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Tropical Storm Karina Discussion Number   3
NWS National Hurricane Center Miami FL       EP162020
900 AM MDT Sun Sep 13 2020
 
Karina's center is a little bit closer to the deep convection this 
morning, resulting in intensity estimates increasing slightly.  
Based on Dvorak estimates of T3.0/45 kt and T2.5/35 kt from TAFB 
and SAB, respectively, and an overnight SATCON estimate of 42 kt, 
Karina's initial intensity is assumed to be 40 kt.  The moderate 
northeasterly shear currently affecting the cyclone is not expected 
to change appreciably during the next few days.  However, Karina 
will remain over ocean waters warmer than 26 degrees Celsius for 
the next 48 hours, which should allow for a gradual intensification 
trend during that period.  The shear is forecast to lighten up in 
3-4 days, but by then Karina will be over colder waters and in a 
drier, more stable environment, which should induce weakening.  
Karina is likely to lose all of its deep convection and become a 
remnant low by the end of the forecast period.  The NHC intensity 
forecast is generally close to the HCCA aid and the IVCN intensity 
consensus and shows weakening starting a little sooner than before.

Karina is moving toward the west-northwest (300/9 kt), south of a 
mid-level ridge axis which extends from northwestern Mexico 
southwestward over the Pacific.  This ridge should keep Karina on 
this general heading with a very gradually decreasing forward speed 
through day 4.  Once the cyclone weakens to a remnant low, it is 
expected to turn westward, steered by lower-level trade winds.  No 
significant changes in the track forecast were required compared to 
the previous prediction, and the official forecast lies generally 
close to the multi-model consensus aids.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  13/1500Z 17.6N 114.7W   40 KT  45 MPH
 12H  14/0000Z 18.3N 115.8W   45 KT  50 MPH
 24H  14/1200Z 19.0N 117.4W   45 KT  50 MPH
 36H  15/0000Z 19.7N 119.0W   50 KT  60 MPH
 48H  15/1200Z 20.2N 120.4W   55 KT  65 MPH
 60H  16/0000Z 20.9N 121.6W   50 KT  60 MPH
 72H  16/1200Z 21.7N 122.8W   50 KT  60 MPH
 96H  17/1200Z 22.6N 125.2W   35 KT  40 MPH
120H  18/1200Z 22.8N 127.7W   25 KT  30 MPH...POST-TROP/REMNT LOW
 
$$
Forecaster Berg
 
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