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Tropical Storm Calvin Discussion Number  22
NWS National Hurricane Center Miami FL       EP032023
500 PM HST Sun Jul 16 2023

Calvin is slowly weakening, with diminishing deep convection mainly 
over the eastern portion of the circulation.  Convective banding 
features have become ill-defined.  The current intensity estimate 
is reduced to 50 kt, based on a blend of subjective Dvorak 
estimates from SAB and TAFB along with objective SATCON estimates 
from UW-CIMSS.

Calvin is traversing SSTs of around 24 deg C, and although water 
temperatures should increase slightly while the cyclone approaches 
Hawaii, drier mid-level air as well as increasingly strong vertical 
shear should cause gradual weakening over the next couple of days.  
Nonetheless, the dynamical guidance, such as the HAFS and GFS 
models, suggests that Calvin will still be producing winds near 
tropical-storm-force, at least over its northern semicircle, when it 
nears the Hawaiian Islands.  The official intensity forecast is 
similar to the previous one and is close to the model consensus.

The official track forecast and its reasoning are basically 
unchanged from the previous advisory.  A mid-level ridge to the 
north of the tropical cyclone should maintain a generally westward 
motion for the next few days.  On this track, Calvin should 
enter the central Pacific basin soon, and move near or over the 
Big Island of Hawaii early Wednesday.  It should then continue 
westward, becoming post-tropical on Thursday before dissipating. 
The official forecast remains close to the latest NOAA corrected 
consensus guidance.
 
While the exact storm track near Hawaii is still uncertain, there is
potential for portions of the state to experience some heavy
rainfall, dangerous surf and rip current conditions, along with 
minor wind impacts from Calvin. A Tropical Storm Watch may be 
required for portions of the main Hawaiian Islands tonight.
 
 
KEY MESSAGES:
 
1. Calvin is forecast to approach the Hawaiian Islands during the
next couple of days or so, bringing the potential for heavy
rainfall and dangerous surf and rip current conditions. A Tropical
Storm Watch could be issued for portions of the main Hawaiian
Islands tonight.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  17/0300Z 16.4N 137.9W   50 KT  60 MPH
 12H  17/1200Z 16.8N 140.4W   45 KT  50 MPH
 24H  18/0000Z 17.3N 144.0W   40 KT  45 MPH
 36H  18/1200Z 17.7N 147.7W   40 KT  45 MPH
 48H  19/0000Z 18.3N 151.5W   35 KT  40 MPH
 60H  19/1200Z 18.8N 155.0W   35 KT  40 MPH
 72H  20/0000Z 19.4N 158.6W   30 KT  35 MPH
 96H  21/0000Z 20.0N 165.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  22/0000Z...DISSIPATED
 
$$
Forecaster Pasch
 
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