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Hurricane Gert Forecast Discussion Number 11
2017-08-15 16:34:27| National Hurricane Center (Atlantic)
Issued at 1100 AM EDT Tue Aug 15 2017 000 WTNT43 KNHC 151434 TCDAT3 Hurricane Gert Discussion Number 11 NWS National Hurricane Center Miami FL AL082017 1100 AM EDT Tue Aug 15 2017 Northerly shear of about 20 kt was inhibiting Gert overnight. A pair of microwave passes around 0900 UTC showed that the mid-level center was displaced about 20 n mi south-southeast of the low-level center. Since the time of the earlier microwave passes, outflow in the northwest quadrant has become re-established, suggesting that the shear may be lessening. The initial intensity has been held at 65 kt based on the latest Dvorak classification from TAFB. Environmental diagnostics from SHIPS indicate that the shear should continue to decrease for about the next 24 h, which should allow for a brief window of intensification. The GFS, ECMWF, and UKMET all indicate that extratropical transition will begin sometime between 36 h and 48 h, while the hurricane crosses a strong SST gradient and the shear increases above 30 kt. Gert is forecast to become fully extratropical about a day later. The initial motion is 015/9 kt. Gert has finally begun to round the western edge of the subtropical ridge, and should begin accelerating northeastward later today. The track guidance is tightly clustered for the first 48 h of the forecast. Beyond two days, there is some along-track spread in the models. The GFS forecasts that Gert will move faster and remain separated from a large extratropical low for nearly 5 days, while the ECMWF and UKMET forecast Gert to move slower, causing it to merge with the extratropical low sooner. The official forecast splits the difference between these scenarios for now and indicates that Gert will be absorbed by the extratropical low shortly after 96 h. Swells from Gert are expected to spread northward along the mid-Atlantic coast of the United States during the next few days. These swells are likely to produce dangerous surf and rip current conditions. Please consult products from your local National Weather Service office. FORECAST POSITIONS AND MAX WINDS INIT 15/1500Z 32.8N 72.0W 65 KT 75 MPH 12H 16/0000Z 34.4N 70.7W 70 KT 80 MPH 24H 16/1200Z 36.7N 67.0W 75 KT 85 MPH 36H 17/0000Z 38.9N 61.2W 75 KT 85 MPH 48H 17/1200Z 41.3N 53.3W 70 KT 80 MPH 72H 18/1200Z 48.8N 38.3W 60 KT 70 MPH...POST-TROP/EXTRATROP 96H 19/1200Z 54.0N 34.5W 45 KT 50 MPH...POST-TROP/EXTRATROP 120H 20/1200Z...DISSIPATED $$ Forecaster Zelinsky
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