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Tropical Storm Gordon Forecast Discussion Number 5
2018-09-03 16:55:54| National Hurricane Center (Atlantic)
Issued at 1100 AM EDT Mon Sep 03 2018 618 WTNT42 KNHC 031455 TCDAT2 Tropical Storm Gordon Discussion Number 5 NWS National Hurricane Center Miami FL AL072018 1100 AM EDT Mon Sep 03 2018 Surface observations from the Florida Keys and southeast Florida, along with Doppler velocity data from the Miami radar, indicate that Gordon has continued to become organized this morning. The center of the cyclone passed over Key Largo between 1100-1200 UTC, producing a west wind in Islamorada and also at an observing site in Florida Bay. Doppler velocity data and surface observations support an intensity of 40 kt for this advisory. An Air Force Reserve Unit reconnaissance aircraft is currently investigating Gordon. The initial motion estimate is 300/14 kt. The latest model guidance has shifted slightly to the right, but this is likely due to the more northerly initial position. Other than that, the models remain tightly packed and agree on a general west-northwestward to northwestward motion for the next 48 hours right up until landfall as the strong ridge to the north of Gordon moves little. The new NHC forecast track was adjusted a little to the right of the previous advisory track, but not as far to the east as some of the model guidance out of respect for the reliable ECMWF deterministic run, which is located on the southern edge of the guidance and shows landfall near the mouth of the Mississippi River, a solution that is also supported by the new 0600Z short-range UKMET model run. Gordon's appearance in both radar and satellite imagery has continued to improve over the past several hours. The GFS- and ECMWF-based SHIPS models indicate that westerly to northwesterly vertical wind shear of about 10 kt is allegedly affecting Gordon, but there are no indications of that in satellite imagery that I can see. The cirrus outflow has continued to expand in all quadrants, so the analyzed westerly shear is likely an artifact of the small circulation being positioned so close to the strong trough located its west. Since Gordon will be moving over sea-surface temperatures near 30 deg C during the next 36-48 hours, and be near or underneath an upper-level anticyclone, steady strengthening seems likely. It is possible that Gordon could peak as a Category 1 hurricane after 36 hours, just before landfall occurs. For that reason, a Hurricane Watch has been issued for portions of the central Gulf Coast. The new intensity forecast is above the previous advisory, and is close to a blend of the consensus models HCCA, FSSE, and IVCN. Key Messages: 1. Gordon will bring heavy rainfall and tropical storm conditions to portions of South Florida and the Florida Keys today and a Tropical Storm Warning remains in effect for these areas. 2. Gordon is expected to bring life-threatening storm surge to portions of the central Gulf Coast and a Storm Surge Warning has been issued from the Mouth of the Pearl River to the Mississippi- Alabama border. Residents in these areas should listen to advice from their local officials and all preparations to protect life and property should be rushed to completion. 3. A Tropical Storm Warning and Hurricane Watch are in effect for portions of the central Gulf Coast. Tropical storm conditions are expected to reach those areas late Tuesday, with hurricane conditions possible in the watch area. 4. Heavy rainfall from Gordon will affect southern Alabama, southern Mississippi and Louisiana, where totals could reach as high as 8 inches. This rainfall could cause flash flooding. FORECAST POSITIONS AND MAX WINDS INIT 03/1500Z 25.3N 81.3W 40 KT 45 MPH 12H 04/0000Z 26.5N 83.4W 45 KT 50 MPH 24H 04/1200Z 28.1N 86.0W 50 KT 60 MPH 36H 05/0000Z 29.9N 88.4W 60 KT 70 MPH 48H 05/1200Z 31.3N 90.3W 40 KT 45 MPH...INLAND 72H 06/1200Z 33.9N 93.2W 25 KT 30 MPH...INLAND 96H 07/1200Z 34.8N 94.9W 20 KT 25 MPH...INLAND 120H 08/1200Z 37.6N 95.1W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Stewart
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