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Tropical Storm Ida Forecast Discussion Number 2
2021-08-26 22:51:12| National Hurricane Center (Atlantic)
Issued at 500 PM EDT Thu Aug 26 2021 000 WTNT44 KNHC 262051 TCDAT4 Tropical Depression Nine Discussion Number 2 NWS National Hurricane Center Miami FL AL092021 500 PM EDT Thu Aug 26 2021 The overall satellite presentation of the tropical cyclone has continued to gradually improve today. Visible imagery and very recent observations from an Air Force Reserve reconnaissance aircraft indicate that the circulation has continued to become better defined. In addition, the convective activity has become a little better organized in a band around the northeastern and eastern portions of the circulation, and the system is likely near tropical storm strength. However, the initial intensity remains 30 kt pending the aircraft fully sampling the eastern portion of the circulation. The initial motion estimate is northwestward or 325/12 kt. The 1200 UTC dynamical model guidance continues to take the system northwestward around the southwestern side of well-established deep-layer ridge over the western Atlantic. On the forecast track, the system is expected to move over portions of western Cuba late Friday, over the southeastern and central Gulf of Mexico on Saturday, and approach the northern Gulf coast on Sunday. Although the track guidance envelope has tightened this cycle, increasing confidence in the overall forecast scenario, some shifts in the track are still likely until the system consolidates and becomes better defined. Users are reminded to not focus on the exact forecast track as storm surge, wind, and rainfall hazards will extend far from the center, and the average NHC track forecast error at day 3 is around 120 miles. The lastest NHC track forecast is close to the previous official forecast, and lies between the TCVA and HCCA consensus aids. There is some evidence of some light to moderate southerly shear over the system, but with the cyclone moving over the high ocean heat content waters of the northwestern Caribbean Sea the shear should not hinder intensification, with steady strengthening anticipated during the next 12 to 24 hours. Once the system moves over the Gulf of Mexico, it will be traversing a warm eddy, and this feature, combined with a favorable upper-level wind pattern and a moist atmosphere, is likely to result in steady to rapid strengthening on Saturday and Saturday night. The NHC intensity forecast again brings the system to near major hurricane strength when it approaches the northern Gulf coast on Sunday. This is supported by the HWRF and CTCI models, and the global model guidance that has consistently showed significant deepening of the system over the Gulf of Mexico over the past several model cycles. Therefore, as mentioned this morning, there is higher-than-normal confidence that a strengthening tropical cyclone will be moving over the Gulf of Mexico this weekend. Key Messages: 1. Tropical storm conditions are expected in portions of the Cayman Islands tonight and in portions of western Cuba and the Isle of Youth Friday. Dangerous storm surge is possible Friday in portions of western Cuba, including the Isle of Youth, in areas of onshore flow. 2. Life-threatening heavy rains, flash flooding and mudslides are expected across Jamaica, the Cayman Islands, and western Cuba, including the Isle of Youth. 3. The system is forecast to approach the northern Gulf coast at or near major hurricane intensity on Sunday, where there is an increasing risk of life-threatening storm surge, damaging hurricane-force winds, and heavy rainfall Sunday and Monday, especially along the coast of Louisiana. Storm Surge and Hurricane watches will likely be issued for a portion of this area later tonight or Friday morning. Interests in these areas should closely monitor the progress of this system and follow any advice given by local officials. FORECAST POSITIONS AND MAX WINDS INIT 26/2100Z 18.0N 79.8W 30 KT 35 MPH 12H 27/0600Z 19.7N 81.0W 45 KT 50 MPH 24H 27/1800Z 21.7N 82.8W 55 KT 65 MPH...INLAND 36H 28/0600Z 23.7N 84.8W 60 KT 70 MPH...OVER WATER 48H 28/1800Z 25.6N 87.0W 70 KT 80 MPH 60H 29/0600Z 27.2N 88.8W 85 KT 100 MPH 72H 29/1800Z 28.9N 90.4W 95 KT 110 MPH 96H 30/1800Z 31.9N 91.4W 50 KT 60 MPH...INLAND 120H 31/1800Z 34.6N 90.0W 25 KT 30 MPH...INLAND $$ Forecaster Brown
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