Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
757 FXHW60 PHFO 030147 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 347 PM HST Tue Sep 2 2025 .SYNOPSIS... Stable, light to moderate trade winds will produce mainly light showers over windward areas into the weekend. Most leeward areas will continue to be rather dry, except the Kona slopes of the Big Island where scattered showers will develop each afternoon. && .DISCUSSION... A stable and somewhat dry light to moderate trade wind flow is in place this afternoon. Trade wind strength has changed little since yesterday, as a subtropical ridge sitting 200 to 300 miles north of the islands continues to be weakened by an area of low pressure farther to the north, and a robust ridge aloft is producing stable conditions. The trades have pushed away a diffuse area of moisture that triggered some heavy showers around Kailua-Kona yesterday afternoon, and precipitable water is now running about 25 percent below seasonal average. As a result of these stable and rather dry conditions, rainfall has been minimal across windward slopes, with only a few hundredths of an inch measured at a handful of stations. Most leeward areas have been dry, and in contrast to yesterday, the Kona slopes of the Big Island have received only a few light showers this afternoon. Expect little change to the stable, light to moderate trade wind weather through Monday. The GFS and ECMWF have been hinting at a band of moisture moving through around Saturday night or Sunday, which could lead to a brief boost in mainly windward showers. Heading into the middle of next week, forecast uncertainty increases considerably due to the passage of now Hurricane Kiko over the region. Given historical forecast errors in that time range, it remains too early to tell what, if any, impacts this system will have on local weather. && .AVIATION... Light to moderate trades are forecast into tomorrow with a brief shower possible especially on windward areas. Overall dry conditions should preclude any mountain obscurations tonight. No AIRMETS are in effect or anticipated tonight. && .MARINE... A weak surface ridge to the north will remain nearly stationary through the forecast period. This will maintain moderate to locally fresh trade winds with some localized sea breezes, especially across leeward waters. Elevated surf will continue along north facing shores with a mix of a short- to medium-period north swell, and a small medium- period northwest swell. These swells will peak this afternoon, then gradually decline through Thursday. Reinforcing small short- to medium-period north-northwest swells are expected through the week which will keep surf elevated. Surf along south facing shores will continue to slowly subside this evening as the current south swell fades. Background medium- to long-period energy will hold through the week before a small to moderate long-period south-southwest swell fills in over the weekend. Below average surf is expected to continue along east facing shores through the week. Peak monthly high tides, combined with water levels running higher than predicted, may lead to minor flooding along the shoreline and in low-lying coastal areas Wednesday through the end of the week. Coastal flooding will mainly be focused around the daily afternoon high tide. && .FIRE WEATHER... Light to moderate trade winds will remain below the critical fire weather threshold through at least the weekend. Dry and stable will prevail, with afternoon relative humidity dropping to around 45 percent each afternoon through Saturday. && .HFO WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Wroe AVIATION...PECHACEK MARINE...Ahue FIRE WEATHER...Wroe