[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT45 KNHC 181443
TCDAT5

Hurricane Nigel Discussion Number  13
NWS National Hurricane Center Miami FL       AL152023
1100 AM AST Mon Sep 18 2023

Nigel is exhibiting a somewhat ragged-looking eye on satellite
imagery, surrounded by bands of very deep convection with cloud
tops to -80 deg C.  High-level outflow has become a bit restricted
over the northeastern quadrant of the circulation, but overall the
system continues to become better organized.  The current intensity
estimate of 70 kt is a blend of subjective and objective
satellite-derived estimates.

During the next day or so, the hurricane should remain in an
environment that is quite conducive for strengthening.  Vertical
shear is forecast to remain very low and SSTs are near 28 deg C.
The SHIPS Rapid Intensification (RI) Index continues to show above
normal probabilities of RI.  Accordingly, the official forecast
calls for a 30-kt increase in intensity during the ensuing 24
hours. In a couple of days, increasing shear and cooler waters are
likely to result in the beginning of a gradual weakening trend.  In
4-5 days, global forecast models depict Nigel becoming involved with
a frontal zone over the North Atlantic.  Therefore, the official
forecast shows the system as extratropical in 5 days, although this
transition could occur a little sooner than that.

Nigel's motion continues toward the northwest, or at about 325/10
kt.  The hurricane is currently situated on the southwestern edge
of a mid-level high pressure area.  Over the next day or two, the
system should move around the western periphery of the high.
On this track, Nigel will turn northward in about 36 hours.
Thereafter,  the cyclone should accelerate in the flow to the
southeast and south of a strong mid-latitude trough, and head into
the higher latitudes of the Atlantic.  The track guidance is
fairly tightly clustered, and the new official forecast is
very similar to the previous one.  This is also in close agreement
with the dynamical model consensus aids, HCCA and TVCA.


FORECAST POSITIONS AND MAX WINDS

INIT  18/1500Z 27.2N  51.4W   70 KT  80 MPH
 12H  19/0000Z 28.4N  52.5W   85 KT 100 MPH
 24H  19/1200Z 30.0N  53.9W  100 KT 115 MPH
 36H  20/0000Z 32.0N  54.8W  100 KT 115 MPH
 48H  20/1200Z 34.6N  54.5W   95 KT 110 MPH
 60H  21/0000Z 37.4N  52.4W   90 KT 105 MPH
 72H  21/1200Z 40.3N  47.7W   85 KT 100 MPH
 96H  22/1200Z 46.5N  33.0W   70 KT  80 MPH
120H  23/1200Z 53.5N  20.0W   50 KT  60 MPH...POST-TROP/EXTRATROP

$$
Forecaster Pasch
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