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Subtropical Depression Leslie Forecast Discussion Number 8
2018-09-25 10:37:46| National Hurricane Center (Atlantic)
Issued at 500 AM AST Tue Sep 25 2018 977 WTNT43 KNHC 250837 TCDAT3 Subtropical Depression Leslie Discussion Number 8 NWS National Hurricane Center Miami FL AL132018 500 AM AST Tue Sep 25 2018 No significant changes have occurred with Leslie overnight. Deep convection is generally confined to the eastern half of the circulation as dry air continues to wrap into the western portion of the cyclone. Satellite images indicate that the circulation has become stretched from north to south, likely due to the approach of a cold front that is currently located a few hundred miles to the northwest of Leslie. The initial intensity is held at 30 kt based on the earlier ASCAT data. The cold front is expected to merge with Leslie by tonight, causing extratropical transition. While transitioning, Leslie is forecast to strengthen for a couple of days due to significant baroclinic forcing, and the NHC intensity forecast takes the peak winds just below hurricane force at 36 and 48 hours. Later in the week, the extratropical system is expected to cut off and gradually lose its frontal features. Although this will likely cause some weakening, it should also allow the system to regain subtropical characteristics. The NHC intensity forecast is fairly similar to the previous one and near the IVCN consensus model. This forecast is also in fairly good agreement with the GFS and ECMWF models, which are usually reliable intensity models for large subtropical systems like Leslie. Based on the latest guidance, Leslie is now expected to transition back to a subtropical cyclone in 96 hours. Leslie has jogged to the southeast during the past several hours, but an eastward to northeastward motion is expected during the next day or so as Leslie makes its extratropical transition. After that time, a turn to the north is expected followed by a slow westward motion when Leslie cuts off from the mid-latitude flow. The models are in fairly good agreement on this looping motion, and the NHC track forecast follows the various consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 25/0900Z 31.9N 46.2W 30 KT 35 MPH 12H 25/1800Z 32.1N 44.8W 40 KT 45 MPH 24H 26/0600Z 32.7N 41.9W 50 KT 60 MPH...POST-TROP/EXTRATROP 36H 26/1800Z 34.5N 40.5W 60 KT 70 MPH...POST-TROP/EXTRATROP 48H 27/0600Z 36.1N 41.1W 60 KT 70 MPH...POST-TROP/EXTRATROP 72H 28/0600Z 36.0N 45.0W 55 KT 65 MPH...POST-TROP/EXTRATROP 96H 29/0600Z 35.3N 48.2W 55 KT 65 MPH...SUBTROPICAL STORM 120H 30/0600Z 35.0N 50.0W 50 KT 60 MPH $$ Forecaster Cangialosi
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