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| #1153492 (Received by flhurricane at: 4:47 AM 19.Sep.2023) TCDAT5 Hurricane Nigel Discussion Number 16 NWS National Hurricane Center Miami FL AL152023 500 AM AST Tue Sep 19 2023 Nigel is sending mixed signals this morning. While the large eye of the hurricane has become better defined and warmer, convection around the eyewall has weakened (and AMSR2 microwave data show the eyewall is open on the north side). This convective disruption appears to be due to persistent dry air and just enough shear to entrain that air into the inner core. Satellite intensity estimates remain about the same as 6 h ago, so the initial wind speed is unchanged at 75 kt. Both of the NOAA Hurricane Hunter P-3 aircraft are scheduled to be in the hurricane late this morning, so we should have a more precise assessment of Nigel this afternoon. The hurricane still has another day or so to intensify while it remains in light-shear and warm-water conditions, which could facilitate mixing out the dry air that has plagued the internal convective structure. However, it seems like changes with Nigel will be gradual since it has formed a large eye (which tends to be more stable). Nigel should undergo a rapid extratropical transition from 48 to 72 h as it comes under the influence of a strong mid-latitude trough. Little change was made to the previous intensity forecast, above the intensity consensus at short range and near the model average at longer range. SAR data from yesterday evening did suggest Nigel that has grown in size, so that`s reflected in the current and near-term forecast wind radii. The track forecast seems straightforward with Nigel, as the current northwestward motion should bend to northward late today while the hurricane moves along the western periphery of the subtropical ridge. Nigel should then move rather quickly northeastward through late week due to fast flow ahead of a mid-latitudes trough dropping out of the Canadian Maritimes, then northward as an extratropical low this weekend as it is captured by the trough south of Iceland. The new forecast is shifted a touch left to come into better agreement with the consensus guidance. FORECAST POSITIONS AND MAX WINDS INIT 19/0900Z 29.6N 53.6W 75 KT 85 MPH 12H 19/1800Z 31.2N 54.5W 85 KT 100 MPH 24H 20/0600Z 33.8N 54.8W 90 KT 105 MPH 36H 20/1800Z 36.7N 53.2W 85 KT 100 MPH 48H 21/0600Z 39.6N 49.2W 80 KT 90 MPH 60H 21/1800Z 42.5N 42.7W 70 KT 80 MPH 72H 22/0600Z 45.0N 34.7W 60 KT 70 MPH...POST-TROP/EXTRATROP 96H 23/0600Z 51.8N 21.8W 50 KT 60 MPH...POST-TROP/EXTRATROP 120H 24/0600Z 58.5N 21.0W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ Forecaster Blake |
