TRANSITIONS TO MORE OF A ZONAL FLOW ACROSS THE CENTRAL
PLAINS WITH A POTENT UPPER LEVEL TROUGH ACROSS THE FOUR CORNERS
REGION. LOW LEVEL MOISTURE WILL LIFT TOWARDS THE NORTH AND A
DRYLINE WILL GRADUALLY MIX TOWARDS THE EAST MONDAY AFTERNOON.
THERE ARE SOME SLIGHT DISCREPANCIES WITH THE POSITION OF THE
DRYLINE ON MONDAY AFTERNOON HOWEVER. THE ECMWF...NAM AND CANADIAN
ALL KEEP THE DRYLINE OUT WEST ACROSS THE BIG COUNTRY WHILE THE GFS
RAPIDLY MIXES THE BOUNDARY TOWARDS THE HIGHWAY 281 CORRIDOR. GIVEN
THE MODELS BIAS TO TEND TO OVER MIX AND PROGRESS THE DRYLINE
FASTER THUS FAR THIS YEAR...I HAVE SIDED WITH THE
ECMWF/NAM/CANADIAN CAMP ON THE POSITION OF THIS BOUNDARY. WHILE
MUCH OF THE AREA WILL BE BENEATH THE WARM SECTOR...IT APPEARS THAT
A VERY STOUT CAP WILL BE IN PLACE WHICH SHOULD SQUELCH
CONVECTION...ESPECIALLY SINCE THERE APPEARS TO BE NO SOURCE OF
APPRECIABLE SYNOPTIC SCALE LIFT. STILL...ANY MESOSCALE LIFT /I.E.
LOW LEVEL DRYLINE CIRCULATIONS/ MAY BE ENOUGH TO ERODE THE CAP IN
ISOLATED SPOTS. IF STORMS DO DEVELOP...THEY WILL LIKELY BECOME
SEVERE GIVEN THE SHEAR-INSTABILITY SPACE WITH A THREAT MAINLY FOR
LARGE HAIL AND DAMAGING WINDS. AGAIN...THIS RISK IS HIGHLY
CONDITIONAL AND ONLY WARRANTS A 10 POP AT THIS TIME. IT SHOULD BE
NOTED THAT FORECAST SOUNDINGS...MAINLY ACROSS SOUTHEASTERN ZONES
DO REVEAL THAT CONVECTIVE TEMPERATURES ARE REACHED. IF THIS IS THE
CASE AND PARCELS CAN ASCEND FREELY PAST THEIR LFC...THERE WILL BE
A SLIGHTLY HIGHER POTENTIAL FOR SEVERE WEATHER HERE MAINLY IN THE
LATE AFTERNOON HOURS.

 

 

[weatherextreme]

FWD has a pretty good discussion on Monday afternoon. If something can get rooted on the other side of the dryline then it would most likely put on a show.

 

From FWD AFD:

 

FOR MONDAY...LOW PRECIPITATION CHANCES WILL CONTINUE AS THE UPPER

AIR PATTERN TRANSITIONS TO MORE OF A ZONAL FLOW ACROSS THE CENTRAL

PLAINS WITH A POTENT UPPER LEVEL TROUGH ACROSS THE FOUR CORNERS

REGION. LOW LEVEL MOISTURE WILL LIFT TOWARDS THE NORTH AND A

DRYLINE WILL GRADUALLY MIX TOWARDS THE EAST MONDAY AFTERNOON.

THERE ARE SOME SLIGHT DISCREPANCIES WITH THE POSITION OF THE

DRYLINE ON MONDAY AFTERNOON HOWEVER. THE ECMWF...NAM AND CANADIAN

ALL KEEP THE DRYLINE OUT WEST ACROSS THE BIG COUNTRY WHILE THE GFS

RAPIDLY MIXES THE BOUNDARY TOWARDS THE HIGHWAY 281 CORRIDOR. GIVEN

THE MODELS BIAS TO TEND TO OVER MIX AND PROGRESS THE DRYLINE

FASTER THUS FAR THIS YEAR...I HAVE SIDED WITH THE

ECMWF/NAM/CANADIAN CAMP ON THE POSITION OF THIS BOUNDARY. WHILE

MUCH OF THE AREA WILL BE BENEATH THE WARM SECTOR...IT APPEARS THAT

A VERY STOUT CAP WILL BE IN PLACE WHICH SHOULD SQUELCH

CONVECTION...ESPECIALLY SINCE THERE APPEARS TO BE NO SOURCE OF

APPRECIABLE SYNOPTIC SCALE LIFT. STILL...ANY MESOSCALE LIFT /I.E.

LOW LEVEL DRYLINE CIRCULATIONS/ MAY BE ENOUGH TO ERODE THE CAP IN

ISOLATED SPOTS. IF STORMS DO DEVELOP...THEY WILL LIKELY BECOME

SEVERE GIVEN THE SHEAR-INSTABILITY SPACE WITH A THREAT MAINLY FOR

LARGE HAIL AND DAMAGING WINDS. AGAIN...THIS RISK IS HIGHLY

CONDITIONAL AND ONLY WARRANTS A 10 POP AT THIS TIME. IT SHOULD BE

NOTED THAT FORECAST SOUNDINGS...MAINLY ACROSS SOUTHEASTERN ZONES

DO REVEAL THAT CONVECTIVE TEMPERATURES ARE REACHED. IF THIS IS THE

CASE AND PARCELS CAN ASCEND FREELY PAST THEIR LFC...THERE WILL BE

A SLIGHTLY HIGHER POTENTIAL FOR SEVERE WEATHER HERE MAINLY IN THE

LATE AFTERNOON HOURS.

 

 

 

 

 

 

 

 

 

 

 

 

Always got to keep an eye out for those little sneaky ' if the cap breaks' scenarios

[weatherextreme]

From the NWS SPC

 

 

'NWS SPC ‏@NWSSPC 1h1 hour ago

Severe weather will be on the increase starting Sunday, April 24th. Have those sheltering areas cleaned out,."

[bubba hotep]

Always got to keep an eye out for those little sneaky ' if the cap breaks' scenarios

 

I'm not convinced anything will take root on Monday but it will be an interesting day to follow from a purely meteorological standpoint. Tuesday seems kind of like a no brainer to me, put me solidly in the Euro camp. Synoptic scale forcing should work on the cap enough during the day to allow storms to fire in our area. There are still a lot of questions to be worked out on the mesoscale level but the dryline looks to go in the afternoon. Now, that could all change and the Euro could fold to the GFS. But back to Monday, you can conceptualize the dryline circulation by looking at soundings on both sides, one of the problems, we have to use model generated soundings.

 

West side

 

 

 

 

East side

 

 

 

 

[bubba hotep]

FWD hasn't changed their thinking much on Tuesday but they have put out a new graphic for Wednesday:

 

[NTXYankee]

FWIW the GFS seems to be moving in the direction of the Euro and has been persistent on developing storms close to the 35 corridor almost each run now including tonight's run.

[bubba hotep]

D3 just catches DFW

 

[NTXYankee]

Euro decides to change it's mind and says south of red river in play more substantially, developing sfc low in tx panhandle and cranking the low level jet in this area after 0z. Guess we'll see if it had too much to drink or other models follow along.

I don't have access to other features for Euro to know what else it generated, but the variations in models at this juncture is just crazy. A lot of folks trust the Euro especially for trends and the other models seemed to be heading in it's direction when it switched gears the other day, but this would be a pretty big shift.

[bubba hotep]

Euro decides to change it's mind and says south of red river in play more substantially, developing sfc low in tx panhandle and cranking the low level jet in this area after 0z. Guess we'll see if it had too much to drink or other models follow along.

I don't have access to other features for Euro to know what else it generated, but the variations in models at this juncture is just crazy. A lot of folks trust the Euro especially for trends and the other models seemed to be heading in it's direction when it switched gears the other day, but this would be a pretty big shift.

 

Euro seems pretty locked in at this point, there isn't a huge difference in the large scale features b/w the Euro and GFS but enough to make a difference. The Euro is farther south with the base of H5 dragging northern Mexico and the 00z dropped the UL jet streak down to Mexico and into the Big Bend area of Texas. The GFS is farther north with all these features. Then there are also differences in orientation and timing to factor in. It seems like the upgraded Euro has had some issues, at times, with surface features and precipitation placement (I don't have any data to back that up and the statement is purely anecdotal). However, it doesn't appear to be having any issues at this time, based on the mid and upper level features. 

 

Then the Euro brings another significant system through over the weekend and the first of next week. It could be a wild period for Texas. Either way, it looks like more rain is on the way.

 

[Quixotic1]

Looking for a high risk before all is said and done. Maybe not here but in OK or KS.

[bubba hotep]

Even if nothing happens, at least we have something to track tomorrow afternoon. The 1-min sat scans will be up here.

 

[Quixotic1]

Any idea what the temperature for free convection is tomorrow? You gotta think anything past 85 would do it.

[bubba hotep]

The last couple of runs of the 4k NAM seem to agree with the Euro that we won't have any trouble breaking the cap on Tuesday.

[bubba hotep]

Any idea what the temperature for free convection is tomorrow? You gotta think anything past 85 would do it.

 

You can trace the mixing ratio to the temp plot and then follow the dry abiabat back to the surface, but luckily, SHARPpy includes ConvT in the table. It looks like it is mid to upper 80s, depending on where you look. The 00z 4k NAM sim sat actually tries to fire off a storm across DFW but it appears to die as it moves off the dryline and over the cap. 

[Quixotic1]

You can trace the mixing ratio to the temp plot and then follow the dry abiabat back to the surface, but luckily, SHARPpy includes ConvT in the table. It looks like it is mid to upper 80s, depending on where you look. The 00z 4k NAM sim sat actually tries to fire off a storm across DFW but it appears to die as it moves off the dryline and over the cap.

Thanks for that! My sounding/hodograph skills are meager. Going to take a look now to see if I can piece it together.

[bubba hotep]

Thanks for that! My sounding/hodograph skills are meager. Going to take a look now to see if I can piece it together.

 

If you have the time, you should watch the SPC Tornado Forecasting Workshop, Rich Thompson does a pretty good crash course on soundings in the 1st session.

[NTXYankee]

The 0z nam spits out decent parameters at 0z Tuesday for the area, cap also looks breakable or gone as well.

Watch everyone is focused on Oklahoma and Kansas and we end up being the sleeper region, though near triple point up north looks good. Highly doubt we would but stranger things have happened.

[bubba hotep]

The 0z nam spits out decent parameters at 0z Tuesday for the area, cap also looks breakable or gone as well.

Watch everyone is focused on Oklahoma and Kansas and we end up being the sleeper region, though near triple point up north looks good.

 

 

The Euro has been stead fast the last few runs on there being enough large scale lift to work the cap by showtime and now the 4K NAM is also showing that the cap will break. I guess the biggest question is what will the main threat be? It looks like large hail is a given and then probably high winds as storms line out. The tornado threat may not be fully resolved until the day of. The DFW area has seemed to be unlucky over the past year with storms always finding some locally enhanced environment to spin up a tornado.  

[NTXYankee]

The Euro has been stead fast the last few runs on there being enough large scale lift to work the cap by showtime and now the 4K NAM is also showing that the cap will break. I guess the biggest question is what will the main threat be? It looks like large hail is a given and then probably high winds as storms line out. The tornado threat may not be fully resolved until the day of. The DFW area has seemed to be unlucky over the past year with storms always finding some locally enhanced environment to spin up a tornado.

Is the jet at 250mb? By 03z it looks to be aiming right at us.

[Quixotic1]

If you have the time, you should watch the SPC Tornado Forecasting Workshop, Rich Thompson does a pretty good crash course on soundings in the 1st session.

Got it bookmarked. Thanks!

[weatherextreme]

Steve McCauley update per 1 hour ago

 

 

New data coming in tonight seems to warrant our deep concern (though not fear) for Tuesday. Although according to this graphic the cap appears to be insurmountable on Tuesday morning, by late Tuesday afternoon it is altogether absent.

These graphics depict a numerical value for cap strength. Without going into the boring details, a general rule of thumb is that when the cap strength exceeds a 100 points, it becomes very difficult to break. As you can see, our cap strength is between 250 and 400 points Tuesday morning across most of north Texas which is essentially unbreakable.

But as daytime heating kicks in, and as our negative-tilt disturbance approaches, the cap will begin to rise, and the atmosphere will destabilize.

You will recall that the cap is a layer of warm air aloft. When warm air is forced to rise, it must cool down (law of thermodynamics). Thus, when you force the cap to rise, it is forced to cool off. And when you cool the cap, you effectively get rid of it. This is why you see a large gaping open channel in the center of the cap from central Texas north into Kansas by Tuesday afternoon.

It is through this breach in the cap that severe storms are expected to fire late in the day Tuesday and continuing into Tuesday evening.

Note, there is no cap in west Texas. That is because the cap is irrelevant in areas that have no chance for storms. West Texas will be in the driest of desert air on Tuesday, so although technically there is "no cap," there can nevertheless be no storms, so cap strength is undefined in that area.

Although Tuesday continues to be the big day to watch, tomorrow (Monday) will also need to be closely monitored for any unexpected weakness in the cap. The atmosphere will be very unstable on Monday, and a paper-thin cap may be the only thing that will stop supercell storms from popping. But it is hoped the cap will be just strong enough on Monday to prevent a "preview performance" of storms we will likely see late Tuesday

 

 

 

[NTXYankee]

Not fond of the supercell and nighttime tornado risk SPC mentioned for the area Tuesday night. Our expected linear mode may not happen till later and in areas of NE Texas instead.

[bubba hotep]

Enhanced extended down to Waco for tomorrow

[bubba hotep]

 

BETTER CHANCES OF THUNDERSTORMS WILL OCCUR TUESDAY AND TUESDAY
NIGHT. THE UPPER LOW WILL TAKE ON A NEGATIVE TILT BY MIDDAY
TUESDAY THEN LIFT NORTHEAST FROM NEW MEXICO INTO THE CENTRAL
PLAINS TUESDAY AFTERNOON AND EVENING. AT THE SURFACE...A DRYLINE
WILL SURGE EAST INTO WESTERN COUNTIES OF NORTH AND CENTRAL TX. THE
BOUNDARY WILL PROVIDE FOCUS FOR CONVECTIVE DEVELOPMENT AS STRONG
LIFT GENERATED BY THE UPPER LEVEL SYSTEM ARRIVES. INSTABILITY AND
SHEAR WILL BE SUFFICIENT FOR THE FORMATION OF SUPERCELLS CAPABLE
OF PRODUCING LARGE HAIL AND DAMAGING DOWNBURST WINDS...ALONG WITH
THE POSSIBILITY OF A FEW TORNADOES.

TIMING OF THE GREATEST THREAT FOR DISCRETE CELLS CAPABLE OF
MAINTAINING STRONG UPDRAFTS AND PRODUCING SEVERE WEATHER WILL BE
DURING THE LATE AFTERNOON AND EARLY EVENING HOURS...WITH THE
LOCATION BEING ALONG AND WEST OF THE I-35 CORRIDOR. STORM MOTION
WILL INITIALLY BE NORTHEAST...BUT WILL BECOME MORE EASTERLY WITH
TIME AS MID LEVEL WINDS VEER. THE LIKELIHOOD OF UPSCALE GROWTH
INTO A SQUALL LINE STILL EXISTS AS ACTIVITY CROSSES THE I-35
CORRIDOR DURING THE EVENING HOURS...WITH DAMAGING WINDS BECOMING
THE BIGGEST SEVERE THREAT ACROSS THE EASTERN HALF OF THE REGION
OVERNIGHT. WE WILL ALSO NEED TO KEEP AN EYE ON THE FLASH FLOOD
THREAT OVERNIGHT...AS SOME OF THE LATEST GUIDANCE HINTS THAT THE
LINE OF CONVECTION WILL BECOME MORE EAST-WEST ORIENTED DURING THE
LATE NIGHT HOURS...LEADING TO A HIGHER POSSIBILITY OF TRAINING
ECHOES.

[NTXYankee]

I could see a scenerio if the 12z models come in with more of the same dynamics and more certainty of storms developing extending the moderate risk down here or splitting it in two areas. The upper jet streak coming in after dark, plus low level jet cranking up is concerning. We also don't seem to have that vbv issue being talked about in the other thread.