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| #900876 (Received by flhurricane at: 10:44 PM 30.Aug.2017) TCDAT1 Tropical Storm Irma Discussion Number 3 NWS National Hurricane Center Miami FL AL112017 1100 PM AST Wed Aug 30 2017 Irma continues to become better organized, with the development of a small CDO feature and increased banding near the center. An earlier high-resolution Windsat microwave overpass showed that Irma has a tight inner core and a low-level eye-like feature was present. A Dvorak classification of T3.5 from TAFB is the basis for the initial intensity of 55 kt. Irma is expected to steadily strengthen during the next couple of days while it moves through a low-shear and moist environment, and remains over warm sea surface temperatures. After that time, slightly cooler SSTs and lower mid-level moisture may temper the intensification process. However, the statistical aids, HWRF, and most of the consensus models make Irma a major hurricane by the end of the forecast period. The NHC forecast is fairly similar to the previous advisory through 48 hours, but is above the earlier forecast thereafter. The new official intensity forecast could still be a little conservative as it remains a little below the SHIPS/LGEM guidance and the ICON consensus at days 4 and 5. Irma is moving westward at about 10 kt to the south of deep-layer ridge over the eastern Atlantic. The track forecast reasoning is about the same as the previous advisory, with Irma expected to turn west-northwestward on Thursday, then continue on that heading for a couple of days. The high pressure ridge over the central Atlantic is forecast to strengthen later this week, which is expected to result in Irma turning west-southwestward by the weekend. There is still some spread among the track models, so the NHC forecast lies near a blend of the typically reliable GFS and ECMWF, and the HFIP corrected consensus. FORECAST POSITIONS AND MAX WINDS INIT 31/0300Z 16.4N 32.2W 55 KT 65 MPH 12H 31/1200Z 16.8N 33.6W 65 KT 75 MPH 24H 01/0000Z 17.3N 35.5W 75 KT 85 MPH 36H 01/1200Z 17.7N 37.3W 85 KT 100 MPH 48H 02/0000Z 18.0N 39.5W 90 KT 105 MPH 72H 03/0000Z 17.6N 44.3W 95 KT 110 MPH 96H 04/0000Z 16.8N 49.0W 100 KT 115 MPH 120H 05/0000Z 16.2N 53.5W 105 KT 120 MPH $$ Forecaster Brown |
