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Hurricane Walaka Discussion Number 14...Corrected
NWS Central Pacific Hurricane Center Honolulu HI CP012018
500 PM HST Tue Oct 02 2018
Walaka's eye has become less distinct in conventional satellite
imagery over the last couple of hours, with subjective intensity
estimates and CIMSS-ADT unanimous at 6.0. Thus, the current
intensity has been lowered to 115 kt for this advisory. Despite
these recent trends, a 0151 UTC SSMI pass continued to show a well-
developed eyewall, and there are well-developed outflow channels to
the northeast and southeast of the hurricane. Outflow is much more
restricted in the western semicircle.
The initial motion estimate is 010/11, as Walaka moves generally
toward a vertically-stacked low pressure area near 31N 170W. Walaka
is expected to soon begin accelerating toward the north-northeast
as it gets caught up in the warm conveyor belt on the east side of
the low. As Walaka begins to get tangled up with this extratropical
feature, the guidance shows the center will dramatically slow it's
forward motion in the 48 to 72 hour time frame and may take a brief
bend back toward the north-northwest, then kick northeast rapidly
again at 96 hours and beyond as the circulation becomes more
shallow. The track guidance remains in remarkably good agreement
considering the rather complex interaction between Walaka and the
extratropical low, and this forecast track is similar to the
previous advisory package.
The UW-CIMSS shear analysis shows that Walaka will be coming under
the influence of moderate to strong shear relatively soon. The shear
is expected to peak at greater than 30 kt by 36 hours, which should
continue the weakening trend. Although the shear diminishes beyond
36 hours, the cyclone will begin moving over increasingly cool sea
surface temperatures. There is some uncertainty as to how Walaka's
interaction with the extratropical low will play out. The global
models seem to be in good agreement that some semblance of a warm
core will remain even afterward, and so the forecast maintains
Walaka as a tropical cyclone through 96 hours. It would not be
surprising if the system becomes extratropical sooner, however. The
forecast shows a slower rate of weakening than most of the dynamical
models, in best agreement with the ECMWF through 48 hours, then
aligns with SHIPS guidance afterward.
FORECAST POSITIONS AND MAX WINDS
INIT 03/0300Z 16.7N 170.2W 115 KT 130 MPH
12H 03/1200Z 18.7N 169.7W 110 KT 125 MPH
24H 04/0000Z 21.9N 168.5W 105 KT 120 MPH
36H 04/1200Z 25.5N 167.4W 95 KT 110 MPH
48H 05/0000Z 28.9N 167.6W 85 KT 100 MPH
72H 06/0000Z 32.0N 166.4W 65 KT 75 MPH
96H 07/0000Z 38.7N 160.6W 50 KT 60 MPH
120H 08/0000Z 46.8N 152.1W 40 KT 45 MPH...POST-TROP/EXTRATROP
$$
Forecaster R Ballard
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