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| #946353 (Received by flhurricane at: 4:48 PM 29.Oct.2018) TCDAT1 Hurricane Oscar Discussion Number 12 NWS National Hurricane Center Miami FL AL162018 500 PM AST Mon Oct 29 2018 The overall cloud pattern of Oscar is somewhat asymmetrical, and convective banding is limited to the eastern semicircle of the cyclone. However, recent visible and microwave imagery indicate that tight eyewall of the hurricane is still very well defined, despite the 20 kt or more of westerly shear analyzed in SHIPS and UW-CIMSS diagnostics. It appears that the shear is not having much of an affect on Oscar`s inner-core, and in fact the small eye of the hurricane has become better defined over the past 6 hours. Recent objective and subjective intensity estimates support an intensity of 75-80 kt, and given the small radius of maximum winds (RMW) of Oscar, it seems more appropriate to round up, yielding an estimated intensity of 80 kt. All of the dynamical intensity guidance calls for additional intensification in the short term. Persistent lightning inside the hurricane`s RMW during the past several hours also supports the notion of additional strengthening, as this signal has been associated with intensifying hurricanes in the past. By 24 h and beyond, Oscar will likely level off in intensity and then begin to weaken while it moves over much cooler SSTs and begins extratropical transition. Although this process will likely result in a rapid expansion of Oscar`s tropical-storm-force wind field, it should also cause the maximum winds associated with the cyclone to steadily decrease through the end of the week. The NHC intensity forecast is similar to the previous advisory, and generally follows IVCN through the forecast period. Oscar`s eye has wobbled during the past several hours, but the hurricane appears to have already begun its expected turn toward the north. The hurricane is essentially on-track, and no major changes were required to the NHC track forecast. A large mid-latitude trough to the west will likely cause Oscar to accelerate north-northeastward or northeastward beginning by late Tuesday, and then rapidly move across the northern central Atlantic in that direction. The global models are in reasonably good agreement on the speed and heading of Oscar through day 5, which is somewhat unusual for a recurving cyclone. The new official track forecast is based on a blend of the simple and corrected multi-model consensus aids, and confidence in the track forecast is fairly high. Although Oscar is not expected to directly affect any land areas, large swells from Oscar will affect Bermuda through Wednesday. Please consult products from your local weather office as these conditions could cause life-threatening surf and rip currents. FORECAST POSITIONS AND MAX WINDS INIT 29/2100Z 26.5N 58.5W 80 KT 90 MPH 12H 30/0600Z 27.8N 58.4W 90 KT 105 MPH 24H 30/1800Z 29.9N 57.2W 90 KT 105 MPH 36H 31/0600Z 33.0N 54.3W 85 KT 100 MPH 48H 31/1800Z 37.3N 50.3W 80 KT 90 MPH 72H 01/1800Z 46.7N 40.0W 60 KT 70 MPH...POST-TROP/EXTRATROP 96H 02/1800Z 54.0N 25.0W 55 KT 65 MPH...POST-TROP/EXTRATROP 120H 03/1800Z 60.0N 12.0W 50 KT 60 MPH...POST-TROP/EXTRATROP $$ Forecaster Zelinsky |
