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Hurricane Douglas Discussion Number 18
NWS Central Pacific Hurricane Center Honolulu HI EP082020
1100 AM HST Fri Jul 24 2020
After a period of rapid intensification yesterday, Douglas'
satellite appearance has degraded somewhat over the past 12 hours
or so. However, a fairly large but ragged and cloud-filled eye is
still noted in conventional satellite images. Subjective Dvorak
current intensity estimates were 5.5/105 kt from SAB and HFO, 5.1/93
kt from ADT, while SATCON estimated was near 100 kt. A blend of
these led to an initial intensity estimate of 100 kt for this
advisory.
The initial motion for this advisory is a steady 295/16 kt, as
Douglas continues to be steered by a robust mid-level ridge
centered to the northeast. As Douglas draws closer to the main
Hawaiian Islands, it will be reaching the western periphery of the
ridge, and model guidance indicates that this will allow the cyclone
to gain some latitude over the next 2 days, with some reduction in
forward speed. Thereafter, the mid-level ridge is forecast to
subtly build to the north of Douglas, potentially inducing a turn
toward the west, with some increase in forward speed. The updated
track forecast is nearly identical to the previous, lies along the
southern side of the guidance, and is very close to ECMWF guidance
that has been performing well thus far with Douglas. On the
forecast track, Douglas will move dangerously close to the Hawaiian
Islands. A Hurricane Watch has been issued for Maui County and
the Big Island, and may need to be expanded to additional areas
later today or tonight.
The intensity forecast continues to anticipate a slow but steady
weakening of the cyclone as it traverses cooler waters, and later
encounters increased vertical wind shear as waters warm somewhat
near the Hawaiian Islands. Little overall change to the ongoing
forecast was made, and the updated forecast closely follows the
GFS- and ECMWF-based SHIPS guidance, and is close to the intensity
consensus IVCN.
Key Messages
1. Douglas will continue to quickly approach the main Hawaiian
Islands, passing dangerously close to, or over, the islands on
Sunday. Dangerous, life-threatening surf will arrive ahead of the
hurricane on Saturday. Heavy rain and increasing winds are possible
on the Big Island starting Saturday night, and could quickly spread
up the chain Sunday.
2. It is important not to focus on the exact forecast track. Due
to Douglas' angle of approach to Hawaii, any small changes in the
track could lead to significant differences in where the worst
weather will occur.
3. Wind gusts near mountains and higher terrain can be
significantly enhanced as they blow downslope.
FORECAST POSITIONS AND MAX WINDS
INIT 24/2100Z 17.0N 143.5W 100 KT 115 MPH
12H 25/0600Z 17.9N 145.9W 90 KT 105 MPH
24H 25/1800Z 19.1N 149.0W 80 KT 90 MPH
36H 26/0600Z 20.0N 151.9W 70 KT 80 MPH
48H 26/1800Z 20.8N 154.7W 65 KT 75 MPH
60H 27/0600Z 21.3N 157.5W 60 KT 70 MPH
72H 27/1800Z 21.8N 160.4W 55 KT 65 MPH
96H 28/1800Z 23.0N 166.7W 50 KT 60 MPH
120H 29/1800Z 24.2N 172.8W 45 KT 50 MPH
$$
Forecaster Birchard
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