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Hurricane Ophelia Forecast Discussion Number 11
2017-10-11 22:31:34| National Hurricane Center (Atlantic)
Issued at 500 PM AST Wed Oct 11 2017 000 WTNT42 KNHC 112031 TCDAT2 Hurricane Ophelia Discussion Number 11 NWS National Hurricane Center Miami FL AL172017 500 PM AST Wed Oct 11 2017 Intensity estimates for Ophelia still range wildly. Dvorak estimates, both subjective and objective, continue to support a much higher intensity than other satellite-derived maximum wind estimates. Adding to the uncertainty, subjective Dvorak classifications at 1800 UTC were higher than 6 hours prior, but since that time, the ragged eye has become obscured in IR imagery. However, a recent SSMIS pass at 1813 UTC indicated that the convective structure of the cyclone has improved during the day, so it wouldn't be surprising if the eye became apparent again shortly. In an attempt to blend all available data, the initial intensity has been increased to 65 kt, making Ophelia a hurricane. However, it should be stressed that the uncertainty of the initial intensity is higher than normal. The hurricane is moving slowly toward the east and the initial motion estimate is 090/3 kt. The hurricane is embedded within weak steering flow, and only a slow northeastward drift is expected for the next 24 h. After that time, an approaching deep-layer trough should force Ophelia to accelerate toward the northeast. All of the deterministic models are in fairly good agreement on the speed and track of Ophelia, however the various model ensembles suggest that the uncertainty is much higher, especially regarding the forward speed of Ophelia beyond 48 h. The official track forecast favors the deterministic model solutions, in part to maintain continuity with the previous advisory. The track forecast is therefore close to the multi-model consensus, but much faster than the various ensemble mean aids. Since it isn't clear exactly how strong Ophelia is, the intensity forecast is low confidence. All of the intensity guidance indicates that strengthening is likely for the next 24 to 36 hours, however the near stationary motion of the hurricane could induce some upwelling and limit the extent to which the hurricane may strengthen. Around 72 hours, the shear should begin to increase substantially as Ophelia begins to interact with the approaching trough, and extratropical transition will likely begin, accompanied by a broadening of the wind field and a gradual decrease of the maximum winds. The global models indicate that this process will complete by 96 h. The new NHC intensity forecast is slightly higher than the previous forecast, but lies on the lower end of the intensity guidance for the first 72 h. It is near the consensus aids thereafter. FORECAST POSITIONS AND MAX WINDS INIT 11/2100Z 30.0N 36.1W 65 KT 75 MPH 12H 12/0600Z 30.3N 35.7W 70 KT 80 MPH 24H 12/1800Z 30.7N 35.2W 75 KT 85 MPH 36H 13/0600Z 31.4N 34.1W 75 KT 85 MPH 48H 13/1800Z 32.3N 31.9W 70 KT 80 MPH 72H 14/1800Z 35.5N 24.5W 70 KT 80 MPH 96H 15/1800Z 43.0N 16.0W 65 KT 75 MPH...POST-TROP/EXTRATROP 120H 16/1800Z 53.5N 10.5W 60 KT 70 MPH...POST-TROP/EXTRATROP $$ Forecaster Zelinsky
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