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| #938536 (Received by flhurricane at: 4:54 PM 04.Sep.2018) TCDAT2 Tropical Storm Gordon Discussion Number 10 NWS National Hurricane Center Miami FL AL072018 400 PM CDT Tue Sep 04 2018 Gordon has been undergoing another convective bursting phase during the past few hours, with a sharp increase in Doppler velocity values noted between 9,000-12,000 ft. Some peak velocity values have been in excess of 80 kt, but average values have been around 65-67 kt, which supports an advisory intensity of 60 kt. Another reconnaissance mission will be conducted in Gordon in a few hours, which provide additional intensity and pressure data. The initial motion estimate is 310/13 kt. There remains no significant change to the previous NHC forecast track or reasoning. The new model guidance has shifted slightly to the east, but not enough to make any appreciable changes to the previous forecast track. As a result, Gordon is expected to move northwestward toward the Mississippi coastline, and the cyclone will make landfall in that area around 0300 UTC. After landfall, steering currents are still expected to weaken, causing Gordon to slow down considerably. The slower forward speed, which will be near 5 kt at times, will act to enhance the heavy rainfall potential. By Friday, a mid- to upper-level trough and a cold front are forecast to cause a break int the subtropical ridge, allowing Gordon to turn northward on Friday, and move northeastward on Saturday. Gordon`s remnant circulation is expected to merge with a cold front by Sunday. The new official track forecast is close to a blend of the consensus models HCCA, FSSE, and TVCA, Gordon still has another 6 hours or so over warm waters near 30C, which in combination with an upper-level environment of diffluent southeasterly upper-level flow and increased surface convergence due to land interaction will provide a brief window of opportunity for Gordon to reach hurricane strength before landfall. Once Gordon moves inland, the small circulation is expected to spin down quickly, with Gordon becoming a remnant low by 48 hours. Key Messages: 1. Gordon is expected to bring life-threatening storm surge and hurricane conditions to portions of the central Gulf Coast, where a Storm Surge Warning and Hurricane Warning are in effect. The highest storm surge is expected along the coasts of Mississippi and Alabama from the Mouth of the Pearl River to Dauphin Island tonight and early Wednesday. Tropical storm conditions and storm surge will also affect portions of the western Florida Panhandle. 2. Heavy rainfall from Gordon will affect the western Florida Panhandle, southwest Alabama, southern and central Mississippi, northeastern Louisiana, and southern Arkansas, where totals could reach as high as 12 inches. This rainfall will cause flash flooding in portions of these areas. FORECAST POSITIONS AND MAX WINDS INIT 04/2100Z 29.4N 87.8W 60 KT 70 MPH 12H 05/0600Z 30.7N 89.3W 55 KT 65 MPH...INLAND 24H 05/1800Z 32.2N 90.7W 30 KT 35 MPH...INLAND 36H 06/0600Z 33.2N 91.9W 25 KT 30 MPH...INLAND 48H 06/1800Z 34.0N 93.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 07/1800Z 35.7N 94.1W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 08/1800Z 38.1N 93.1W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 09/1800Z 41.0N 89.5W 20 KT 25 MPH...POST-TROP/EXTRATROP $$ Forecaster Stewart |
