November 2014: Nice Seanonal Thanksgiving Ahead

General Weather Discussions and Analysis
SLM87TX
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So basically

Sun=Bad Weather

Cloud/Rain=Not as Bad Weather?
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SLM87TX wrote:So basically

Sun=Bad Weather

Cloud/Rain=Not as Bad Weather?
Not necessarily. It mainly means that less sun would decrease tornado chances but with such a dynamic system with plenty of forcing expect a good chance of strong winds with or without sun. Especially if you are to the SW of College Station to Houston line .
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SLM87TX
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What will general storm movement be sw of this line?
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SLM87TX wrote:What will general storm movement be sw of this line?

General individual cell movement will be to the Northeast and the eventual line/ front will be to the East-ENE.
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SLM87TX
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Will these storms be like the standard supercell you see in the midwest where the hooks would be on the SW side of the storm? Or would the discrete storms have them on the leading edge?
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SLM87TX wrote:Will these storms be like the standard supercell you see in the midwest where the hooks would be on the SW side of the storm? Or would the discrete storms have them on the leading edge?

Any single cells ahead of the main boundary could produce tornadoes, but expect HP (high precip) super cells. Most likely won't see too many classic hook type cells. Could see some rotation along the MCS
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SPC AC 211730

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1130 AM CST FRI NOV 21 2014

VALID 221200Z - 231200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS A LARGE PORTION OF TX
EWD INTO THE CENTRAL GULF COAST REGION...

...THERE IS A MRGL RISK OF SVR TSTMS FROM TX TO THE FL PANHANDLE...

...SUMMARY...
STRONG/SCATTERED SEVERE STORMS ARE EXPECTED TO DEVELOP FROM CENTRAL
TEXAS SOUTHEASTWARD TO THE TEXAS GULF COAST ON SATURDAY. OTHER
STRONG/LOCALLY SEVERE STORMS ARE POSSIBLE FROM SOUTHERN LOUISIANA
INTO SOUTHERN MISSISSIPPI SATURDAY NIGHT. PRIMARY THREATS WILL BE
LOCALLY DAMAGING WIND AND A FEW TORNADOES.

...SYNOPSIS...
AMPLIFICATION OF THE LARGE-SCALE PATTERN IS EXPECTED OVER THE U.S.
SATURDAY...AS NRN-STREAM SHORT-WAVE TROUGHING DIGGING SEWD ACROSS
THE WRN U.S. GRADUALLY PHASES WITH A SRN-STREAM TROUGH SHIFTING
ACROSS NRN MEXICO/TX WITH TIME. BY SUNDAY MORNING...CYCLONIC FLOW
IS PROGGED TO ENCOMPASS A BROAD SWATH OF THE U.S. FROM THE W COAST
EWD TO THE MS VALLEY VICINITY.

AT THE SURFACE...A COLD FRONT ASSOCIATED WITH THE AFOREMENTIONED
NRN-STREAM TROUGH IS PROGGED TO CROSS THE ROCKIES AND EMERGE INTO
THE NRN AND CENTRAL PLAINS STATES OVERNIGHT. MEANWHILE...MUCH
WEAKER SURFACE RESPONSE IS PROGGED ACROSS THE SRN PLAINS AS THE SRN
STREAM UPPER SYSTEM EMERGES -- WITH A WEAK CYCLONE LIKELY TO CROSS
PARTS OF SRN/ERN TX THROUGH THE PERIOD.

...TX EWD INTO THE CENTRAL GULF COASTAL AREAS...
NNWWD RETURN OF PARTIALLY MODIFIED GULF MOISTURE WILL CONTINUE
SATURDAY ACROSS THE SRN PLAINS...AHEAD OF THE APPROACHING MID-LEVEL
SRN-STREAM FEATURE. RESULTING MODEST DESTABILIZATION --
PARTICULARLY ABOVE A LIKELY-TO-BE-CLOUDY BOUNDARY LAYER -- IN
CONJUNCTION WITH THE BROAD/INCREASING ASCENT SPREADING OVER THE
REGION IS EXPECTED TO YIELD WIDESPREAD CONVECTIVE DEVELOPMENT. AS A
RESULT OF THE PERSISTENT BOUNDARY-LAYER CLOUDINESS AND INCREASINGLY
WIDESPREAD PRECIPITATION...DEEP/MOIST-ADIABATIC THERMODYNAMIC
PROFILES ARE EXPECTED TO PREVAIL ACROSS MUCH OF THE REGION. GIVEN
THIS...AND A STORM MODE LIKELY TO FAVOR NUMEROUS CLUSTERS OF STORMS
ACROSS A LARGE AREA...OVERALL SETUP DOES NOT APPEAR TO FAVOR A MORE
SUBSTANTIAL SEVERE WEATHER EVENT DESPITE THE ADVANCE OF THE
RELATIVELY VIGOROUS UPPER SYSTEM.

WITH THAT SAID...A FEW STRONGER CELLS WILL LIKELY EVOLVE -- MOST
LIKELY ALONG THE SRN AND WRN FRINGES OF THE MORE WIDESPREAD
CONVECTIVE ZONE...WHERE STEEPER LAPSE RATES/GREATER CAPE SHOULD
RESIDE. GIVEN SHEAR SUPPORTIVE OF ORGANIZED UPDRAFTS...THESE
THERMODYNAMICALLY FAVORED ZONES SUGGEST THAT RISK FOR LOCALLY
DAMAGING WINDS AND A COUPLE OF TORNADOES WILL BE POSSIBLE...AND
PERHAPS A FEW INSTANCES OF MARGINALLY SEVERE HAIL.

GIVEN THESE CONCERNS...WILL OPT TO CARRY ONLY SLIGHT RISK/15%
PROBABILITY THIS FORECAST. ONCE ANY MORE FAVORABLE SMALLER-SCALE
CORRIDORS OF POTENTIAL TORNADO RISK BECOME EVIDENT...A DAY 1 UPGRADE
TO 10% TORNADO PROBABILITY/ENHANCED RISK MAY BECOME NECESSARY.

LATER IN THE PERIOD...LIMITED SEVERE RISK IS EXPECTED TO SPREAD EWD
ACROSS PARTS OF LA AND INTO SRN MS/AL IN CONJUNCTION WITH THE
CONTINUED EWD ADVANCE OF THE UPPER SYSTEM. LOCALLY GUSTY WINDS AND
A TORNADO OR TWO WILL BE POSSIBLE ACROSS THESE AREAS.

..GOSS.. 11/21/2014
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tireman4
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First, a big kudos to Andrew for taking time out of his busy day ( trust me, he is busy folks..LOL) to answer these questions. We appreciate it. As the timing and idea of what, where and how this affects comes into clearer view tonight and tomorrow, please be weather wary.
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tireman4 wrote:First, a big kudos to Andrew for taking time out of his busy day ( trust me, he is busy folks..LOL) to answer these questions. We appreciate it. As the timing and idea of what, where and how this affects comes into clearer view tonight and tomorrow, please be weather wary.

Trust me it's hard to concentrate with weather going on outside. Plus everyone else is busy including yourself but we all do a great job of answering each others questions. Later tonight when hi-res models come in a better update can be given.
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tireman4
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Andrew wrote:
SLM87TX wrote:Will these storms be like the standard supercell you see in the midwest where the hooks would be on the SW side of the storm? Or would the discrete storms have them on the leading edge?

Any single cells ahead of the main boundary could produce tornadoes, but expect HP (high precip) super cells. Most likely won't see too many classic hook type cells. Could see some rotation along the MCS
Yeah, it is the MCS is what is worrying me. It was mentioned long track tornadoes, but I am not thinking that..right now...
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The 12Z Texas Tech 4km WRF continues to advertise a rather potent MCS developing near Victoria and heading NE across Metro Houston into the Piney Woods of E Texas into Louisiana. Remember this is a cold core upper low with a lot of dynamics that generally cannot be accurately predicted beyond 6 to 10 hours... ;)
Carla/Alicia/Jerry(In The Eye)/Michelle/Charley/Ivan/Dennis/Katrina/Rita/Wilma/Humberto/Ike/Harvey

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tireman4
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And that is what worries me....LOL
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So much for an upgrade, at least for now. I suspect we'll be stuck in the soup.
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srainhoutx wrote:The 12Z Texas Tech 4km WRF continues to advertise a rather potent MCS developing near Victoria and heading NE across Metro Houston into the Piney Woods of E Texas into Louisiana. Remember this is a cold core upper low with a lot of dynamics that generally cannot be accurately predicted beyond 6 to 10 hours... ;)
Actually, that is the 6z run of the TTU WRF. The 12z run is currently running and is out through 20 hours so far. ;)
But yes, that model run has been pretty consistently showing an MCS affecting the Houston area tomorrow.
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srainhoutx
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South_Texas_Storms wrote:
srainhoutx wrote:The 12Z Texas Tech 4km WRF continues to advertise a rather potent MCS developing near Victoria and heading NE across Metro Houston into the Piney Woods of E Texas into Louisiana. Remember this is a cold core upper low with a lot of dynamics that generally cannot be accurately predicted beyond 6 to 10 hours... ;)
Actually, that is the 6z run of the TTU WRF. The 12z run is currently running and is out through 20 hours so far. ;)
But yes, that model run has been pretty consistently showing an MCS affecting the Houston area tomorrow.

Opps. I had clicked on the TT 12km ensemble run for 12Z ... :P
11212014 12Z  TT WRF 12km dom_12kmmean_sfc_dbz_f41.gif
Carla/Alicia/Jerry(In The Eye)/Michelle/Charley/Ivan/Dennis/Katrina/Rita/Wilma/Humberto/Ike/Harvey

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South_Texas_Storms wrote:
srainhoutx wrote:The 12Z Texas Tech 4km WRF continues to advertise a rather potent MCS developing near Victoria and heading NE across Metro Houston into the Piney Woods of E Texas into Louisiana. Remember this is a cold core upper low with a lot of dynamics that generally cannot be accurately predicted beyond 6 to 10 hours... ;)
Actually, that is the 6z run of the TTU WRF. The 12z run is currently running and is out through 20 hours so far. ;)
But yes, that model run has been pretty consistently showing an MCS affecting the Houston area tomorrow.
Also showing some nice localized helicity updrafts with some of those storms that track close to the Houston area. 0-3km EHI values show strong returns too. These stronger storms are embedded in the MCS but are associated with the stronger mid level Jet once the shortwave gets closer. 700mb winds are also showing more promise, especially from the Euro which lags the LLJ behind more than previously. If that is the case I suspect storms could hold off some throughout the day tomorrow. I just have trouble seeing widespread elevated convection at 15z tomorrow like the NAM and GFS (to some degree) are showing. Timing (as usual) is a big concern but looks a lot more promising. Still see two camps between models, the GFS and NAM v.s. the Euro.
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BlueJay
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I see that the UH v. Tulsa football game has been rescheduled for tomorrow morning (pre-game is 9:30 am) instead of the original 2:00 pm kickoff. http://www.khou.com/story/sports/colleg ... /19342713/

I hope that the game can be safely played and everyone is out of the stadium before the bad weather hits.

Go Coogs!
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srainhoutx
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Update from Jeff:

Severe Weather Outbreak remains likely Saturday afternoon and evening

Reduction in tornado threat

Increase in flash flood threat

There has been little to no change in the forecast reasoning from this morning, but incoming meso scale models and ongoing air mass trends over the coastal bend and SE TX suggest refinement of the severe weather threats on Saturday are needed.

While incoming data suggest the warm sector air mass will become unstable and shear profiles will be significant, the formation of numerous clusters of strong to severe thunderstorms across the warm sector from late morning to early afternoon suggest a decrease in the tornado risk. Large scale forcing will result in significant lift and widespread development of thunderstorms more in favor of clusters and lines versus the more concerning discrete supercell structures that tend to produce the more longer lived and stronger tornadoes. While supercells in the warm sector are still possible, the overall threat appears to be more from clusters and lines which support more of a wind damage versus tornado threat. Weaker tornadoes are also more likely in this setup especially along the leading edge of any bowing line segments. Any discrete cells that do manage to develop away from other storms will have an enhanced tornado threat and this would most likely be along and south of I-10.

Forecast models have also showed a slight slowing of the weather system and significantly more development of warm sector thunderstorms. This is increasing the threat for cell training and a more prolonged period of heavy rainfall potential. In fact the latest run of the TX Tech 3km WRF model shows nearly continuous thunderstorm development over SE TX from late morning through late evening on Saturday and supports training bands. WPC upped the QPF totals on their morning outlook and this certainly appears reasonable with widespread amounts of 1-3 inches possible and isolated totals of up to 4 inches. This increases the threat for urban flooding under cores of excessive rainfall where hourly rates may exceed 2.0 inches.

The damaging wind threat still remains as discussed earlier as there is good wind energy aloft that can and will be transported down to the surface in storm downdrafts supporting corridors of wind damage. This will be highlighted on Saturday once it becomes clear where this potential is greatest.

Residents across SE TX should be aware of the severe weather potential Saturday afternoon and evening and stay updated on current weather conditions and warning products. If a warning is issued for your area act quickly. Research shows that the ability of warning information to reach the public on the weekend decreases as “other activities” increase and many people are not as “in tune” as they are during the work week. Make it a point to at least check weather conditions a few times Saturday afternoon and evening.
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Latest models are coming in stronger. Suggesting both discrete cells and then a MCS along the frontal boundary/ closer to the shortwave. Looks like an active day tomorrow
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NWS Houston is forecasting this comes in waves. The first are scattered thunderstorms in the afternoon and second wave happens at night to early Sunday morning in the form of MCS.
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