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Tropical Storm Walaka Discussion Number  24
NWS Central Pacific Hurricane Center Honolulu HI   CP012018
500 AM HST Fri Oct 05 2018
 
The satellite appearance of Walaka has deteriorated overnight, with
the low level circulation center now becoming exposed. The latest
satellite intensity estimates were 3.5 (55 knots) from PHFO, 2.5 (35
knots) from SAB, while the ADT came in at 2.9 (43 knots). A 0755Z
ASCAT pass caught a portion of the western edge of the circulation
and showed a 43 knot wind barb. Given the data from the ASCAT only
sampling the weaker western side of the circulation along with
support from the PHFO intensity estimate, the initial intensity of
Walaka was lowered to 55 knots for this advisory. The initial motion
was set at 010/07 knots.

Walaka continues to interact with a deep mid-upper level low in the 
vicinity of 27/28N 167W. This mid-upper low is forecast to fill 
today as a broad north Pacific upper trough moves in from the 
northwest. This should pick Walaka up and accelerate the cyclone
off to the northeast through Saturday night, with Walaka expected to
undergo the extra-tropical transition late Saturday or Saturday
night. The official forecast track is very close to that of the
previous advisory and is very close to the TVCE, GFEX, and HCCA
consensus guidance.

Walaka will be over cool sea surface temperatures below 25C
throughout the duration of its journey across the north Pacific,
with vertical wind shear expected to increase substantially tonight
and Saturday. Although conditions will become increasingly hostile,
the transition over to an extra-tropical low will likely keep the
intensity from dropping off too much during the next couple of days.
As a result, the official intensity forecast calls for slow and
steady weakening and closely follows a blend of the dynamical
guidance. Walaka is expected to become an extra-tropical low late
Saturday or Saturday night, with dissipation by forecast hour 72.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  05/1500Z 31.5N 168.3W   55 KT  65 MPH
 12H  06/0000Z 32.8N 167.2W   50 KT  60 MPH
 24H  06/1200Z 36.2N 164.5W   50 KT  60 MPH
 36H  07/0000Z 42.2N 160.0W   45 KT  50 MPH
 48H  07/1200Z 49.1N 153.6W   40 KT  45 MPH...POST-TROP/EXTRATROP
 72H  08/1200Z...DISSIPATED
 
$$
Forecaster Jelsema
 
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