Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
325 FXHW60 PHFO 130142 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 342 PM HST Wed Jun 12 2024 .SYNOPSIS... Broad high pressure north of the state will drive moderate to breezy trade winds through the week. Showers will be focused over windward areas, and leeward communities will be rather dry, though the Kona slopes Big Island will experience clouds and showers each afternoon and evening. && .DISCUSSION... A wetter trade wind weather pattern will linger over most areas into tonight. Broad surface high pressure located nearly 1,000 miles north of Kauai is maintaining moderate to locally breezy trade winds, and a mid-level ridge continues to produce stable conditions, capping low clouds at around 7,000 to 8,000 ft. In contrast to the dry weather Monday and Tuesday, there was a noticeable increase in showers overnight, as a shallow area of open celled cumulus clouds with precipitable water in excess of 1.5 inches moved in on the trades. Since then, many windward sites picked up between a quarter to a half of an inch of rainfall. Most leeward areas have experienced little accumulation, while sites on the Kona slopes of the Big Island have picked up between a tenth to a quarter of an inch. Expect this shower regime to linger into the evening and diminish late tonight. Only subtle changes are due this week. Recent runs of the GFS and ECMWF are showing the surface high moving into the northeast Pacific, while a firm trailing surface ridge holds north of Hawaii. As a result, expect moderate to locally breezy trade winds to continue, with some increase possible by the middle of next week. Precipitable water is forecast to lower back to around seasonal average by Thursday, suggesting a slight decrease in showers and typical June conditions. A resilient mid-level ridge will maintain stability, even as an upper-level trough develops over the region this weekend. The GFS and ECMWF are hinting that this upper trough may strengthen early next week, but it is too far out to confidently expect any increase in shower activity. && .AVIATION... Moderate to breezy trade winds will persist across the Hawaiian Islands over the next couple of days. Clouds and showers will favor windward and mauka areas, especially overnight, and bring brief periods of MVFR conditions to those areas. Otherwise, VFR conditions should generally prevail. AIRMET Sierra for tempo mountain obscuration is in effect for windward portions of the smaller islands this afternoon due to more persistent low clouds and showers. This AIRMET may be needed for windward areas along portions of the island chain overnight into tomorrow morning. && .MARINE... Fresh to strong easterly trades will continue through the weekend, as the surface ridge remains north of the area. This supports the Small Craft Advisory (SCA) continuing for the windier channels and waters around Maui County and the Big Island each day. A slight uptick is expected Thursday into Friday, which could expand the SCA to other zones. Surf along south facing shores will slowly ease through Thursday as the current south-southwest swell fades. Expect a mix of this fading south-southwest swell and a small, medium-period southeast swell through Thursday. 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 then gradually decline Sunday into early next week. Surf along north-facing shores will remain up above the summertime average (flat) through a good portion of the week and into next 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 possible on Friday as the winds upstream of the state strengthens. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 PM HST Saturday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Wroe AVIATION...Farris MARINE...Kino