[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT45 KNHC 170241
TCDAT5

Tropical Storm Nigel Discussion Number   7
NWS National Hurricane Center Miami FL       AL152023
1100 PM AST Sat Sep 16 2023

The satellite presentation of the cyclone has improved this evening
as there has been an increase in convective banding over the
northern portion of the circulation.  The center appears to be
located near the southern portion of the convective mass.  Dvorak
Data T-numbers from both SAB and TAFB were T2.5 (35 kt) at 0000 UTC
and objective satellite estimates from UW/CIMSS are in the 35 to 40
kt range.  Based on these data, the initial intensity has been
raised to 35 kt.  Nigel becomes the 10th named storm to form in
the Atlantic basin since August 20th.

Nigel is moving northwestward at about 14 kt.  A mid-level ridge
to the northeast of the cyclone should steer the storm
northwestward during the next few days.  After that time, Nigel is
expected to turn northward around the western side of the ridge. By
the middle of next week, the global model guidance indicates that
the storm should turn northeast ahead of a broad mid-latitude
trough over the western Atlantic.  There is fairly good agreement
in the global model guidance on the overall scenario, but there are
some timing or forward speed difference later in the period.  The
NHC forecast track is near the HFIP corrected consensus which is
close to a blend of the latest GFS and ECMWF models.

Environmental conditions are expected to be conducive for steady
intensification during the next few days, with low vertical wind
shear and warm sea surface temperatures along the forecast track.
A period of rapid intensification is is certainly possible within
the next two to three days.  Although the SHIP RI probabilities are
not very high at the moment, DTOPS gives a 50 percent chance of a 65
kt increase in intensity during the next 72 hours. The NHC forecast
is close to that, showing a 60 kt increase in strength during the
time.  After 72 hours, increasing southwesterly shear is likely to
cause gradual weakening.  The NHC wind speed forecast is closest to
the HFIP corrected consensus.


FORECAST POSITIONS AND MAX WINDS

INIT  17/0300Z 22.0N  48.0W   35 KT  40 MPH
 12H  17/1200Z 23.6N  49.2W   45 KT  50 MPH
 24H  18/0000Z 25.3N  50.6W   55 KT  65 MPH
 36H  18/1200Z 26.7N  52.2W   65 KT  75 MPH
 48H  19/0000Z 27.8N  54.0W   75 KT  85 MPH
 60H  19/1200Z 29.4N  55.7W   85 KT 100 MPH
 72H  20/0000Z 31.3N  56.7W   95 KT 110 MPH
 96H  21/0000Z 36.0N  55.6W   85 KT 100 MPH
120H  22/0000Z 41.9N  47.3W   80 KT  90 MPH

$$
Forecaster Brown
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