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

General Weather Discussions and Analysis
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
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MontgomeryCoWx
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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.
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srainhoutx
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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.

Image

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
Carla/Alicia/Jerry(In The Eye)/Michelle/Charley/Ivan/Dennis/Katrina/Rita/Wilma/Humberto/Ike/Harvey

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djjordan
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Ed Mahmoud wrote:I'll wait for better model agreement before begging Houston be spared from the sharknado...
LOL Ed ..... now that's funny!!!!!
~~~When Thunder Roars Go Indoors~~~
~~~Turn Around Don't Drown~~~
~~~Run From The Water, Hide From The Wind~~~
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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.
Carla/Alicia/Jerry(In The Eye)/Michelle/Charley/Ivan/Dennis/Katrina/Rita/Wilma/Humberto/Ike/Harvey

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srainhoutx
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Ed Mahmoud wrote: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.
Attachments
1026203 Day 3 to 7 Surface Charts 5dayfcst_wbg_conus.gif
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Andrew
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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.
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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
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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
$$

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Image
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Guess we are going to get our traditional storm before Halloween. Glad I did not put the spider webs out yet.
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thunder lightning and torrential downpours!!!! what a way to bw awaken on a sunday morning!!! is it colder behind the front?
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About .80" after the heavy line so far here in Katy and 61 degrees
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Well it made it here! Been raining all morning and had a well defined bow echo move through. More needed benificial rain!
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What has happened to all of our khou local/county radars?
Paul Robison

Not sure whether or not I should feel better even though I saw this:

Image


Now, seriously, people: Who out there expects the damage from the Halloween storms to be even worse than today's? Is this front analagous to the massive storm that is currently threatening the U.K? Look:
http://www.mirror.co.uk/news/uk-news/uk ... us-2645894
http://www.click2houston.com/news/Brita ... index.html
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Morning e-mail from Jeff:

Significant storm system will bring severe weather and heavy rainfall to the southern plains by the middle of the week.

Robust short wave on Sunday morning brought a line of strong to severe thunderstorms to the region and widespread soaking rainfall. Wind damage from two bow echoes affected southern Montgomery into NE Harris and Liberty Counties with the second affecting Waller into western Harris into northern Galveston County.

This short wave has moved eastward with a low level boundary having pushed offshore yesterday afternoon. Water vapor images show the next important weather makers dropping southward through the western US and will drop into the SW US today and then begin to track eastward. This will result in increasing SE winds and onshore flow from midday morning today through mid week. Low level moisture will increase as the Gulf opens up. Position of the trough over the SW US will help guide mid and high level moisture from Hurricane Raymond toward the state by mid week. Large storm system will eject into the high plains on Wednesday with its cold front pushing southward across TX Wednesday and Thursday. Moisture values continue to deepen and peak in the 2.0-2.3 inch of PW range by early Thursday morning. Strongest wind energy and dynamics appear aimed at N TX and northward, but there will be some decent wind energy over our area with a strong low level jet of 30-40kts just off the surface by Thursday morning.

Appears the warm sector may be capped on Wednesday, but with moisture increasing to summer levels and upper air disturbances ejecting across in the SW flow aloft, think rain chances will begin to increase after lunch on Wednesday. Main dynamics and slow moving frontal boundary arrive into the area on Thursday. Suspect a well organized line of thunderstorms over N and C TX Thursday morning will sweep ESE/SE into the area during the day on Thursday. Some severe weather and very heavy rainfall looks possible. Think the heavy rainfall threat is greater than the severe threat at this time given the saturated moisture profiles and potential for a slowing frontal boundary and cell training along this boundary. Front should be near the coast or offshore by late afternoon, but rain may linger in the post frontal air mass for a period of time into the evening hours. Current timing of weather could be a little on the slow side should a well defined complex of storms develop which would help speed things up a bit.

Drier air should finally filter in by Friday morning clearing skies and ending rain chances.
Carla/Alicia/Jerry(In The Eye)/Michelle/Charley/Ivan/Dennis/Katrina/Rita/Wilma/Humberto/Ike/Harvey

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What happened with all the talk about a blue northern? Has that gone out the window? Is the front right after halloween, was that "supposed" to be the blue northern?
Mike
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(IH-10 & College Street)
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Yes Mike, this is the one that was supposed to be the blue norther, which it won't be. Just forecasters hyping up what models were showing well over a week ago. You figured they would of learned by now.
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redneckweather wrote:Yes Mike, this is the one that was supposed to be the blue norther, which it won't be. Just forecasters hyping up what models were showing well over a week ago. You figured they would of learned by now.
I don't think anyone was hyping anything up. I feel like it is forgotten sometimes what this forum (and most forums of this nature) is about. This forum is a place for individuals to gather around and discuss weather in both the general and technical sense. It is a place to learn, forecast, and have fun at the same time. This site is not a place of paid forecasts that generate forecasts for your well being. There are many other places (NWS, NHC, HPC) that are paid to make these forecasts and if you notice, they don't forecast 2-3 weeks in advance for that specific reason. What this site does do is allow people to look into not only the short range but the longer range forecasts. I don't think there was a single person who said with certainty that there was going to be a "blue norther". There were individuals who speculated on this possibility from the synoptic patterns that were presented, and made educated forecasts because of this. Longer range models did a fantastic job at forecasting the magnitude of this trough so far out and I feel like a lot of people picked up on this. Yes the degree of cold air advection is less than originally forecasted, but the central plains severe weather and degree of cold air that will make it south will still be nice for late October. So I don't think it is right to call anyone out on a site that is specifically focused on the forecasts and possibilities that other sites can't make due to the uncertainty that exists. Of course that is just my two cents.
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