Tropical Storm KARINA

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TROPICAL STORM KARINA DISCUSSION NUMBER  37
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP112014
800 PM PDT THU AUG 21 2014

Deep convection has continued to develop near the center of Karina,
especially in the southern semicircle, and the low-level center is
embedded in the middle of the more circular cloud shield. Two
earlier ASCAT passes showed 50 kt and 52 kt peak surface winds to
the southeast of the center, so the intensity has been bumped up to
55 kt for this advisory.

The initial motion estimate is 090/02 kt based on microwave
satellite positions over the past several hours. After nearly three
days of saying the same thing in our discussions, there isn't much
more to add. Karina will gradually get pulled eastward and
northeastward by the larger circulation of Tropical Storm Lowell, as
the latter cyclone passes to the northeast of Karina in 2-3 days.
The majority of the NHC track guidance is now indicating a
considerably slower forward speed on Days 4 and 5 as Karina weakens
over cold water and becomes more vertically shallow. The official
advisory track is similar to but a little faster than the consensus
model TVCE out of respect for the faster GFS model.

Recent microwave images continue to show a partial eyewall
structure. The vertical shear is forecast to subside to around 5 kt
during the next 12 hours, so there is a brief window of opportunity
for Karina to strengthen. However, the vertical shear is forecast to
increase again at 24 hours and beyond as the cyclone begins to move
over cooler water. This combination of unfavorable conditions should
induce gradual weakening, with the Karina becoming a non-convective
remnant low pressure by 96 hours when the cyclone is moving over
22-23C sea-surface temperatures and into a much cooler and drier
airmass. The NHC intensity forecast closely follows the intensity
consensus model ICON.

FORECAST POSITIONS AND MAX WINDS

INIT  22/0300Z 14.8N 136.5W   55 KT  65 MPH
 12H  22/1200Z 15.1N 135.9W   55 KT  65 MPH
 24H  23/0000Z 15.7N 135.1W   50 KT  60 MPH
 36H  23/1200Z 16.4N 134.1W   45 KT  50 MPH
 48H  24/0000Z 17.3N 132.8W   40 KT  45 MPH
 72H  25/0000Z 19.0N 129.8W   35 KT  40 MPH
 96H  26/0000Z 21.5N 129.0W   30 KT  35 MPH...POST-TROP/REMNT LOW
120H  27/0000Z 25.5N 130.5W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Stewart

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