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Subtropical Storm Leslie Forecast Discussion Number 10
2018-09-28 22:47:45| National Hurricane Center (Atlantic)
Issued at 500 PM AST Fri Sep 28 2018 295 WTNT43 KNHC 282047 TCDAT3 Subtropical Storm Leslie Discussion Number 10 NWS National Hurricane Center Miami FL AL132018 500 PM AST Fri Sep 28 2018 Central convection associated with Post-Tropical Storm Leslie has gradually increased during the last couple of days and is now organized into a group of bands that wraps most of the way around the center. In addition, scatterometer data show that the cyclone has lost much of its large baroclinic wind field, and that the radius of maximum winds has contracted from 120-180 n mi yesterday to 90 n mi or less today. While the storm has also developed a warm core and shed some of its baroclinic characteristics, it is embedded in a large deep-layer low pressure system, and thus it is designated subtropical instead of tropical. The initial intensity is set at 45 kt based on the scatterometer data. Leslie has been moving generally westward for the the past few days. The large-scale models forecast a general southwesterly motion for the next 3-4 days as the cyclone is steered by a segment of the subtropical ridge to its west and another large deep-layer low forming to its east over the eastern Atlantic, with a decrease in forward speed near the end of the forecast period as the ridge to the west weakens. The forecast guidance is tightly clustered through 120 h, and the forecast track is near the center of the guidance envelope and the consensus models. The forecast track takes the center of Leslie over increasing sea surface temperatures during the next several days, although the temperatures may not be as warm as those indicated in the SHIPS model. The global models suggest that little change in strength will occur during the first 48-72 h as Leslie gradually develops the upper-level outflow pattern of a tropical cyclone and transitions to a tropical storm. After that time, they are in good agreement that the cyclone will strengthen. Based on this, the intensity forecast shows only modest intensification during the first 48 h, followed by strengthening to a probably conservative 60 kt. The forecast also calls for transition to a tropical storm between 48-72 h, with the caveat that this could occur earlier. FORECAST POSITIONS AND MAX WINDS INIT 28/2100Z 36.1N 48.1W 45 KT 50 MPH 12H 29/0600Z 35.4N 49.6W 45 KT 50 MPH 24H 29/1800Z 34.4N 51.2W 45 KT 50 MPH 36H 30/0600Z 33.8N 52.2W 50 KT 60 MPH 48H 30/1800Z 33.2N 53.1W 50 KT 60 MPH 72H 01/1800Z 32.5N 54.5W 55 KT 65 MPH...TROPICAL STORM 96H 02/1800Z 31.0N 56.0W 60 KT 70 MPH 120H 03/1800Z 31.0N 57.0W 60 KT 70 MPH $$ Forecaster Beven
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