Mesoscale Precipitation Discussion 0079
NWS Weather Prediction Center College Park MD
621 PM EST Tue Feb 26 2019
Areas affected...Near and southwest of Houston, TX
Concerning...Heavy rainfall...Flash flooding possible
Valid 262320Z - 270320Z
Summary...Thunderstorms continue to broaden to the west of the
Houston Metroplex, with some indications of embedded mesocyclones.
Hourly rain totals to 1.5" with local amounts to 3" are possible.
Discussion...Storms continue to blossom to the southeast of an
upper level disturbance moving across the TX Hill Country and
somewhat northeast of a frontal wave near Bloomington, TX.
Equally troubling is the backbuilding/redeveloping storms into
southern Lavaca county. Precipitable water values have risen to
1.5-1.7". Inflow at 850 hPa is 15-20 kts from the southwest.
Effective bulk shear is near 40 kts, which has been enough to
develop the occasional mesocyclone over the past few hours. ML
CAPE within the warm sector is 1000-1500 J/kg, while MU CAPE
values of 1000-2000 J/kg inhabit the Piney Woods and Big Thicket
of eastern TX.
Correcting for hail contamination, hourly rain totals have
recently jumped to 1.5". The mesoscale guidance, particularly the
18z 3 km NAM CONEST, show the potential for local 2-3" of rainfall
near and southwest of Houston, which appears to be becoming
realized at this time. This is close to the regional flash flood
guidance values. Should the storms propagate into Houston itself,
the usual heavy rain related issues within their urban area would
result. Believe that storms should become more mobile with any
cell backbuilding/ redevelopment ceasing by 01z and increased
elevation over the boundary with time as the incoming shortwave
begins to progress and the 700 hPa wind flow begins to veer
thereafter. Used a four hour window as a precaution.
550p: We're seeing signs of very large hail 10-15k feet above the ground in the warned storm. Some of that will melt away before anything hits the ground, but it does increase confidence in seeing quarter to ping pong ball sized hail in the most intense part of the storm.
Severe Weather Statement
National Weather Service Houston/Galveston TX
557 PM CST TUE FEB 26 2019
TXC039-157-481-270015-
/O.CON.KHGX.SV.W.0007.000000T0000Z-190227T0015Z/
Wharton TX-Fort Bend TX-Brazoria TX-
557 PM CST TUE FEB 26 2019
...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 615 PM CST
FOR EASTERN WHARTON...SOUTH CENTRAL FORT BEND AND WEST CENTRAL
BRAZORIA COUNTIES...
At 557 PM CST, a severe thunderstorm was located near Needville, or
13 miles south of Rosenberg, moving east at 25 mph.
HAZARD...Ping pong ball size hail.
SOURCE...Radar indicated.
IMPACT...People and animals outdoors will be injured. Expect damage
to roofs, siding, windows, and vehicles.
Locations impacted include...
Needville and Damon.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Prepare immediately for large hail and deadly cloud to ground
lightning. Seek shelter inside a well-built structure. Stay away from
windows.
To report severe weather contact your nearest law enforcement agency.
They will send your report to the National Weather Service office in
League City.
Special Weather Statement
National Weather Service Houston/Galveston TX
609 PM CST TUE FEB 26 2019
TXZ227-237-337-270100-
Inland Brazoria TX-Fort Bend TX-Coastal Brazoria TX-
609 PM CST TUE FEB 26 2019
...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN FORT BEND AND
NORTHEASTERN BRAZORIA COUNTIES UNTIL 700 PM CST...
At 609 PM CST, Doppler radar was tracking a strong thunderstorm over
Brazos Bend State Park, or 13 miles north of West Columbia, moving
east at 25 mph.
Dime size hail will be possible with this storm.
Locations impacted include...
Alvin, southern Manvel, Danbury, Iowa Colony, Hillcrest, Liverpool,
Bonney, Brazos Bend State Park, Chocolate Bayou, Rosharon and Juliff.
League City down to Galveston expect some intense C2G lightning as this storm moves through. Quarter size and Ping Pong Ball size hail is also likely.
Relieved to see it will miss Pasadena.
First image is 'Vertically Integrated Liquid" which is an estimate of the total mass of precipitation in the clouds. Essentially this is a nice little hail core.
Attachments
Hail core
Last edited by Belmer on Tue Feb 26, 2019 6:50 pm, edited 1 time in total.
Katdaddy wrote: ↑Tue Feb 26, 2019 6:52 pm
The worst of the cell looks to pass just S of my location in W League City thankfully but will be a close call.
Looks like the storm is jumping north a little bit, Katdaddy. Watch it closely...
Looks like that cell is headed my direction and will pass between Alvin and Friendswood on the way to League City. Seeing lots of high level sheet lightening but little thunder which is not what I would expect with a cell that close.
Outlined in blue have the greatest chance of some flash flooding the next two hours as the storm behind the main cell begins to strengthen. This is going to provide a long-stretch of heavy rain over the area that is impacted by the leading thunderstorm.
Severe storm just about to our house in W League City. Strobe light ongoing outside.
BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Houston/Galveston TX
706 PM CST TUE FEB 26 2019
The National Weather Service in League City has issued a
* Severe Thunderstorm Warning for...
Northwestern Galveston County in southeastern Texas...
Northeastern Brazoria County in southeastern Texas...
Southeastern Harris County in southeastern Texas...
* Until 730 PM CST.
* At 706 PM CST, a severe thunderstorm was located over Alvin, moving
east at 30 mph.
HAZARD...Quarter size hail.
SOURCE...Radar indicated.
IMPACT...Damage to vehicles is expected.
* Locations impacted include...
Southeastern Pasadena, League City, Texas City, Friendswood, Alvin,
Dickinson, La Marque, Santa Fe, Seabrook, Webster, Hitchcock,
Kemah, southeastern Clear Lake, Nassau Bay, Taylor Lake Village, El
Lago, Clear Lake Shores, Hillcrest, San Leon and The Johnson Space
Center.
The National Weather Service in League City has issued a
* Flood Advisory for...
Central Harris County in southeastern Texas...
* Until 815 PM CST.
* At 714 PM CST, Doppler radar indicated a persistent cell over the
southwest Houston area that has produced close to 2 inches of
rain. Latest trends show some slow weakening, but there could be
some ponding on low lying roadways or those with poor drainage.
* Some locations that will experience flooding include...
Bellaire, West University Place, Hunters Creek Village, Greater
Eastwood, Midtown Houston, Greater Fifth Ward, Downtown Houston,
Memorial Park, Greenway / Upper Kirby Area, Greater Third Ward,
Second Ward, Fourth Ward, University Place, Astrodome Area,
Macgregor, Neartown / Montrose, Afton Oaks / River Oaks Area, Near
Northside Houston, southeastern Greater Heights and Southside
Place.
It's nice to hear the thunder again. Kinda calming in a way. Looks like areas around Pearland need to be watched for flooding. Some training has already occurred and will continue for the short term.
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