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Tropical Storm Dorian Forecast Discussion Number 3
2019-08-25 04:48:49| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Sat Aug 24 2019 000 WTNT45 KNHC 250248 TCDAT5 Tropical Storm Dorian Discussion Number 3 NWS National Hurricane Center Miami FL AL052019 1100 PM AST Sat Aug 24 2019 Dorian's structure hasn't changed substantially since the last advisory. Although southeasterly shear and surrounding dry air appear to be limiting convection, the most recent available microwave imagery showed that the small cyclone is maintaining well-defined convective banding. The initial intensity is still 35 kt, based primarily on the most recent TAFB Dvorak fix. Confidence in the intensity forecast is particularly low due to a number of factors. The small size of Dorian could make it susceptible to large short-term swings in intensity (up or down). While SHIPS diagnostics suggest that the wind shear will be below 10 kt for at least the next 72 h, UW-CIMSS shear diagnostics indicate that the current shear is higher, more like 15-20 kt. And the intensity guidance spread is also notably large, further decreasing confidence in the forecast. For now, the NHC intensity forecast has not been significantly changed, and shows Dorian near hurricane strength when it approaches the Lesser Antilles in a few days. This is a little above the intensity consensus and it should be stressed that it is still too soon to pinpoint potential wind impacts across those islands, given the large uncertainty in the forecast. The official forecast then shows Dorian maintaining hurricane strength across the northeast Caribbean, but it is certainly possible that it could be weaker, especially given the expected surrounding dry environment and a possible increase in wind shear forecast by the GFS and ECMWF models. By the end of the forecast period, the NHC intensity forecast is very close to HCCA and IVCN. An ASCAT-B overpass at 0024 UTC revealed that Dorian is moving slightly faster than previously estimated, now 280/12 kt. Unlike the intensity guidance, the track models are in quite good agreement on the track of Dorian. The tropical storm should continue moving westward to west-northwestward at a similar forward speed, steered primarily by a mid-level ridge stretching across most of the central Atlantic. The NHC forecast is nearly on top of the previous advisory and remains very near the TVCN and HCCA consensus aids. Key Messages: 1. Dorian is forecast to strengthen and could be near hurricane strength when it approaches the Lesser Antilles on Tuesday. 2. It is too soon to determine the specific timing or magnitude of impacts in the Lesser Antilles, but tropical storm or hurricane watches will likely be needed for a portion of the islands on Sunday. FORECAST POSITIONS AND MAX WINDS INIT 25/0300Z 10.9N 50.4W 35 KT 40 MPH 12H 25/1200Z 11.2N 52.0W 40 KT 45 MPH 24H 26/0000Z 11.7N 54.1W 45 KT 50 MPH 36H 26/1200Z 12.5N 56.2W 50 KT 60 MPH 48H 27/0000Z 13.2N 58.2W 55 KT 65 MPH 72H 28/0000Z 15.0N 62.3W 65 KT 75 MPH 96H 29/0000Z 17.0N 66.5W 70 KT 80 MPH 120H 30/0000Z 19.0N 70.0W 55 KT 65 MPH...INLAND $$ Forecaster Zelinsky
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