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Hurricane Oscar Forecast Discussion Number 9
2018-10-29 03:45:42| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Sun Oct 28 2018 000 WTNT41 KNHC 290245 TCDAT1 Hurricane Oscar Discussion Number 9 NWS National Hurricane Center Miami FL AL162018 1100 PM AST Sun Oct 28 2018 Satellite imagery indicates that the structure of Oscar has changed little over the past several hours. Microwave imagery has shown a ring or eye feature which is at least partly encircled by deep convection, and an eye has made occasional appearances in infrared imagery. Satellite intensity estimates have changed little, so the initial intensity remains 65 kt. One change from the previous advisory is that recent scatterometer data show that Oscar has smaller 34-kt wind radii than previously thought, so the initial and forecast wind radii have been modified. The initial motion remains 270/14. Oscar is approaching the western end of a large low- to mid-level ridge over the central Atlantic, and thus it should turn northwestward with a decrease in forward speed during the next 24 h or so. From 24-72 h, the hurricane should recurve into the mid-latitude westerlies on the east side of a deep-layer trough moving eastward through the western and central Atlantic. The models are in good agreement on the forecast track through 72 h, then show significant differences based on whether Oscar merges with a new cut-off low pressure area over the central Atlantic or remains a separate system in the westerlies. The latest GFS has joined the UKMET in showing Oscar racing northeastward into the northeastern Atlantic by 120 h as a separate system. In contrast, the HWRF and the FV3 models show a sharp turn toward the south as the new low captures Oscar. The ECMWF is between these extremes in showing a more gradual turn toward the east well to the east of the HWRF/FV3 and well to the southwest of the GFS/UKMET. The new forecast track is a little west of the previous track in the early part of the forecast based on the current position and motion. Later in the forecast period, it has been shifted a little to the east in best agreement with the ECMWF. Oscar is forecast to remain in a moist and unstable environment for the next 36-48 h, and the trough approaching from the west is likely to create a divergent outflow pattern. Based on this, the intensity forecast now shows a faster rate of strengthening than the previous advisory. After reaching its peak intensity in 36-48 h, it appears likely that the extratropical transition will occur near the 72 h point before the winds drop below hurricane force. After transition, Oscar is expected to gradually decay. It should be noted that if the FV3 scenario verifies, Oscar may maintain tropical cyclone status beyond 72 h. FORECAST POSITIONS AND MAX WINDS INIT 29/0300Z 25.6N 57.0W 65 KT 75 MPH 12H 29/1200Z 25.9N 58.3W 70 KT 80 MPH 24H 30/0000Z 27.1N 59.0W 80 KT 90 MPH 36H 30/1200Z 29.1N 58.3W 85 KT 100 MPH 48H 31/0000Z 32.0N 56.0W 85 KT 100 MPH 72H 01/0000Z 39.0N 48.5W 75 KT 85 MPH...POST-TROP/EXTRATROP 96H 02/0000Z 44.0N 38.0W 60 KT 70 MPH...POST-TROP/EXTRATROP 120H 03/0000Z 45.0N 29.0W 55 KT 65 MPH...POST-TROP/EXTRATROP $$ Forecaster Beven
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