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Tropical Storm Gonzalo Forecast Discussion Number 11
2020-07-24 10:42:38| National Hurricane Center (Atlantic)
Issued at 500 AM AST Fri Jul 24 2020 000 WTNT42 KNHC 240842 TCDAT2 Tropical Storm Gonzalo Discussion Number 11 NWS National Hurricane Center Miami FL AL072020 500 AM AST Fri Jul 24 2020 Conventional satellite imagery indicates that Gonzalo's cloud pattern has changed little during the past several hours. The cyclone continues to produce an area of deep convection, although quite shapeless, with very cold cloud tops. A compromise of the subjective T-numbers from TAFB and SAB along with an earlier SATCON estimate of 55 kt yields an initial intensity of 50 kt for this advisory. An Air Force Reserve reconnaissance aircraft scheduled to investigate the storm later this afternoon will provide a more precise intensity estimate. The statistical-dynamical intensity guidance as well as the deterministic models all show Gonzalo strengthening as it approaches the southern Windward Islands. The HWRF, Decay SHIPS and the LGEM are the only guidance indicating a hurricane around the 36 hour period. Afterward, Gonzalo is forecast to move into a more inhibiting thermodynamic environment over the weekend. Accordingly, the intensity forecast calls for weakening on Sunday as Gonzalo enters the eastern Caribbean sea and dissipation in 96 hours, or sooner as a couple of the large-scale models suggest. The intensity forecast is basically an update of the previous advisory through 36 hours, indicating a hurricane approaching and moving over the southern Windward Islands, and a faster weakening trend afterward, out of respect to the global model's prediction. The initial motion is estimated to be westward, or 275/12 kt and Gonzalo is being steered by a building subtropical ridge to the system's north. The cyclone is expected to increase in forward speed toward the west and west-northwest through the entire period. The NHC official forecast is an update of the previous advisory and is based on the various consensus aids. Key Messages 1. The risk of wind and rain impacts from Gonzalo in portions of the southern Windward Islands this weekend continues to increase, however there is significant uncertainty in how strong Gonzalo will be when it moves across the islands. 2. Despite the uncertainty in Gonzalo's future intensity, hurricane or tropical storm conditions are possible across portions of the southern Windward Islands Saturday and Saturday night. Hurricane and Tropical Storm Warning and Watches are currently in effect for some of the islands. Interests in the southern Windward Islands should monitor the progress of Gonzalo and follow any advice given by local officials. FORECAST POSITIONS AND MAX WINDS INIT 24/0900Z 10.0N 51.8W 50 KT 60 MPH 12H 24/1800Z 10.3N 53.9W 55 KT 65 MPH 24H 25/0600Z 11.0N 56.7W 60 KT 70 MPH 36H 25/1800Z 12.0N 59.9W 65 KT 75 MPH 48H 26/0600Z 13.0N 63.3W 55 KT 65 MPH 60H 26/1800Z 13.7N 66.6W 40 KT 45 MPH 72H 27/0600Z 14.0N 69.9W 35 KT 40 MPH 96H 28/0600Z...DISSIPATED $$ Forecaster Roberts
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