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Hurricane JOAQUIN Forecast Discussion Number 38
2015-10-07 04:56:01| National Hurricane Center (Atlantic)
Issued at 1100 PM AST TUE OCT 06 2015 000 WTNT41 KNHC 070255 TCDAT1 HURRICANE JOAQUIN DISCUSSION NUMBER 38 NWS NATIONAL HURRICANE CENTER MIAMI FL AL112015 1100 PM AST TUE OCT 06 2015 Until just a couple of hours ago, Joaquin continued to display a tight inner core, with deep convection surrounding a 20 n mi diameter eye. The most recent geostationary infrared imagery is finally showing that the convection is becoming asymmetric with the 25 kt of tropospheric vertical shear adversely affecting the cyclone. The intensity remains 70 kt, since both the SAB and TAFB Dvorak Current Intensity values are unchanged. The hurricane is about to cross over the north wall of the Gulf Stream and will be traversing very chilly 21-22C waters by tomorrow. The combination of cold SSTs, dry air, and strong vertical shear should cause the deep convection to either completely dislocate or cease and the forecast calls for Joaquin to become a strong post-tropical cyclone in about a day. The FSU Cyclone Phase Space diagrams, based upon the global and regional models, suggest that Joaquin will gradually become more frontal and extratropical transition is anticipated by Thursday. Baroclinic forcing should allow for only a gradual winding down as depicted by the models, and dissipation is anticipated in about five days. Joaquin is moving toward the east-northeast at a rather quick pace of 25 kt, as it is being advected along by the mid-latitude westerlies. The system should accelerate east-northeastward for about 36 hours, before slowing down in the eastern north Atlantic. The track forecast is based upon the tightly clustered global and regional models through 72 hours. By day four, the guidance becomes divergent with some solutions turning northeastward toward Ireland and Great Britain, but most turning east-southeastward toward Portugal and Spain. This latter scenario is the basis for the track forecast at day 4. The track, intensity, and wind radii forecasts from 36 hours and beyond are based upon guidance provided by the Ocean Prediction Center. A last-minute-arriving ASCAT scatterometer pass indicated that Joaquin continues to expand in size. The 34- and 50-kt wind radii analyses and forecasts were adjusted accordingly. FORECAST POSITIONS AND MAX WINDS INIT 07/0300Z 40.0N 53.1W 70 KT 80 MPH 12H 07/1200Z 41.0N 47.7W 65 KT 75 MPH 24H 08/0000Z 42.1N 39.3W 60 KT 70 MPH...POST-TROPICAL 36H 08/1200Z 43.4N 31.2W 60 KT 70 MPH...POST-TROP/EXTRATROP 48H 09/0000Z 44.7N 25.0W 50 KT 60 MPH...POST-TROP/EXTRATROP 72H 10/0000Z 44.0N 17.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 96H 11/0000Z 43.0N 13.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 120H 12/0000Z...POST-TROP/EXTRATROP $$ Forecaster Landsea
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