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Tropical Storm Elsa Forecast Discussion Number 36
2021-07-09 04:35:23| National Hurricane Center (Atlantic)
Issued at 1100 PM EDT Thu Jul 08 2021 000 WTNT45 KNHC 090235 TCDAT5 Tropical Storm Elsa Discussion Number 36 NWS National Hurricane Center Miami FL AL052021 1100 PM EDT Thu Jul 08 2021 Elsa has become slightly better organized this evening. Convection near the center of Elsa has deepened, and the surface pressures have fallen a few mb since this afternoon based on observations over eastern Virginia. Although there are no wind reports above 40 kt during the past several hours, recent Doppler velocity data shows stronger winds offshore of the mid-Atlantic states, so the initial wind speed will remain 45 kt. It appears that the early stages of extratropical transition have begun with Elsa, with almost all of the deep convection north of the center. A shortwave moving out of the Great Lakes should cause the storm to deepen on Friday but also expand in size, resulting in the maximum winds staying about the same as they are now. Elsa should transition into an extratropical cyclone within 24 hours due to the shortwave and cold waters south of New England, and then gradually weaken over Atlantic Canada and northeast of Newfoundland after it loses its baroclinic support. The new intensity forecast is similar to the previous one and the consensus of the global models. The storm is moving faster to the northeast this evening and will gradually accelerate northeastward during the next day or two due to speedy mid-latitude southwesterly flow ahead of a broad mid-tropospheric trough over the eastern North America. Elsa should move over southeastern New England and Atlantic Canada within the next 12-36 hours. The model guidance remains tightly packed on that solution, and the new official track forecast remains close to the previous one. Key Messages: 1. As Elsa moves across the eastern mid-Atlantic overnight, heavy rainfall may result in limited flash and urban flooding. Heavy rainfall across New England through Friday could lead to considerable flash and urban flooding. 2. Tropical storm conditions should continue along portions of the mid-Atlantic coast overnight. Tropical storm conditions are expected in portions of the southern New England states and New York by Friday. Gusty winds are expected over portions of Atlantic Canada Friday night and Saturday. FORECAST POSITIONS AND MAX WINDS INIT 09/0300Z 37.6N 76.5W 45 KT 50 MPH...INLAND 12H 09/1200Z 40.5N 72.7W 45 KT 50 MPH...OVER WATER 24H 10/0000Z 44.6N 66.9W 45 KT 50 MPH...POST-TROP/EXTRATROP 36H 10/1200Z 49.4N 59.1W 40 KT 45 MPH...POST-TROP/EXTRATROP 48H 11/0000Z 54.5N 48.5W 35 KT 40 MPH...POST-TROP/EXTRATROP 60H 11/1200Z 58.5N 40.5W 30 KT 35 MPH...POST-TROP/EXTRATROP 72H 12/0000Z...DISSIPATED $$ Forecaster Blake
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