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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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