ZCZC MIATCDAT4 ALL TTAA00 KNHC DDHHMM Tropical Storm Harvey Discussion Number 4 NWS National Hurricane Center Miami FL AL092017 500 AM AST Fri Aug 18 2017 Harvey's cloud pattern has changed very little in organization during the past several hours. The low-level center is difficult to find even using the 1-min images from GOES 16, but it appears to be located on the eastern edge of the convection due to the prevailing easterly shear. Dvorak estimates from both TAFB and SAB support keeping the intensity at 35 kt. Another Air Force plane will be investigating Harvey at sunrise. The moderate easterly shear affecting the cyclone is expected to increase a little during the next day or so, and this factor should not allow significant strengthening. Once the cyclone reaches the western Caribbean Sea in 3 or 4 days, an environment of lower shear and high moisture is forecast to prevail, and Harvey should then gather some strength. The cyclone could be near hurricane strength by the time it is approaching Central America or the Yucatan peninsula. The NHC forecast is very similar to the previous one and is very close to the intensity consensus. The GFS and the ECMWF global models are just a little more enthusiastic in keeping the cyclone from dissipating in this last run, but who knows what they might forecast the next time. Harvey has not changed in track or speed, and it is still moving toward the west or 270 degrees at 16 kt. The cyclone is well embedded within the easterlies south of a persistent subtropical ridge. This steering pattern will keep Harvey trapped in the Caribbean Sea while moving westward for the next few days. The track forecast is similar to the one issued by my predecessor and it follows closely the multi-model consensus. The guidance envelope is quite tight and is bounded by the northernmost ECMWF and the GFS to the south. FORECAST POSITIONS AND MAX WINDS INIT 18/0900Z 13.1N 59.1W 35 KT 40 MPH 12H 18/1800Z 13.2N 61.7W 35 KT 40 MPH 24H 19/0600Z 13.5N 65.2W 40 KT 45 MPH 36H 19/1800Z 13.9N 68.8W 40 KT 45 MPH 48H 20/0600Z 14.1N 72.7W 50 KT 60 MPH 72H 21/0600Z 15.0N 80.2W 60 KT 70 MPH 96H 22/0600Z 16.5N 86.5W 60 KT 70 MPH 120H 23/0600Z 17.5N 90.0W 35 KT 40 MPH...INLAND $$ Forecaster Avila NNNN
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