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Hurricane Calvin Discussion Number  11
NWS National Hurricane Center Miami FL       EP032023
1100 PM HST Thu Jul 13 2023
 
Conventional satellite and microwave imagery shows that Calvin is
maintaining a well-defined 15-n mi wide eye, with a symmetric
surrounding deep convective inner core.  The upper-level wind
pattern is also quite impressive this evening, with poleward and
equatorward diffluent flow above 250 mb.  Using a compromise of all
of the subjective and objective intensity estimates yields an
initial intensity of 90 kt.  A 0204 UTC RADARSAT Constellation
Mission (3) overpass indicated that the strongest surface winds
were located in the north and east quadrants with a maximum
sustained wind estimate of about 88 kt. 
 
Conducive atmospheric and oceanic conditions should support some 
further strengthening during the next 12-18 hours. Afterward, 
sea surface temperatures will gradually decrease along the 
hurricane's expected track and the mid-tropospheric humidity should 
also decrease with a slight increase in deep-layer shear.  These 
inhibiting contributions are likely to result in a weakening trend 
through day 5.  Both the GFS and ECMWF global simulated infrared 
satellite predictions show Calvin losing its associated convection 
by the 120-hour period, and the new intensity forecast follows suit 
by indicating the cyclone degenerating to a remnant low at that 
time.  The intensity forecast is based on a blend of the IVCN, HFIP 
Corrected Consensus models while showing a slightly faster 
weakening trend than the previous forecast, and is adjusted more 
toward the global models beyond day 3.
 
The initial motion is estimated to be westward, or 275/14 kt.
There is little change to the forecast synoptic-scale steering
scenario.  The hurricane is moving along the southern periphery of a
well-established subtropical ridge, and a westward to
west-northwestward motion is expected through the 5-day period.
Only slight adjustments were made to the previous forecast and the
NHC forecast remains in good agreement with the latest consensus
aids.
 
The 34-kt wind radii were adjusted based on the previously
mentioned RCM3 overpass.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  14/0900Z 13.2N 121.9W   90 KT 105 MPH
 12H  14/1800Z 13.6N 124.0W  100 KT 115 MPH
 24H  15/0600Z 14.3N 126.8W   95 KT 110 MPH
 36H  15/1800Z 14.9N 129.6W   85 KT 100 MPH
 48H  16/0600Z 15.6N 132.5W   75 KT  85 MPH
 60H  16/1800Z 16.3N 135.4W   65 KT  75 MPH
 72H  17/0600Z 16.9N 138.7W   50 KT  60 MPH
 96H  18/0600Z 17.6N 145.9W   40 KT  45 MPH
120H  19/0600Z 18.3N 153.2W   30 KT  35 MPH...POST-TROP/REMNT LOW
 
$$
Forecaster Roberts
 
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