Marine Weather and Tide Forecast for Kailua, HI

SHORT TERM UPDATE
Satellite imagery shows mostly dry conditions across the western half of the state this morning and increasing low cloud and shower coverage over the eastern end. This increasing moisture beginning to nudge into windward slopes of the Big Island is a part of the leading edge of a larger plume of moisture associated with a westward-moving surface trough expected to pass south of the state this weekend. Looking aloft, a broad upper level trough remains just to the northwest of Kauai and is continuing to supply some thin high clouds to the western half of the state this morning.

Model guidance remains in good agreement in the short term, showing breezy trades persisting through the weekend with limited showers moving into windward and mauka areas of the western half of the state today, and more showers concentrated over the eastern half as the plume of moisture moves in.

PREV DISCUSSION
Issued at 453 AM HST Sat Aug 8 2026

Generally light to breezy trades as the state falls in between a 1027 mb high located off the U.S. West Coast and lower equatorial pressure. Thick multi-layered cloud cover streaming up along the eastern side of a weakening west upper trough will spread west- to-east across the islands today. Despite these clouds, the afternoon will still warm up in the middle 80s to around 90 F across many lower lying spots. Trades will be welcome as wind- sheltered coastal areas feel the muggiest under low 70 F dew points. Recent area soundings depict a deep and moist enough boundary layer that will be able to support continued widely- scattered easterly showers caught up within moderate trade flow.

A moist easterly air mass in association with a tropical wave or disturbance passing south of the islands near 10N will increase cloud cover and initiate more late day through Sunday rainfall.
The highest probability of precipitation is forecast to impact the Big Island and its surrounding eastern and southern waters tonight through tomorrow. Locally heavy rainfall is also possible.
If enough early day sun heats up Mauna Kea and Mauna Loa's (primarily western) slopes, in tandem with the higher moisture flux from the south, there is a mentionable chance for an isolated thunderstorm or two Sunday afternoon. Once this slug of southern moisture advects west southwest of the area Tuesday, a drier air mass will briefly pass through the middle of the week. Thus, clearer skies are forecast Tuesday through Thursday with limited shower activity. Trades will not undergo much change so they will be a relief from what will be a few days of muggy, very warm weather in lower lying, more wind-protected communities.

There are increasing probabilities that an easterly wave near 10N135W may develop a low center and strengthen into something more past 48 hours. Please refer to the latest NHC forecasts concerning this potential early to mid next week evolution. The late week forecast will be dependent upon the state of the tropics. The majority of the NWP guidance, from deterministic to ensemble suites to AI, are latching on to a more active pattern this time next week. Many of the solutions are leaning toward the development of a tropical cyclone from an active western east Pacific region. While still too early to definitively discuss any details of a potential tropical cyclone, this active area will warrant close monitoring the next few days.

AVIATION
Moderate to fresh trade winds will prevail through the weekend.
MVFR ceilings will be focused over typical windward slopes, but will be more extensive over windward Big Island today as an area of deeper moisture moves in on the trades. AIRMET Sierra is in effect for windward Big Island and will likely be expanded tonight or Sunday to cover windward Big Island, Maui, and Molokai as the above mentioned moisture spreads westward. VFR conditions will prevail over most leeward areas, though portions of leeward Big Island could experience extensive MVFR conditions with scattered heavy SHRA Sunday afternoon.

AIRMET Tango is in effect for mod turb downwind of island terrain. This AIRMET will likely be needed for next several days.

MARINE
Fresh to locally strong trade winds will persist through most of the week as high pressure remains anchored northeast of the state. A Small Craft Advisory has been extended through Sunday afternoon for the typical windy channels and waters around Maui County and the Big Island. This advisory many need to be extended further, as borderline conditions will prevail through at least Wednesday. Late in the week, the focus will shift to the deep tropics southeast of the state, where a tropical cyclone could develop.

A pair of south-southwest swells will produce south shore surf near August average this weekend and near to above average Monday and Tuesday. A larger swell will arrive Tuesday night and may push surf to the High Surf Advisory level late Wednesday through Friday. This swell should slowly decrease next weekend.

Along east-facing shores, short-period trade wind swell will generate surf just below August average through Thursday.
Depending on how potential tropical cyclone development plays out southeast of the islands, an increase in east swell is possible Friday and next weekend. Surf along north-facing shores will remain flat to tiny through the week.

Due to a combination of peak monthly high tides and water levels running higher than predicted in a few locations, minor coastal flooding will be possible around the afternoon high tide as early as Sunday, with peak conditions Monday through Wednesday.

HFO WATCHES/WARNINGS/ADVISORIES
Small Craft Advisory until 6 PM HST Sunday for Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters- Maalaea Bay-Pailolo Channel.