Marine Weather and Tide Forecast for Halaula, HI

DISCUSSION
Radar and satellite imagery show widely scattered showers across the state this morning with clouds favoring windward and mauka areas. Recent obs continue to show the region under the influence of a relatively unstable and moist air mass with an upper level trough to the northeast of the islands. Expect this trough to gradually weaken later today as upper level ridging expands towards the west.

Trade winds are expected to return today as high pressure far north of the islands builds. However, trades will be light enough this afternoon to allow for the development of afternoon sea breezes. Could see some localized flooding this afternoon as sea breeze showers are enhanced by lingering instability. Moderate easterly trades return by Sunday and continue into Monday, with clouds and showers over mainly windward and mauka areas.

The next weather maker will come in the form of an closed-off upper low that will sink down along and near 170W longitude and come within 600 miles northwest of Kauai. The west northwest positioning of this low will pull up a more moisture-rich air over the state from the southwest. As heights begin to lower and mid to upper layers cool from the west, enhanced instability within a moistened air mass will likely induce another round or three of widespread showers and thunderstorms. Ensemble guidance places the higher probability for measurable precipitation along the upper trough axis (centered on Maui County and points northeastward) and on windward slopes this week. With the approach of either a broad open wave trough or a closed low northwest of the islands next week, the highest rain probabilities (or areas to receive more frequent rain episodes) will be across the western half of the state. Flooding concerns may be re-awakened next Tuesday through Thursday as locally heavy precipitation falls upon saturated soils.

AVIATION
Moderate trades will return today and continue to usher in clouds and showers to windward and mauka areas. However, winds will still be light enough to support sea breeze development by the afternoon, which will bring additional clouds and showers to leeward and interior areas that will diminish overnight with the loss of daytime heating. MVFR conditions will be possible in any showers, otherwise VFR conditions should prevail.

AIRMET Sierra is in effect for mountain obscuration for windward Maui and Oahu through the morning.

MARINE
Gentle to moderate trades continue through Monday, then veer to southeasterly in advance of a deep low that will develop NW of the islands. Winds further veer through midweek and then hold steady out of the southerly quadrant where they will remain for the balance of the week. There will be a chance of thunderstorms during this time, particularly over the western waters.

A moderate, medium period NNW swell has shifted more N and will gradually trend down through Sunday producing below average surf along N and W facing shores. A tiny, long period NW swell will fill in Monday into Tuesday before subsiding Wednesday which will prevent surf from going flat. In the long range, guidance depicts a gale forming Monday near the Kurils then tracking northeast to the western Aleutians by Wednesday. In this scenario, Hawaii would experience an uptick in the NW swell next weekend.

Surf along E facing shores will remain below the April average through the weekend. E shore surf could becomes tiny by mid week as southerly winds emerge.

A tiny, long period S swell will move through this weekend providing a small boost in surf along S facing shores. A larger, long- period SSW swell will fill in Monday into Tuesday and produce near to above average surf along S facing shores.

HFO WATCHES/WARNINGS/ADVISORIES
None.