Powerful coastal storm system over the NW Gulf of Mexico

Flash Flood Watch in effect until 600pm S of I-10

Coastal Flood Warning in effect until 600pm for Brazoria, Galveston, Harris, Chambers counties.

Discussion

Surface low has developed over the western Gulf of Mexico in region of strong upper level forcing by the approaching upper trough over W TX. Low has deepened this morning with a tight pressure gradient developing. Buoy 60 NM S of Freeport has been gusting to near 50mph with sustained winds of 35-40mph. Tight circulation is noted on long range 88D images out of HGX and CRP. Appears the low will track across our outer coastal waters this afternoon with the highest winds staying over the Gulf waters and the heaviest rains remaining offshore.

Rainfall

Impressive amounts fell overnight near Port Aransas where 88D shows upwards of 10” was recorded. Large NW Gulf rain shield has spread to about I-10, but last several radar frames show the shield organizing off the upper TX coast closer to the core of the surface low. Upper level dynamics will move in from the west where thunderstorms are ongoing along I-35. Feel the flash flood threat is lower due to the heaviest rains focusing off the coast and the track of the surface low through the outer waters instead of along the coast. Still a widespread 1-2 inches with isolated 3-4” looks likely especially along the coast.

Tides

Big issue is the tides and coastal flooding. Long overnight ebb tide is slowing falling, but strong E winds are keeping this tide trapped at the coast. Water levels continue to run 2-3 feet above normal in both Galveston and Matagorda Bays and along the coast. Next high tide will be this evening and strong E winds today and building long period swells will point toward some issues at this high tide. Current expectations of 3.5-4.5ft tide support overwashing parts of the west end of Galveston and eastern Bolivar along with water reaching into low lying areas surrounding the above mentioned bays. Matagorda Bay, may go to N winds before this tide occurs helping to ease levels down south. As the surface low passes E of the area late tonight winds will become strong out of the north flushing the water out of the bays and lowering the tides. Some concern that strong N winds late tonight may slosh Galveston Bay tides onto the backside of the Island resulting in some flooding…similar to our last event. High water levels and battering waves will result in beach erosion and possible loss of some coastal roads (HWY 87 and Blue Water Highway)

Winds:

Impressive winds being reported off the coast with some of the platforms gusting to over 60mph. Winds gusted to 40mph at Eagle Point this morning and near 40mph at Freeport. Will see winds come up a little more today with sustained 25-35mph on the coast with frequent gust or 40mph or greater.

SATELLITE PRECIPITATION ESTIMATES..DATE/TIME 11/20/09 0806Z
SATELLITE ANALYSIS BRANCH/NESDIS---NPPU---TEL.301-763-8678
LATEST DATA USED: GOES-EAST:0800Z JS
.
LOCATION...SOUTHEASTERN TEXAS
.
ATTN WFOS...HGX...CRP...EWX...BRO...
ATTN RFCS...WGRFC...
.
EVENT...RENEWED CONVECTIVE DEVELOPMENT INLAND OVER SOUTHERN AND
SOUTHEASTERN TEXAS.
.
SATELLITE ANALYSIS AND TRENDS...THE PAST FEW IR IMAGES HAVE SHOWN AN
INCREASE IN COVERAGE AND INTENSITY OF CONVECTION OVER S AND SE TX AS CELLS
MOVING UP FROM FAR S TX ENCOUNTER SFC WARM FRONT AND OUTFLOW FROM ORIGINAL
LARGE COMPLEX JUST OFF THE SE TX COAST. OBJECTIVE SFC ANALYSIS INDICATES
THIS CONVERGENT AREA VERY WELL WITH MOISTURE CONVERGENCE BULLSEYE CENTERED
BETWEEN CELLS OVER KLEBERG/KENEDY COUNTIES AND ACTIVITY FARTHER TO THE
NORTH AND NORTHEAST AROUND GOLIAD/REFUGIO/ARANSAS COUNTIES. BELIEVE THERE
IS A GOOD POSSIBILITY THAT THIS AREA WILL CONTINUE TO FILL DURING THE NEXT
HOUR AS CELLS MERGE AND ENCOUNTER OUTFLOW FROM COMPLEX OFFSHORE. SATELLITE
ESTIMATED RAIN RATES HAVE INCREASED TO OVER 1.5"/HR WITH THE STRONGER
CELLS WITHIN THIS REGION AND WILL LIKELY INCREASE FURTHER TO OVER 2"/HR
WITHIN THE NEXT HALF HOUR AS CLOUD TOPS COOL/EXPAND. GIVEN THE AMOUNT OF
MOISTURE PRESENT (70F SFC DEWPOINTS AND AT LEAST 1.75" PW VALUES) AND
THE PRESENCE OF SIGNIFICANT UPPER LEVEL DIFFLUENCE, THERE IS AT LEAST
THE POTENTIAL FOR RAIN RATES TO EVEN APPROACH OR BRIEFLY EXCEED 3"/HR
AS PER EARLIER OBSERVATIONS FROM KRKP(ROCKPORT). AN ANNOTATED SATELLITE
GRAPHIC SHOWING HEAVY RAINFALL THREAT AREA SHOULD BE AVAILABLE ON THE
INTERNET ADDRESS LISTED BELOW IN APPROXIMATELY 10 MINUTES.

Rainfall will be increasing from west to east this evening as upper level storm system approaches.

Coastal surface low continues to deepen over the NW Gulf of Mexico while the heaviest rains have remained offshore where radar amounts of 4-7 inches have been recorded. Inland amounts have averaged 1-2 inches S of US 59 and 3-4 inches around Matagorda Bay. Surface pattern has become chaotic over the Gulf waters where this morning’s strong vort center tracked leading to a messy wind pattern. Much anticipated surface low development has been so for muddled within this meso-scale pattern that has unfolded.

With Gulf of Mexico complex weakening and lift from approaching upper level trough moving into the region expect the rains entering Lavaca and Victoria counties to overspread the area in the next 2-3 hours. Additional rainfall of 1-2 inches is likely this evening. While grounds are wet…especially over the Matagorda Bay area…this rainfall should be handled well.

Tides continue to run above normal with strong easterly fetch. Offshore buoys and platforms have been gusting well over 40mph today and this will continue into the overnight hours. Winds remain backed and show little to no sign of switching in any direction as of yet indicating the lower pressures in the W Gulf are not on the move. Should see winds swing around to the NE and N overnight as the surface low deepens and then passes to our east offshore. Still feel the high tide this evening will result in water levels of 2.5-4.5 feet above normal and this will cause some problems. May need to keep a close eye down around Matagorda as winds have not switched there and may not before the evening high tide creating some issues on the beach front and around Indianola.

Extended:

Nice weather will return by Sunday as weak high pressure builds over the region. Next front due in Monday with a slight chance of rainfall. Cooler next week and mainly dry for Thanksgiving although the sun-tropical jet will be close by. Damp and cold conditions forecasted earlier this week have reversed in the models.

Prayers were indeed answered today as the predicted heavier rain, wind and storms stayed offshore for the most part. It was still cold and wet all day but not the bad stuff as forecasted for our area. I'm ready for a warm glass of hot chocolate and a warm bed now...........it does make for good sleeping weather. LOL

Yes mam it does. WE have another round of moderate rain moving into/through the Houston metro area right now. I hadn't looked at radar for quite a while so this was somewhat unexpected. Looks like we could pick up another inch or so in some areas. Now off to bed again.

The freaking drizzle/mist finally ended around 7:30 pm or so and I actually saw the moon and some stars. There were still clouds around so who knows what's next? High today was a blazing 57ºf.