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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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