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Tropical Storm JOAQUIN Forecast Discussion Number 41
2015-10-07 22:33:36| National Hurricane Center (Atlantic)
Issued at 500 PM AST WED OCT 07 2015 000 WTNT41 KNHC 072033 TCDAT1 TROPICAL STORM JOAQUIN DISCUSSION NUMBER 41 NWS NATIONAL HURRICANE CENTER MIAMI FL AL112015 500 PM AST WED OCT 07 2015 Joaquin has begun its transition into an extratropical cyclone. The cyclone's cloud pattern has become rather asymmetric, with the center partially exposed on the west side of weakening deep convection. In addition, cold air is wrapping into the western periphery of the circulation, with a warm frontal band becoming better defined well northeast of the center. Earlier ASCAT data still showed a large area of 55 to 60 kt winds, so the initial wind speed is held at 60 kt. The storm should gradually lose strength while it moves over progressively colder waters north of the Gulf Stream. Deep convection should disappear tonight when the SSTs drop below 20C, and Joaquin is expected to become post-tropical at that time. Global models are in good agreement on the cyclone becoming a large extratropical low on Thursday when frontal features are forecast to form near the center. The official intensity forecast is basically an update of the previous one, and remains in close agreement with the GFS forecast. Joaquin is speeding eastward at 32 kt, embedded in strong westerly flow north of the subtropical ridge, which should keep the cyclone moving to the east or east-northeast at a slower forward speed for another day or two. Thereafter, the cyclone should slow down even more and turn east-southeastward due to it coming under the influence of a developing deep-layer trough over western Europe. The guidance continues to migrate southward, and the official forecast is moved in that direction, near a blend of the Florida State Superensemble and the ECMWF models. The track, intensity, and wind radii forecasts for 12 hours and beyond are primarily based upon guidance provided by the Ocean Prediction Center. FORECAST POSITIONS AND MAX WINDS INIT 07/2100Z 41.5N 41.0W 60 KT 70 MPH 12H 08/0600Z 42.0N 35.3W 50 KT 60 MPH...POST-TROPICAL 24H 08/1800Z 42.7N 28.3W 45 KT 50 MPH...POST-TROP/EXTRATROP 36H 09/0600Z 43.6N 23.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 48H 09/1800Z 43.8N 19.4W 35 KT 40 MPH...POST-TROP/EXTRATROP 72H 10/1800Z 43.0N 14.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 96H 11/1800Z 41.5N 10.0W 30 KT 35 MPH...POST-TROP/EXTRATROP 120H 12/1800Z...DISSIPATED $$ Forecaster Blake
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