000 WTPA42 PHFO 250255 TCDCP2 Hurricane Douglas Discussion Number 19 NWS Central Pacific Hurricane Center Honolulu HI EP082020 500 PM HST Fri Jul 24 2020 The eye of Douglas has remained visible in conventional satellite imagery through the day today, and even cleared out for a little while this afternoon, indicating that Douglas remains a powerful hurricane. Subjective satellite current intensity estimates ranged from 4.5/90 kt to 5.5/105 kt, while ADT was near 5.5. Although the eye is clouding up again this afternoon, and surrounding convection is cooling, the initial intensity has been held at 100 kt for this advisory. The forward motion vector has changed little over the past 24 hours, and is measured to be 295/17kt, as Douglas continues to be steered by a mid-level ridge centered to the distant northeast. As Douglas draws closer to the main Hawaiian Islands the next 2 days, it will round the western periphery of the ridge, allowing the cyclone to gain some latitude, with some reduction in forward speed. Thereafter, 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 track forecast is nearly identical to the previous, lies along the southern side of a fairly tightly-clustered guidance envelope, and is very close to ECMWF ensemble guidance. On the forecast track, Douglas will move dangerously close to the Hawaiian Islands, and a Hurricane Watch is posted for all islands except Kauai County, which may need to be added on Saturday. Douglas will be traversing an area of sub-26C SST for the next 36 hours or so, which is expected to lead a gradual weakening trend, despite vertical wind shear on the lighter side, especially by central Pacific standards. SSTs along the forecast track increase from 48 hours onward, at the same time that Douglas is expected to move into an area of increased vertical wind shear as it rounds the southwestern periphery of an upper-level ridge. This is expected to lead to a continued weakening trend, although at a fairly slow rate. The intensity forecast is very close to the SHIPS guidance, and close to the IVCN intensity consensus. A Hurricane Hunter aircraft is en route to fly an initial mission into Douglas, and this valuable data is expected to be available for the next forecast update. Additional flights into Douglas are scheduled for tomorrow. In the meantime, a morning ASCAT pass was used to fine tune the wind radii analysis. Key Messages 1. Douglas continues to approach the main Hawaiian Islands, potentially passing dangerously close to, or over, the islands Saturday night 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, and remain prepared for changes to the forecast. 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. Winds will also be stronger at the upper floors of high rise buildings. FORECAST POSITIONS AND MAX WINDS INIT 25/0300Z 17.9N 145.1W 100 KT 115 MPH 12H 25/1200Z 18.8N 147.5W 90 KT 105 MPH 24H 26/0000Z 20.0N 150.7W 80 KT 90 MPH 36H 26/1200Z 20.8N 153.5W 70 KT 80 MPH 48H 27/0000Z 21.4N 156.4W 65 KT 75 MPH 60H 27/1200Z 22.0N 159.4W 60 KT 70 MPH 72H 28/0000Z 22.6N 162.5W 55 KT 65 MPH 96H 29/0000Z 24.0N 169.5W 50 KT 60 MPH 120H 30/0000Z 25.0N 175.5W 45 KT 50 MPH $$ Forecaster Birchard