Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
816 FXHW60 PHFO 111954 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 954 AM HST Tue Jun 11 2024 .SYNOPSIS... Broad high pressure north of the state will drive moderate to breezy trade winds for the next several days with a slight decrease expected by the weekend. Stable conditions will focus showers over windward areas, and leeward areas will be rather dry, though leeward Big Island will experience clouds and showers each afternoon and evening. && .DISCUSSION... A moderate to breezy, stable and somewhat dry trade wind flow remains in place this morning. Broad surface high centered about 900 miles north of Kauai is driving the trades, and a mid-level ridge is maintaining an inversion around 5,000 to 6000 feet. Rainfall was sparse overnight and should remain limited over windward slopes today. Leeward areas will be dry, with the exception of afternoon clouds and a few showers over the Kona slopes of the Big Island. Some increase in trade wind showers is expected tonight through Wednesday as the trades hold near current strength. The cloud field just upwind of the island chain has changed from mostly stable stratocumulus to be more dominated by shower bearing, open celled cumulus with precipitable water in the 1.3 to 1.6 inch range. Persistent mid-level ridging will maintain stability, so rainfall totals will not be significant. Thus, expect a more typical pattern of windward rainfall to develop overnight and persist through at least Wednesday and possibly into Thursday. A slight decrease in trade winds is expected heading into the weekend. The ridge to the north will be pushed southward on Friday and Saturday, then meander about 400 to 600 miles north of Kauai into early next week. With the ridge a little closer to the islands, we should experience a slight decrease in the trades. A typical distribution of trade wind showers over mainly windward slopes will prevail. && .AVIATION... Moderate to breezy trade winds will persist across the Hawaiian Islands through tomorrow. Clouds and showers will favor windward and mauka areas, especially overnight, and bring periods of MVFR conditions to those areas. A plume of low-level moisture will move in tonight, bumping up cloud and shower coverage slightly compared to last night. Outside of the potential for MVFR conditions across windward and mauka areas, VFR conditions should generally prevail. No AIRMETs are currently in effect. AIRMET Sierra may be needed tonight for tempo mountain obscuration for windward areas. In addition, AIRMET Tango may be needed for tempo moderate turbulence below 7,000 ft downwind of island terrain later today or tonight as winds edge up towards 25 kts below the inversion. && .MARINE... Fresh to strong easterly trades will likely continue through the weekend, as the surface ridge remains north of the area. This supports the Small Craft Advisory continuing for the windier channels and waters around Maui County and the Big Island. Surf along south facing shores will hold just under the advisory level this morning as the south-southwest swell that peaked early Monday steadily lowers. Observations at the offshore buoys reflect this lowering trend early this morning, with the peak energy shifting down into the 13 to 15 second bands. This trend will continue through midweek, with mainly a mix of the fading south- southwest swell and a small, medium-period southeast swell. A fresh, long-period south swell is expected to arrive Thursday night into Friday, then peak late Friday into Saturday. This swell should produce advisory level surf Friday into Saturday. Surf along north-facing shores will remain up above the summertime average (flat) through a good portion of the week as small, short-period north to north-northwest swells move through. Surf along east-facing shores will remain small and choppy over the next several days due to limited trade wind fetch upstream of the islands. A slight increase is expected towards the end of the week as the winds upstream of the state strengthens. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 PM HST Wednesday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Wroe AVIATION...Farris MARINE...Kino