Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
339 FXHW60 PHFO 191326 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 326 AM HST Thu Sep 19 2024 .SYNOPSIS... A fairly dry moderate to locally breezy trade wind pattern will continue through Friday afternoon. An weak disturbance moving through the Hawaii region by this weekend will increase shower trends for all islands, especially over windward and mountain areas. Isolated thunderstorms are possible for Kauai and Oahu from Saturday night through Sunday. Drier trends return from next week Monday onward. && .DISCUSSION... Local radar imagery shows little shower activity across the state this morning with only brief showers reaching windward and mountain areas. Stable looking stratocumulus clouds are drifting into the islands on the easterly trade winds this morning with bands of high level cirrus clouds passing over the island chain. These cirrus clouds, made of ice crystals, will likely enhance sunrise and sunset colors into the weekend. In the larger scale, a high pressure ridge remains far north of the Hawaiian Islands and this ridge will continue to produce moderate to locally breezy trade winds through Friday. Wind speeds will decrease slightly this weekend, as the ridge weakens in response to a cold front passing through the Central Pacific basin. Fairly strong subsidence (downward vertical motions) across the region will limit rainfall coverage through Friday afternoon. A weak low level trough riding in on the easterly trade winds will link up with an upper level low drifting into the islands from the north. These two systems will produce more unstable conditions statewide and increase shower trends statewide from Friday night through Sunday. Isolated thunderstorms are possible over Kauai and Oahu from Saturday night through Sunday. The development of any thunderstorms will highly depend on the strength of this developing upper low near the western islands this weekend. Drier conditions will return from next week from Monday onward as these low pressure systems diminish and move westward away from the state. Moderate to locally breezy trade winds continue with brief overnight to early morning showers possible over windward and mountain areas. && .AVIATION... Breezy easterly trade winds will continue through the 24 h TAF period, with clouds and showers favoring windward and mauka locations. Brief periods with MVFR CIGS/VSBYS are possible as showers pass through. Otherwise, VFR conditions will prevail. AIRMET Tango for low-level turbulence over and downwind of island terrain is possible later today. && .MARINE... Moderate to locally strong trades should remain in place through the weekend due to high pressure northeast of the islands. A slight weakening of the high could decrease wind speeds early next week. A Small Craft Advisory is in effect for the typical windy waters around Maui and the Big Island through 6 AM Saturday. North shore surf will remain very small through the weekend until mid-week when a 3 to 5 foot medium to long-period northwest swell could arrive. East shore surf will hold near seasonal levels today then slowly lower through early next week. A mix of southeast, south and southwest swells will keep small surf rolling into south facing shores through Monday. A slight bump in south shore surf is possible around middle of next week as a slightly larger long- period southwest swell moves through. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 AM HST Saturday for windier waters surrounding Maui and the Big Island. && $$ DISCUSSION...Bohlin AVIATION...Gibbs MARINE...Walsh/Jelsema