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Tropical Storm Harvey Forecast Discussion Number 2
2017-08-17 22:49:02| National Hurricane Center (Atlantic)
Issued at 500 PM AST Thu Aug 17 2017 000 WTNT44 KNHC 172048 TCDAT4 Tropical Storm Harvey Discussion Number 2 NWS National Hurricane Center Miami FL AL092017 500 PM AST Thu Aug 17 2017 An Air Force Reserve Hurricane Hunter aircraft found a well-defined circulation in the low pressure area east of the Lesser Antilles, with the center near a cluster of sheared, but strong, convection. The aircraft data suggest that the maximum winds are near 35 kt and that the central pressure is near 1004 mb. Based on these data, the disturbance is upgraded to Tropical Storm Harvey. The initial motion is 270/16. There is no change to the forecast philosophy since the previous advisory. A deep-layer ridge to the north of the system should steer it quickly just north of due west through the forecast period, with this motion expected to bring the system through the Lesser Antilles and into the eastern Caribbean Sea in 12-24 h, into the central Caribbean by 48-72 h, and to the western Caribbean by 96-120 h. One adjustment is that the 96-120 h points have been nudged a little southward in response to a shift in the guidance, and thus now lie closer to Central America than on the previous forecast. The forecast track again lies near the center of the tightly clustered guidance envelope and the various consensus models. The system is in an area of moderate easterly vertical shear, and the large-scale models suggest that light/moderate shear should continue through at least 72 h. The conflicting forecast scenarios alluded to in the previous advisory remain, with the SHIPS and LGEM models still showing steady intensification while the GFS and ECMWF models still forecast degeneration to an easterly wave over the central Caribbean. The new intensity forecast again follows the trend of the SHIPS/LGEM models, but it remains on the low side of the guidance envelope out of respect for the GFS/ECMWF. The 96-120 h intensities have been decreased a little due to the forecast track showing more land interaction. FORECAST POSITIONS AND MAX WINDS INIT 17/2100Z 13.0N 55.8W 35 KT 40 MPH 12H 18/0600Z 13.1N 58.3W 35 KT 40 MPH 24H 18/1800Z 13.4N 61.6W 40 KT 45 MPH 36H 19/0600Z 13.7N 65.1W 45 KT 50 MPH 48H 19/1800Z 14.0N 68.8W 45 KT 50 MPH 72H 20/1800Z 14.5N 76.5W 55 KT 65 MPH 96H 21/1800Z 15.5N 83.5W 60 KT 70 MPH 120H 22/1800Z 17.0N 88.5W 55 KT 65 MPH...INLAND $$ Forecaster Beven
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