Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
283 FXHW60 PHFO 051339 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 339 AM HST Sat Jul 5 2025 .SYNOPSIS... Stable and breezy trade winds will continue through Wednesday as a strong high pressure ridge anchors in place north of the state. Brief passing showers will favor windward and mountain slopes, and late afternoon to evening showers along the Kona slopes of the Big Island, other leeward areas will be mostly dry. && .DISCUSSION... Weather conditions are fairly similar to what we saw 24 hours ago. Fairly stable low clouds are riding the breezy easterly trade winds and producing a few showers over windward island mountains this morning. An upper level ridge will produce a fairly stable subsidence across the Hawaii Region with temperature inversion heights ranging from the 5,500 to 6,500 foot elevation range, limiting shower coverage across the state. A subtropical jet stream northwest of the islands will continue to produce some high level ice crystal cirrus clouds mainly over the western half of the state. These high level clouds may enhance sunrise and sunset colors. In the big picture, a strong high pressure ridge will remain locked in place north of the Hawaiian Islands through much of next week, resulting in a fairly stable and breezy typical summer time trade wind weather pattern. One wrinkle in the forecast is a weak upper level trough, shown on both 500mb and 700mb model streamlines, drifting over the islands later tonight. This weak trough may lift subsidence inversion heights enough for a subtle increase in local island shower activity later tonight through early Sunday morning. Otherwise the ridge builds back in rather quickly with a return to dry and breezy summer time weather through much of next week. In the long range outlook, operational models and model blends are suggesting a slight increase in low level moisture and possibly a modest increase in shower activity from Wednesday night onward. && .AVIATION... A strong high pressure ridge anchored north of the Hawaiian Islands will keep fairly stable and breezy easterly trade winds across the region lasting into much of next week. A fairly stable environment will keep only brief passing showers in the forecast, favoring windward and mountain areas in the overnight to early morning hours. AIRMET Tango remains in effect for moderate low-level turbulence over and downwind of island terrain. This AIRMET will likely persist into early next week as breezy trade winds continue. && .MARINE... Moderate trade winds will strengthen to areawide fresh to locally strong today in response to a tight pressure gradient downstream of a large high north of the islands. This has prompted an all water Small Craft Advisory that will be in effect through the weekend. The high will slightly weaken and slide east by the middle of next week. This will result in trades dropping back to more moderate magnitudes through the end of the week. Winds in the notoriously winder eastern island bays/channels and south of Big Island will remain fresh to strong through the majority of next week. A slowly declining south swell will have surf along south-facing shores gradually falling below summer averages this weekend. Background, long period southerly swell will hold into next week until the arrival of a near 3 foot long period swell fills in late Tuesday through Wednesday. This swell may boost south-facing shore surf heights to near summertime averages (~5 ft) Wednesday. East-facing shore chop will increase over the weekend, becoming rough and choppy, in response to strengthened trade flow. && .FIRE WEATHER... Breezy, gusty, and rather dry conditions will continue into early next week. Minimum relative humidity at lower leeward elevations will likely fall at or below 45 percent each afternoon. Temperature inversion heights will drop as low as 5,000 feet. This will result in near critical fire weather conditions over dry leeward areas at times, though no headlines (watches or warnings) will be issued since the Keetch Byram Drought Index will remain below the 600 threshold at Honolulu. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 AM HST Monday for all Hawaiian waters. && $$ DISCUSSION...Bohlin AVIATION...Bohlin MARINE...Blood FIRE WEATHER...Bohlin