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Tropical Storm Calvin Discussion Number   3
NWS National Hurricane Center Miami FL       EP032023
300 AM MDT Wed Jul 12 2023
 
Deep convection associated with the cyclone has continued to become
better organized overnight.  There has been a noticeable increase
in banding and the center appears to be located beneath a
developing CDO.  Data T-numbers from TAFB and SAB were 2.5 and 
3.0, respectively although the final T-number from SAB was lower. 
A couple of scatterometer passes shortly before 0600 UTC revealed 
winds of 32-34 kt.  Based on the continued improvement in 
structure since that time and the Dvorak data-T numbers, the 
initial intensity is raised to 40 kt for this advisory.  Calvin 
becomes the third named storm of the 2023 eastern Pacific hurricane 
season.
 
Environmental conditions consisting of light-to-moderate shear, 
warm sea surface temperatures, and plentiful low- to mid-level 
moisture favor continued intensification of the system during the 
next couple of days.  Given the fairly small radius of maximum 
wind (RMW) noted in the recent scatterometer data and the conducive 
environment, steady strengthening is predicted, and Calvin is now 
forecast to become a hurricane within 36 hours.  It would not be 
surprising to see the storm go through a period of rapid 
strengthening, however the model guidance is not very bullish on 
that scenario.  The NHC intensity forecast is near the upper-end of 
the guidance, but this could be somewhat conservative.  By 72 hours, 
Calvin is expected to encounter cooler sea surface temperatures 
which is likely to induce gradual weakening during the 
remainder of the period. 

Calvin is moving westward or 270/14 kt.  A strong low- to mid-level 
ridge located to the north of Calvin should steer the cyclone 
westward during the next several days.  After that time, Calvin is 
forecast to move westward to west-northwestward to the south of the 
ridge.  Although the guidance is in good agreement on that overall 
scenario, there are some differences in the predicted forward speed 
of the cyclone. 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  12/0900Z 12.4N 110.6W   40 KT  45 MPH
 12H  12/1800Z 12.6N 112.8W   45 KT  50 MPH
 24H  13/0600Z 12.7N 115.5W   55 KT  65 MPH
 36H  13/1800Z 12.9N 118.2W   65 KT  75 MPH
 48H  14/0600Z 13.4N 121.1W   70 KT  80 MPH
 60H  14/1800Z 14.1N 124.1W   75 KT  85 MPH
 72H  15/0600Z 14.7N 127.1W   75 KT  85 MPH
 96H  16/0600Z 15.8N 133.3W   65 KT  75 MPH
120H  17/0600Z 16.9N 139.8W   50 KT  60 MPH
 
$$
Forecaster Brown
 
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