Tropical Depression One Forecast Discussion Number 1

By | May 16, 2020

Issued at 500 PM EDT Sat May 16 2020

WTNT41 KNHC 162039
Tropical Depression One Discussion Number   1
NWS National Hurricane Center Miami FL       AL012020
500 PM EDT Sat May 16 2020
Satellite images, Doppler radar data, and surface observations
indicate that the low pressure system located just east of the coast
of central Florida has developed sufficient organization to now be
classified as a tropical depression.  The low-level center is well
defined and deep convection has persisted near the center and in
bands on the east side of the circulation for the past several
hours.  The cyclone is considered tropical instead of subtropical
because it has central deep convection and a relatively small radius
of maximum wind.  The initial intensity is estimated to be 30 kt
based on data collected earlier today by the Air Force Hurricane
Hunters.  Another aircraft is scheduled to investigate the system
this evening.
Based on satellite data and the earlier reconnaissance fixes, the
initial motion of the system is north-northeastward at 11 kt.  A
continued north-northeastward motion at about the same forward speed
is expected during the next 24 hours or so, keeping the cyclone
offshore, but parallel to, the east coast of Florida.  After that 
the model solutions begin to diverge and the details of the track
forecast become more complicated.  The important features for the
future track of the depression appear to be a pair of mid- to
upper-level troughs currently over the central U.S. The specific
amplitude, timing, and location of those troughs will ultimately
result in how close to the coast of North Carolina this system gets.
The GFS and HWRF models are on the left side of the guidance and
bring the system inland or along the coast, while the ECMWF and
UKMET models show an offshore track. The NHC track forecast splits
the difference of these solutions, and lies close to the various
consensus models, which usually perform best.  It should be noted
that forecast uncertainty is typically larger for weak systems like
this one.
The system should gradually strengthen during the next couple of
days as it remains over the Gulf Stream current and in relatively
low wind shear conditions. However, the surrounding air mass is not
particularly moist, so that and the marginally warm SSTs should
limit significant intensification. The NHC intensity forecast calls
for the system to become a tropical storm tonight or on Sunday with
continued slow strengthening as it nears the North Carolina coast.
Extratropical transition should occur in about 3 days, or sooner.
The NHC intensity forecast generally lies roughly near the middle of
the guidance envelope.
Key Messages:
1. A tropical storm watch has been issued for a portion of the
North Carolina coast.  Tropical-storm-force winds and heavy rains
are possible there on Monday.
2. Dangerous coastal surf conditions and rip currents are expected 
to spread northward from Florida to the mid-Atlantic states during 
the next few days.  See products from your local National Weather
Service for more details.
INIT  16/2100Z 28.4N  78.6W   30 KT  35 MPH
 12H  17/0600Z 29.7N  78.0W   35 KT  40 MPH
 24H  17/1800Z 31.4N  77.4W   35 KT  40 MPH
 36H  18/0600Z 33.0N  76.6W   40 KT  45 MPH
 48H  18/1800Z 35.2N  74.8W   45 KT  50 MPH
 60H  19/0600Z 37.1N  72.3W   50 KT  60 MPH
 72H  19/1800Z 38.0N  70.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
 96H  20/1800Z 38.0N  68.5W   45 KT  50 MPH...POST-TROP/EXTRATROP
120H  21/1800Z...DISSIPATED
Forecaster Cangialosi

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