WTPA45 PHFO 100919
Hurricane Olivia Discussion Number 39
NWS Central Pacific Hurricane Center Honolulu HI EP172018
1100 PM HST Sun Sep 09 2018
Olivia's small eye surrounded by cold cloud tops is evident in
infrared satellite imagery this evening. The U.S. Air Force
Reserves 53rd Weather Reconnaissance Squadron aircraft just
completed a mission sampling the inner core and outer winds of
Olivia. They found the pressure was lower and the surface winds
stronger than their previous mission Sunday morning. Their SFMR,
flight-level and dropsonde measurements suggested the maximum winds
are near 75 kt. In addition, the satellite fix agencies (JTWC,
SAB, and PHFO) provided unanimous subjective Dvorak current
intensity estimates of 4.5/77 kt. Based on all of this information,
we are increasing the initial intensity to 75 kt for this advisory.
Olivia continues to move due west, but has slowed slightly, so the
current motion is 270/8 kt. This motion is being induced by a deep
layer ridge to the north and northwest of the tropical cyclone. In
12 to 24 hours, the ridge is expected to strengthen and build
southward ahead of Olivia, forcing the tropical cyclone to shift
toward a west-southwest track. This motion is expected to continue
through day 4. The track guidance appears to be more tightly
clustered through 48 hours now, but the spread increases from days
3 through 5. The current forecast track is very close to the
previous, except it is slightly slower during the first 72 hours.
This closely follows the latest TVCE, FSSE, GFEX and HCCA guidance.
Again, since there remains some spread in the track guidance, this
emphasizes the uncertainty in our track forecast. It is important
to not focus on the exact forecast track of Olivia's center across
Vertical wind shear remains relatively weak in the vicinity of
Olivia. Water temperatures, as well as ocean heat content values,
are expected to increase along the forecast track. Therefore, Olivia
will likely remain a hurricane through 36 hours. After that,
increasing vertical wind shear is forecast to take its toll on
Olivia, so that it may be a strong tropical storm within 48 hours.
Additional slow weakening is expected to persist during days 3
through 5. The latest forecast is close to the IVCN and CTCI. Note
that based on the latest track and intensity along with the wind
speed probabilities, Tropical Storm Warnings will likely be required
for portions of the Hawaiian Islands on Monday.
1. It is important to not focus on the exact forecast track and
intensity when planning for Olivia. Persons on all of the main
Hawaiian Islands should continue preparing for the likelihood of
direct impacts from this system Monday and early Tuesday. Those
impacts could include intense flooding rainfall, damaging winds,
large and dangerous surf, and storm surge.
2. Regardless of the exact track and intensity that Olivia takes
as it approaches the islands, significant effects often extend far
from the center. In particular, the mountainous terrain of Hawaii
can produce localized areas of strongly enhanced winds and
rainfall, even well away from the tropical cyclone center.
FORECAST POSITIONS AND MAX WINDS
INIT 10/0900Z 21.7N 146.9W 75 KT 85 MPH
12H 10/1800Z 21.6N 148.3W 75 KT 85 MPH
24H 11/0600Z 21.5N 150.2W 75 KT 85 MPH
36H 11/1800Z 21.2N 152.2W 70 KT 80 MPH
48H 12/0600Z 20.8N 154.5W 60 KT 70 MPH
72H 13/0600Z 19.9N 159.3W 45 KT 50 MPH
96H 14/0600Z 19.5N 164.5W 40 KT 45 MPH
120H 15/0600Z 20.5N 169.5W 35 KT 40 MPH
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