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Tropical Storm Calvin Discussion Number   6
NWS National Hurricane Center Miami FL       EP032023
500 PM HST Wed Jul 12 2023
 
Calvin continues to steadily strengthen.  A couple microwave passes 
from within the past few hours showed that storm had a nearly closed 
low-level eye and a mid-level eye open to the northwest.  Recent 
geostationary satellite imagery suggests the storm's inner core may 
have experienced some dry air entrainment from that quadrant.  
However, deep convection with over-shooting tops is still present in 
the eastern portion of the circulation.  Subjective satellite Dvorak 
estimates from SAB and TAFB were T4.0/65 kt and T3.5/55 kt, 
respectively.  The initial intensity has been increased to 60 kt 
based on a blend of these estimates.

Atmospheric and oceanic conditions are conducive for additional 
strengthening.  Calvin is forecast to be in a generally moist 
environment, with low vertical wind shear, and warm sea surface 
temperatures for the next few days.  After 72 h, the SSTs beneath 
the storm are expected to gradually cool, while vertical wind shear 
increases and mid-level humidity decreases.  The combination of 
these factors should induce a weakening trend during this portion of 
the forecast period.  The official intensity prediction is similar 
to the previous advisory and is stronger than most of the guidance 
due to the potential for rapid intensification in the short-term 
forecast.

The storm is moving westward at about 15 kt.  A ridge to the north 
is steering Calvin at a brisk pace and a west to west-northwest 
motion should continue through the end of the forecast period.  
There is still notable spread in the model guidance related to the 
along-track speed of the cyclone.  The NHC track forecast is similar 
to the previous advisory and favors the faster model guidance, 
falling between the simple and corrected consensus aids. 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  13/0300Z 12.6N 114.9W   60 KT  70 MPH
 12H  13/1200Z 12.7N 117.0W   70 KT  80 MPH
 24H  14/0000Z 13.0N 119.7W   80 KT  90 MPH
 36H  14/1200Z 13.7N 122.5W   85 KT 100 MPH
 48H  15/0000Z 14.4N 125.4W   85 KT 100 MPH
 60H  15/1200Z 15.0N 128.4W   80 KT  90 MPH
 72H  16/0000Z 15.6N 131.4W   75 KT  85 MPH
 96H  17/0000Z 16.7N 138.0W   60 KT  70 MPH
120H  18/0000Z 17.7N 144.7W   50 KT  60 MPH
 
$$
Forecaster Bucci
 
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