Kauai hurricane warning.
Hurricane Douglas Discussion Number 24
NWS Central Pacific Hurricane Center Honolulu HI EP082020
1100 PM HST Sat Jul 25 2020
Hurricane Hunters from the Air Force 53rd Weather Reconnaissance
Squadron have been flying through and around the center of Douglas
through the evening, providing valuable ground truth. Latest data
support maintaining Douglas' initial intensity at 80 kt, with
maximum flight-level winds near 90 kt, SFMR winds as high as 78 kt,
and a central pressure near 983 mb. Worth noting that the data also
indicate that the low-level center is south of the center that is
seen in conventional satellite imagery. Recent microwave images
confirm that the cyclone is tilted to the north with height, due to
southerly vertical wind shear.
Despite the vertical wind shear, Douglas is expected to only slowly
weaken as it comes dangerously close to the Hawaiian Islands. This
is primarily due to steadily increasing SSTs along the forecast
track, and also likely due to the fact that most of the shear is in
the upper levels. While Douglas has rounded the southwestern 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, likely allowing the low- to mid-level core of the cyclone
to remain intact. The updated intensity forecast closely follows
the consensus IVCN, and maintains Douglas as a hurricane as it
passes near Oahu and Kauai County.
The mid-level ridge will continue to drive Douglas toward the west-
northwest, with the current motion vector estimated to be 290/14
kt. The forecast track takes the center of Douglas dangerously close
to Oahu and Kauai on Sunday, with some of the guidance indicating a
slight jog toward the west Sunday evening near Oahu, necessitating
a Hurricane Warning for Kauai County. Douglas will potentially
impact parts of the Papahanaumokuakea Marine National Monument on
Monday and Tuesday. The updated forecast track is very close to the
previous forecast, the track consensus TVCN, and is on the southern
side of most of the guidance. However the GFS and ECMWF ensemble
means are just left of the official forecast, suggesting a
potentially more impactful scenario for Kauai County and Oahu.
Key Messages
1. Douglas continues to approach the main Hawaiian Islands, and
will pass dangerously close to, or over, the islands Sunday. 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 26/0900Z 20.4N 152.8W 80 KT 90 MPH
12H 26/1800Z 21.1N 155.0W 75 KT 85 MPH
24H 27/0600Z 21.8N 157.9W 70 KT 80 MPH
36H 27/1800Z 22.5N 160.6W 65 KT 75 MPH
48H 28/0600Z 23.2N 163.6W 55 KT 65 MPH
60H 28/1800Z 23.6N 166.8W 50 KT 60 MPH
72H 29/0600Z 24.0N 170.0W 45 KT 50 MPH
96H 30/0600Z 24.0N 177.3W 35 KT 40 MPH
120H 31/0600Z 25.0N 175.0E 30 KT 35 MPH
$$
Forecaster Birchard
