000 WTNT45 KNHC 300240 TCDAT5 Tropical Storm Isaac Discussion Number 17 NWS National Hurricane Center Miami FL AL102024 300 AM GMT Mon Sep 30 2024 Isaac's expected transition to an extratropical cyclone continues. The tropical storm's cloud pattern has become asymmetrical, with cold clouds limited mostly to the north of the surface center, and it is beginning to take the form of an extratropical rain shield. Partial ASCAT data indicated maximum winds of 45-50 kt, supporting an intensity of 55 kt after accounting for undersampling. This also agrees with the most recent tropical Dvorak analysis from TAFB. The tropical storm should become fully extratropical later today. Models unanimously indicated that Isaac will continue to gradually spin down as a post-tropical low during the next several days. By 96 h, the center of Isaac is expected to become poorly-defined as it interacts with another large non-tropical low pressure system over the north Atlantic. Models are in reasonably good agreement for Isaac's track forecast. It should stay on a generally northeastward track for the next day or so. Beyond that time, there is some disagreement on exactly how soon Isaac's post-tropical remnants will turn north-northeastward, however all of the guidance shows the same generally idea that Isaac will turn toward a broad trough over the north Atlantic. No significant changes were made to the NHC forecast, which is based on the IVCN consensus for intensity and the TVCN consensus for the track. FORECAST POSITIONS AND MAX WINDS INIT 30/0300Z 44.4N 32.8W 55 KT 65 MPH 12H 30/1200Z 45.1N 30.1W 50 KT 60 MPH...POST-TROP/EXTRATROP 24H 01/0000Z 46.7N 26.4W 45 KT 50 MPH...POST-TROP/EXTRATROP 36H 01/1200Z 48.6N 24.1W 40 KT 45 MPH...POST-TROP/EXTRATROP 48H 02/0000Z 50.7N 23.1W 40 KT 45 MPH...POST-TROP/EXTRATROP 60H 02/1200Z 52.4N 22.4W 35 KT 40 MPH...POST-TROP/EXTRATROP 72H 03/0000Z 54.4N 20.8W 35 KT 40 MPH...POST-TROP/EXTRATROP 96H 04/0000Z...DISSIPATED $$ Forecaster D. Zelinsky
Originally Posted at:
NATIONAL HURRICANE CENTER and CENTRAL PACIFIC HURRICANE CENTER
At The NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION
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