Tropical Storm ELSA Advisory Sex, 09-07

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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