Tropical Storm KARINA

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TROPICAL STORM KARINA DISCUSSION NUMBER  20
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP112014
200 PM PDT SUN AUG 17 2014

Karina's convective pattern has continued to wax and wane over the
past 6 hours. Another burst of deep convection with cloud tops to
-80C has developed near and to the west through southwest of the
partially exposed, well-defined low-level circulation center. Recent
objective intensity analyses from CIMSS AMSU and ADT yield estimates
of 42-44 kt, and a recent ASCAT-B overpass at 1847 UTC indicated
several 36-37 kt surface wind vectors northwest and west of the
center. Based on a blend of these values, the initial intensity is
held at 40 kt.

Karina appears to have made the much expected turn toward the
west-southwest, and the initial motion is now 255/11 kt. Karina is
expected to continue moving toward the west-southwest and slow down
considerably over the next 72 hours as a broad high pressure system
builds to the north and west of the cyclone. Karina could even stall
on Day 3 as steering currents collapse. After that, a large
developing disturbance located about 700 n mi east of the cyclone is
forecast by all of the global models to evolve into an unusually
large low pressure system that will gradually pull Karina back
to the east-northeast and northeast on Days 4 and 5. The official
forecast track has been shifted farther west, but not as far west
as the consensus model TVCE due to the uncertainly involved in
exactly how much influence and timing that the large disturbance
east of Karina will have on the tropical cyclone.

Moderate easterly mid- to upper-level shear is expected to affect
Karina for the next 18 hours or so, which should inhibit any
significant intensification. After that, however, the shear is
forecast by the SHIPS model to decrease to less than 10 kt, during
which time some intensification could occur while the cyclone
remains over marginal SSTS of at least 26C. By 48 hours and beyond,
the easterly shear is expected to increase again due to strong
upper-level outflow associated with the aforementioned large
disturbance to the east of Karina. The increasing shear, coupled
with decreasing SSTs, should cap any intensification that might have
occurred. The GFDL and HWRF models bring Karina back to hurricane
strength at around 120 hours, but this seems unlikely due to the
cyclone being over sub-26C SSTs at that time. The NHC intensity
forecast is similar to the previous advisory and TO the ICON
intensity consensus model.

FORECAST POSITIONS AND MAX WINDS

INIT  17/2100Z 17.7N 129.5W   40 KT  45 MPH
 12H  18/0600Z 17.3N 130.8W   40 KT  45 MPH
 24H  18/1800Z 16.7N 132.3W   45 KT  50 MPH
 36H  19/0600Z 16.3N 133.4W   45 KT  50 MPH
 48H  19/1800Z 16.3N 134.3W   50 KT  60 MPH
 72H  20/1800Z 16.4N 135.0W   45 KT  50 MPH
 96H  21/1800Z 16.7N 135.2W   45 KT  50 MPH
120H  22/1800Z 17.1N 134.4W   45 KT  50 MPH

$$
Forecaster Stewart

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