textproduct: Honolulu

SYNOPSIS

A frontal boundary will move over Kauai tonight into Thursday and stall and dissipate around Oahu Thursday into Friday. This will bring an increase of wet weather over the western half of the state especially over Kauai. Breezy to locally strong trade winds should return on Friday. A showery trade wind pattern will continue to persist over Kauai through the weekend due to the lingering moisture, while typical trade wind showers are expected elsewhere.

DISCUSSION

A frontal boundary currently located west of Kauai will gradually weaken as it slowly shifts eastward through Thursday. Satellite imagery this afternoon is showing a broad NE to SW oriented line of showers and thunderstorms roughly 100 to 150 miles west of Kauai. This line of heavier showers is expected to weaken some as it moves over Kauai tonight into Thursday.

From late tonight into Thursday, the frontal boundary should reach Kauai and will bring the threat for heavier showers. The greatest rainfall is expected to be over the northern half of Kauai and showery weather is expected to persist from Thursday through Friday with frequent showers. With precipitable water values of around 1.8 inches and some marginal instability aloft from the upper level trough, some minor flooding impacts will be possible across Kauai. For Oahu, showers will not be as widespread as Kauai, but some brief downpours should be expected on Thursday especially in the afternoon and evening hours. For rest of the state, sea breezes will allow for afternoon cloud build ups once again with some scattered showers over interior and mountain areas during the afternoon. Any showers in the afternoon should dissipate in the evening as land breezes develop.

The frontal boundary is expected to weaken and stall somewhere around Oahu on Friday. Breezy to locally strong trade winds will also return on Friday with our typical trade wind pattern returning across most of the state. The one exception is over Kauai, where lingering moisture will continue to produce showery weather through the weekend. Typical breezy trade wind weather is expected early next week with passing showers over windward and mauka areas and a few leeward showers.

AVIATION

Winds will become light and variable over much of the state as a cold front slowly approaches from the northwest. Expect an uptick in shower activity across Kauai and Oahu later tonight through Thursday as moisture streams in from the south ahead of the front. Periods of MVFR are likely within the heavier showers. The eastern half of the state will see moderate to locally breezy southeasterly winds continue, with localized sea breezes in sheltered areas. Conditions should remain mostly VFR.

No AIRMETs are currently in effect.

All areas will continue to see some Vog due to the ongoing eruption of Kilauea. However, Vog is not expected to impact visibilities enough to warrant a mention in any TAF.

MARINE

A slow moving cold front over the far northwest waters will move over Kauai tonight, stall just west of Oahu on Thursday, then gradually dissipate. Light to moderate southeast winds ahead of the front will weaken and become more southerly by morning. Behind the front, winds will shift to the north northwest. Moderate to locally strong trade winds will reestablish themselves across the Islands Friday night or Saturday and persist into the coming week.

A Small Craft Advisory (SCA) remains in effect for locally accelerated east and southeast winds in waters around the Big Island, but conditions are expected to end by early evening.

A small west northwest (290-310) swell will gradually fade even as a small north swell (350 degree) gradually builds in. Together, they will maintain small surf along north and west facing shores through Thursday. On Friday, the north (350) swell will continue to build, possibly producing advisory level surf. Then on Saturday, a second large to extra large, long period, north to north north west (330-350) swell is forecast to arrive and produce warning level surf along north facing shores with advisory level surf across west and east facing shores through the weekend. This swell, aside from being hazardous to small craft, could generate harbor surges along north facing bays and inlets.

Surf along south facing shores will remain low through this weekend with mainly background energy dominating.

Surf along east facing shores will remain low through Thursday, but bump up slightly over the weekend with the return of trade wind flow over and upstream of the Islands.

HFO WATCHES/WARNINGS/ADVISORIES

None.