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Hurricane Douglas Discussion Number 27
NWS Central Pacific Hurricane Center Honolulu HI EP082020
500 PM HST Sun Jul 26 2020
In spite of increasing southerly vertical wind shear of more than
20 kt, a large burst of convection redeveloped around a ragged eye
late this afternoon. Hurricane Hunters from the Air Force 53rd
Weather Reconnaissance Squadron have departed Douglas after spending
much of the day sampling the system, and another mission is
scheduled for this evening. While the last passes through continued
to show a slow increase in central pressure, aircraft data indicated
that the winds had not changed much, and recent land-based radar
showed winds in excess of 90 kt at around 6,000 ft. As a result, the
initial intensity will be held at 75 kt for this advisory, which is
in line with the PHFO Dvorak CI of 4.5.
Of greater importance, the aircraft data and land-based radars
indicated that Douglas has taken a jog to the north today. While
the low-level ridge to the north is providing significant steering,
a weakness in the ridge aloft and increasing vertical wind shear,
mainly at higher levels, have likely caused the hurricane to make a
northward shift, resulting in an initial motion of 295/14 kt.
Douglas will continue on this general motion tonight as it passes
near Oahu and Kauai, eventually making a turn and an acceleration
toward the west late Monday through Thursday. Due to the northward
jog, the track forecast was nudged slightly to the north through
Monday and is close to the middle of a tightly clustered guidance
envelope through Thursday.
Slow weakening will continue, though Douglas will remain a
hurricane as it passes near Oahu and Kauai tonight. SSTs will slowly
increase along the forecast track, but southerly vertical wind shear
will tilt the system and disrupt the circulation aloft, leading to
gradual weakening through at least the next four days. The
intensity forecast was changed little from the prior advisory and is
near IVCN in the middle of the guidance envelope, though lower than
the statistical guidance.
The motion of Douglas has allowed the Hurricane Warning for Maui
County to be canceled. Given the close approach to both Oahu and
Kauai along with the ongoing development of deep convection, the
Hurricane Warning remains in place for Oahu and Kauai.
1. Douglas will pass dangerously close to Oahu and Kauai tonight,
producing a triple threat of hazards, including but not limited to
damaging winds, flooding rainfall, and dangerously high surf,
especially along east facing shores.
2. It 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 drastic differences in where
the worst weather occurs. Even if the center remains offshore,
severe impacts could extend well from the center and be realized
over Oahu and Kauai.
3. Terrain effects can cause strong localized acceleration of the
wind through gaps and where winds blow downslope. These
areas will shift with time as Douglas passes near Oahu and Kauai.
FORECAST POSITIONS AND MAX WINDS
INIT 27/0300Z 22.0N 157.3W 75 KT 85 MPH
12H 27/1200Z 22.5N 159.6W 70 KT 80 MPH...NEAR KAUAI
24H 28/0000Z 23.1N 162.7W 60 KT 70 MPH
36H 28/1200Z 23.5N 166.3W 55 KT 65 MPH
48H 29/0000Z 23.9N 170.0W 50 KT 60 MPH
60H 29/1200Z 24.1N 173.8W 45 KT 50 MPH
72H 30/0000Z 24.2N 177.7W 40 KT 45 MPH
96H 31/0000Z 25.0N 174.6E 35 KT 40 MPH
120H 01/0000Z 27.2N 167.7E 35 KT 40 MPH