Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
222 FXHW60 PHFO 211933 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 933 AM HST Tue May 21 2024 .SYNOPSIS... Moderate to locally breezy trades will hold over the eastern islands, while lighter east southeast winds allow for some localized land and sea breezes over the western end of the state today and Wednesday. Showers will favor windward and mauka areas overnight and during the morning hours, with a few showers developing over interior and leeward sections each afternoon and evening. A more typical moderate to breezy trade wind pattern will overspread the state Wednesday night or Thursday and linger through early next week, with showers favoring windward and mauka areas, along with the occasional leeward spillover. && .DISCUSSION... Currently at the surface, a trough of low pressure is located around 300 miles west-northwest of Kauai, while a 1035 mb high is centered around 1600 miles north-northeast of Honolulu. This light gradient will maintain moderate to locally breezy trade winds over the eastern islands, while light to moderate east southeast winds remain over the western end of the state today into Wednesday. This pattern will allow localized leeward sea breezes in the most sheltered areas over Kauai and Oahu. Infrared and visible satellite imagery shows a mix of high and low clouds bringing mostly cloudy conditions to the state this morning, with an area of enhanced clouds just east of the Big Island. Radar imagery shows relatively dry conditions across the state, with scattered showers moving into windward areas of the Big Island and streaming from the south to north over Kauai County. Rainfall chances will increase for windward Big Island today and for the rest of the windward areas statewide tonight into Wednesday as this area of enhanced clouds and showers moves over the state. Moderate to breezy easterly trades will return statewide Thursday as the trough to the west- northwest of the state gradually shifts westward and the high to the northeast shifts north of the state. A series of reinforcing highs will build north of the state Friday through early next week, while the trough continues to shift further west and away from the area. This will maintain moderate to breezy trade winds across the island chain. In addition drier air will filter in from the east allowing for a more stable trade wind pattern featuring mainly windward/mauka showers and the occasional leeward spillover. Showers will be mostly prevalent in the overnight and early morning hours. This pattern should hold through early next week. && .AVIATION... Light to moderate east to east southeast winds will persist through tomorrow. A few leeward showers are possible this afternoon where localized sea breezes form. Also, a plume of moisture will move towards the eastern end of the state this afternoon/evening and could bring an uptick in showers and cloud cover to windward Big Island and Maui...which could lead to periodic MVFR conditions. Otherwise, VFR conditions will prevail. AIRMET Sierra is in effect for mountain obscuration over the windward slopes of Kauai. Conditions should improve through the mid- to late-morning hours. AIRMET Sierra may also be needed for mountain obscuration across windward Big Island and Maui later this afternoon or evening. && .MARINE... Strong high pressure centered nearly 1300 nm northeast of the state is driving fresh to strong easterly trade winds around the Big Island and Maui, and a surface trough sitting roughly 250 nm northwest of Kauai is causing winds to shift out of the east- southeast and ease slightly around Oahu and Kauai. A Small Craft Advisory (SCA) is currently in place for all waters around the Big Island, waters north of Maui, and the Pailolo Channel. As the trough weakens and drifts westward, expect the stronger easterly trades winds to spread to Oahu and Kauai by Wednesday, with the SCA likely adjusted to cover the typically windy waters around the Big Island and Maui County. Moderate to strong easterly trade winds will persist into the weekend. The current south swell is on a gradual decline, though recent PacIOOS buoys are still measuring about 3 feet at 13 to 14 seconds. The south shore surf forecast was edged up slightly for the morning, but expect a slow downward trend over south and exposed west shores during the next couple of days, with only small inconsistent pulses of southwest swell for the remainder of the week. Rough surf along east facing shores will slowly rise over the next few days as the trades strengthen upstream of the state. Surf along north shores will remain small with a slight bump possible around Monday. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 PM HST Wednesday for Maui County Windward Waters-Pailolo Channel-Alenuihaha Channel-Big Island Windward Waters-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Almanza AVIATION...Farris MARINE...Wroe