Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
535 FXHW60 PHFO 041339 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 339 AM HST Thu Jul 4 2024 .SYNOPSIS... A broad high pressure ridge north of the Hawaiian Islands will keep moderate trade winds in the forecast through the first half of next week. Satellite imagery this morning shows an unsettled patch of clouds moving through the western islands with more stable clouds east of the state drifting into the Big Island and Maui on the trade winds. Only brief periods of showers are forecast over windward and mountain areas from this afternoon into early next week as an upper level ridge settles in over the region. && .DISCUSSION... Satellite imagery this morning shows an unsettled patch of clouds moving through the western islands with more stable clouds east of the state drifting into the Big Island and Maui on the trade winds. This weakly unstable patch of clouds will keep passing showers in the forecast for windward and mountain areas of Oahu and Kauai through the early morning hours. Drier conditions will spread to all islands starting later this morning and last into early next week. A broad subtropical ridge will remain in place north of the Hawaiian Islands into next week. An upper level ridge will then settle in over the islands producing strong and stable subsidence today through Monday. Increasing downward vertical motions (subsidence) under this upper ridge will lower the trade wind thermal inversion heights, limiting vertical cloud development and thereby decreasing shower coverage. This upper level ridge will lift north on Monday and Tuesday, opening the door for a slight increase in windward and mountain shower coverage trends. Long range global weather models continue to suggest that another low level wave in the easterlies may transit through the Hawaii Region by the middle of next week, potentially increasing our shower trends as this trough passes from east to west down the island chain. This next weak system may be our next best chance for decent rainfall amounts over windward and mountain areas. More numerous showers are possible over windward and mountain areas from Tuesday night through Wednesday night as this system slowly passes through each island. Rainfall amounts will also increase in this pattern during the typical overnight to early morning diurnal rainfall maximum with some windward and mountain areas possibly seeing 0.10 to 0.25 inch amounts. Forecast rainfall coverage and amounts were increased for the middle of next week to cover for this passing trough scenario. && .AVIATION... Moderate to locally breezy trades will continue for the next few days. SHRA and brief MVFR conds should be confined to windward and mauka locations. Otherwise VFR should prevail. No AIRMETs currently in effect. && .MARINE... The upstream pressure gradient from surface high pressure far northeast of the islands will weaken the next couple of days as troughing develops over the eastern Pacific. Trades may occasionally become locally fresh, especially in the Alenuihaha Channel, through Friday morning. Sea heights will remain in the 4 to 6 foot range the next several days. No significant swells are expected from any direction for the remainder of the week. A series of small, medium period south southeast swells will keep south-facing shores from going completely flat through the weekend. A small fetch of strong northeast winds off the U.S. Pacific Northwest coast will generate a very small, medium period northeast swell that is scheduled to arrive this holiday weekend. Higher than normal water levels, in tandem with new moon tides, has produced higher than normal water levels around Big Island. Water levels have exceeded 3 feet above Mean Lower Low Water (MLLW) during the past few afternoon`s high tides. This will continue to create minor coastal flooding issues through the weekend. Peak water levels of around 3.5 feet are expected during periods of high tides. Therefore, a Coastal Flood Statement highlighting this flooding will remain in effect for Big Island`s coastal zones for the remainder of the week. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 PM HST this evening for Maalaea Bay- Pailolo Channel-Alenuihaha Channel. && $$ DISCUSSION...Bohlin AVIATION...SMW MARINE...Blood