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Tropical Storm Harvey Forecast Discussion Number 5
2017-08-18 16:50:53| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Fri Aug 18 2017 000 WTNT44 KNHC 181450 TCDAT4 Tropical Storm Harvey Discussion Number 5 NWS National Hurricane Center Miami FL AL092017 1100 AM AST Fri Aug 18 2017 The structure of Harvey has changed little during the past several hours, and overall the storm is poorly organized. The low-level center is near the eastern edge of the convective mass due to the affects of 15 kt of vertical wind shear. In addition, surface observations and Air Force Reserve Hurricane Hunter data suggest that the 850-mb center is located west or southwest of the surface center. Based on the aircraft and surface data, the central pressure is near 1005 mb and the initial intensity remains 35 kt. The initial motion is a quick 270/18. A strong low- to mid-level ridge north of the cyclone should keep Harvey on this general motion for the next 3-4 days, with the system moving from the eastern to the western Caribbean Sea during this time. Late in the forecast period, a more northerly motion is expected when Harvey passes near or over portions of Central America, the Yucatan Peninsula, and eastern Mexico. The new forecast track remains in the center of the guidance, and only minor changes were made to the previous track. The current shear should persist for the next 48 h or so, and thus the intensity forecast continues the trend of slow strengthening during this time. After that, conditions appear favorable for strengthening, with the main uncertainty being how much land Harvey will encounter. The ECMWF keeps the cyclone a little north of Nicaragua and Honduras and allows more room for development, while the GFS forecasts landfall in northeastern Nicaragua and thus has a weaker intensity. The new NHC forecast is close to the previous one in showing a peak intensity below hurricane strength, but the confidence in this portion of the forecast is low. FORECAST POSITIONS AND MAX WINDS INIT 18/1500Z 13.1N 61.3W 35 KT 40 MPH 12H 19/0000Z 13.3N 63.8W 35 KT 40 MPH 24H 19/1200Z 13.6N 67.3W 40 KT 45 MPH 36H 20/0000Z 14.0N 71.1W 40 KT 45 MPH 48H 20/1200Z 14.3N 75.0W 50 KT 60 MPH 72H 21/1200Z 15.0N 82.0W 60 KT 70 MPH 96H 22/1200Z 16.5N 87.5W 55 KT 65 MPH 120H 23/1200Z 18.5N 91.0W 30 KT 35 MPH...INLAND $$ Forecaster Beven
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