092 WTPA42 PHFO 260259 TCDCP2 Hurricane Douglas Discussion Number 23 NWS Central Pacific Hurricane Center Honolulu HI EP082020 500 PM HST Sat Jul 25 2020 In spite of marginal SSTs near 26C and increasing vertical wind shear, convection increased around the center of Douglas a few hours ago, and a ragged eye briefly reemerged in conventional satellite imagery. As a result, data sampled by the U.S. Air Force 53rd Weather Reconnaissance Squadron earlier in the day showed little change in the intensity of Douglas. A blend of adjusted flight levels winds and SFMR data supports holding the initial intensity at 80 kt with a central pressure of 982 mb. Reconnaissance aircraft will conduct another mission into Douglas tonight. Aircraft and satellite data indicate that Douglas continues to move toward the west-northwest (290 deg) and that the forward motion has slowed to 14 kt. Douglas is being steered by a low- to mid-level ridge to the northeast and is approaching a weakness in the mid- level ridge that is causing the slight deceleration. A continued motion toward the west-northwest will bring Douglas over, or very near, portions of the main Hawaiian Islands Sunday and Sunday night, then to parts of the Papahanaumokuakea Marine National Monument on Monday and Tuesday. The updated forecast track is very close to the previous forecast and during the next couple of days, remains near the ECMWF toward the southern end of a tightly clustered guidance envelope. Model spread increases on days four and five, when the official forecast trends toward the middle of the guidance envelope. Gradual weakening is expected through the forecast. SSTs will gradually warm along the forecast track. However, vertical wind shear will steadily increase over the next couple of days and is expected to be strong enough to induce weakening. The official intensity forecast has changed very little from the previous advisory, and continues to follow a blend of the corrected consensus and statistical model guidance. Based on the latest forecast, a Tropical Storm Warning has been issued for Kauai County. A Tropical Storm Warning and Hurricane Watch remain in effect for Hawaii County and Maui County. A Tropical Storm Watch has also been issued for portions of the Papahanaumokuakea Marine National Monument from Nihoa to French Frigate Shoals. Key Messages: 1. Douglas continues to approach the main Hawaiian Islands, and will pass 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 26/0300Z 19.9N 151.4W 80 KT 90 MPH 12H 26/1200Z 20.6N 153.6W 75 KT 85 MPH 24H 27/0000Z 21.5N 156.4W 65 KT 75 MPH 36H 27/1200Z 22.3N 159.1W 60 KT 70 MPH 48H 28/0000Z 23.0N 162.1W 55 KT 65 MPH 60H 28/1200Z 23.6N 165.4W 50 KT 60 MPH 72H 29/0000Z 24.0N 168.8W 45 KT 50 MPH 96H 30/0000Z 24.6N 176.0W 40 KT 45 MPH 120H 31/0000Z 25.7N 178.0E 35 KT 40 MPH $$ Forecaster Wroe