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Hurricane KARINA (Text)

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HURRICANE KARINA DISCUSSION NUMBER   8
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP112014
200 PM PDT THU AUG 14 2014

Despite moderate northeasterly vertical wind shear, Karina has
managed to develop a closed mid-level eye with a diameter of around
10-12 nmi since the previous advisory as noted in recent SSMI/S and
AMSU microwave imagery. Visible satellite imagery also indicates
that a cloud-filled eye has appeared in the middle of the nearly
circular CDO during past hour or so. Satellite intensity estimates
are a consensus T4.0/65 kt, and ADT estimates from UW-CIMSS ADT
have been steady at T4.4/75 kt for the past couple of hours. As a
result of these data, the intensity has been increased to 65 kt.

The initial motion estimate is 270/13 kt, which is based primarily
on passive microwave satellite position fixes. Karina's apparent
westward acceleration is likely due to the low-level center moving
or reforming underneath the well-defined mid-level eye. As a result,
this westward jog is expected to be a temporary motion, and Karina
should slow down somewhat in the near-term. Otherwise, the
hurricane is expected to remain on a basic westward track for the
next 4 days as Karina is steered by a deep-layer ridge to its north.
Afterwards, the cyclone is expected to slow down significantly and
make a turn toward the west-southwest or southwest as Karina begins
to interact with possible multiple tropical cyclones developing in
the central Pacific and eastern Pacific basins. As mentioned in the
previous discussion, rather than committing to any one particular
model solution this far out in time, the NHC track forecast instead
just shows a significant slow down in Karina's motion. The official
forecast track is just an extension of the previous advisory track,
and lies south of the consensus model TVCE, near the extreme
southern edge of the NHC guidance envelope.

The GFS-based SHIPS model indicates that the vertical shear is
expected to increase to near 20 kt during the 12-24 hour period,
while the shear vector veers around to the east. Given the
well-defined and small eye mentioned previously, some additional
strengthening is expected while Karina remains in favorable
thermodynamic and oceanic environments. By 36 hours and beyond, the
shear is forecast to decrease significantly, but this will occur
when the cyclone is moving over marginal SSTs. The result is that
a general leveling off of the intensity is expected, although there
could obviously be some fluctuations in the intensity due to
internal eyewall dynamics that can not be forecast this far in
advance. The official intensity forecast remains well above the
consensus model ICON due to the persistent weakening of Karina
shown by the GFDL and HWRF models thus far, and instead follows the
trend of the SHIPS and LGEM models.

FORECAST POSITIONS AND MAX WINDS

INIT  14/2100Z 17.1N 117.6W   65 KT  75 MPH
 12H  15/0600Z 17.4N 119.1W   75 KT  85 MPH
 24H  15/1800Z 17.8N 121.3W   80 KT  90 MPH
 36H  16/0600Z 18.1N 123.6W   80 KT  90 MPH
 48H  16/1800Z 18.2N 125.8W   80 KT  90 MPH
 72H  17/1800Z 18.1N 129.5W   80 KT  90 MPH
 96H  18/1800Z 17.7N 132.6W   75 KT  85 MPH
120H  19/1800Z 17.6N 134.2W   70 KT  80 MPH

$$
Forecaster Stewart

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