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Tropical Storm Gonzalo Forecast Discussion Number 10
2020-07-24 04:40:41| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Thu Jul 23 2020 000 WTNT42 KNHC 240240 TCDAT2 Tropical Storm Gonzalo Discussion Number 10 NWS National Hurricane Center Miami FL AL072020 1100 PM AST Thu Jul 23 2020 After ingesting a hefty portion of dry high statically stable air this morning, Gonzalo appears to be on the comeback trail. Enhanced infrared BD-curve imagery shows that a small Central Dense Overcast with cloud tops of -80C is redeveloping over the surface center. A compromise of the available subjective and objective satellite intensity estimates supports maintaining 50 kt for this advisory. This morning's upper air sounding from Barbados revealed a very dry, high statically stable atmosphere with a mean RH of 23 percent and a CAPE of only 327 J/Kg. Consequently, Gonzalo will be moving into a rather harsh thermodynamic environment over the weekend. As a result, the NHC forecast calls for weakening beyond the 48 hour period as it enters the eastern Caribbean sea and dissipation well south of Hispaniola at day 5, or sooner as a few of the global models suggest. The intensity forecast is basically an update of the previous advisory through 48 hours, indicating a hurricane approaching and moving over the southern Windward Islands, and a faster weakening trend beyond day 2, similar to a consensus of the large-scale models. The initial motion is estimated to be westward, or 275/12 kt within the stiff mid-tropospheric steering flow provided by an anchored subtropical ridge to the cyclone's north. The song remains the same, with Gonzalo expected to speed up toward the west and west-northwest through the entire period. The NHC official forecast is based on a blend of the various consensus aids and is down the middle of the tightly clustered guidance. 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 Watches are currently in effect for some of the islands, and additional watches or warnings could be required tonight or early Friday. 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 24/0300Z 9.9N 50.6W 50 KT 60 MPH 12H 24/1200Z 10.2N 52.5W 55 KT 65 MPH 24H 25/0000Z 10.7N 55.1W 60 KT 70 MPH 36H 25/1200Z 11.5N 58.2W 65 KT 75 MPH 48H 26/0000Z 12.3N 61.3W 65 KT 75 MPH 60H 26/1200Z 13.3N 64.4W 55 KT 65 MPH 72H 27/0000Z 13.9N 67.3W 45 KT 50 MPH 96H 28/0000Z 14.4N 73.7W 35 KT 40 MPH 120H 29/0000Z...DISSIPATED $$ Forecaster Roberts
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