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Tropical Storm Elsa Forecast Discussion Number 25
2021-07-06 16:46:29| National Hurricane Center (Atlantic)
Issued at 1100 AM EDT Tue Jul 06 2021 000 WTNT45 KNHC 061446 TCDAT5 Tropical Storm Elsa Discussion Number 25 NWS National Hurricane Center Miami FL AL052021 1100 AM EDT Tue Jul 06 2021 Elsa's overall cloud pattern has changed little in organization since earlier today. There continues to be minimal shower and thunderstorm activity over the western semicircle of the circulation, with some bursting of deep convection near and east of the estimated center. A slightly-elevated observing site on Sand Key, near Key West Florida, recently reported a peak 1-minute wind of 49 kt with a gust to 56 kt. This supports the current intensity estimate of 50 kt. Recent WSR-88D Doppler velocities from the Key West radar suggest that the storm could be a little stronger than that. The Air Force Hurricane Hunter mission into the storm has been delayed due to bad weather at the Keesler base, but is rescheduled to investigate Elsa in a few hours. This flight should provide updated information on the intensity of the system. Recently, the storm has been moving a little slower toward the north-northwest and the initial motion is about 340/9 kt. Elsa should move generally northward today and tonight between the western periphery of a subtropical ridge and an area of low pressure over the northwestern Gulf of Mexico. A gradual turn toward the north-northeast should occur on Wednesday as the system moves along the northwestern periphery of the ridge. Thereafter, the cyclone is expected to accelerate northeastward ahead of a trough over the eastern United States and eastern Canada. This will take the system across the southeastern United States within the next couple of days, near the coast of New England in about 3 days and near or over Atlantic Canada in 4 days or so. The official forecast is nearly the same as the previous one and, again, very close to the model consensus. The environment over the eastern Gulf of Mexico is not ideal for strengthening, with moderate westerly shear and some dry mid-level air. However, upper-level divergence ahead of a trough over the east-central Gulf could result in some intensification of the system during the next 12-24 hours. The official forecast continues to show the cyclone nearing hurricane strength while it approaches the north Florida Gulf coast, but this is at the high end of the numerical intensity guidance. Key Messages: 1. Heavy rain will impact Cuba today resulting in significant flooding and mudslides. As Elsa moves near or along the western Florida Peninsula through Wednesday, heavy rainfall may result in isolated flash, urban, and minor river flooding, with considerable flash and urban flooding possible in southwest and western portions of Florida. Mid to late week, heavy rainfall across coastal Georgia, South Carolina, North Carolina, and southeastern Virginia may result in isolated flash and urban flooding, with considerable flash and urban flooding possible across coastal Georgia and the Lowcountry of South Carolina. 2. There is a danger of life-threatening storm surge along portions of the west coast of Florida tonight and Wednesday, and a Storm Surge Warning is in effect for that area. 3. Hurricane conditions are possible tonight and early Wednesday along a portion of the west coast of Florida, where a Hurricane Watch is in effect. Tropical storm conditions are occurring across portions of the Florida Keys and are expected to spread northward along much of the west coast of the state through Wednesday morning, where a Tropical Storm Warning is in effect. 4. A Tropical Storm Watch is in effect for the Georgia coast and portions of the South Carolina coast, where tropical storm conditions are possible late Wednesday and early Thursday. FORECAST POSITIONS AND MAX WINDS INIT 06/1500Z 24.9N 82.8W 50 KT 60 MPH 12H 07/0000Z 26.6N 82.9W 55 KT 65 MPH 24H 07/1200Z 28.9N 83.0W 60 KT 70 MPH 36H 08/0000Z 31.3N 82.0W 35 KT 40 MPH...INLAND 48H 08/1200Z 33.8N 80.0W 30 KT 35 MPH...INLAND 60H 09/0000Z 36.7N 76.4W 35 KT 40 MPH...INLAND 72H 09/1200Z 39.5N 72.5W 40 KT 45 MPH...OVER WATER 96H 10/1200Z 48.0N 60.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 120H 11/1200Z...POST-TROP/EXTRATROP $$ Forecaster Pasch
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