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Tropical Storm Elsa Forecast Discussion Number 33
2021-07-08 11:01:06| National Hurricane Center (Atlantic)
Issued at 500 AM EDT Thu Jul 08 2021 000 WTNT45 KNHC 080901 TCDAT5 Tropical Storm Elsa Discussion Number 33 NWS National Hurricane Center Miami FL AL052021 500 AM EDT Thu Jul 08 2021 Doppler radar and surface observation indicate that the center of Elsa is moving into southern South Carolina at this time. The organization of the storm has changed little during the past several hours, with a complex of bands in the eastern semicircle. The initial intensity is 35 kt, and these winds are occurring along an area of the coast and coastal waters well southeast of the center. The initial motion is now 035/16. The track guidance is in good agreement that Elsa should accelerate northeastward during the next few days as it becomes entrained into the mid-latitude southwesterly flow, with the track carrying the system across the Carolinas and the mid-Atlantic states during the next 24 hours, then near or over southeastern New England and Atlantic Canada. The new forecast track is basically an update of the previous track, and it is very close to the consensus models. Rawinsonde data and GOES-16 RGB airmass imagery show an upper-level shortwave trough over the southeastern United States to the west of Elsa, and the global models forecast this system to follow the cyclone northeastward and take on a negative tilt. This should result in increasing upper-level divergence over Elsa, which in turn should lead to some strengthening as the storm moves near or over the east coast of the United States. The 00Z ECMWF model is not as bullish on intensification as its previous run, but it and the 00Z UKMET still call for strengthening, and even the weaker GFS forecasts the favorable upper-air pattern. Based on this, the new intensity forecast shows a little more strengthening than the previous forecast. Based on the new forecast track, the tropical storm warning has been extended northward along the United States east coast to Massachusetts. Non-tropical gale warnings are in effect for the coastal areas to the north of the tropical storm warning due to the likelihood that Elsa will become extratropical as it reaches that area. Key Messages: 1. As Elsa moves across the Carolinas Thursday, heavy rainfall may result in limited flash and urban flooding. Heavy rainfall from the Mid-Atlantic into New England Thursday and Friday could lead to considerable flash and urban flooding. 2. Tropical storm conditions are expected along portions of the coasts of Georgia and South Carolina this morning. Tropical storm conditions are also expected along the coasts of North Carolina starting later today and the mid-Atlantic by this afternoon or tonight. Tropical storm conditions are expected in portions of the southern New England states and New York by Friday. Gale winds are expected over the portions of the New Hampshire and Maine coasts by late Friday or Friday night, and those conditions are possible over portions of Atlantic Canada Friday night and Saturday. FORECAST POSITIONS AND MAX WINDS INIT 08/0900Z 33.4N 81.3W 35 KT 40 MPH...INLAND 12H 08/1800Z 35.5N 79.3W 35 KT 40 MPH...INLAND 24H 09/0600Z 38.8N 75.2W 40 KT 45 MPH...INLAND 36H 09/1800Z 42.5N 70.1W 45 KT 50 MPH...OVER WATER 48H 10/0600Z 46.9N 63.6W 45 KT 50 MPH...POST-TROP/EXTRATROP 60H 10/1800Z 51.9N 54.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 72H 11/0600Z 56.6N 44.8W 35 KT 40 MPH...POST-TROP/EXTRATROP 96H 12/0600Z...DISSIPATED $$ Forecaster Beven
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