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Tropical Storm Douglas Discussion Number 32
NWS Central Pacific Hurricane Center Honolulu HI EP082020
1100 PM HST Mon Jul 27 2020
Douglas finally relented to persistent south to southwest vertical
wind shear earlier today, when the low-level circulation center
became exposed in visible satellite imagery. Convection has been
limited to the northern semicircle since, and detached well away
from the center, leading to a rapid weakening trend over the past
24 hours. Subjective Dvorak current intensity estimates for this
advisory ranged from 3.0/45 kt from HFO/SAB and 3.5/55 kt from
PGTW. Meanwhile, the multi-platform satellite surface wind analysis
from RAMMB-CIRA suggested maximum winds up to 56 kt, albeit limited
to the northern semicircle. A conservative blend of these estimates
yields an initial intensity estimate of 50 kt.
The initial motion for this advisory is 285/12 kt, with Douglas
being steered by a low- to mid-level ridge to the north. As
significant convection is not expected to be able to persist over
the center, Douglas will become increasingly shallow the next
day or two, degenerating to a post-tropical remnant low as it
gradually spins down. The updated intensity forecast is close to
HWRF guidance. As it weakens, dynamical global guidance indicates
that Douglas will accelerate toward the west-northwest, and the
official forecast follows suit.
NDBC buoys 51001 and 51101 reported peak wave heights near 20 feet
and sustained winds near 31 kt earlier today, verifying GFS- and
ECWMF-based wave model guidance, which indicated peak values near
21 feet in the same area. This data also led to a slight expansion
of the gale radii in the northeast quadrant.
FORECAST POSITIONS AND MAX WINDS
INIT 28/0900Z 23.4N 164.7W 50 KT 60 MPH...NEAR NECKER ISLAND
12H 28/1800Z 23.8N 167.5W 40 KT 45 MPH
24H 29/0600Z 24.3N 171.2W 35 KT 40 MPH
36H 29/1800Z 24.7N 175.2W 30 KT 35 MPH
48H 30/0600Z 25.6N 179.2W 30 KT 35 MPH...POST-TROP/REMNT LOW
60H 30/1800Z 26.5N 177.0E 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 31/0600Z...DISSIPATED
$$
Forecaster Birchard
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