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Subtropical Storm Oscar Forecast Discussion Number 3
2018-10-27 16:45:00| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Sat Oct 27 2018 000 WTNT41 KNHC 271444 TCDAT1 Subtropical Storm Oscar Discussion Number 3 NWS National Hurricane Center Miami FL AL162018 1100 AM AST Sat Oct 27 2018 Oscar's organization has improved this morning. Although the subtropical storm is still entangled with an upper-level low, convection has increased near the center of the cyclone since last night. The most recent Hebert-Poteat subtropical intensity estimate from TAFB has increased accordingly to 45-50 kt. Furthermore, Canadian drifting buoy 47546 recently reported a minimum pressure of just below 996 mb to the east of Oscar's center, suggesting the central pressure of the cyclone has decreased since the last advisory. The initial intensity is therefore increased to 50 kt for this advisory. Little change has been made to the intensity forecast. The GFS and many of its associated models (HWRF, DSHP, LGEM) have changed abruptly and forecast far less intensification than they did just 6 hours ago. However, the CTCI, HMON, and ECMWF-based statistical guidance still show Oscar reaching hurricane strength within a few days. Rather than chase a possible short-term trend in the intensity guidance, the official intensity forecast will stay the course for now and is a little above the intensity consensus, bringing Oscar to hurricane strength in around 48 h. After that time, some slight additional intensification is possible, but Oscar is ultimately expected to undergo extratropical transition by the end of the forecast period, which should cause the cyclone to steadily weaken. Oscar has turned toward the west and the initial motion estimate is now 270/11 kt. A west-southwestward motion is anticipated later today as Oscar moves around the back side of an mid- to upper-level trough over the central Atlantic, followed by a turn toward the west on the south side of a subtropical ridge to the north. As long as Oscar intensifies as forecast, it should turn sharply northeastward early next week ahead of a mid-latitude trough advancing across the western and central Atlantic, and then accelerate in that direction while undergoing extratropical transition. The GFS is an outlier, showing a much weaker and vertically shallow cyclone that does not fully recurve, but all of the other global models are in generally good agreement with the scenario listed above. Despite the inconsistency of the GFS, the model consensus has not changed significantly since the last advisory, so only minor adjustments were made to the NHC track forecast. FORECAST POSITIONS AND MAX WINDS INIT 27/1500Z 27.3N 48.4W 50 KT 60 MPH 12H 28/0000Z 26.9N 50.6W 55 KT 65 MPH 24H 28/1200Z 26.2N 53.5W 60 KT 70 MPH...TROPICAL CYCLONE 36H 29/0000Z 25.9N 56.1W 60 KT 70 MPH 48H 29/1200Z 26.5N 57.4W 65 KT 75 MPH 72H 30/1200Z 30.2N 57.0W 70 KT 80 MPH 96H 31/1200Z 37.0N 50.0W 70 KT 80 MPH 120H 01/1200Z 47.0N 38.0W 60 KT 70 MPH...POST-TROP/EXTRATROP $$ Forecaster Zelinsky
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