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| #901021 (Received by flhurricane at: 10:50 PM 31.Aug.2017) TCDAT1 Hurricane Irma Discussion Number 7 NWS National Hurricane Center Miami FL AL112017 1100 PM AST Thu Aug 31 2017 The period of rapid intensification that began in earnest about 24 hours ago appears to have ended, at least for now. Although a ring of very cold cloud tops continues to surround a small eye, the eye appears to have filled somewhat during the evening hours. This may be due to an eyewall replacement cycle that was noted to have begun earlier today. A lack of recent microwave imagery makes it difficult to confirm that, however. The initial intensity remains 100 kt based on a blend of subjective and objective Dvorak current intensity estimates. Even though the intensification of Irma seems to have stopped for now, the hurricane is still embedded within a favorable environment. For the next couple days, internal convective variability, especially eyewall replacement cycles, may cause the intensity to fluctuate up or down. Most of the guidance through this period shows very little change in strength. Beyond 48 hours, Irma will move over much warmer SSTs, and all of the hurricane models forecast some strengthening. The NHC forecast remains a little above the intensity consensus, and is close to the HWRF and HMON models. The initial motion estimate is 295/10 kt. No significant changes have been made to the track forecast. While there remains good agreement among the dynamical models that a ridge building over the central Atlantic will steer Irma toward the west on Friday, and the west-southwest through the weekend, there is large spread beyond 72 h. For example, the GFS shows a somewhat weaker Irma and a weaker ridge, forcing the hurricane to move slower and make a sharper turn back toward the west-northwest. On the other hand, the ECMWF and HWRF depict a stronger ridge and a stronger hurricane on a more southern track. Since my forecast calls for strengthening, the NHC forecast remains south of the multi-model consensus, but is a little north of the corrected consensus, HCCA. FORECAST POSITIONS AND MAX WINDS INIT 01/0300Z 17.8N 35.6W 100 KT 115 MPH 12H 01/1200Z 18.1N 37.0W 100 KT 115 MPH 24H 02/0000Z 18.3N 39.2W 100 KT 115 MPH 36H 02/1200Z 18.2N 41.5W 100 KT 115 MPH 48H 03/0000Z 17.7N 43.8W 105 KT 120 MPH 72H 04/0000Z 16.7N 48.2W 110 KT 125 MPH 96H 05/0000Z 16.3N 52.4W 115 KT 130 MPH 120H 06/0000Z 17.0N 57.0W 120 KT 140 MPH $$ Forecaster Zelinsky |
