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Tropical Depression FIONA Forecast Discussion Number 23
2016-08-22 16:34:16| National Hurricane Center (Atlantic)
Issued at 1100 AM AST MON AUG 22 2016 000 WTNT41 KNHC 221434 TCDAT1 TROPICAL DEPRESSION FIONA DISCUSSION NUMBER 23 NWS NATIONAL HURRICANE CENTER MIAMI FL AL062016 1100 AM AST MON AUG 22 2016 The satellite depiction of Fiona currently features an exposed low-level circulation with a few small areas of convection southeast of the center. Subjective satellite intensity estimates from TAFB and SAB are 30 kt, while the various objective estimates range from 25-45 kt. The initial intensity remains 30 kt based mainly on the subjective estimates. The dynamical models forecast that the current westerly vertical shear will subside somewhat by 48 hours as Fiona moves under an upper-level trough into an area of easterly upper-level winds to the north of the trough. By 72 hours, the models forecast the cyclone or its remnants to encounter a second trough, which should produce another round of strong southwesterly shear. Based on the premise that the cyclone will not be able to respond to the brief period of more favorable conditions, the new intensity forecast calls for Fiona to gradually decay and become a remnant low in about 36 hours. This would be followed by the system weakening to a trough after 96 hours. The initial motion is 285/16. The guidance remains in good agreement on the forecast track through 72 hours, with Fiona moving west-northwestward to northwestward toward a developing break in the subtropical ridge. Beyond that time, the guidance diverges, with the ECMWF turning the remnants of the system northeastward while the GFS and UKMET show a westward turn. The new forecast track will compromise between these extremes in showing a slow north-northwestward motion. The new forecast track is shifted a little to the west of the previous track and lies near the various consensus models. FORECAST POSITIONS AND MAX WINDS INIT 22/1500Z 24.6N 59.7W 30 KT 35 MPH 12H 23/0000Z 25.3N 61.5W 30 KT 35 MPH 24H 23/1200Z 26.1N 63.5W 30 KT 35 MPH 36H 24/0000Z 27.0N 65.2W 30 KT 35 MPH...POST-TROP/REMNT LOW 48H 24/1200Z 28.1N 66.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 25/1200Z 30.0N 68.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 26/1200Z 31.5N 68.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 27/1200Z...DISSIPATED $$ Forecaster Beven
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