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Tropical Storm Ophelia Forecast Discussion Number 9
2017-10-11 10:36:31| National Hurricane Center (Atlantic)
Issued at 500 AM AST Wed Oct 11 2017 000 WTNT42 KNHC 110836 TCDAT2 Tropical Storm Ophelia Discussion Number 9 NWS National Hurricane Center Miami FL AL172017 500 AM AST Wed Oct 11 2017 Ophelia has become better organized during the past several hours, with convective banding now wrapping almost all of the way around the center. Satellite intensity estimates from TAFB and SAB have increased to 55 kt and 65 kt, respectively, and several recent microwave-based intensity estimates are in the 55-65 kt range. Based on this, the initial intensity is increased to a possibly conservative 55 kt. The initial motion is now 125/5. Ophelia should continue to move southeastward or east-southeastward during the next 12-24 hours with a decrease in forward speed while it remains embedded within a mid- to upper-level trough to the south of the mid-latitude westerlies. After that, the cyclone is forecast to turn northeastward and accelerate by day 3 ahead of a deepening mid-latitude trough over the north-central Atlantic. The latest track guidance is in good agreement with this scenario. However, there has been a significant northward shift in the 120 h forecasts since the last advisory. The new official forecast track is similar to the previous track through 72 h, and then is adjusted northward at the 96 and 120 h points. It should be noted, though, that the 120 h point is to the south of the consensus and large-scale models, and additional northward adjustments may be required later. The cyclone is expected to be within a low shear environment and over marginally warm sea surface temperatures during the next 2 to 3 days. These conditions favor strengthening and the NHC forecast now calls for Ophelia to become a hurricane in about 24 hours. Extratropical transition is likely to start around day 4 and be complete by day 5, with the associated baroclinic dynamics expected to keep Ophelia a strong cyclone over the northeastern Atlantic. FORECAST POSITIONS AND MAX WINDS INIT 11/0900Z 30.2N 37.0W 55 KT 65 MPH 12H 11/1800Z 29.9N 36.4W 60 KT 70 MPH 24H 12/0600Z 30.1N 35.9W 65 KT 75 MPH 36H 12/1800Z 30.5N 35.3W 75 KT 85 MPH 48H 13/0600Z 31.2N 34.0W 75 KT 85 MPH 72H 14/0600Z 33.5N 28.5W 70 KT 80 MPH 96H 15/0600Z 37.5N 20.5W 70 KT 80 MPH 120H 16/0600Z 43.0N 13.0W 65 KT 75 MPH...POST-TROP/EXTRATROP $$ Forecaster Beven
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