Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
505 FXHW60 PHFO 041353 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 353 AM HST Fri Jul 4 2025 .SYNOPSIS... A high pressure ridge will build north of the Hawaiian Islands lasting into early next week. Expect stable trade winds with brief passing showers and breezy winds through at least Tuesday. Shower activity will favor windward slopes, and aside from afternoon showers over the Kona slopes of the Big Island, leeward areas will remain mostly dry. && .DISCUSSION... The satellite imagery this morning shows fairly stable clouds riding into the windward slopes of each island on the trade winds. These clouds will not produce much shower activity due to the stable conditions created by a high pressure ridge aloft, shown on 500 mb streamlines. Subsidence temperature inversion heights will remain in the 5,000 to 6,000 foot elevation range today in a fairly dry environment. Brief passing showers are possible in this stable boundary layer, mainly over windward and mountain areas in the overnight to early morning hours. A broad high pressure ridge will remain locked in place north of the state through much of next week. Moderate to breezy easterly trade winds will continue during this extended forecast time period. The interaction of the breezy trade wind flow with the islands should generate wind gusts around 40 mph over and downwind of terrain, though isolated areas on the Big Island and Maui County could approach Wind Advisory criteria at times. The GFS and ECMWF are showing no distinct organized areas of shower activity or instability. This will limit windward rainfall activity into the isolated to scattered range over windward and the Kona slopes of the Big Island with dry conditions continuing over leeward areas. See the Fire Weather section below for additional discussion. A slight decrease in trade winds is expected Wednesday. && .AVIATION... A high pressure ridge will strengthen north of the state over the next several days producing moderate to breezy trade winds. A fairly stable environment will keep only brief passing showers in the forecast into the weekend. AIRMET Tango has been issued today for moderate low-level turbulence over and downwind of island terrain. This AIRMET will likely persist into the weekend as breezy trades continue. && .MARINE... High pressure to the north will strengthen, causing strong trade winds to develop through the weekend and into the beginning of next week. The high will then weaken slightly next week, causing trade winds to marginally decrease into the breezy to locally strong range by the later half of next week. The current Small Craft Advisory has been expanded in coverage to include the rest of the channels and is in effect through the weekend. It will likely be extended into next week if trade winds remain strong. Surf for south facing shores will gradually decline through the weekend below the summertime average as the current S swell declines. Tiny, long period S swells will then hold into next week until a new small long period swell looks to fill in by Tuesday night. This new swell could boost surf heights near the summertime averages (5 ft) by the middle of next week. Surf for east facing shores will increase this weekend and become more rough and choppy as trade wind speeds increase and the north shore surf will remain seasonally tiny. && .FIRE WEATHER... Breezy, gusty, and rather dry conditions will develop on Saturday and persist into early next week. Relative humidity at lower leeward elevations will likely fall below 45 percent each afternoon, and with the inversion dropping to as low as 5,000 feet winds will become gusty over and downwind of terrain. This will result in near critical fire weather conditions over dry leeward areas, though no headlines (watches or warnings) are due since the Keetch Byram Drought Index will remain below the 600 threshold at Honolulu. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 PM HST Sunday for Kauai Northwest Waters-Kauai Leeward Waters-Kauai Channel-Oahu Leeward Waters- Kaiwi Channel-Maui County Windward Waters-Maui County Leeward Waters-Maalaea Bay-Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Bohlin AVIATION...Bohlin MARINE...Tsamous FIRE WEATHER...Bohlin