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Hurricane Walaka Discussion Number   9
NWS Central Pacific Hurricane Center Honolulu HI   CP012018
1100 AM HST Mon Oct 01 2018

Hurricane Walaka is an impressive tropical cyclone. A 20 nm wide
clear eye is surrounded by a large ring of -70 to -76C cloud tops
with excellent upper level outflow in all quadrants. Banding
features are also present though not as well-formed as early
this morning. Intensity estimates came in at 6.0/115 kt from PHFO
and JTWC, and 6.5/127 kt from SAB. ADT was 6.7/132 kt at 1800 UTC.
Given the overall appearance and intensification trend, the initial
intensity for this advisory leans on the higher end of the estimates
at 130 kt.

Walaka is moving at 305/9 kt as it rounds the southwestern flank of
a subtropical ridge. A developing low pressure system is expected to
produce a break in the ridge to the north of the hurricane and cause
a turn toward the north on Tuesday. The numerical models are in
agreement with the scenario and the track guidance is tightly
packed, especially through 72 hours. Walaka is expected to
accelerate toward the north under the influence of the low on
Wednesday and into Thursday. The forecast track for this advisory is
essentially a refresh of the previous forecast and is close to the
HCCA consensus, especially through 72 hours. 

Rapid intensification has been occurring since last night. With sea
surface temperatures under Walaka expected to remain near 30C
through tonight, high ocean heat content, and low vertical wind
shear, there is no reason to believe that peak intensity has been
reached. SHIPS forecasts 147 kt from 18 to 24 hours so the forecast
calls for a peak intensity of 145 kt tonight before starting a
weakening trend. This will put Walaka in Category 5 territory on
the Saffir-Simpson scale and exceeds the maximum intensity achieved
by Hurricane Ioke in 2006.

The forecast track will take Walaka near Johnston Island on Tuesday
and the Hurricane Warning remains in effect for this location. The
northeastward track after Tuesday is also expected to take the
hurricane across the Papahanaumokuakea Marine National Monument
between French Frigate Shoals and Laysan Island on Thursday, and a
Hurricane Watch may be needed for these locations later today or
tonight.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  01/2100Z 12.9N 169.3W  130 KT 150 MPH
 12H  02/0600Z 14.0N 170.1W  140 KT 160 MPH
 24H  02/1800Z 15.6N 170.7W  145 KT 165 MPH
 36H  03/0600Z 17.7N 170.5W  140 KT 160 MPH
 48H  03/1800Z 20.7N 169.5W  125 KT 145 MPH
 72H  04/1800Z 27.1N 167.3W  100 KT 115 MPH
 96H  05/1800Z 31.0N 167.0W   75 KT  85 MPH
120H  06/1800Z 35.0N 163.0W   65 KT  75 MPH
 
$$
Forecaster Kodama
 
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