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Texas/New Mexico/Louisiana/Mexico Obs And Discussion Thread Part 4


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#71
Srain

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Guidance has come into a bit better agreement regarding the weekend into next Monday as yet another deep Western trough and upper low drop S into the AZ/NM region suggesting a dry line developing across W Texas providing a focal point for a severe weather outbreak.

Storms appear to begin out W late Saturday and slowly sag E in time as the dry line/Pacific frontal boundary takes shape and begins to progress E on Sunday across N Central/Central TX and points N and E. The SPC has been suggesting for several days a possible significant severe weather episode will unfold for parts of the Lone Star State into OK and KS. What remains to be seen is imbedded short wave impulses rounding the base of the trough/H5 low providing a trigger for rounds of strong to severe storms and the potential for super cells as rich Gulf moisture returns in earnest late week.

The main threat appears to be strong damaging winds with large hail and isolated tornadoes as the storms become linear in nature Sunday night into Monday for areas along and E of the I-35 Corridor. We’ll need to watch the Metroplex and points N and E for the potential of additional super cells developing during the day on Monday as the dry line pushes E.

For SE TX, the main threat appears to be a squall line with strong storms along and N of the I-10 Corridor for Monday as the upper dynamics head into the Plains. We’ll need to monitor future guidance output for any subtle changes/mesoscale features that cannot be determined this far out regarding the sensible weather we can expect.

#72
Ed Lizard

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Nuisance sprinkles possible for the Saturday evening show at the Great American Racetrack, but, thankfully, the models have settled in on generally decent weather for the race weekend.

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#73
Srain

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Morning e-mail from Jeff:

Calm spring weather of late will transition back to stormy by the end of the weekend and early next week as the next storm system moves toward the state.

Upper level trough will dig into the western US over the weekend and then eject into the plains early next week. Short waves lifting out into the plains ahead of the main trough will produce daily rounds of severe thunderstorms over the high plains from western TX into the central plains. Saturday is looking likely a particularly dangerous day from northern TX into the central plains where a significant threat for dangerous long tracked tornadoes appears at least possible.

Surface low pressure developing in the lee of the Rockies over the next 24 hours will encourage stronger SE surface flow off the Gulf of Mexico starting on Friday through the weekend. Fairly pleasant humidity levels will rise into the sticky range by late Friday and remain through the weekend as dewpoints rise into the upper 60’s. Gusty SE winds of 15-25mph will be common each day Fri-Sun. Rain chances will be on the low side through much of the weekend until Sunday afternoon/evening when advancing short wave energy may skirt close enough to the region to allow thunderstorms to develop.

Bigger event appears slated for the Sunday night-Monday time period as the main upper trough lifts into the plains dragging a cold front eastward across TX. Thunderstorms are likely to developing along and ahead of this feature Sunday afternoon over west/central TX and progress eastward toward SE TX overnight into Monday. Track of the main upper trough toward the central plains instead of the southern plains may result in a lessened severe threat this far south along with potential for portions of the area to be dry slotted. Still several days to watch how event may unfold and adjust both the timing and intensity of the potential event.

#74
DoctorMu

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This looks like a pretty potent trough on Monday...in SE Texas we are approaching one of the last cold fronts of the season...until maybe September. I still miss after many years those backdoor cold fronts in the mid-Atlantic during late Spring.

Then our 75 day popcorn shower season begins before we're completely capped...

#75
Srain

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This looks like a pretty potent trough on Monday...in SE Texas we are approaching one of the last cold fronts of the season...until maybe September. I still miss after many years those backdoor cold fronts in the mid-Atlantic during late Spring.

Then our 75 day popcorn shower season begins before we're completely capped...


Meh, my hunch is the tropics will offer a bit of excitement this summer before those fall fronts return.

#76
Ed Lizard

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Who needs tropics? while the strong fun-derstorms are mainly well North, GFS and Euro both see impressive rainfall totals, and as long as it doesn't actually flood, banana plants growing like crazy, what isn't there to like?

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#77
DoctorMu

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Meh, my hunch is the tropics will offer a bit of excitement this summer before those fall fronts return.


Right. It's a tightrope between wishing for late summer rain and a major cyclone. With ENSO- subsiding things could kick up this year


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#78
Ed Lizard

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Still don't know how a squall line might shake out for Sunday for SETX, but benefitical rains still seem on track. Soundings from GFS ahead of the line looks not whammydyne for severe, but not without potential, and a PW of 1.8" in April, I'd shake hands with that.

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#79
Srain

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Morning e-mail from Jeff:

Excessive rainfall/flash flood event unfolding across the coastal bend into SE TX overnight/this morning.

Extremely narrow corridors of very heavy rainfall developed throughout the night producing excessive amounts of rainfall in parts of Brazoria County and between Corpus Christi and Victoria. Doppler radar estimates rainfall amounts of 5-8 inches in a narrow corridor over southern Brazoria County.

Frontal boundary has stalled along the US 59 corridor from Livingston to Spring to Katy to Wharton to Alice with several outflow boundaries moving in various directions across the area per radar and surface observations. Unstable air mass continues to support periods/waves of thunderstorms developing in training bands across the region from south of San Antonio to western LA. Recent upward trend in radar coverage W/SW of the region over the coastal bend and SC TX appears to be the result of favorable diffluence aloft and an approaching impulse out of NE MX. Additionally, thunderstorms overnight have left behind a boundary near the coast which has been a good focus for the flooding rainfall over Brazoria County, although repeated development has ended on this boundary in the last 2 hours.

While the global models have a decent handle on the situation the event is highly mesoscale driven with slow moving low level boundaries focusing very heavy rainfall in small narrow SW to NE oriented bands. Where these bands set up and drop 2-4 inches of rainfall in a few hours is extremely difficult to forecast until it is underway. Would think the main frontal boundary would be the primary focus, and recently (past 1-2 hours) it has become that. With the near coastal activity weakening, better moisture may begin to push back northward toward the main frontal boundary focusing more sustained development in this region (near or just north of US 59). This is what some of the shorter term meso models are suggesting, but they have not preformed overly well with this event.

With moisture levels remaining high and the threat for cell training, some high totals in narrow corridors are possible. This is more of a localized flash flood threat than a widespread flood threat….but where those training bands set up those locations could easily get over 5 inches in a few hours.

Tail end of the upper trough and stalled boundary will remain over the area for the next 12-18 hours and this will continue the threat of storms and heavy rainfall. Larger scale models are even more sluggish in clearing the region…not until later on Tuesday. Will trend toward the storms gradually ending this evening as the air mass becomes overturned (worked over) and the best dynamics and moisture shift south and east with time.

Nice weather by late Tuesday-early Thursday with another faster moving system which may bring a rounds of showers and thunderstorms again Thursday night-Friday.

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#80
Srain

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From NESDIS:

SATELLITE PRECIPITATION ESTIMATES..DATE/TIME 04/16/12 1243Z
SATELLITE ANALYSIS BRANCH/NESDIS---NPPU---TEL.301-763-8678
LATEST DATA USED: GOES-13 1230Z KUSSELSON
NOAA AMSU:0830Z/1028Z
.
LOCATION...SE TEXAS...
.
ATTN WFOS...HGX...CRP...
ATTN RFCS...WGRFC...
.
EVENT...HIGH MOISTURE AND UPPER LEVEL FEATURE COMING ACROSS TEXAS AND
ALLOWING CONVECTION HANG IN ALONG THE COAST AND S CENTRAL TEXAS...
.
SATELLITE ANALYSIS AND TRENDS..THIS MORNING IT'S ONE OF THOSE DEALS
WHERE THE DEEP MOISTURE IS HAVING A HARD TIME MAKING ANY EAST PROGRESS
AND ACTUALLY HAS SETTLED FOR REMAINING AND PERSISTING S TO SE TX AT THE
SAME TIME AN UPPER LEVEL FEATURE WAS ROUNDING AND NOW OUT AHEAD OF WESTERN
TEXAS TROUGH TO HELP DESTABILIZE AREA ENOUGH TO KEEP THE CONVECTION GOING
ALONG OLD OUTFLOW BOUNDARIES. THIS HAPPENING CENTERED ON SAN PATRICIO
COUNTY THIS MORNING. SATELLITE RAIN ESTIMATES DISPLACE THE HEAVY RAIN
FURTHER NORTHEAST WITH AMOUNTS OF NEAR 4"/6HRS. EXPERIENCE SAYS THAT
HIGH CLOUDS DISPLACING HVY RAIN TOO FAR EAST...SO THINK AMOUNTS ESTIMATED
ARE OKAY..BUT JUST DISPLACED TO FAR NORTHEAST...SO FF A GOOD POSSIBILITY
CENTERED ON SAN PATRICIO AND ENVIRONS.
ALSO EYEING SW TO NE CONVECTIVE WEDGE JUST TO THE WEST...IE NEAR MCMULLEN
COUNTY BUT MOISTURE NOT QUITE AS GOOD. OTHER AREAS ARE EITHER MOVING
OR RAINFALL NOT AS HEAVY OR PERSISTENT AS IN SAN PATRICIO COUNTY.
.
AN ANNOTATED SATELLITE GRAPHIC SHOWING THE HEAVY PRECIPITATION THREAT AREA
SHOULD BE AVAILABLE ON THE INTERNET ADDRESS LISTED BELOW IN APPROXIMATELY
10-15 MINUTES.
.
SHORT TERM OUTLOOK VALID 1245-1545ZZ...MEDIUM CONFIDENCE FACTOR IN SHORT
TERM OUTLOOK...AS LONG AS DEEP MOISTURE IS IN PLACE AND FORCING TO WEST
WITH NOW A JET MAX SHOWING...BOUNDARY CAN BE ACTIVE AND SAN PATRICIO IS
THE SPOT AT LEAST IN IMMEDIATE TERM.

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#81
Srain

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Update from NESDIS:

SATELLITE PRECIPITATION ESTIMATES..DATE/TIME 04/16/12 1437Z
SATELLITE ANALYSIS BRANCH/NESDIS---NPPU---TEL.301-763-8678
LATEST DATA USED: GOES-13 1415Z KUSSELSON
NOAA AMSU:0846Z/0838Z DMSP SSMIS: 1310Z
.
LOCATION...SE TEXAS...
.
ATTN WFOS...LCH...HGX...CRP...
ATTN RFCS...WGRFC...
.
EVENT...CONVECTIVE WEDGE COMPLEX CONTINUES HANGING IN ALONG THE CENTRAL
TX GULF COAST...MESO CELL FROM THAT COMPLEX PUSHING THROUGH BRAZORIA
COUNTY...
.
SATELLITE ANALYSIS AND TRENDS...WITH UPPER LEVEL TROUGH STILL WAY BACK
CLOSE TO THE CO-
TX-NM BORDER...SWLY FLOW OVER CONCERN AREA CONTINUES AND THAT MEANS
CONVECTIVE WEDGE HANGING IN THERE AND BEING FUELED BY DEEP LAYERED
MOISTURE. LATEST MAX GPS PW ALONG MID TX COAST JUST SOUTH OF KCRP WAS
CLOSE TO 2.0" AND THAT WELL ABOVE 2 STANDARD DEVIATIONS ABOVE NORMAL...12Z
KCRP SOUNDING HAD 1.8" VALE AND THAT RIGHT AT 2 STANDARD DEVIATIONS.
AND THAT ALONE WOULD BE A CONCERN FOR CONTINUED HEAVY RAIN...BUT THEN
THERE ARE THE MESO JET PUSHING THRU CENTRAL TEXAS JUST AHEAD UP AN UPPER
LEVEL AND THAT FORCING EXTENDING ITS REACH TO NEAR THE HIGHEST MOISTURE.
ACTIVITY COULD GO ON FOR A SEVERAL MORE HRS WITH NO REAL KICKER TO
THE WEST.
CELL/COLD CLOUD TOP THAT CAME OUT OF THE COASTAL CONVECTIVE WEDGE NOW
SPREADING COLD TOP HEAVY THROUGH AREA CENTERED ON BRAZORIA COUNTY AND
RAIN RATE IN THE 1-1.5"/HR RANGE...BUT THERE COULD BE SOME ISOLATED
HIGHER RATES...BUT PROBABLY NOT AS HIGH AS WITH THE SAN PATRICIO COUNTY
CELLS THAT ARE FEEDING ON EXISTING AND ANOMALOUS MOISTURE CONTENT.
.
AN ANNOTATED SATELLITE GRAPHIC SHOWING THE HEAVY PRECIPITATION THREAT AREA
SHOULD BE AVAILABLE ON THE INTERNET ADDRESS LISTED BELOW IN APPROXIMATELY
10-15 MINUTES.
.
SHORT TERM OUTLOOK VALID 1430-1800Z...MEDIUM CONFIDENCE FACTOR IN SHORT
TERM OUTLOOK...NO KICKER...EXCESSIVE MOISTURE...BUT DIURNAL SHOULD SAY
WEAKEN...BUT IT IS NOT AND SAN PATRICIO AT THE EPICENTER OF EXCESSIVE
RAINFALL. MOISTURE TRANSPORT, EVEN THOUGH IT IS NOT GREAT IN THE
IMMEDIATE VIC...IS PRETTY GOOD CLOSE BY IMPORTING HIGH MOISTURE JUST
OFF S COAST AND BRING IT INLAND TO THE MID TX COAST...SO HVY RAIN THAT
FALLS IS KIND OF REPLENISHED AND CAN CONTINUE MOST OF THIS PERIOD WITH
CONTINUED FLOODING.

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#82
Srain

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Update from Jeff:

Stalled frontal boundary along HWY 35 from north of Port Aransas to Port Lavaca to Bay City to Angleton then offshore of Galveston Island continues to be the focus for near continuous thunderstorm formation and heavy training rainfall.

Favorable position of the upper level trough over W TX and continued feed of very moist high PWS air mass inland off the western Gulf of Mexico is resulting in very heavy rainfall in a band from just north of Corpus Christi to Matagorda Bay to Galveston County. Extremely heavy rainfall has focused over San Patricio County this morning around Portland and Gregory where rainfall estimated over 8-12 inches has fallen (at the intersection of the frontal boundary and moist low level feed of untapped air over S TX).

With additional upstream energy moving through the upper through expect to continue to see thunderstorms develop and train ENE to E along the coastal counties and possibly the US 59 corridor through much of the day. Air mass remains very capable of producing rapid short term rainfall amounts of 1-2 inches in a hour. Where cell training develops flooding is likely with this kind of rainfall. Additionally, the duration of the event is starting to result in watershed responses along the coastal creeks and smaller scale rivers and some will likely rise to flood stage with continued slow moving excessive rainfall under training cells.

Additional rainfall of 1-3 inches across the coastal counties is likely with isolated totals upwards of 4-6 inches on top of what has already fallen. Would not be surprised to see a few storm totals since yesterday evening approach and exceed 10-12 inches along/near the Hwy 35 corridor.

Note:
Severe Thunderstorm Watch has been issued from Matagorda Bay southward to deep south TX as air mass in that region is becoming increasingly unstable ahead of southward sagging frontal boundary. Intersection of this boundary with strong low level inflow has produced a few severe and at time rotating tornadic cells this morning from north of Corpus to north of Brownsville….in fact the public reported a tornado over King Ranch earlier this morning.

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#83
wxmx

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North and East of Monterrey last night. Not me, I live in the west part of the city.

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#84
Ed Lizard

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I'd say the drought worries are almost officially over in San Patricio County.

There was hail (damaging even), but ground truth seems to support 15 inch rainfall.

000
NWUS54 KCRP 161630
LSRCRP

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CORPUS CHRISTI TX
1129 AM CDT MON APR 16 2012

..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..

1023 AM FLASH FLOOD 7 S BAYSIDE 27.97N 97.24W
04/16/2012 SAN PATRICIO TX EMERGENCY MNGR

MORE THAN 15 INCHES OF STORM TOTAL RAINFALL.

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#85
Srain

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Update from Jeff:

NWS has issued a Flash Flood Watch for the following counties: Galveston, Brazoria, Matagorda, Wharton, and Jackson

Stalled surface boundary continues to produce near continuous rainfall along the coast early this afternoon. Radar indicates rainfall amounts of 4-6 inches have fallen over portions of Jackson, Matagorda, and Brazoria Counties overnight and this morning and thunderstorms continue to develop and train over these counties. A few locations in southern Brazoria County are nearing 8 inches of rainfall. Additional rainfall of 2-4 inches is likely in the watch area this afternoon as storms develop and track over the same areas.

With grounds saturated run-off will be increasing with the threat for more widespread flooding. Flash Flood Warning is in effect for Brazoria and Matagorda Counties until 145pm.

Note:
Large HP supercell over San Patricio County has finally moved offshore after dropping 10-15 inches of rainfall over the Portland and Gregory areas this morning. San Patricio emergency manager reported more than 15.0 inches of total rainfall since 400am this morning 7 miles south of Bayside and this matches well with radar rainfall estimates. Severe flooding is in progress over eastern San Patricio County.

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#86
Srain

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What a change from last year when we were already in the grip of a drought and early Spring heat. It was 52F here this morning. Some 40's are likely this weekend for SE TX with frost warnings for portions of the Lone Star State. Must be April.

#87
Srain

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Morning e-mail from Jeff:

Upper air pattern will become highly amplified for mid April this weekend sending a strong low pressure system and cold front through TX on Friday.

At the surface winds will swing around to the south later today starting the return of Gulf moisture back into the region ahead of a late Friday frontal passage. Air mass will moisten on Friday, but forecast soundings show a decent capping inversion in place and very dry mid level air mass. With that said, the incoming front will have strong lift and the boundary will be moving through at least part of the area during peak heating. Feel at least a few strong to severe thunderstorms will develop along a thin band of convection with the boundary. Best chances for any severe weather will be from roughly Galveston to Katy to College Station and southwestward into deep S TX where instability will be greatest.

This system is fairly fast moving and should clear the area before sunrise Saturday. The surface low will begin to deepen over the NC Gulf of Mexico Saturday while strong high pressure builds into TX from the north. A very tight pressure gradient will be in place Saturday over eastern TX producing strong winds. Additionally, clearing skies will allow downward momentum transfer of some higher winds aloft during the day. Expect winds to rapidly come up Saturday morning out of the north into the 15-25mph range and then increase into the 20-30mph range by early afternoon with gust at or above 40mph. Cold air advection on Saturday will keep highs only near 70 (about 10 degrees below average) even under full sun.

Extended:
Cool surface high pressure will settle over the region Sunday with lows falling into the 50’s and possibly upper 40’s in some locations and highs in the mid 70’s. Nice weather with low humidity will continue into early next week.

Fire Weather:
Very strong winds expected on Saturday across the area along with low afternoon RH values in the 20-30% range. Typically this would be of some concern, but wet grounds and healthy vegetation cover should mitigate any significant fire weather concerns.

MS 150:
All storms will be east of the area by Saturday morning, but very strong winds out of the N and NW will blast the route all day Saturday. Winds will rapidly increase Saturday morning and remain strong and gusty all day sustained in the 20-30mph range and at times gusting 35-40mph. Air mass will be very dry with low RH and temperatures in the 60’s to lower 70’s. Sunday should feature calmer winds early, then breezes picking back up out of the N and NE by late morning into the 10-15mph range.

SPC Day 2 (Friday) Severe Weather Outlook:

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#88
bubba hotep

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Posted Image

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 183
NWS STORM PREDICTION CENTER NORMAN OK
640 PM CDT THU APR 19 2012

THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

SOUTH CENTRAL OKLAHOMA
WESTERN NORTH TEXAS

EFFECTIVE THIS THURSDAY NIGHT AND FRIDAY MORNING FROM 640 PM
UNTIL 100 AM CDT.

HAIL TO 2.5 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70
MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 55
STATUTE MILES EAST AND WEST OF A LINE FROM 35 MILES WEST OF
MINERAL WELLS TEXAS TO 20 MILES NORTHEAST OF OKLAHOMA CITY
OKLAHOMA. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU3).

REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE
FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY
DO PRODUCE TORNADOES.

DISCUSSION...THUNDERSTORMS ARE BEGINNING TO FORM ALONG SURFACE COLD
FRONT/DRYLINE OVER WESTERN NORTH TX...AND ARE EXPECTED TO FORM IN
THE NEXT 1-2 HOURS OVER PARTS OF SOUTHWEST OK. THIS ACTIVITY WILL
BE IN A REGION OF RELATIVELY WEAK LOW LEVEL SHEAR. BUT...SUFFICIENT
EFFECTIVE SHEAR VALUES AND MODERATE CAPE WILL PROMOTE SUPERCELL
STRUCTURES CAPABLE OF LARGE HAIL AND DAMAGING WINDS. ACTIVITY MAY
PERSIST NEAR THE RED RIVER FOR MUCH OF THE EVENING.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM
MOTION VECTOR 27030.

#89
Srain

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MESOSCALE DISCUSSION 0571
NWS STORM PREDICTION CENTER NORMAN OK
1235 PM CDT FRI APR 20 2012

AREAS AFFECTED...PORTIONS MIDDLE-UPPER TX COASTAL PLAIN...WRN LA.

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 201735Z - 202000Z

ELEVATED CONVECTION BEARING HAIL RISK HAS INCREASED IN
COVERAGE/INTENSITY OVER PORTIONS E TX AND SHOULD MOVE INTO WRN LA
WITH CONTINUED/SPORADIC RISK OF SVR HAIL. POTENTIAL IS INCREASING
FOR MORE ORGANIZED/SFC-BASED TSTMS FARTHER SW ACROSS MID-UPPER TX
COASTAL PLAIN...WITH RISK FOR DAMAGING GUSTS AND OCNL LARGE HAIL.

16Z SFC MESOANALYSIS SHOWED SFC COLD FRONT FROM SWRN AR AND NE TX
SWWD ACROSS CENTRAL TX BETWEEN ACT-CLL...JUST S HDO...THEN RIO
GRANDE VALLEY BETWEEN DRT AND EAGLE PASS. SEPARATE TROUGH/WIND
SHIFT LINE WAS DRAWN FROM SAT AREA SSWWD ACROSS LRD TO NEAR MMMY.
FRONT SHOULD CONTINUE SEWD...IMPINGING ON BOUNDARY LAYER THAT WILL
BE DESTABILIZING AND WEAKENING CINH WITH TIME. MOISTURE CHANNEL
IMAGERY AND OVERLAID VWP/PROFILER DATA SHOW WELL-DEFINED SHORTWAVE
TROUGH ACROSS CENTRAL OK...TX HILL COUNTRY AND RIO GRANDE VALLEY
NEAR DRT. AS RELATED PLUME OF LARGE-SCALE ASCENT SHIFTS ESEWD OVER
DISCUSSION AREA...AND AS POCKETS OF RELATIVELY STG SFC DIABATIC
HEATING CONTINUE...INITIALLY STG CAPPING WILL ERODE RAPIDLY. THIS
WILL LEAVE BOUNDARY LAYER PRONE TO RAPID DEVELOPMENT AND UPSCALE
GROWTH OF TSTMS...ESPECIALLY ALONG COLD FRONT...BUT PERHAPS INVOF
LOCALIZED SEA-BREEZE CONVERGENCE MAXIMA AS WELL. RESULTANT
STEEPENING OF LOW-MIDDLE LEVEL LAPSE RATES...JUXTAPOSED WITH SFC DEW
POINTS MAINLY MID-60S F...YIELD MLCAPE 2000-3000 J/KG IN MODIFIED
RAOBS AND RUC FCST SOUNDINGS.

EFFECTIVE SHEAR IS RATHER WEAK OVER MOST OF DISCUSSION AREA...DUE TO
STG VEERING/BACKING PROFILE IN LOW-MIDDLE LEVELS AND LACK OF MORE
ROBUST BOUNDARY-LAYER WINDS INLAND. THIS SHOULD REMAIN TRUE OVER
MID-UPPER TX COASTAL PLAIN...THOUGH VERTICAL SHEAR MAY BECOME MORE
FAVORABLE THIS AFTERNOON IN AREA OF DEEP S TX TO BE COVERED IN
SEPARATE MCD LATER. EFFECTIVE SHEAR ALSO WILL BE STRONGER FOR
CONVECTION BEHIND SFC FRONT. CLUSTERED AND LINEAR STORM MODES
APPEAR MOST PROBABLE...WITH GREATER WIND THREAT ALONG/AHEAD OF FRONT
AND HAIL RISK WITH CONVECTION ON BOTH SIDES OF FRONT.

..EDWARDS.. 04/20/2012


ATTN...WFO...LCH...SHV...HGX...CRP...EWX...

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#90
Srain

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#91
Srain

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MESOSCALE DISCUSSION 0572
NWS STORM PREDICTION CENTER NORMAN OK
0130 PM CDT FRI APR 20 2012

AREAS AFFECTED...PORTIONS DEEP S TX...LOWER RIO GRANDE VALLEY
REGION...COASTAL PLAIN SW OF WW 184.

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 201830Z - 202030Z

SVR POTENTIAL FCST TO INCREASE THROUGH LATE AFTERNOON OVER
DISCUSSION AREA...INCLUDING CONDITIONAL POTENTIAL FOR A FEW
SUPERCELLS. MAIN CONCERN WILL BE LARGE/DAMAGING HAIL. SVR
DOWNDRAFT GUSTS ALSO ARE POSSIBLE...RELATED BOTH TO PRECIP LOADING
AND POTENTIAL FOR EVENTUAL UPSCALE COLD-POOL GROWTH. TORNADO THREAT
IS MORE CONDITIONAL ON BOUNDARY INTERACTIONS AND STORM-SCALE
PROCESSES...BUT A TORNADO OR TWO IS POSSIBLE.

SFC MESOANALYSIS SHOWED COLD FRONT FROM NE TX SWWD ACROSS SAT AREA
TO JUST W COT. PREFRONTAL WIND SHIFT WAS DRAWN JUST E OF I-35
BETWEEN SAT-LRD THEN SSWWD TO MMMY. FRONT IS FCST TO MOVE SEWD
THROUGH AFTERNOON...OVERTAKING WIND SHIFT AND MOVING INTO
DESTABILIZING AIR MASS WITH WEAKENING CINH. MODIFIED RAOBS AND FCST
SOUNDINGS SUGGEST MLCAPE INCREASING TO 2000-3000 J/KG RANGE WITH SFC
DEW POINTS REMAINING MID-60S F...AND CONTINUED STG INSOLATION.
BOUNDARY-LAYER FLOW IS NOT PARTICULARLY STG...LIMITING EFFECTIVE
SRH. HOWEVER...SUBSTANTIAL DIRECTIONAL VEERING WITH HEIGHT SHOULD
BE MAINTAINED THROUGH AT LEAST LATE AFTERNOON. 850 MB WINDS HAVE
VEERED FARTHER N ACROSS CRP AREA...APPARENTLY IN RESPONSE TO
SEWD-MOVING...MESOBETA-SCALE PERTURBATION ACCOMPANYING
EARLIER/WEAKENING PLUME OF CLOUDS/PRECIP. HOWEVER...SFC FLOW THAT
VEERED LAST HOUR IN THAT AREA...HAS BACKED AGAIN. AS MID-UPPER
TROUGH PASSING ACROSS NRN PORTIONS OF THIS AREA ENHANCES HEIGHT
GRADIENT...MIDLEVEL WINDS AND THUS DEEP-LAYER SHEAR WILL
STRENGTHEN...ESPECIALLY WHERE LOW-LEVEL WINDS REMAIN RELATIVELY
BACKED. RESULT SHOULD BE 40-50 KT EFFECTIVE SHEAR MAGNITUDES...AND
ELONGATED...SOMEWHAT HOOK-SHAPED LOW-LEVEL HODOGRAPHS DEVELOPING
THAT MOST FAVOR SUPERCELLS FOR ANY DISCRETE TSTMS EXHIBITING
STRONGLY DEVIANT/SWD MOTIONS.

..EDWARDS.. 04/20/2012


ATTN...WFO...CRP...BRO...

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#92
Srain

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#93
JoMo

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Tornado Warning for the Corpus Christi area.

Posted Image

#94
Ellinwood

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Haven't seen anything other than weak rotation on radar... wouldn't be surprised if Texas ended up with 0 tornadoes. The warning issued by the Brownsville NWS might have been legitimate, but I've been scratching my head a little WRT the warnings coming out of CRP.

#95
Ellinwood

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Galveston: http://abclocal.go.c...enow?id=7292434

4:42pm CDT:

Attached File  20120420_Galveston1.png   268.29KB   3 downloads

#96
Srain

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CRP NWS employee reported some weak rotation. The line has produced a lot of hail. I had penny to nickle size here in NW Harris County with winds gusting to 50 mph.

Edit to add: Strongest rotation was near CC NAS a moment ago via CRP

#97
Srain

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MESOSCALE DISCUSSION 0574
NWS STORM PREDICTION CENTER NORMAN OK
0448 PM CDT FRI APR 20 2012

AREAS AFFECTED...DEEP S TX

CONCERNING...SEVERE THUNDERSTORM WATCH 185...

VALID 202148Z - 202245Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 185
CONTINUES.

A LARGE TO VERY LARGE HAIL THREAT...IN ADDITION TO DMGG WINDS AND AN
ISOLD TORNADO RISK...WILL CONTINUE UNTIL THE STORMS OVER THE AREA
MOVE SEWD AND OFFSHORE INTO THE WRN GULF.

RADAR MOSAIC/SURFACE CHART ANALYSIS SHOWS AN EXTENSIVE SQUALL LINE
EXTENDING FROM THE MIDDLE TX COAST NEWD THROUGH THE HOUSTON METRO
VICINITY WITH A BROKEN LINE/CLUSTER OF QUASI-DISCRETE SUPERCELLS
DEVELOPING FARTHER SW OVER DEEP S TX FROM CRP TO 40 MI NNW MFE. THE
AIRMASS IMMEDIATELY AHEAD OF THE ESEWD MOVING CONVECTIVE COMPLEX HAS
WARMED INTO THE UPPER 80S WITH MID-UPPER 60S DEWPOINTS. THIS
POTENTIALLY UNSTABLE BOUNDARY LAYER RESIDES UNDERNEATH A STOUT CAP
/PER 18Z BRO RAOB/ WITH VERY STEEP H7-H5 LAPSE RATES /NEAR 9 DEG C
PER KM/. HOWEVER...LARGE SCALE FORCING FOR ASCENT DUE TO AN
EQUATORWARD DIGGING UPPER TROUGH OVER TX AND LOW LEVEL LIFT OWING TO
A COLD FRONT MOVING THROUGH THE AREA WILL CONTINUE TO STRONGLY FAVOR
FURTHER STORM DEVELOPMENT. STRONG UPPER TROPOSPHERIC FLOW SAMPLED
BY AREA 88D VAD/S AND RAOB DATA WILL SUPPORT ROTATION WITH THE
STRONGER UPDRAFTS. THIS WILL LEND TO THE POSSIBILITY OF HAIL OF
BEING GOLFBALL SIZE OR LARGER WITH THE MOST INTENSE STORMS...OWING
TO LARGE CAPE IN THE -10 TO -30 DEG C LAYER. AN ISOLD TORNADO RISK
CANNOT BE RULED OUT DESPITE WEAK LOW LEVEL FLOW...DUE TO VEERING LOW
LEVEL WINDS WITH HEIGHT AND SUPERCELLULAR STORM MODE.

..SMITH.. 04/20/2012


ATTN...WFO...CRP...BRO...

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#98
Ellinwood

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By the way... does anyone know why CRP isn't cancelling old warnings? The storms moved out of the tornado warning 20 minutes ago and the warning doesn't expire for another 10 minutes. Not enough staff to issue the severe warnings and cancel old ones?

EDIT: I've been informed of server issues.

#99
Ellinwood

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I guess I'll have to take back my earlier statement about no tornadoes... not too long after I said that this happened:

2245 ... 1 SE Raymondville ... Willacy ... TX
Brief touchdown and lift up. No damage reported.

The two scans before the report (which was at 2245... around the same time they expired the warning):

Attached File  20120420_TXtor1.png   361.75KB   0 downloads

Attached File  20120420_TXtor2.png   343.04KB   0 downloads

#100
JoMo

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Tornado warning down near Brownsville, multiple funnel clouds reported. (Edit: And cancelled)

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#101
Ed Lizard

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Official NWS forecast high at San Angelo, TX is 101ºF. May can't be far behind.

#102
Ed Lizard

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In main forum tropical thread, 12Z Crazy Uncle brings a very weak but trackable 850 mb feature with a hint of a surface low Northwest across the Gulf to rain on Louisiana mid-week.

Nothing like that on the more reliable GFS, but we get close to getting South of the 700 mb ridge axis at the end of the month for a couple of days before we get back into SW low-mid-level flow.

#103
Ed Lizard

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Still immensely boring locally, but SPS area in a hatched hail risk area, and mid-week, GFS seems a bit on the Canadian train with a barely perceptible disturbance from the East enhancing rain chances in Louisana.

#104
goobagooba

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Seeing lightning here in Collin Co but not a thing on the radar.

#105
Srain

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  • Joined November 11, 2010

...SERN TX TODAY...

A WELL-DEFINED MCV SE OF AUS WILL CONTINUE EWD TODAY...LIKELY
SERVING AS THE FOCUS FOR DIURNALLY ENHANCED TSTM DEVELOPMENT.
MODIFICATION OF 12Z CRP SOUNDING FOR FORECAST AFTERNOON SURFACE
CONDITIONS SUGGESTS AIR MASS WILL BECOME MODERATELY UNSTABLE WITH
MLCAPE OF 1500-2000 J/KG. MOREOVER...CURRENT CRP VWP SHOWS THE
PRESENCE OF MODESTLY STRONG LOW-LEVEL SHEAR WHICH MAY PROMOTE A FEW
ROTATING STORMS WITH AN ATTENDANT RISK FOR HAIL...LOCALLY DAMAGING
WINDS AND PERHAPS A TORNADO.

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