OCTOBER: Halloween Storm: Severe Storms/Flash Flood Threat?

[Paul Robison]

I don't know if this means anything to y'all, but HGX has this about our "potent" storm system.

.PREV DISCUSSION... /ISSUED 336 PM CDT WED OCT 23 2013/

DISCUSSION...
HIGH PRESSURE WILL DRIFT EAST AND ALLOW FOR ONSHORE WINDS TO
RETURN LATER TONIGHT AND THURSDAY. THE UPPER LEVEL RIDGE WILL ALSO
BREAK DOWN AND ALLOW FOR A STRONG SHORTWAVE TROUGH TO MOVE
OVERHEAD AT THE END OF THIS WEEK. AFTER ANOTHER COOL NIGHT...
EXPECT A WARMING TREND TO BEGIN THAT WILL MAINLY AFFECT NIGHTTIME
TEMPERATURES ON THURSDAY. AS THE SHORTWAVE TROUGH APPROACHES...
RAIN CHANCES WILL RETURN ON SATURDAY. THE MODELS DIFFER A BIT BUT
BEST CHANCES APPEAR TO START IN THE WEST ON SATURDAY AND THEN AREA
WIDE SATURDAY NIGHT AND SUNDAY.

A MORE WESTERLY UPPER LEVEL PATTERN AND A SURFACE RIDGE WILL
BRING A BRIEF BREAK FROM THE RAIN CHANCES SUNDAY NIGHT THROUGH
MONDAY NIGHT. RETURN FLOW FROM THE GULF WILL THEN HELP TO RETURN
ISOLATED RAIN CHANCES BY TUESDAY. BOTH THE GFS AND ECWMF MOVE A
STRONG UPPER TROUGH INTO THE PLAINS DURING THE MID WEEK PERIOD.
FOR NOW THE MAIN IMPACTS STILL LOOK TO BE OUT OF THE FORECAST AREA
AND MORE INTO THE SOUTHERN PLAINS ON WEDNESDAY.

And this tidbit from Dallas WX says:

THE NEXT SYSTEM...WHICH HAS THE COLD WEATHER AFICIONADOS ENDING
THEIR SUMMER HIBERNATION...APPEARS TO BE ABOUT A DAY SLOWER THAN
MY FORECAST YESTERDAY. THE GFS...WHICH HAD THE UPPER LOW CUT OFF
OVER THE COASTAL TX PLAINS...NOW KEEPS THE UPPER TROF OPENED UP
ACROSS THE MIDWEST AND SLOWS THE COLD FRONT/S NORTH TX ENTRY
UNTIL THURSDAY AFTERNOON. THE ECMWF 00Z RUN FORECASTS EXTREMELY
COLD 850 MB AIR OVER NORTH TEXAS UNDER THE CUTOFF LOW...BUT THE
12Z RUN HAS ALSO BACKED OFF A BIT ON THE COLD AIR AND KEPT THE
UPPER LOW CENTER FARTHER NORTH IN OKLAHOMA. IT BRINGS THE COLD
FRONT INTO NORTH TX WEDNESDAY EVENING.

WITH LITTLE RUN TO RUN OR MODEL TO MODEL CONTINUITY...WILL
FORECAST A HYBRID OF THE TWO MODELS...AND BACK UP THE FROPA UNTIL
AFTER THIS FORECAST PACKAGE. I DID KEEP LOW CHANCES FOR THUNDER
FOR TUESDAY AFTERNOON AND INTO THE OVERNIGHT HOURS GIVEN THE
UNCERTAINTY ON SYSTEM PROGRESSION...AND UPPED THE POPS TO 30
PERCENT ON WEDNESDAY AND WEDNESDAY NIGHT GIVEN 48 HOURS OF MODEL
PREFERENCE FOR WEDNESDAY PRECIP.

IF THE STRENGTH OF THE UPPER TROF FOR MID WEEK CONTINUES TO WEAKEN
AND MOVE NORTH...THE SEVERE THUNDERSTORM THREAT WILL DECREASE.
CURRENT SOLUTIONS SHOW ENOUGH INSTABILITY AND SHEAR FOR AN
EVENT...BUT AGAIN...WITH NO MODEL CONSISTENCY CONFIDENCE ON
TIMING/EXTENT IS LOW. 84

Oh, I almost forgot: Anybody have any ideas on what Houston can expect windwise? 20-30 mph? 40-50mph?

[unome]

chamber of commerce weather

http://www.srh.noaa.gov/hgx/

http://innovation.srh.noaa.gov/ROC/gcastgis/

http://www.weather.gov/

http://www.spc.noaa.gov/

http://www.ospo.noaa.gov/Products/atmosphere/spe/

love, love, love this time of year !

[snowman65]

What happened to the pre-Halloween cold front we were expecting??? Looks rather dull now

[srainhoutx]

What happened to the pre-Halloween cold front we were expecting??? Looks rather dull now

Not really. There remains so much uncertainty as to what actually happens to the deep trough and eventually closed upper low that develops to our W over the Great Basin that no one wants to bite on a final solution that is likely 6-7 days out.

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
147 AM EDT THU OCT 24 2013

VALID 12Z SUN OCT 27 2013 - 12Z THU OCT 31 2013

...OVERVIEW AND MODEL PREFERENCES...

THE RATHER EXTENDED PERIOD OF AMPLIFIED FLOW MAY REACH A TURNING
POINT LATE NEXT WEEK... BUT UNTIL THEN THE STRONG RIDGING IN THE
NE PACIFIC AND SE ALASKA SHOULD PERSIST/DOMINATE. 500MB HEIGHT
STANDARDIZED ANOMALY NEAR +3 TO +3.5 IS FORECAST TO LINGER NEAR
THE PANHANDLE AND ALLOW TROUGHING TO PLUNGE SOUTHWARD THROUGH THE
INTERIOR WEST CLOSING OFF A MID-LEVEL CENTER OVER ID/UT INTO CO.
THE SIMULTANEOUS EXTRATROPICAL TRANSITION OF TYPHOONS FRANCISCO
AND LEKIMA SHOULD MAINTAIN THE STRONG RIDGING AHEAD OF DEEP
TROUGHING ALONG 175W... INTO WHICH THE SYSTEMS SHOULD GRAVITATE.

THE ENSEMBLES CONTINUE TO SHOW A LARGE AMOUNT OF SPREAD IN BOTH
DEPTH/PATH/SPEED OF THE WESTERN TROUGHING. IN-HOUSE ENSEMBLE
CLUSTERING METHOD SHOWS A NEARLY EVEN SPLIT AMONG A MAJORITY OF
THE 70 GEFS/ECENS MEMBERS THAT END UP MORE THAN 1000 MILES APART
BY TUE/D5... LEAVING ESPECIALLY THE ECENS MEAN TO A BIMODAL
PATTERN. PREFERENCE REMAINS FOR A SLOWER SOLUTION THAT THE SEVERAL
RECENT DETERMINISTIC RUNS OF THE GFS/ECMWF HAVE SHOWN. A VARYING
BLEND BETWEEN THEM AND THE 18Z GEFS MEAN... WHICH WAS OVERALL
SLOWER THAN THE ECMWF ENSEMBLE MEAN... WAS USED FOR THE BASE OF
THE FORECAST. THE EC MEAN HAS TRENDED TOWARD LOWER HEIGHTS IN THE
WEST FROM ITS RUN 24 HRS AGO... AGAIN LENDING CREDENCE TOWARD THE
GEFS MEAN SOLUTION. AS THE ENERGY EXITS THE ROCKIES... IT IS QUITE
UNCLEAR AS TO WHAT SPEED AND WHETHER OR NOT IT WILL OPEN UP. OPTED
TO RELY ON THE GEFS MEAN BUT ENSEMBLE DIFFERENCES BY THU/D7 EXCEED
2000 MILES... SO ALMOST ANYTHING IS POSSIBLE.


...SENSIBLE WEATHER HIGHLIGHTS...

DESPITE THE SOUTHWARD PLUNGE OF 500MB HEIGHTS... COLDEST AIR AND
BULK OF RAIN/SNOW SHOULD FOCUS ALONG/EAST OF THE DIVIDE... THOUGH
THE ENTIRE WEST SHOULD EXPERIENCE A COOL DOWN. TIGHT PRESSURE
GRADIENT OVER MT/WY/CO SHOULD DEVELOP A ROBUST UPSLOPE EVENT WITH
A BRISK EAST WIND. NOT TO BE LEFT OUT... THE NORTHEASTERN THIRD OF
THE CONUS SHOULD SEE SOME PRECIP AS A COUPLE SYSTEMS SWING
TROUGH... WITH MUCH MORE UNCERTAINTY BY WED-THU/D6-7 TIED TO THE
WESTERN TROUGH EVOLUTION.


FRACASSO

[srainhoutx]

The trends via the 12Z suite of guidance is beginning to suggest a more neutral trough that being a more N to S axis ~vs~ that of a positive tilt that would favor a SW to NE axis that previous guidance had been suggesting as well as a further S track of the closed cold core upper low. What that mean regarding the sensible weather we could expect around Tuesday through Thursday of next week is a more likely chance of heavy snowfall accumulations across Northern New Mexico, the Texas and Oklahoma Panhandles and possibly extending E along the Red River Valley on N into Oklahoma and Kansas. Severe weather potential may have to be increased further S in the warm sector as the Gulf opens up and allows deep moisture returns ahead of that strong Winter like storm complex. Such a pattern also suggests a very strong cold front will drop S across all of Texas as rather chilly Canadian air is pulled S into the Plains as the storm system wraps up. Halloween could be very chilly with blustery cold NW to N winds. If we do see some snow fall across the Southern Plains, those breezes would bring the coldest air of the season into Central and SE Texas. We will see.

[snowman65]

I like it!!

[kayci]

I need 24 hr notice before I can officially go into hibernation.

[cperk]

I'm ready for some cold weather.

[Paul Robison]

The trends via the 12Z suite of guidance is beginning to suggest a more neutral trough that being a more N to S axis ~vs~ that of a positive tilt that would favor a SW to NE axis that previous guidance had been suggesting as well as a further S track of the closed cold core upper low. What that mean regarding the sensible weather we could expect around Tuesday through Thursday of next week is a more likely chance of heavy snowfall accumulations across Northern New Mexico, the Texas and Oklahoma Panhandles and possibly extending E along the Red River Valley on N into Oklahoma and Kansas. Severe weather potential may have to be increased further S in the warm sector as the Gulf opens up and allows deep moisture returns ahead of that strong Winter like storm complex. Such a pattern also suggests a very strong cold front will drop S across all of Texas as rather chilly Canadian air is pulled S into the Plains as the storm system wraps up. Halloween could be very chilly with blustery cold NW to N winds. If we do see some snow fall across the Southern Plains, those breezes would bring the coldest air of the season into Central and SE Texas. We will see.

Sounds like we'd could have an extremely serious weather emergency on our hands, srainhoutx.

GOD, SAVE ME FROM HOUSTON WEATHER!

[Andrew]

The trends via the 12Z suite of guidance is beginning to suggest a more neutral trough that being a more N to S axis ~vs~ that of a positive tilt that would favor a SW to NE axis that previous guidance had been suggesting as well as a further S track of the closed cold core upper low. What that mean regarding the sensible weather we could expect around Tuesday through Thursday of next week is a more likely chance of heavy snowfall accumulations across Northern New Mexico, the Texas and Oklahoma Panhandles and possibly extending E along the Red River Valley on N into Oklahoma and Kansas. Severe weather potential may have to be increased further S in the warm sector as the Gulf opens up and allows deep moisture returns ahead of that strong Winter like storm complex. Such a pattern also suggests a very strong cold front will drop S across all of Texas as rather chilly Canadian air is pulled S into the Plains as the storm system wraps up. Halloween could be very chilly with blustery cold NW to N winds. If we do see some snow fall across the Southern Plains, those breezes would bring the coldest air of the season into Central and SE Texas. We will see.

Sounds like we'd could have an extremely serious weather emergency on our hands, srainhoutx.

GOD, SAVE ME FROM HOUSTON WEATHER!

Trolling at its best right there.

[Paul Robison]

Want to know why there's a problem determining what's going to happen on Halloween? Dallas WX explains:

THE MID-WEEK SYSTEM REMAINS VERY PROBLEMATIC. FORECAST CONTINUITY
REMAINS POOR. AS AN EXAMPLE...FOR 12Z/7AM WEDNESDAY...THE GFS
SHOWS A CLOSED LOW IN THE TX PANHANDLE MOVING EAST. THE ECMWF HAS
A CLOSED LOW OVER THE NV/UT/AZ BORDERS MOVING EAST. THE CMC HAS A
CLOSED LOW OVER THE ND/SD/MT BORDER MOVING NORTHEAST. IF ONE WERE
TO USE THOSE THREE POINTS AS ENDPOINTS OF A TRIANGLE....THERE IS
OVER 180,000 SQUARE MILES OF AREA WHERE THE UPPER LOW COULD BE.
WHERE`S WALDO INDEED. (Heh-heh-heh) TRACING THE UPPER LOW BACK TO TODAY PLACES
IT IN THE NORTH PACIFIC SOMEWHERE SOUTH OF THE ALEUTIAN
ISLANDS...A DATA SPARSE AREA. WITHOUT A GOOD DETAILED
INITIALIZATION IT IS NO WONDER THE MODEL SOLUTIONS VARY SO
WIDELY.

Moral: Don't be an Alaska weatherman!

BTW: I don't want to see this cold front cause HER to have to go to work here:
http://www.youtube.com/watch?v=WxKqhOdh86I

[MontgomeryCoWx]

Come on cold weather!!!!! I'm ready to fire up the fire pit and wear warm weather clothes.

It's time to send Summer back where it belongs.... hell.

[srainhoutx]

After a week of pleasant weather across the Region, changes are ahead with a very complex and complicated forecast as we head toward the end of October. Rain chance look to increase to about a 30-40% range Saturday night into Sunday as upper air disturbance nearing New Mexico travels E across N Texas. A return flow off the Gulf has began and should continue into early next week and increased available moisture streaming inland. A deep Western trough is still in the cards with a variety of weather across the Great Basin and Inter Mountain West. As the trough digs deeper into the Great Basin, a closed upper low should develop and that feature is what the guidance is having a great deal of difficulty determining what the sensible weather will be as we head into mid next week. The European guidance remains slower while the GFS has flipped bay to a more positive tilted open wave pattern and is faster with that trough arriving. It will likely be a another day or two before we see some consensus in the models, but all in all it does appear that an active weather pattern may well develop in the Tuesday through Thursday time frame.



DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0400 AM CDT FRI OCT 25 2013

VALID 281200Z - 021200Z

...DISCUSSION...
AN ACTIVE/MULTI-DAY SEVERE RISK WILL BE A DISTINCT POSSIBILITY FOR
AT LEAST PARTS OF THE SOUTH-CENTRAL CONUS ESPECIALLY AROUND DAYS 5-6
TUESDAY/WEDNESDAY...AND PERHAPS INTO DAY 7/THURSDAY. WHILE AT LEAST
CATEGORICAL SLIGHT RISKS SEEM POSSIBLE ON ONE OR MORE
DAYS...CONSIDERABLE GUIDANCE VARIABILITY REGARDING THE EVOLUTION OF
THE SOUTHWEST STATES UPPER TROUGH PRECLUDES ANY SPECIFIC DELINEATION
OF 30 PERCENT EQUIVALENT SEVERE RISK AREAS. IN GENERAL...THE 00Z
ECMWF FEATURES A MUCH SLOWER SOLUTION AS COMPARED TO THE FASTER/MORE
POSITIVE-TILT 00Z GFS/UKMET GUIDANCE.

THAT SAID...CURRENT SPECULATIONS ARE THAT SOME SEVERE TSTMS MAY BE
POSSIBLE ACROSS THE SOUTHERN HIGH PLAINS SUCH AS WEST/NORTHWEST TX
INTO WESTERN OK ON DAY 5/TUESDAY...WITH STRONGER TSTMS POTENTIALLY
ALSO POSSIBLE ACROSS SOUTHERN PORTIONS OF AZ/NM. A MORE WIDESPREAD
SEVERE RISK COULD OCCUR ACROSS THE SOUTHERN PLAINS INTO DAY
6/WEDNESDAY...WITH ALL SEVERE FACETS POTENTIALLY POSSIBLE ESPECIALLY
ACROSS OK/TX AND PERHAPS PORTIONS OF KS/ARKLATEX.

..GUYER.. 10/25/2013

[djjordan]

I'll wait for better model agreement before begging Houston be spared from the sharknado...

LOL Ed ..... now that's funny!!!!!

[srainhoutx]

Afternoon update from Jeff:
Short wave currently over the SW US will move across TX over the next 24-36 hours bringing a quick shot at rainfall.

Moisture is slowly increasing as noted by surface observations and visible images showing a widespread cumulus field SW of Matagorda Bay into the TX Hill Country. Winds will continue to veer to the ESE and SE tonight allowing Gulf moisture return to begin. Lift from the short wave will come to bear across areas N of I-10 Saturday evening into Sunday with scattered showers and thunderstorms possible. Greatest chances will be over our northern counties with lowering rain chances toward the coast.

Short wave exits to the east Sunday, but low level flow remains onshore with Gulf moisture advection continuing. This is all ahead of a healthy looking storm system for the middle of next week. Models are still not in great agreement on when this system will affect the area, but unfortunately it does appear to be some consensus that Halloween could be fairly rough. System looks fairly potent so a severe weather outbreak in the warm sector Wednesday into Thursday is possible. Not as much cooling indicated behind the front, but the latest GFS run keeps mid and high level moisture in place, so skies may not clear out. Still plenty of time to watch and hope for a faster or slower frontal passage to get the main impacts off Halloween.

Smoke:

Dense smoke event from a large wildfire of SW Jefferson County in progress this afternoon over much of Galveston Bay into metro Houston. Radar showed fire spiked to nearly 30dbz this afternoon likely helped by gusty seabreeze winds. Visible images show a dense plume of Chambers County into Galveston Bay and smoke as far west as Columbus. ESE transport winds will result in continued smoke advection into metro  Houston and most areas S of I-10. Winds weakening tonight will allow for some potentially low visibilities in smoke. These types of situations when mixed with ground fog can reduce visibilities to less than .25 of a mile and have in the past caused some large car pile-ups on I-10 east.

[srainhoutx]

GFS still ends rainfall just before trick or treating.

I guess most kids would prefer that.

And a tenth to a quarter this weekend and an inch to an inch and a quarter with the Halloween/pre-Halloween storm, that isn't terrible. Heaviest rain just after sunrise on Halloween would limit instability.

Summer like lapse rates/PW (skinny CAPE) and unidirectional winds suggests any severe threat Thursday morning would be marginal, gusty winds from precip loading. PW over 2.2 inches almost to November is pretty impressive.

Althuogh the severe risk per GFS doesn't look great, Paul should continue to stock milk and toilet paper, and flashlight batteries, because you just never know.

The WPC is going with a bit slower solution on the arrival of the front. If the Euro and the various ensembles are correct that the progression of the trough and associated upper air energy is a bit slower to eject out of the Great Basin across the Southern Rockies, it could be a stormy evening as the kids head out for their Halloween festivities.

[Andrew]

One thing that is of interest to me is the possible severe weather around Oklahoma/ Upper Texas border. Still low on confidence with each model run showing something different, but something definitely to keep an eye on.

[TexasBreeze]

The line of storms up north currently messing with the TCU and Horns game looks like it is going more east than south. Unless the whole boundary creating it moves south, I don't think much will make it here. The mid-week system could be the one to watch!

[unome]

it's here now

http://forecast.weather.gov/wwamap/wwat ... %20warning

SEVERE THUNDERSTORM WARNING
TXC201-339-271030-
/O.NEW.KHGX.SV.W.0132.131027T1004Z-131027T1030Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
504 AM CDT SUN OCT 27 2013

THE NATIONAL WEATHER SERVICE IN LEAGUE CITY HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
SOUTHERN MONTGOMERY COUNTY IN SOUTHEAST TEXAS...
SOUTHWESTERN HARRIS COUNTY IN SOUTHEAST TEXAS...

* UNTIL 530 AM CDT

* AT 503 AM CDT...DOPPLER RADAR INDICATED A SEVERE THUNDERSTORM
CAPABLE OF PRODUCING DAMAGING WINDS IN EXCESS OF 60 MPH. THIS
STORM WAS LOCATED TOMBALL AND SPRING...AND MOVING SOUTHEAST AT 40
MPH. PENNY SIZE HAIL MAY ALSO ACCOMPANY THE DAMAGING WINDS.

* LOCATIONS IMPACTED INCLUDE...
HUMBLE...GALENA PARK...TOMBALL...JACINTO CITY...NORTHSIDE /
NORTHLINE...NEAR NORTHSIDE HOUSTON...ALDINE...GREATER FIFTH WARD...
CLOVERLEAF...SPRING...GREATER GREENSPOINT...THE WOODLANDS...
BARRETT...SECOND WARD...CHANNELVIEW...KINGWOOD...CROSBY...OAK RIDGE
NORTH...SHENANDOAH AND HIDDEN VALLEY.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

SEVERE THUNDERSTORMS PRODUCE DAMAGING WINDS...DESTRUCTIVE HAIL...
DEADLY LIGHTNING AND VERY HEAVY RAIN. FOR YOUR PROTECTION...MOVE TO
AN INTERIOR ROOM ON THE LOWEST FLOOR OF YOUR HOME OR BUSINESS. HEAVY
RAINS FLOOD ROADS QUICKLY SO DO NOT DRIVE INTO AREAS WHERE WATER
COVERS THE ROAD.

TO REPORT SEVERE WEATHER...CONTACT YOUR NEAREST LAW ENFORCEMENT
AGENCY. THEY WILL RELAY YOUR REPORT TO THE NATIONAL WEATHER SERVICE
OFFICE IN LEAGUE CITY .

&&

LAT...LON 3006 9561 3018 9546 2989 9505 2970 9527
TIME...MOT...LOC 1003Z 314DEG 34KT 3007 9548
$$

[txflagwaver]

Guess we are going to get our traditional storm before Halloween. Glad I did not put the spider webs out yet.