000 WTPA42 PHFO 242057 TCDCP2 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