Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
935 FXHW60 PHFO 251935 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 935 AM HST Tue Jun 25 2024 .SYNOPSIS... A stable trade wind pattern will persist through much of the week with breezy to locally windy trades. Periodic light showers will focus over windward and mauka areas during this time. An increase in shower activity is possible over the weekend as an upper-level disturbance approaches the region. && .DISCUSSION... This morning, surface high pressure remains centered roughly 900 miles north of Kauai. Stable and fairly dry conditions are prevailing across the state, with the early morning 12z soundings showing sharp trade wind inversions between 4,000 and 6,000 feet and limited moisture trapped below the inversion. This is also evident on the latest satellite and radar imagery, which shows a dry slot over the central and eastern islands with only isolated light showers embedded within breezy trade winds moving into windward and mauka areas. Two distinct cloud bands are noted on regional satellite imagery, one moving into the western end of the state and the other passing near the far eastern end. For the rest of the day, expect these stable, breezy trade wind conditions to continue. Showers will tend to favor windward and mountain areas, particularly for Kauai. Afternoon cloud buildups and a few showers will also be possible over the Kona slopes of the Big Island this afternoon. High pressure to the north is expected to weaken slightly over the next couple of days. This should relax our local pressure gradient a bit, but will still remain breezy through much of the week. Impulses of moisture embedded in the trade wind flow will continue to favor windward and mauka areas, though rainfall accumulation will be limited. Aside from some brief afternoon/evening showers over Kona slopes of the Big Island, leeward areas will remain mostly dry. Conditions start to change near the end of this week and into the weekend as guidance continues to show a disturbance aloft moving across the islands from east to west. While it remains early to discern specific details, this upper disturbance will increase instability as it moves near the western end of the state. This instability could enhance trade wind showers statewide and introduce isolated thunderstorm chances over the Big Island slopes Friday and Saturday afternoons. Precipitable water values may be the limiting factor, however, preventing showers and thunderstorms from reaching their full potential. Therefore, expect some refinements to the forecast for the Friday through Sunday period as details become more clear. && .AVIATION... Breezy to locally windy trade winds will persist over the next 24 hours across the island chain. Showers and brief MVFR conditions will be focused over windward and mauka locations. Otherwise, VFR conditions will prevail. AIRMET Tango remains in effect for moderate low-level turbulence over and downwind of island terrain due to the breezy trade winds under a strong tradewind inversion. AIRMET Sierra may be needed sometime this evening as shower coverage increases slightly. && .MARINE... High pressure will dominate the Central North Pacific through the weekend and possibly beyond. Moderate to locally strong easterly trades will hold through today, then weaken to gentle to fresh on Thursday in response to a slight weakening of the Northeast Pacific High. The Small Craft Advisory (SCA) for the typically windier waters around Maui County and the Big Island remains in effect, and will likely remain necessary through at least tomorrow morning. Meanwhile, rough and choppy surf along east-facing shores will persist through today before gradually trending down Wednesday through Thursday. A small, medium-period, south swell will peak today before gradually trending down tonight and Wednesday. Multiple small, medium- to long- period south swells are expected Thursday through Saturday morning. With high pressure dominating to the north, surf along north and west facing beaches will be minimal. A tiny boost in the northwest swell is expected today and also on Thursday, before trending even lower over the weekend. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 AM HST Wednesday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Vaughan AVIATION...Farris MARINE...Kino/Bedal