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| #946439 (Received by flhurricane at: 10:50 AM 30.Oct.2018) TCDAT1 Hurricane Oscar Discussion Number 15 NWS National Hurricane Center Miami FL AL162018 1100 AM AST Tue Oct 30 2018 Cloud-top temperatures have warmed a bit overall, and the convective pattern is becoming more asymmetric as dry air is infiltrating the southern and eastern part of Oscar`s circulation. However, the hurricane is still producing plenty of inner-core convection and some lightning strikes. Dvorak Current Intensity numbers from TAFB and SAB still support maximum winds of 90-100 kt, but objective numbers are much lower (65-75 kt), so Oscar`s initial intensity is lowered slightly to 85 kt. Increasing shear and stronger upper-level divergence will likely offset each other in the short term, causing Oscar to maintain its intensity or only slightly weaken during the next 24 hours. However, a cold front is quickly approaching Oscar from the northwest, and their interaction is expected to cause Oscar to complete extratropical transition and become fully embedded within the frontal zone in about 36 hours. Oscar`s winds should gradually diminish after it becomes extratropical, but the NHC official forecast remains above the various consensus aids from 36 hours and beyond and lies closest to the GFS and ECMWF global models, which should have a good handle on the cyclone`s structure during the post-tropical phase. Oscar continues to accelerate and has turned north-northeastward, or 020/12 kt, while entering the flow between a large high over the eastern/central Atlantic and a mid-latitude trough now moving over the western Atlantic. Oscar is expected to become embedded within the trough by 36 hours (the completion of extratropical transition), with the entire system becoming a cut-off low north of the jet stream by days 4 and 5. The track models are in fairly good agreement on Oscar`s future path, but there are speed differences by the end of the forecast period. Of particular note, the ECMWF is much faster than the other models, showing a more progressive pattern on day 5. The NHC track forecast lies close to the previous official forecast to maintain continuity, but it is still faster than the GFS, HWRF, and the TVCN multi-model consensus at day 5. 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 30/1500Z 29.7N 57.7W 85 KT 100 MPH 12H 31/0000Z 31.8N 56.1W 80 KT 90 MPH 24H 31/1200Z 35.6N 52.6W 80 KT 90 MPH 36H 01/0000Z 40.6N 48.7W 75 KT 85 MPH...POST-TROP/EXTRATROP 48H 01/1200Z 45.1N 44.4W 65 KT 75 MPH...POST-TROP/EXTRATROP 72H 02/1200Z 52.6N 31.8W 55 KT 65 MPH...POST-TROP/EXTRATROP 96H 03/1200Z 59.0N 18.0W 50 KT 60 MPH...POST-TROP/EXTRATROP 120H 04/1200Z 63.5N 6.5W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ Forecaster Berg |
