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Tropical Storm Elsa Forecast Discussion Number 37
2021-07-09 10:44:57| National Hurricane Center (Atlantic)
Issued at 500 AM EDT Fri Jul 09 2021 000 WTNT45 KNHC 090844 TCDAT5 Tropical Storm Elsa Discussion Number 37 NWS National Hurricane Center Miami FL AL052021 500 AM EDT Fri Jul 09 2021 Elsa has become better organized this early Friday morning as evidenced by a tightly coiled convective band that wraps completely around the low-level circulation center, along with Doppler radar velocities of more than 80 kt detected between 3000-7000 ft. Upper-level outflow has expanded in all directions except the southwestern quadrant, and the GFS and ECMWF models have assessed the vertical wind shear to only be 10 kt and 13 kt, respectively, over the center. Wind gusts to 68 kt and 62 kt were recently measured in Ludlam Bay, New Jersey, and Beach Haven, New Jersey, respectively. However, radar data suggest that these wind gusts were possibly associated with the passage of nearby tornadic circulations and were not due to Elsa's larger wind field. The central pressure of 1000 mb is based on a nearby pressure report of 1000.6 mb from the Ludlam Bay, New Jersey, WeatherFlow site, but this value could be conservative. The initial wind speed remains 45 kt based on recent observations from offshore buoys. The initial motion is estimated to be 045/27 kt. Elsa is forecast by the latest global and regional models to continue accelerating northeastward today through Saturday due to the system being embedded within deep-layer southwesterly mid-latitude flow. Elsa should move over southeastern New England today and over Atlantic Canada late tonight and on Saturday. The new NHC track forecast lies on top of the previous advisory track and is close to the middle of the tightly packed simple- and corrected-consensus track models. Elsa will be moving over 22-deg-C and cooler sea-surface temperatures by 6 hours and beyond, which should further hasten the ongoing extratropical transition process. This transition is expected to be completed in 18 hours or so when Elsa is forecast to be located over Atlantic Canada. Key Messages: 1. As Elsa moves near Long Island and southern and coastal New England today, heavy rainfall could lead to considerable flash and urban flooding. 2. Tropical storm conditions should continue along portions of the mid-Atlantic coast early this morning. Tropical storm conditions are expected in portions of the southern New England states and New York by late this morning and afternoon. Gusty winds are expected over portions of Atlantic Canada tonight and Saturday. FORECAST POSITIONS AND MAX WINDS INIT 09/0900Z 39.4N 74.3W 45 KT 50 MPH...OVER WATER 12H 09/1800Z 42.2N 70.3W 45 KT 50 MPH...OVER WATER 24H 10/0600Z 46.6N 63.4W 45 KT 50 MPH...POST-TROP/EXTRATROP 36H 10/1800Z 51.3N 54.5W 40 KT 45 MPH...POST-TROP/EXTRATROP 48H 11/0600Z 55.4N 45.2W 35 KT 40 MPH...POST-TROP/EXTRATROP 60H 11/1800Z 59.5N 36.0W 30 KT 35 MPH...POST-TROP/EXTRATROP 72H 12/0600Z...DISSIPATED $$ Forecaster Stewart
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