May 2015 Record Setting May Rainfall Totals For Region

[srainhoutx]

FLOOD ADVISORY
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
1115 AM CDT THU MAY 21 2015

HARRIS TX-MONTGOMERY TX-
1115 AM CDT THU MAY 21 2015

THE NATIONAL WEATHER SERVICE IN LEAGUE CITY HAS ISSUED A

* FLOOD ADVISORY FOR...
CENTRAL HARRIS COUNTY IN SOUTHEASTERN TEXAS...
SOUTHEASTERN MONTGOMERY COUNTY IN SOUTHEASTERN TEXAS...

* UNTIL 115 PM CDT

* AT 1111 AM CDT...DOPPLER RADAR INDICATED HEAVY RAIN DUE TO
THUNDERSTORMS. THIS WILL CAUSE MINOR FLOODING IN THE ADVISORY
AREA. UP TO TWO INCHES OF RAIN HAS FALLEN AND ADDITIONAL RAINFALL
IS EXPECTED.

* SOME LOCATIONS THAT WILL EXPERIENCE FLOODING INCLUDE...
BELLAIRE...HUMBLE...WEST UNIVERSITY PLACE...JERSEY VILLAGE...
HUNTERS CREEK VILLAGE...BUNKER HILL VILLAGE...PINEY POINT
VILLAGE...SPRING VALLEY...GREATER FIFTH WARD...FOURTH WARD...SPRING
BRANCH WEST...NEARTOWN / MONTROSE...GREATER GREENSPOINT...DOWNTOWN
HOUSTON...ADDICKS PARK TEN...GREATER HEIGHTS...NEAR NORTHSIDE
HOUSTON...GREENWAY / UPPER KIRBY AREA...SPRING AND KINGWOOD.

[srainhoutx]

FLOOD ADVISORY
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
140 PM CDT THU MAY 21 2015

BRAZORIA TX-MATAGORDA TX-
140 PM CDT THU MAY 21 2015

THE NATIONAL WEATHER SERVICE IN LEAGUE CITY HAS ISSUED A

* FLOOD ADVISORY FOR...
WEST CENTRAL BRAZORIA COUNTY IN SOUTHEASTERN TEXAS...
NORTHWESTERN MATAGORDA COUNTY IN SOUTHEASTERN TEXAS...

* UNTIL 345 PM CDT

* AT 139 PM CDT...DOPPLER RADAR INDICATED HEAVY RAIN DUE TO
THUNDERSTORMS. THIS WILL CAUSE MINOR FLOODING IN THE ADVISORY
AREA. TWO TO THREE INCHES OF RAIN HAVE ALREADY FALLEN AND ANOTHER
INCH OF RAIN WILL BE POSSIBLE BY 230 PM.

* SOME LOCATIONS THAT WILL EXPERIENCE FLOODING INCLUDE...
BAY CITY...WEST COLUMBIA...SWEENY...BRAZORIA...VAN VLECK...
MARKHAM...WILD PEACH VILLAGE...BLESSING AND MIDFIELD.

[srainhoutx]

FLOOD ADVISORY
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
152 PM CDT THU MAY 21 2015

BRAZORIA TX-GALVESTON TX-
152 PM CDT THU MAY 21 2015

THE NATIONAL WEATHER SERVICE IN LEAGUE CITY HAS ISSUED A

* FLOOD ADVISORY FOR...
NORTHEASTERN BRAZORIA COUNTY IN SOUTHEASTERN TEXAS...
WEST CENTRAL GALVESTON COUNTY IN SOUTHEASTERN TEXAS...

* UNTIL 400 PM CDT

* AT 152 PM CDT...DOPPLER RADAR INDICATED HEAVY RAIN DUE TO
THUNDERSTORMS. THIS WILL CAUSE MINOR FLOODING IN THE ADVISORY AREA.
UP TO TWO INCHES OF RAIN HAVE ALREADY FALLEN.

* SOME LOCATIONS THAT WILL EXPERIENCE FLOODING INCLUDE...
SOUTHEASTERN PEARLAND...SOUTHWESTERN LEAGUE CITY...SOUTHWESTERN
FRIENDSWOOD...ALVIN...SANTA FE...SOUTHEASTERN MANVEL...IOWA
COLONY...HOLIDAY LAKES...HILLCREST...LIVERPOOL...BONNEY AND
ROSHARON.

[srainhoutx]

Updated Quantitative Precipitation Forecast concerning the late Memorial Day Holiday Weekend timeframe suggests some impressive rainfall totals may be possible over a 48 hour period across Coastal Texas.

05212015 1728Z Day 4 to 5 QPF 95ep48iwbg_fill.gif

QPF Totals through Day 5:

05212015 1945Z 5 Day QPF p120i.gif

[srainhoutx]

FLOOD ADVISORY
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
353 PM CDT THU MAY 21 2015

BRAZORIA TX-WHARTON TX-MATAGORDA TX-FORT BEND TX-
353 PM CDT THU MAY 21 2015

THE NATIONAL WEATHER SERVICE IN LEAGUE CITY HAS ISSUED A

* FLOOD ADVISORY FOR...
WEST CENTRAL BRAZORIA COUNTY IN SOUTHEASTERN TEXAS...
SOUTHEASTERN WHARTON COUNTY IN SOUTHEASTERN TEXAS...
NORTHERN MATAGORDA COUNTY IN SOUTHEASTERN TEXAS...
SOUTHWESTERN FORT BEND COUNTY IN SOUTHEASTERN TEXAS...

* UNTIL 600 PM CDT

* AT 353 PM CDT...DOPPLER RADAR INDICATED HEAVY RAIN DUE TO
THUNDERSTORMS. THIS WILL CAUSE MINOR FLOODING IN THE ADVISORY AREA.
UP TO TWO INCHES OF RAIN HAVE ALREADY FALLEN.

* SOME LOCATIONS THAT WILL EXPERIENCE FLOODING INCLUDE...
WHARTON...NEEDVILLE...FAIRCHILDS...BOLING-IAGO AND DAMON.

[srainhoutx]

Afternoon briefing from Jeff:

***Potentially serious flood situation developing for the Memorial Day weekend.***

Models continue to come into better agreement that a slow moving potent upper air storm system will move into TX from the SW US late in the weekend. Deep tropical moisture surges into the region Saturday evening and by Sunday afternoon the air mass is saturated…this will result in efficient rainfall production. Upper level winds become strongly divergent Sunday night into much of Monday and possibly into Tuesday resulting in sustained lifting of the very moist air mass. Potential is there for several rounds of excessive rainfall Sunday-Tuesday with flooding likely.

Rainfall rates will increase Sunday with 2.0 inches per hour common under the stronger storms with greater hourly rates nearing 4.0 inches possible given the moisture profile expected by late Sunday. Widespread rainfall amounts of 3-5 inches with isolated totals of 5-8 inches will be possible.

With grounds saturated and area rivers already near or above flood stage significant flooding will be generated with the potentially forecasted rainfall amounts. Rapid flash flooding is also possible with the high hourly rainfall rates.

Given the ground and river conditions and the forecasted rainfall amounts along with the extended period of strong divergence aloft…this event is the most worrying of all those we have faced the last several weeks.

Residents are urged to keep up to date on weather conditions over the weekend and be prepared to act should flooding develop.

[Paul Robison]

Afternoon briefing from Jeff:

***Potentially serious flood situation developing for the Memorial Day weekend.***

Models continue to come into better agreement that a slow moving potent upper air storm system will move into TX from the SW US late in the weekend. Deep tropical moisture surges into the region Saturday evening and by Sunday afternoon the air mass is saturated…this will result in efficient rainfall production. Upper level winds become strongly divergent Sunday night into much of Monday and possibly into Tuesday resulting in sustained lifting of the very moist air mass. Potential is there for several rounds of excessive rainfall Sunday-Tuesday with flooding likely.

Rainfall rates will increase Sunday with 2.0 inches per hour common under the stronger storms with greater hourly rates nearing 4.0 inches possible given the moisture profile expected by late Sunday. Widespread rainfall amounts of 3-5 inches with isolated totals of 5-8 inches will be possible.

With grounds saturated and area rivers already near or above flood stage significant flooding will be generated with the potentially forecasted rainfall amounts. Rapid flash flooding is also possible with the high hourly rainfall rates.

Given the ground and river conditions and the forecasted rainfall amounts along with the extended period of strong divergence aloft…this event is the most worrying of all those we have faced the last several weeks.

Residents are urged to keep up to date on weather conditions over the weekend and be prepared to act should flooding develop.

On the other hand, the latest model run of the GFS (12Z) I've just posted shows Houston/Galveston is not being bulls-eyed the way points north of us are. Not that you're wrong, srainhoutex, Texas may indeed have a problem. Maybe Houston not as much, eh?

[Katdaddy]

A quiet morning across SE TX with a few showers and thunderstorms along the Middle TX Coast near the cool front boundary. This will push N today and allow some additional development to occur. Another round of thunderstorms will be possible Saturday across inland portions of SE TX. Sunday through Tuesday could be very active with severe weather and flooding. The SPC has S, Central and SE TX in a slight risk area for Sunday. The grounds are already saturated so hopefully not much rain will occur today or tomorrow. Be aware of the weather this holiday weekend.

[srainhoutx]

The Weather Prediction Center issues a somewhat large Moderate Risk for Excessive Rainfall effective Sunday morning into Monday morning.

[srainhoutx]

Morning briefing from Jeff:

***Heavy rainfall and flooding likely this weekend***

***Major river flooding increasingly likely next week***

Today:
A weak cool front has stalled overnight near the coast with surface winds out of the NE this morning advecting in a refreshingly drier air mass. Large surface high will slide eastward today allowing this boundary to begin to return northward as a warm front. Air mass along and south of this boundary will become increasingly unstable and areas radars already show showers/thunderstorms ongoing around Matagorda Bay this morning. Expect showers and thunderstorms to develop once low 80 degree convective temperatures are reached by early afternoon. Yet again…main threat is excessive rainfall with 1-2 inch per hour rates under the stronger cells.

Saturday:
Warm front will clear the area Saturday morning with a moist and unstable air mass firmly in place. Surface heating will likely bubble up more showers and thunderstorms during the afternoon hours with the greatest concentration likely along and N of US 59. Heavy rainfall remains likely with PWS starting to surge to 1.8 inches. Additionally, CAPE values rise into the 2500-3500 range which would support a few strong to severe storms.

Sunday-Tuesday:

Critical weather period is likely with excessive rainfall and high flash flood threat.

Numerous flash flood watches will be required during this period.

An unusually strong upper level storm system will slowly move into TX late in the weekend while a surge of extremely moist Caribbean Sea air moves into the region. PWS rise to near 2.1 inches by late Sunday. Jet stream dynamics become very favorable for spreading (venting) of the upper levels resulting in sustained lift across the region. Appears a large slow moving thunderstorm complex will develop over W/C TX late Saturday and progress into SE TX Sunday afternoon. High potential for repeat cell training with this complex and slow forward complex motion…yet cell motions along the leading band may be on the order of 20mph. Air mass will be nearly saturated and tropical by Sunday afternoon supporting “tremendous” rainfall rates. Could easily see rainfall rates of 2-4 inches per hour with the stronger storms. Severe threat will also be possible given the arrival of storm during the afternoon hours. Position of the core upper level divergence will keep high rain chances into Sunday night and all day Monday with either rounds of storms (best option) or a sustained period of cell training (worst option).

Hydrologic set up is very concerning with several rivers already near or above flood stage and grounds completely saturated. Flash Flood Guidance is running around 2.5 inches for 1-hr and 4.0 inches for 6-hr…this could easily be exceeded in 1-hr with the incoming setup. Given the rainfall setup and saturated grounds significant run-off will result from excessive rainfall and push already flooding rivers into moderate or major flood levels.

Rainfall amounts will average 2-4 inches across the region with isolated totals of 4-6 inches possible. This is certainly the setup where 10 inches or greater of rainfall can occur and we have been such totals at least 5 times over SE TX in the last 10 days.

Hydro:

Trinity River:
Major river flooding is in progress at Liberty with homes threatened and numerous subdivisions and residences cu –off. River crossed over into major flood level this morning and will hold at this level for the next several days. Releases will continue from Lake Livingston due to upstream flood flow moving downstream from N TX (river is still rising this morning at Dallas). Releases may have to be increased this weekend to manage the upcoming rainfall event and upstream flows. The river at Liberty, TX is currently 1.9ft below record flood level set in October 1994.

Brazos River:
River is above flood stage at Rosharon with minor flooding in progress. Flood wave from Monday’s rainfall on the Brazos River above Hempstead has passed Richmond yesterday and moving toward Rosharon today. River will begin a slow fall today as the flood wave passes, but forecasted rainfall this weekend will likely result in a new rise early next week.

Navasota River:
River is above flood stage below Lake Limestone and will crest this weekend. Heavy rainfall will likely impact the basin before the river is able to fall back within banks

San Bernard River:
The river has crested and is falling back within banks today. Heavy rainfall this weekend will almost certainly push this river above flood stage.

Guadalupe River:
Moderate flooding is in progress at both Victoria and Bloomington. River will crest late today into this weekend, but remain above flood stage into the weekend. Additional rainfall will only worsen ongoing flooding.

Nueces River:
Major flooding is in progress along much of the entire river basin from Asherton, TX downstream to near Corpus Christi, TX. River is potentially more than a mile wide along portions of the channel with several sections of the floodplain inundated and livestock along the river potentially cut-off and drown.

Neches River:
Flooding is in progress along the entire river basin.

Sabine River:
Flooding is in progress both above and below Sam Rayburn Reservoir. River will remain in flood for the next several days.

As one may guess….additional rainfall is only going to make the current river flood situation worse!

[Texaspirate11]

Anyone catch this in the morning disco from HGX?

FOR
WHAT IT IS WORTH NEXT WEEKEND ALSO LOOKS WET BUT NOT WITH SUCH A
POTENT SYSTEM. THE ECMWF ALSO TRYING TO DEVELOP A TROPICAL SYSTEM
IN THE EAST PAC FOR AT LEAST 2 RUNS IN A ROW.

[srainhoutx]

Anyone catch this in the morning disco from HGX?

FOR
WHAT IT IS WORTH NEXT WEEKEND ALSO LOOKS WET BUT NOT WITH SUCH A
POTENT SYSTEM. THE ECMWF ALSO TRYING TO DEVELOP A TROPICAL SYSTEM
IN THE EAST PAC FOR AT LEAST 2 RUNS IN A ROW.

Thanks for bringing attention to this Texaspirate. Be sure to check out our Hurricane Central area where we are currently following two areas of disturbed weather being monitored by the National Hurricane Center between Mexico and Hawaii as well as the potential development much closer to the Pacific Coast of Mexico near the Gulf of Tehuantepec which is awfully close to the Bay of Campeche, just the other side of the Isthmus of Tehuantepec.

http://forums.khou.com/viewtopic.php?f=4&t=2013

[jasons2k]

Update from Eric Berger:

http://blog.chron.com/weather/2015/05/m ... orm-watch/

[jasons2k]

The Weather Prediction Center issues a somewhat large Moderate Risk for Excessive Rainfall effective Sunday morning into Monday morning.

That's the largest Mod risk area I can recall in a long time.

[jasons2k]

Update from Jeff:

All,

Be advised that the integrity of the dam on Lewis Creek Reservoir in Montgomery County is in question. SJRA is meeting with officials at the moment to access the situation. Current elevations of Lewis Creek Reservoir suggest that most of the water in the event of a failure can be absorbed into the Lake Conroe pool resulting in a rise on the lake of about 1 ft, but will require flood gate operations at the lake and downstream rises on the West Fork of the San Jacinto River.

The situation is “serious”, but at the moment a failure does not appear imminent.

[BlueJay]

Update from Jeff:

All,

Be advised that the integrity of the dam on Lewis Creek Reservoir in Montgomery County is in question. SJRA is meeting with officials at the moment to access the situation. Current elevations of Lewis Creek Reservoir suggest that most of the water in the event of a failure can be absorbed into the Lake Conroe pool resulting in a rise on the lake of about 1 ft, but will require flood gate operations at the lake and downstream rises on the West Fork of the San Jacinto River.

The situation is “serious”, but at the moment a failure does not appear imminent.

That is scary especially in light of all of the rain that is expected this weekend.

https://www.twdb.texas.gov/surfacewater ... /index.asp

[srainhoutx]

The 12Z reliable European and GFS guidance is in good agreement suggesting a very potent storm system with embedded disturbances both from the riding E from the Eastern Pacific as well as additional energy dropping S along the California Coast from the Pacific NW rounding the base of the upper trough will affect our Region over the Holiday weekend into early next week. The afternoon QPF outlooks for the next 4 to 5 days should be telling and certainly will be worth monitoring the weather as we celebrate Memorial Day. Stay safe folks and have a great Holiday Weekend!

Day 1 to 3 QPF:

05222015 19Z Day 1 to 3 QPF d13_fill.gif

Day 4 to 5 QPF:

05222015 1730Z Day 4 to 5 QPF 95ep48iwbg_fill.gif

05222015 12Z Euro 48 ecmwf_z500a_sd_namer_3.png

05222012 12Z GFS 48 gfs_z500a_sd_namer_9.png

[srainhoutx]

Update from Jeff regarding the Lewis Creek Reservoir situation near Willis:

Inspection of the dam today has revealed 8 locations where portions of the dam face have eroded. At least 50 personnel are onsite actively working several of these “potential failure” locations. Some of the locations will require roads to be constructed to reach the areas damaged due to extremely soft ground. Sandbags and berms are being constructed and deployed around the potential failure locations along with tarps covering the erosion to help prevent additional damage to the dam. Additionally, Entergy, the reservoir owner, is releasing water to help relieve pressure against the dam. All measures are currently being taken to attempt to secure the integrity of the structure and to prevent a failure or breach.

Breach analysis preformed this morning indicated that a failure of the Lewis Creek Dam would result in 10-12 inch rise in the pool elevation of Lake Conroe. Significant downstream flooding along Lewis Creek to Lake Conroe would be possible.

With the current increased releases from Lewis Creek ongoing, the pool elevation of Lake Conroe already elevated, and the potential for excessive rainfall SJRA has started controlled releases at Lake Conroe this afternoon of 4230cfs to start lowering the lake level in anticipation of the upcoming rainfall event and the remote possibility of a failure at Lewis Creek.

Additional information and press releases can be found at the Montgomery County EOC website:
http://www.mctxoem.org/go/site/1945/

[BlueJay]

Thank you for that update srain. This is important information.

[unome]

looks like storms are popping up along the front's western side as it returns north



surface analysis loop: http://www.wpc.ncep.noaa.gov/html/sfclo ... c_wbg.html