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Hurricane Douglas Discussion Number 25
NWS Central Pacific Hurricane Center Honolulu HI EP082020
500 AM HST Sun Jul 26 2020
Hurricane Hunters from the Air Force 53rd Weather Reconnaissance
Squadron spent most of the night with Douglas, making 5 passes
through the center. The final pass contained some of the strongest
winds of the entire mission, with flight-level winds near 100 kt,
SFMR winds up to 79 kt, and a relatively steady pressure reading
near 983 mb. The initial intensity was maintained at 80 kt based on
these valuable data points. Also of extreme value is the fact that
the low-level center is south of the apparent center seen in
conventional satellite imagery, and closer to the islands than
might be otherwise expected. Although island-based radars are also
detecting Douglas' circulation, they are sampling the upper
portions of the cyclone that are sheared northward due to southerly
vertical wind shear.
Despite the vertical wind shear, Douglas has been slow to weaken,
and this trend will continue today as Douglas passes near, or
potentially over, the islands. Steadily increasing SSTs along the
forecast track are expected to limit the rate of weakening, while
the noted vertical wind shear may be confined to the upper-levels.
While Douglas is on the western edge of a ridge aloft, leading to
high-level southerly shear, a mid-level ridge is expected to build
westward to the north of Douglas through Monday, likely allowing
the low- to mid-level core of the cyclone to remain intact. The
updated intensity forecast once again closely follows the consensus
IVCN, and maintains Douglas as a hurricane until it passes west of
the islands. Steady weakening will occur thereafter due to
persistent southwesterly shear.
The mid-level ridge will continue to drive Douglas toward the west-
northwest, with the current motion vector estimated to be 285/14
kt. The forecast track takes the center of Douglas dangerously close
to the islands from Maui to Kauai through tonight, where a Hurricane
Warning is in effect. The updated forecast track is very close to
the previous forecast and the high-performing ECMWF guidance, and
anticipates some acceleration toward the west in the later periods
as the increasingly shallow system gets steered by the low-level
trade wind flow.
1. Douglas will pass dangerously close to, or over, the islands
today, bringing a triple threat of hazards, including but not
limited to damaging winds, flooding rainfall, and dangerously high
surf, especially along east and north facing shores.
2. It is remains important that you do not focus on the exact
forecast track of Douglas. Due to Douglas' angle of approach to the
islands, any wobble in the track could lead to significant
differences in where the worst weather occurs. Even if the center
remains offshore, severe impacts could still be realized over the
islands, as they extend well away from the center.
3. Terrain effects can cause strong localized acceleration of the
wind through gaps and where winds blow downslope. These acceleration
areas will shift with time as Douglas passes near the islands.
Hurricane force wind gusts are possible even within the tropical
storm warning area. Winds will also be stronger at the upper floors
of high rise buildings.
FORECAST POSITIONS AND MAX WINDS
INIT 26/1500Z 20.7N 154.3W 80 KT 90 MPH
12H 27/0000Z 21.4N 156.6W 75 KT 85 MPH...NEAR MAUI COUNTY
24H 27/1200Z 22.3N 159.5W 70 KT 80 MPH...NEAR KAUAI
36H 28/0000Z 22.8N 162.7W 60 KT 70 MPH
48H 28/1200Z 23.3N 166.1W 55 KT 65 MPH
60H 29/0000Z 23.7N 169.5W 50 KT 60 MPH
72H 29/1200Z 24.0N 173.0W 45 KT 50 MPH
96H 30/1200Z 24.5N 179.5E 35 KT 40 MPH
120H 31/1200Z 25.5N 172.0E 30 KT 35 MPH