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| #900946 (Received by flhurricane at: 10:56 AM 31.Aug.2017) TCDAT1 Hurricane Irma Discussion Number 5 NWS National Hurricane Center Miami FL AL112017 1100 AM AST Thu Aug 31 2017 Satellite imagines indicate that Irma is rapidly intensifying. Very deep convection has formed in the central dense overcast, which is now displaying a small and clearing eye. Dvorak estimates were up to 77 kt at 1200 UTC, and since the cloud pattern continues to quickly become more organized, the initial wind speed is set to 85 kt. Irma has moved somewhat south of and slower than all of the model guidance since yesterday. Consequently, it stayed longer over the warmer ocean temperatures away from the drier air to the north, possibly allowing the rapid strengthening. Irma should move over cooler waters tomorrow with some increase in mid-level dry air, so hopefully the hurricane`s intensity will level off by then. In a few days, the hurricane will be moving over warmer waters with light shear shown by all of the model guidance. This should promote further strengthening of Irma, and the NHC forecast shows an extremely dangerous category 4 hurricane next week, similar to the solutions provided by the HWRF and the ECMWF models. The intensity forecast is raised considerably from the previous one due to initial trends, and is on the high end of the guidance at long range. The hurricane has turned west-northwestward at about 9 kt. This motion should continue for the next day or so before a ridge builds over the central Atlantic Ocean. This ridge should force Irma to turn westward by the weekend, and west-southwestward early next week. Guidance continues to trend southward, following the trend of the ECMWF model starting yesterday. Given the strength of the ridge and depth of the tropical cyclone, there are no obvious reasons to discount the anomalous west-southwestward motion seen in most of the guidance. Little change is made to the track forecast in short range, but the track is shifted southward and westward at long range, though not as far southwest as the overnight ECMWF and ECMWF ensemble models. FORECAST POSITIONS AND MAX WINDS INIT 31/1500Z 16.9N 33.8W 85 KT 100 MPH 12H 01/0000Z 17.5N 35.2W 100 KT 115 MPH 24H 01/1200Z 18.0N 37.1W 105 KT 120 MPH 36H 02/0000Z 18.2N 39.2W 105 KT 120 MPH 48H 02/1200Z 18.1N 41.6W 105 KT 120 MPH 72H 03/1200Z 17.0N 46.5W 110 KT 125 MPH 96H 04/1200Z 16.0N 51.0W 110 KT 125 MPH 120H 05/1200Z 16.0N 55.5W 115 KT 130 MPH $$ Forecaster Blake |
