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Hurricane Douglas Discussion Number 23
NWS Central Pacific Hurricane Center Honolulu HI EP082020
500 PM HST Sat Jul 25 2020
In spite of marginal SSTs near 26C and increasing vertical wind
shear, convection increased around the center of Douglas a few
hours ago, and a ragged eye briefly reemerged in conventional
satellite imagery. As a result, data sampled by the U.S. Air Force
53rd Weather Reconnaissance Squadron earlier in the day showed
little change in the intensity of Douglas. A blend of adjusted
flight levels winds and SFMR data supports holding the initial
intensity at 80 kt with a central pressure of 982 mb.
Reconnaissance aircraft will conduct another mission into Douglas
tonight.
Aircraft and satellite data indicate that Douglas continues to move
toward the west-northwest (290 deg) and that the forward motion has
slowed to 14 kt. Douglas is being steered by a low- to mid-level
ridge to the northeast and is approaching a weakness in the mid-
level ridge that is causing the slight deceleration. A continued
motion toward the west-northwest will bring Douglas over, or very
near, portions of the main Hawaiian Islands Sunday and Sunday
night, then to parts of the Papahanaumokuakea Marine National
Monument on Monday and Tuesday. The updated forecast track is very
close to the previous forecast and during the next couple of
days, remains near the ECMWF toward the southern end of a tightly
clustered guidance envelope. Model spread increases on days four and
five, when the official forecast trends toward the middle of the
guidance envelope.
Gradual weakening is expected through the forecast. SSTs will
gradually warm along the forecast track. However, vertical wind
shear will steadily increase over the next couple of days and is
expected to be strong enough to induce weakening. The official
intensity forecast has changed very little from the previous
advisory, and continues to follow a blend of the corrected
consensus and statistical model guidance.
Based on the latest forecast, a Tropical Storm Warning has been
issued for Kauai County. A Tropical Storm Warning and Hurricane
Watch remain in effect for Hawaii County and Maui County. A
Tropical Storm Watch has also been issued for portions of the
Papahanaumokuakea Marine National Monument from Nihoa to French
Frigate Shoals.
Key Messages:
1. Douglas continues to approach the main Hawaiian Islands, and
will pass dangerously close to, or over, the islands late tonight
through Sunday night. The close passage of Douglas brings 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 is vital that you do not focus on the exact forecast track or
intensity of Douglas. Due to Douglas' angle of approach to the
islands, any small changes 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 26/0300Z 19.9N 151.4W 80 KT 90 MPH
12H 26/1200Z 20.6N 153.6W 75 KT 85 MPH
24H 27/0000Z 21.5N 156.4W 65 KT 75 MPH
36H 27/1200Z 22.3N 159.1W 60 KT 70 MPH
48H 28/0000Z 23.0N 162.1W 55 KT 65 MPH
60H 28/1200Z 23.6N 165.4W 50 KT 60 MPH
72H 29/0000Z 24.0N 168.8W 45 KT 50 MPH
96H 30/0000Z 24.6N 176.0W 40 KT 45 MPH
120H 31/0000Z 25.7N 178.0E 35 KT 40 MPH
$$
Forecaster Wroe
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