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Tropical Storm Karina Discussion Number   4
NWS National Hurricane Center Miami FL       EP162020
200 PM PDT Sun Sep 13 2020
 
A midday ASCAT pass revealed that Karina still has an elongated 
circulation and is likely still attached to the ITCZ/monsoon trough. 
The center is also displaced to the northeast of the deepest 
convection due to ongoing moderate northeasterly shear.  The ASCAT 
data confirmed that the storm currently has maximum winds of 40 k, 
with most of the tropical-storm-force winds located over the 
southern semicircle.  With the shear not expected to decrease from 
its current magnitude, only modest strengthening is expected during 
the next 36 hours or so while Karina remains over waters warmer than 
26 degrees Celsius.  The peak intensity shown in the official 
forecast has been adjusted downward to 50 kt, which is now the 
highest intensity shown by any of the intensity models.  Colder 
waters and a drier, more stable atmosphere should induce gradual 
weakening after day 2, with Karina likely to lose all of its deep 
convection and become a remnant low by day 4.

Karina turned a little bit to the left today but still has a 
west-northwestward heading (290/10 kt).  A mid-level ridge located 
to the north should keep Karina on a west-northwestward trajectory 
with some reduction in forward speed through day 4.  Once it weakens 
to a remnant low, Karina is expected to turn westward, steered by 
lower-level trade winds.  There is some north-south divergence among 
the track models during Karina's expected remnant low stage, but the 
overall guidance envelope has not shifted.  Therefore, the updated 
NHC track forecast is not too different from the previous one and 
lies close to the HCCA, Florida State Superensemble, and TVCE 
multi-model consensus.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  13/2100Z 17.8N 116.0W   40 KT  45 MPH
 12H  14/0600Z 18.5N 117.1W   45 KT  50 MPH
 24H  14/1800Z 19.1N 118.6W   45 KT  50 MPH
 36H  15/0600Z 19.8N 120.1W   50 KT  60 MPH
 48H  15/1800Z 20.5N 121.3W   45 KT  50 MPH
 60H  16/0600Z 21.2N 122.4W   40 KT  45 MPH
 72H  16/1800Z 21.9N 123.6W   35 KT  40 MPH
 96H  17/1800Z 22.5N 126.0W   30 KT  35 MPH...POST-TROP/REMNT LOW
120H  18/1800Z 22.5N 128.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
 
$$
Forecaster Berg
 
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