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Hurricane Calvin Discussion Number  19
NWS National Hurricane Center Miami FL       EP032023
1100 PM HST Sat Jul 15 2023
 
The cloud pattern and overall organization of Calvin has been 
deteriorating this evening.  The eye and eyewall are unraveling and 
opening up on the western side. Dry air entrainment and cool water 
temperatures are also causing the convective banding to diminish 
with cloud tops warming and the inner core dissipating. Subjective 
Dvorak estimates, as well as CIMMS ADT and AiDT estimates, have come 
down with this advisory ranging from 55 kt to 78 kt. Based on these 
data, the initial intensity is lowered to 70 kt.
 
Calvin is currently moving over cooler SSTs near 25C and will 
continue to be over even cooler water temps the next 24-36 hours. 
Calvin is also moving into a drier mid-level airmass and a more 
stable environment.  Given the current satellite trends and the 
environment Calvin is beginning to encounter, weakening is forecast 
for the remainder of the period. However, the system is still likely 
to continue to have bursts of convection as it approaches the 
Hawaiian Islands in a few days.  Regardless of how much convection 
is present, it appears likely that Calvin will maintain tropical 
storm force winds as it passes near the Big Island of Hawaii.  After 
it passes Hawaii, stronger shear should cause the cyclone to 
degenerate to a remnant low pressure area or trough.
 
The initial motion is estimated to be 285/15 kt. A westward to 
west-northwestward motion will continue through the forecast period 
as the cyclone remains steered by a mid-level ridge over the eastern 
Pacific. On the forecast track, Calvin is forecast to cross 140W and 
enter the central Pacific basin Sunday night or early Monday 
morning and approach the Hawaiian Islands on Tuesday into early 
Wednesday.  There remains some cross-track spread in the models, so 
while the new forecast track calls for Calvin to pass close to the 
Big Island of Hawaii it remains unclear exactly how it will track 
relative to the island.  The new forecast track has only minor 
adjustments from the previous track.
 
 
KEY MESSAGES:
 
1. Calvin is forecast to move across the central Pacific Ocean and 
approach the Hawaiian Islands within the next few days. Interests in 
Hawaii should closely monitor the latest forecast updates and a 
Tropical Storm Watch could be issued for portions of the main 
Hawaiian Islands late Sunday.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  16/0900Z 15.7N 133.4W   70 KT  80 MPH
 12H  16/1800Z 16.2N 135.8W   60 KT  70 MPH
 24H  17/0600Z 16.7N 139.1W   50 KT  60 MPH
 36H  17/1800Z 17.2N 142.6W   45 KT  50 MPH
 48H  18/0600Z 17.6N 146.1W   40 KT  45 MPH
 60H  18/1800Z 18.2N 149.6W   40 KT  45 MPH
 72H  19/0600Z 18.6N 153.2W   35 KT  40 MPH
 96H  20/0600Z 19.9N 160.0W   30 KT  35 MPH
120H  21/0600Z 20.3N 166.2W   25 KT  30 MPH...POST-TROP/REMNT LOW
 
$$
Forecaster Kelly/Cangialosi
 
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