Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
827 FXHW60 PHFO 260105 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 305 PM HST Sat May 25 2024 .SYNOPSIS... Broad high pressure north and northeast of the state will maintain moderate to locally breezy easterly trade winds through the week. Showers will mainly favor windward slopes, and areas of high clouds will pass overhead at times. && .DISCUSSION... Moderate to locally breezy easterly trade winds remain in place, with little change expected through the holiday weekend. The trades are being driven by broad surface high pressure sitting nearly 1600 miles north of the state, and a surface trough parked about 600 miles west of Kauai is causing the winds to be more easterly than usual, especially over the western end of the island chain. Mid-level ridging over the islands is maintaining somewhat stable conditions, and shallow moisture moving along the trade wind flow will continue to focus modest rainfall of around a quarter of an inch per day across most windward slopes. An upper- level trough generally collocated with the surface trough is producing heavy showers thunderstorms about 200 miles west of Kauai, and westerly winds aloft are sending high clouds from this area over Kauai and Oahu, while a separate shield of thin high clouds is streaming over the Big Island. Thunderstorm activity will remain west of the state through the holiday weekend, but the inversion will could be weakened at times near Kauai, where brief periods of enhanced showers will be possible. In addition, expect spotty afternoon and evening showers, some briefly heavy, across leeward Big Island. Little change is expected Tuesday onward. The surface high will settle far northeast of the state and hold into Friday, and the surface trough will linger west of the islands, resulting in breezy easterly trade winds. The nearby upper-level trough will weaken. This will lead to grater stability and support a typical rainfall pattern with showers continuing to favor windward slopes. && .AVIATION... Moderate to locally breezy trade winds will prevail across the Hawaiian Islands for the next several days. As a result, AIRMET Tango remains in effect for moderate low-level turbulence downwind of island terrain. This AIRMET will likely remain in effect though much of next week. A fairly stable pattern will remain over the state into next week with a few high clouds streaming overhead. However, shallow moisture embedded within the trade wind flow will allow passing showers to favor north through southeast sections of the islands, especially during the overnight through early morning hours each day. While VFR conditions will prevail over most locations, brief MVFR ceilings and visibilities will be possible as showers move through. && .MARINE... High pressure north of the state will maintain moderate to locally strong easterly trade winds across the state through most of next week. A Small Craft Advisory (SCA) remains in effect for the windiest waters around Maui and the Big Island. A trough will amplify and linger west of the islands Sunday through the middle of next week, resulting in a shift to a more east-southeast direction over the western end of the state. This slight shift should decrease the winds a touch over the leeward waters of Kauai and Oahu. But generally, moderate to locally strong easterly trades will continue to prevail throughout the new week. A small southeast swell and background energy from the south will maintain surf just below the summer average the next several days. The next significant south-southwest swell (200 degrees) is currently being generated by a strong low pressure system southeast of New Zealand. As this low occludes tonight, we should see a wide swath of gales aimed towards Hawaii. This should produce a steady supply of south swells starting next weekend and into the first half of the following week. Surf heights may approach advisory levels on the biggest days. East shore surf will decrease slightly this weekend then hold steady through late next week. Surf along north shores will remain very small with a slight bump possible late Sunday through Monday. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 PM HST Monday for Pailolo Channel- Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Wroe AVIATION...Vaughan MARINE...Kino