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Tropical Storm Calvin Discussion Number   4
NWS National Hurricane Center Miami FL       EP032023
500 AM HST Wed Jul 12 2023

Tropical Storm Calvin continues to strengthen this morning with 
increased curved banding beginning to wrap around the center, as 
well as cold cloud tops associated with a developing central dense 
overcast. Microwave satellite from this morning also showed the 
overall structure of the system is becoming better defined, with 
a prominent curved band beginning to wrap around the center of 
Calvin. Subjective satellite Dvorak estimates from TAFB and SAB 
were T3.0/45 kt and T2.5/35 kt, respectively, while the latest 
objective estimates from UW-CIMSS are higher than 50 kt. Given the 
improved structure based on recent satellite trends, the initial 
intensity is raised to 45 kt for this advisory based on a blend of 
the various intensity estimates. 
  
The storm is currently in a conducive environment for strengthening, 
with light-to-moderate vertical wind shear, and warm sea surface 
temperatures. Given the environment, steady strengthening is 
predicted, with Calvin now forecast to become a hurricane in 24 
hours. There is some guidance showing a roughly 1-in-5 chance for 
rapid intensification to occur during the next 24 hours, however it 
is not explicitly forecast at this time. The NHC intensity forecast 
is near the upper end of the guidance and similar to the previous 
forecast. By the weekend, Calvin is expected to cross over cooler 
SSTs which will likely cause gradual weakening through the remainder 
of the forecast period.
 
Calvin is moving westward or 280/14 kt.  A strong ridge located to 
the north of Calvin, over Mexico, should steer the cyclone westward 
to west-northwestward throughout the forecast.  Model guidance is in 
fairly good agreement with the track--the main difference is the 
forward speed of Calvin with some models moving the storm a little 
faster (particularly HCCA). The updated NHC track forecast lies 
near the center of the guidance envelope, close to the various 
consensus aids to account for those speed differences.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  12/1500Z 12.7N 112.2W   45 KT  50 MPH
 12H  13/0000Z 12.8N 114.3W   55 KT  65 MPH
 24H  13/1200Z 12.9N 117.1W   65 KT  75 MPH
 36H  14/0000Z 13.3N 119.9W   75 KT  85 MPH
 48H  14/1200Z 13.8N 122.8W   80 KT  90 MPH
 60H  15/0000Z 14.5N 125.8W   80 KT  90 MPH
 72H  15/1200Z 15.0N 128.9W   75 KT  85 MPH
 96H  16/1200Z 16.1N 135.2W   65 KT  75 MPH
120H  17/1200Z 17.3N 141.5W   50 KT  60 MPH
 
$$
Forecaster Kelly/Berg
 
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