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Tropical Depression Twelve Forecast Discussion Number 1
2021-08-31 22:35:19| National Hurricane Center (Atlantic)
Issued at 800 PM CVT Tue Aug 31 2021 142 WTNT42 KNHC 312035 TCDAT2 Tropical Depression Twelve Discussion Number 1 NWS National Hurricane Center Miami FL AL122021 800 PM CVT Tue Aug 31 2021 Satellite imagery, along with earlier scatterometer data, indicates that the low pressure area over the eastern tropical Atlantic has a well-defined circulation and sufficient organized convection to be considered a tropical depression. Thus, advisories are being initiated on Tropical Depression Twelve. The initial intensity is set at 30 kt based on satellite intensity estimates from TAFB and SAB as well as the scatterometer data. The initial motion is a somewhat uncertain 285/14. A strong low- to mid-level ridge to the north should cause the cyclone to move westward at a faster forward speed for the next 36 h or so, followed by a gradual turn toward the west-northwest and northwest by the end of the period as the depression moves along the southwest side of the ridge. There is some spread in the guidance after 36-48 h, with the GFS and GFS ensemble mean showing a more northward motion while the UKMET and the UKMET ensemble mean show a more westward motion. The official forecast is near the middle of the guidance envelope and is close to the HFIP corrected consensus model, which is a little to the south of the other consensus models. Conditions appear favorable for intensification during the next 72 h or so as the cyclone is in a moist environment with light shear and warm sea surface temperatures. The intensity forecast thus calls for the cyclone to become a tropical storm in 12 h or so and reach hurricane strength in 48-60 h. By the end of the forecast period, the forecast track takes the cyclone over slightly cooler water and into a drier air mass. Based on this, the intensity forecast calls for a slower development rate. The official intensity forecast is in the middle of the intensity guidance, and it is possibly conservative given that many of the global models are showing the development of a large and powerful tropical cyclone. FORECAST POSITIONS AND MAX WINDS INIT 31/2100Z 11.2N 21.1W 30 KT 35 MPH 12H 01/0600Z 11.6N 23.9W 35 KT 40 MPH 24H 01/1800Z 12.0N 27.5W 40 KT 45 MPH 36H 02/0600Z 12.1N 30.7W 50 KT 60 MPH 48H 02/1800Z 12.5N 33.7W 60 KT 70 MPH 60H 03/0600Z 13.3N 36.5W 70 KT 80 MPH 72H 03/1800Z 14.3N 39.0W 80 KT 90 MPH 96H 04/1800Z 16.5N 43.5W 85 KT 100 MPH 120H 05/1800Z 19.5N 47.5W 90 KT 105 MPH $$ Forecaster Beven
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