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Hurricane Douglas Discussion Number  22
NWS Central Pacific Hurricane Center Honolulu HI   EP082020
1100 AM HST Sat Jul 25 2020
 
The satellite presentation of Douglas is degrading somewhat, likely 
due to restricted outflow to the south and 26C SSTs. The U.S. Air 
Force 53rd Weather Reconnaissance Squadron sampled the hurricane 
this morning, and a blend of SFMR, flight level winds, and dropsonde 
data from two passes supports decreasing the intensity to 80 kt with 
a central pressure of 984 mb.  

Douglas continues to move toward the west-northwest (290 deg) at 16 
kt. Douglas is being steered by a low- to mid-level ridge to the 
northeast and is nearing a weakness in the mid-level ridge. A 
continued motion toward the west-northwest and a slight decrease in 
forward motion will bring Douglas over or very near portions of the 
main Hawaiian Islands on Sunday. On Monday, a mid-level ridge is 
forecast to build to the north of Douglas, potentially inducing a 
turn toward the west, with some increase in forward speed. The 
updated forecast track is very close to the previous forecast and 
lies close to the ECMWF toward the southern end of a rather tightly 
clustered guidance envelope.

Weakening is expected through the forecast. Douglas will remain 
over an area of 26C SST today, which is expected to continue the 
gradual weakening trend. SSTs along the forecast track increase 
tonight, at the same time that Douglas will move into an area of 
increased vertical wind shear. This is expected to maintain a 
weakening trend, although at a fairly slow rate. The official 
intensity forecast has changed very little from the previous 
advisory, and generally follows a blend of the corrected consensus 
and statistical model guidance.

Based on the latest forecast, a Hurricane Warning has been issued 
for Oahu. Tropical Storm Warnings remain in effect for Hawaii 
County and Maui County. A Hurricane Watch remains in effect for 
Hawaii County and Maui County, and a Tropical Storm Watch is in 
effect for Kauai County. 

Key Messages: 

1. Douglas continues to approach the main Hawaiian Islands, 
potentially passing 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  25/2100Z 19.5N 150.1W   80 KT  90 MPH
 12H  26/0600Z 20.1N 152.1W   75 KT  85 MPH
 24H  26/1800Z 21.0N 154.9W   70 KT  80 MPH
 36H  27/0600Z 21.8N 157.7W   65 KT  75 MPH
 48H  27/1800Z 22.5N 160.4W   60 KT  70 MPH
 60H  28/0600Z 23.1N 163.5W   55 KT  65 MPH
 72H  28/1800Z 23.7N 167.0W   50 KT  60 MPH
 96H  29/1800Z 24.5N 173.7W   45 KT  50 MPH
120H  30/1800Z 25.8N 180.0E   35 KT  40 MPH
 
$$
Forecaster Wroe
 
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