Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
784 FXHW60 PHFO 040627 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 827 PM HST Wed Jul 3 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. A few unsettled clouds just east of the state will enhance overnight to early morning showers, only brief periods of showers are forecast from Independence Day onward as an upper level ridge settles in over the region. && .DISCUSSION... Satellite imagery this evening shows an unsettled patch of clouds just east of the islands drifting in on the trade winds. This weakly unstable patch of clouds will likely keep passing showers in the forecast for windward and mountain areas through the overnight to early morning hours. Drier conditions are forecast from tomorrow afternoon onward. 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 from tomorrow afternoon 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 rainfall trends. Long range global weather models are suggesting that another low level wave in the easterlies may transit through the Hawaii Region by the middle of next week, increasing our shower trends as this trough passes from east to west down the island chain. More numerous showers are possible over windward and mountain areas from Tuesday night through Wednesday night as this system 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. Rainfall coverage will likely be increased for the extended day 6 and 7 forecast period to cover this passing trough. && .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 the holiday weekend. 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 this evening`s high tide times. This will continue to create minor coastal flooding issues through Saturday. Peak water levels of around 3.5 feet are expected during Friday and Saturday`s high tide times. Therefore, a Coastal Flood Statement 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 AM HST Thursday for windier area around Maui and the Big Island. && $$ DISCUSSION...Bohlin AVIATION...SMW MARINE...Blood