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Tropical Storm Olivia Discussion Number  49
NWS Central Pacific Hurricane Center Honolulu HI   EP172018
1100 AM HST Wed Sep 12 2018
 
The partially exposed low-level center of Olivia made landfall over
northwest Maui at approximately 1910 UTC (910 AM HST), then exited
Maui to the west to make another landfall on the island of Lanai
around 1954 UTC (954 AM HST). Deep convection continues to pulse to
the north and northeast of the center of Olivia, as the system
remains under strong westerly vertical wind shear of 30 kt.
Subjective Dvorak current intensity estimates ranged from 2.0/30 kt
from SAB and JTWC to 2.5/35 kt at HFO. However, WSR-88D velocity
data from Molokai has been consistently showing velocities of 50 kt
to the north of the center around 5,000 ft, and there has been
little change in the satellite presentation since last night. Thus,
the initial intensity will be maintained at 40 kt. 

The motion has become west (265 degrees) and increased to a
short-term average of 13 kt. As strong wind shear persists and
Olivia interacts with the high terrain of Molokai and Maui, the
system is expected to weaken, which will likely maintain an erratic
motion through the afternoon. However, a turn toward the
west-southwest is expected as the weaker system becomes increasingly
steered by the low-level trade wind flow. This motion will continue
into Friday, followed by a turn toward west or west-northwest
thereafter as Olivia interacts with the upper low responsible for
the wind shear. The forecast track was nudged slightly north of the
last advisory and lies near GFEX and TVCE in the middle of a tightly
clustered guidance envelope during the initial 48 hours, with
increasing spread beyond. Olivia is forecast to become a tropical
depression by Thursday and a post-tropical remnant low on Friday.
This could occur sooner if Olivia is significantly weakened by
island terrain. The intensity forecast closely follows SHIPS, which
is slightly more aggressive in the weakening of Olivia than the
other statistical and dynamical guidance.
 
 
Key Messages:
 
1. Flooding rainfall, high surf, and damaging winds are expected in
the warning area. Significant impacts can occur well away from the
center, especially when considering that the mountainous terrain of
Hawaii can produce localized areas of strongly enhanced wind gusts
and rainfall.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  12/2100Z 20.9N 157.1W   40 KT  45 MPH
 12H  13/0600Z 20.6N 159.0W   35 KT  40 MPH
 24H  13/1800Z 20.1N 161.7W   30 KT  35 MPH
 36H  14/0600Z 19.9N 164.5W   30 KT  35 MPH
 48H  14/1800Z 20.0N 167.1W   30 KT  35 MPH...POST-TROP/REMNT LOW
 72H  15/1800Z 21.2N 172.2W   30 KT  35 MPH...POST-TROP/REMNT LOW
 96H  16/1800Z 22.5N 176.8W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  17/1800Z...DISSIPATED
 
$$
Forecaster Wroe
 
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