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

[Paul Robison]

What bothers me, Texas Pirate, is the duration of any power outages that may occur. If those thunderstorms get REALLY nasty, some people, myself included, would probably end up spending several days, maybe even a week, in the dark. Center Point is THAT slow, sometimes.

[Texas Pirate]

Then by all means fire up that generator!

[srainhoutx]

Paul, by all means buy into the hype of Accuweather if you so choose and even TWC since I hear they have a TORCON of 3 already out as a forecast. The main issue at this time looks to be the flood threat from slow moving training storms and the greatest threat for that very heavy rain is along the I-35 Corridor from Austin on NE into Dallas and possibly into the Bryan/College Station area on E to Lake Livingston. If the upper trough and attending low pressure system currently over Nevada is a little slower and doesn't push through SE Texas during the daytime hours of Halloween, then we could see some stronger storms. I sort of doubt 2 million customers will be without power at one time like we were during Ike, so we can leave that nonsense out of our discussions.

[tireman4]

What I worry about is that my son's soccer practice will be rained out. It is on for Wednesday at 6 pm. I am thinking no way.

[Ptarmigan]

I don't think 2 days is enough time after 3 or 5 inches of rain for the dirt and gravel parking lots at Texas Motor Speedway to dry. Clear skies and fairly low humidities will help DTO area dry out Thursday and Friday. Lets hope it is enough.


2.2 inch or above PWs, Wednesday night/Thursday rains, potential ugly commutes.

And again, although I doubt millions wind up in the dark for weeks, despite somewhat meager instability (but ~500J/Kg can sometimes get the job done with ~350 J/Kg helicity and cloud bases 500 meters up) GFS soundings suggest an isolated weak tornado or three is possible early Thursday morning.

I am more worried about flooding than the severe thunderstorms on Halloween.

[tireman4]

What I worry about is that my son's soccer practice will be rained out. It is on for Wednesday at 6 pm. I am thinking no way.

It is looking bleaker and bleaker by the moment.


Wednesday Showers and thunderstorms likely, mainly after 1pm. Mostly cloudy, with a high near 80. Southeast wind 10 to 15 mph, with gusts as high as 20 mph. Chance of precipitation is 70%.
Wednesday Night Showers and thunderstorms. Some of the storms could produce heavy rain. Low around 73. South wind 10 to 15 mph. Chance of precipitation is 80%.

[Texas Pirate]

What I worry about is that my son's soccer practice will be rained out. It is on for Wednesday at 6 pm. I am thinking no way.

I am working TV production for the Dynamo Soccer Game at BBVA Stadium on Thursday - its an OPEN STADIUM....who created that concept?
I know it will be slippin and sliddin time and a little soccer thrown in.

[srainhoutx]

The WPC (HPC) has increased their Excessive Rainfall forecast to a Moderate Risk for NE Texas extending into the Little Rock area. Areas NW of Austin into the Metroplex are in a Slight Risk.

[unome]

days 1-3 QPF, not bad !

[Katdaddy]

Heavy rainfall event still forecasted by the models for SE TX. This afternoon's Hou-Gal AFD indicates a small window from early Thursday into late morning for possible severe weather. The million dollar question remains……will trick or treating be a washout or just wet streets? Hopefully a much better idea Halloween morning.

[Paul Robison]

A response Eric Berger gave to me on his blog about the midweek halloween storms:


Paul Robison says:
October 29, 2013 at 5:40 pm
What can Center Point Energy customers expect Wednesday and Thursday, Eric?


Eric Berger says:
October 29, 2013 at 5:53 pm
Possible power outages.

Two concerns:

1.It's been my understanding, though, that the best chance for severe thunderstorms lies in points north of I-10, true?

2. Somebody please tell me that Eric's wrong!

[unome]

HGX updated Youtube http://youtu.be/wqp-72oHq7s

[Paul Robison]

HGX updated Youtube http://youtu.be/wqp-72oHq7s

Thanks for the video, unome. The forecaster said areas north and northeast of Houston stand a slight chance of getting severe T-storms, right? Is that a Center Point service region?

[srainhoutx]

Evening update from Jeff:

Heavy Rainfall and flooding possible Wednesday/Thursday.

Factors coming together to produce a period of excessive rainfall across much of eastern TX over the next 36 hours. A powerful upper level storm system over the SW US will be moving into the southern plains on Wednesday and this will send a slow moving frontal boundary southward into TX. Tremendous tropical moisture advection from the NW Caribbean to the TX coast along with moisture streaming NE from EPAC tropical cyclone Raymond will push PWS into the maximum category for this time of year. PWS are forecasted to exceed 2.0 inches and may reach 2.3 inches which put in other words will be August like “tropical moisture” being worked on by strong winter like dynamics. A strong low level jet of 40-50kts will develop on Wednesday and help feed a continuous supply of tropical moisture northward into developing convection. Upper level winds will become increasingly divergent favoring sustained lift and the approaching frontal boundary/any meso scale outflow boundaries will aid in strong low level lift. Everything appears in place for a classic high rainfall/flash flood event over NE TX into SE TX.

Expect disturbances riding up in the SW flow aloft to begin to develop showers and thunderstorms Wednesday morning with rain chances increasing during the day. Expect fairly fast storm motions to limit rainfall amounts on Wednesday, but this will only help wet an already wet ground over the area. Main event looks to be late Wednesday night into much of Halloween. Slow motion frontal boundary will focus deep and near continuous convection with excessive rainfall rates. Upper flow nearly parallel to the boundary supports prolonged cell training of excessive rainfall. Saturated forecast profiles and deep warm layer will support little evaporation and maximum rainfall production from storm cores. Hourly rates of 2-3 inches are likely under the heavy rain cores.

Widespread rainfall of 2-3 inches is becoming likely with isolated totals up to 6 inches. Focused cell training will determine where these maximum amounts fall, but best estimations at the moment are north of I-10 where dynamics will be the strongest. Exact location of any flooding rainfall will not be known until the event is well underway and training bands establish. Given the recent rainfall and wet grounds, run-off generation will be greater than the previous events in October. Additionally, the widespread nature of this event will likely impact river conditions with rises likely on most mainstem points. Urban flooding will also be possible given the high hourly rainfall rates.

A marginal severe weather threat will also reside across mainly the eastern and northeastern parts of the area…roughly from College Station to Conroe to Galveston. Low level shear does become fairly strong Thursday morning, but instability is lacking. Such dynamic systems in very moist air masses can produce low topped supercells that produce brief weak tornadoes. Not looking at widespread severe weather, but a weak tornado or two/or a damaging wind gust is possible.

Halloween Evening:

Larger scale models are a little faster at pushing the large rainfall axis toward the coast by sunset on Thursday. Some of the shorter range models are slower and keep widespread activity going into the evening hours. With meso scale processes likely guiding some of the activity on Thursday, I would not put much faith in any particular model solution nor attempt to time the exact rainfall ending time. Do think the NW counties will likely be drying out by 5-6pm, metro Houston is much more debatable, and the coast looks fairly wet. Will not have much better timing until likely Thursday morning to see how the activity evolves during the day.

 

[Paul Robison]

Evening update from Jeff:

Heavy Rainfall and flooding possible Wednesday/Thursday.

Factors coming together to produce a period of excessive rainfall across much of eastern TX over the next 36 hours. A powerful upper level storm system over the SW US will be moving into the southern plains on Wednesday and this will send a slow moving frontal boundary southward into TX. Tremendous tropical moisture advection from the NW Caribbean to the TX coast along with moisture streaming NE from EPAC tropical cyclone Raymond will push PWS into the maximum category for this time of year. PWS are forecasted to exceed 2.0 inches and may reach 2.3 inches which put in other words will be August like “tropical moisture” being worked on by strong winter like dynamics. A strong low level jet of 40-50kts will develop on Wednesday and help feed a continuous supply of tropical moisture northward into developing convection. Upper level winds will become increasingly divergent favoring sustained lift and the approaching frontal boundary/any meso scale outflow boundaries will aid in strong low level lift. Everything appears in place for a classic high rainfall/flash flood event over NE TX into SE TX.

Expect disturbances riding up in the SW flow aloft to begin to develop showers and thunderstorms Wednesday morning with rain chances increasing during the day. Expect fairly fast storm motions to limit rainfall amounts on Wednesday, but this will only help wet an already wet ground over the area. Main event looks to be late Wednesday night into much of Halloween. Slow motion frontal boundary will focus deep and near continuous convection with excessive rainfall rates. Upper flow nearly parallel to the boundary supports prolonged cell training of excessive rainfall. Saturated forecast profiles and deep warm layer will support little evaporation and maximum rainfall production from storm cores. Hourly rates of 2-3 inches are likely under the heavy rain cores.

Widespread rainfall of 2-3 inches is becoming likely with isolated totals up to 6 inches. Focused cell training will determine where these maximum amounts fall, but best estimations at the moment are north of I-10 where dynamics will be the strongest. Exact location of any flooding rainfall will not be known until the event is well underway and training bands establish. Given the recent rainfall and wet grounds, run-off generation will be greater than the previous events in October. Additionally, the widespread nature of this event will likely impact river conditions with rises likely on most mainstem points. Urban flooding will also be possible given the high hourly rainfall rates.

A marginal severe weather threat will also reside across mainly the eastern and northeastern parts of the area…roughly from College Station to Conroe to Galveston. Low level shear does become fairly strong Thursday morning, but instability is lacking. Such dynamic systems in very moist air masses can produce low topped supercells that produce brief weak tornadoes. Not looking at widespread severe weather, but a weak tornado or two/or a damaging wind gust is possible.

Halloween Evening:

Larger scale models are a little faster at pushing the large rainfall axis toward the coast by sunset on Thursday. Some of the shorter range models are slower and keep widespread activity going into the evening hours. With meso scale processes likely guiding some of the activity on Thursday, I would not put much faith in any particular model solution nor attempt to time the exact rainfall ending time. Do think the NW counties will likely be drying out by 5-6pm, metro Houston is much more debatable, and the coast looks fairly wet. Will not have much better timing until likely Thursday morning to see how the activity evolves during the day.

Well, I must be safe from the severe stuff, since I live on the Southwest side of Houston. Somebody still hasn't told me whether or not Eric's right about "possible power outages," though.

[nairbecaps]

I think what Paul is trying to say is, "Katy, start your engines!"

(I was waiting all summer to try to post that somewhere...)

[biffb816]

Well, I must be safe from the severe stuff, since I live on the Southwest side of Houston. Somebody still hasn't told me whether or not Eric's right about "possible power outages," though.

Until Frankie MacDonald posts a video about it, I wouldn't worry too much. Maybe go ahead and get your pizzas and Chinese food just to be safe.

Edit - Oops, Frankie has a video up now.

[Paul Robison]

Well, I must be safe from the severe stuff, since I live on the Southwest side of Houston. Somebody still hasn't told me whether or not Eric's right about "possible power outages," though.

Until Frankie MacDonald posts a video about it, I wouldn't worry too much. Maybe go ahead and get your pizzas and Chinese food just to be safe.

Edit - Oops, Frankie has a video up now.

Who's Frankie MacDonald? Where is this video?

[Katdaddy]

Deep Gulf moisture is streaming N into SE TX with areas of showers and thunderstorms developing over the area. Heavy rains and the potential for severe weather beginning tonight and into Halloween. Flash Flood Watches for Central and NE TX …..would not be surprised to see SE TX included this afternoon. The Hou-Gal morning area forecast discussion has some good news for now regarding trick or treating:

VAST MAJORITY OF MODELS ARE ACTUALLY IN EXCELLENT AGREEMENT SHIFTING ALMOST ALL THE PRECIP OFFSHORE BY 7PM FOR THE TRICK-OR-TREATERS. GALVESTON/CHAMBERS COUNTY BEACHES MAY NEED ANOTHER HOUR OR SO BUT CONFIDENCE IS QUITE HIGH AT THIS TIME.

[srainhoutx]

The radar trends this morning are a bit worrisome. It appears that PW's of 2.5 Inches has arrived earlier than expected and the storm system and associated cold front to our W is still about 36 hours away. I would not be surprised to see Flash Flood Watches hoisted for a large potion of SE Texas later today. Keep an eye on the weather as we near the evening drive time and tonight when convective activity will likely ramp up and more widespread heavy training rainfall begins in earnest.