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Tropical Storm Harvey Forecast Discussion Number 34
2017-08-28 22:51:41| National Hurricane Center (Atlantic)
Issued at 400 PM CDT Mon Aug 28 2017 000 WTNT44 KNHC 282051 CCA TCDAT4 Tropical Storm Harvey Discussion Number 34...Corrected NWS National Hurricane Center Miami FL AL092017 400 PM CDT Mon Aug 28 2017 Corrected initial intensity in first paragraph Radar and surface data show that the center of Harvey remains near or just off the Texas coast south of Matagorda. The associated convection has increased in intensity and coverage in a cluster extending from just north of the center northeastward into the Houston metropolitan area. Surface observations indicate that the central pressure is around 997 mb, and there are recent reports of sustained tropical-storm-force winds about 50-60 n mi southwest of the center. Based on these, the initial intensity is increased to 40 kt. Very heavy rains and life-threatening flash flooding continue over southeastern Texas and southwestern Louisiana. There have been reports of 2-day rainfall totals of close to 35 inches in the Greater Houston area. With the additional rains that are expected over the next several days, rainfall totals could reach 50 inches in some locations, which would be historic for the area. While Harvey continues to produce widespread heavy rain, the convective structure is not well organized in terms of being a tropical cyclone. In addition, a dry slot is seen in water vapor imagery over the southern and southeastern parts of the circulation, and the intensity guidance is not showing much additional development as Harvey crosses the northwestern Gulf of Mexico. The intensity forecast reflects these issues by showing little change in strength before landfall. Weakening and eventual decay into a remnant low are expected after landfall. The center has drifted erratically eastward since the last advisory, although a longer-term motion is 110/3. Harvey is currently between the subtropical ridge over the Gulf of Mexico and a large deep-layer ridge over the western United States, with a large trough in the westerlies weakening the Gulf ridge just enough to allow an east-southeastward motion. The large-scale models suggest that the westerlies should erode the western ridge to some extent during the forecast period, which should allow Harvey to turn north-northeastward under the greater influence of the Gulf ridge. The track guidance has changed little since the previous advisory except to show a faster motion from 96-120 h. The new forecast track remains close to that of the previous track, except for an increased forward speed by 120 h. Key Messages: 1. Ongoing catastrophic and life-threatening flooding will continue across southeastern Texas. Additional rainfall accumulations of 15 to 25 inches are expected across the upper Texas coast, with isolated storm totals as high as 50 inches. Please heed the advice of local officials. Do not attempt to travel if you are in a safe place, and do not drive into flooded roadways. Refer to products from your local National Weather Service office and the NOAA Weather Prediction Center for more information on the flooding hazard. A summary of rainfall totals compiled by the Weather Prediction Center can be found at: www.wpc.ncep.noaa.gov/discussions/nfdscc1.html 2. The flood threat is spreading farther east into Louisiana. Additional rainfall amounts of 15 to 25 inches are expected in southwestern Louisiana, with rainfall amounts of 5 to 15 inches expected in south-central Louisiana and 5 to 10 inches in southeastern Louisiana. Please heed the advice of local officials and refer to products from your local National Weather Service office and the NOAA Weather Prediction Center for more information on the flooding hazard in these areas. 3. While Tropical Storm Warnings have been extended eastward along the coast of Louisiana and a Storm Surge Watch has been issued, the impacts of winds and storm surge are expected to be secondary compared to that of the rains. FORECAST POSITIONS AND MAX WINDS INIT 28/2100Z 28.5N 95.7W 40 KT 45 MPH 12H 29/0600Z 28.4N 95.5W 40 KT 45 MPH 24H 29/1800Z 28.6N 95.0W 40 KT 45 MPH 36H 30/0600Z 29.2N 94.5W 40 KT 45 MPH 48H 30/1800Z 30.3N 94.1W 35 KT 40 MPH...INLAND 72H 31/1800Z 32.5N 93.0W 30 KT 35 MPH...INLAND 96H 01/1800Z 34.5N 91.5W 25 KT 30 MPH...INLAND 120H 02/1800Z 37.0N 89.0W 20 KT 25 MPH...POST-TROP/INLAND $$ Forecaster Beven
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