000 WTPA42 PHFO 261451 TCDCP2 Hurricane Douglas Discussion Number 25 NWS Central Pacific Hurricane Center Honolulu HI EP082020 500 AM HST Sun Jul 26 2020 Hurricane Hunters from the Air Force 53rd Weather Reconnaissance Squadron spent most of the night with Douglas, making 5 passes through the center. The final pass contained some of the strongest winds of the entire mission, with flight-level winds near 100 kt, SFMR winds up to 79 kt, and a relatively steady pressure reading near 983 mb. The initial intensity was maintained at 80 kt based on these valuable data points. Also of extreme value is the fact that the low-level center is south of the apparent center seen in conventional satellite imagery, and closer to the islands than might be otherwise expected. Although island-based radars are also detecting Douglas' circulation, they are sampling the upper portions of the cyclone that are sheared northward due to southerly vertical wind shear. Despite the vertical wind shear, Douglas has been slow to weaken, and this trend will continue today as Douglas passes near, or potentially over, the islands. Steadily increasing SSTs along the forecast track are expected to limit the rate of weakening, while the noted vertical wind shear may be confined to the upper-levels. While Douglas is on the western edge of a ridge aloft, leading to high-level southerly shear, a mid-level ridge is expected to build westward to the north of Douglas through Monday, likely allowing the low- to mid-level core of the cyclone to remain intact. The updated intensity forecast once again closely follows the consensus IVCN, and maintains Douglas as a hurricane until it passes west of the islands. Steady weakening will occur thereafter due to persistent southwesterly shear. The mid-level ridge will continue to drive Douglas toward the west- northwest, with the current motion vector estimated to be 285/14 kt. The forecast track takes the center of Douglas dangerously close to the islands from Maui to Kauai through tonight, where a Hurricane Warning is in effect. The updated forecast track is very close to the previous forecast and the high-performing ECMWF guidance, and anticipates some acceleration toward the west in the later periods as the increasingly shallow system gets steered by the low-level trade wind flow. Key Messages 1. Douglas will pass dangerously close to, or over, the islands today, bringing a triple threat of hazards, including but not limited to damaging winds, flooding rainfall, and dangerously high surf, especially along east and north facing shores. 2. It is remains important that you do not focus on the exact forecast track of Douglas. Due to Douglas' angle of approach to the islands, any wobble 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 26/1500Z 20.7N 154.3W 80 KT 90 MPH 12H 27/0000Z 21.4N 156.6W 75 KT 85 MPH...NEAR MAUI COUNTY 24H 27/1200Z 22.3N 159.5W 70 KT 80 MPH...NEAR KAUAI 36H 28/0000Z 22.8N 162.7W 60 KT 70 MPH 48H 28/1200Z 23.3N 166.1W 55 KT 65 MPH 60H 29/0000Z 23.7N 169.5W 50 KT 60 MPH 72H 29/1200Z 24.0N 173.0W 45 KT 50 MPH 96H 30/1200Z 24.5N 179.5E 35 KT 40 MPH 120H 31/1200Z 25.5N 172.0E 30 KT 35 MPH $$ Forecaster Birchard