Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
263 FXHW60 PHFO 281305 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 305 AM HST Tue May 28 2024 .SYNOPSIS... High pressure to the north will maintain moderate to locally breezy trade winds through early next week. Showers will favor windward slopes and coasts, especially during the overnight and early morning hours. A trough aloft will move over the islands Friday through early next week, bringing an increase in trade wind shower coverage and intensity. && .DISCUSSION... Currently at the surface, a trough of low pressure is located around 800 miles west-northwest of Kauai, while a 1027 mb high is centered around 1100 miles north of Honolulu. Moderate to locally breezy trade winds prevail, strongest over the eastern end of the state. Infrared satellite imagery shows a mix of high and low clouds resulting in partly to mostly cloudy conditions. Radar imagery shows isolated to scattered showers moving into windward slopes and coasts, with mostly dry conditions in leeward locales. Main short term focus revolves around rain chances and trade wind trends. High pressure will build eastward and strengthen well north of the state during the next couple days, while the trough of low pressure remains nearly stationary west of the island chain. Wind speeds will change little, with the trades holding in the moderate to locally breezy range. The trough will shift westward and dampen out Thursday and Friday, with high pressure northeast of the state then settling southward and closer to the islands through the weekend. This should give a slight boost to the trade wind speeds, with moderate to breezy conditions holding in place through early next week. As for the remaining weather details, relatively dry trade wind weather should prevail during the next few days, with showers favoring windward slopes and coasts particularly at night and during the early morning hours. Troughing aloft appears to move over the islands Friday and linger through early next week, bringing an increase in trade wind shower coverage and intensity. && .AVIATION... Moderate to breezy trade winds will bring SHRA with periodic MVFR conds to windward and mauka areas. Otherwise VFR conds will prevail. AIRMET Sierra is in effect for mtn obsc for windward Big Island and N through SE sections of Maui through Kauai. AIRMET Tango remains in effect for moderate low-level turb downwind of island terrain. Conds for mod low-level turb look marginal through the next couple of days and AIRMET Tango may be needed on and off through the period. AIRMET Zulu may be needed for light to mod icing around Kauai and possibly Oahu later this afternoon, due to the low off to the west. && .MARINE... Fresh to strong easterly trades will continue through the week as the surface ridge remains positioned north of the state. The strongest winds are expected over the windier waters and channels from Oahu to the Big Island, supporting the Small Craft Advisory being expanded. The winds over the Kauai waters will fluctuate between east and east-southeast through Wednesday due to a persistent surface trough to the west. A shift out of the east- northeast is expected beginning around Thursday as the trough weakens and drifts away from the region. Surf along exposed south-facing shores will remain small throughout much of the week, due to a combination of background south-southwest and southeast swell energy. An upward trend is expected from Friday through the first week of June due to an active pattern evolving within our swell window near New Zealand. Altimeter and ASCAT passes over the past couple of days reflected the potential for the weekend, showing a broad swath of gale-to storm-force winds with seas up to 30 feet focused at the state within the 190-200 degree directional bands. This will mark the beginning of a long-lived event with additional reinforcements expected within the same area over the next several days. Surf along exposed east-facing shores will remain small and choppy throughout the week as the trades persist. Surf along north-facing shores will remain near the summertime average each day. Guidance depicts a small, long-period swell arriving early next week from a gale that is forecasted to track northeastward today over the far northwest Pacific near the Kuril Islands. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 PM HST Wednesday for Kaiwi Channel- Maui County Windward Waters-Maalaea Bay-Pailolo Channel- Alenuihaha Channel-Big Island Windward Waters-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Jelsema AVIATION...Walsh MARINE...Gibbs