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Tropical Storm Dorian Forecast Discussion Number 2
2019-08-24 22:52:16| National Hurricane Center (Atlantic)
Issued at 500 PM AST Sat Aug 24 2019 000 WTNT45 KNHC 242052 TCDAT5 Tropical Storm Dorian Discussion Number 2 NWS National Hurricane Center Miami FL AL052019 500 PM AST Sat Aug 24 2019 Visible and passive microwave satellite imagery indicate that the inner-core of the small cyclone has noticeably improved since the previous advisory. A 1705Z AMSR-2 overpass showed the development of tightly curved bands and a 10 mile wide eye-like feature. In addition, a 1935Z SSMI/S microwave pass revealed a tightly curved band in 91 GHz data that wrapped almost 75 percent around the center. Based on the much improved inner-core structure and 33-kt wind vectors in an earlier ASCAT-B pass, the depression has been upgraded to Tropical Storm Dorian on this advisory. Upper-level outflow has been improving to the northwest, but remains slightly restricted to the southeast due to some modest southeasterly vertical wind shear. The initial motion is 280/11 kt. The latest NHC model guidance remains in excellent agreement that Dorian will generally move west-northwestward for the next 5 days around the southern periphery of the sprawling Bermuda-Azores high pressure ridge that is located to the north of the Lesser and Greater Antilles. This motion is expected to bring Dorian through the central or northern Lesser Antilles on Tuesday, possibly as a hurricane, and then into the northeastern Caribbean Sea on Wednesday and Thursday. The official forecast track was shifted slightly north of the previous advisory track, and is close to the consensus model TVCN, which remains north of the NOAA HCCA corrected-consensus model. The moderate to strong vertical wind shear that has been hindering development of this system for the past several days is forecast to diminish significantly during the next 12 h, and remain near 5 kt through Tuesday. The low shear conditions, along with warm SSTs and the significantly improved small, inner-core structure, should allow for at least slow but steady strengthening despite the abundance of dry mid-level air nearby. However, the low vertical wind shear and tight inner-core wind field are also harbingers of possible rapid intensification. For now, the new intensity forecast remains conservative and similar to the previous advisory, and is above all of the available intensity guidance, including the HWRF model. 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 may be needed for a portion of the area on Sunday. FORECAST POSITIONS AND MAX WINDS INIT 24/2100Z 10.7N 49.1W 35 KT 40 MPH 12H 25/0600Z 11.0N 50.7W 40 KT 45 MPH 24H 25/1800Z 11.4N 52.8W 45 KT 50 MPH 36H 26/0600Z 11.9N 54.9W 50 KT 60 MPH 48H 26/1800Z 12.7N 57.0W 55 KT 65 MPH 72H 27/1800Z 14.6N 61.1W 65 KT 75 MPH 96H 28/1800Z 16.5N 65.3W 75 KT 85 MPH 120H 29/1800Z 18.4N 69.0W 70 KT 80 MPH...INLAND $$ Forecaster Stewart
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