Marine Weather and Tide Forecast for Wailua, HI

SHORT TERM UPDATE
Diving into the smaller scale (mesoscale) analysis this evening, we see a long lived low level convergence band just east of Oahu, this band is drifting slowly eastward. A very unstable atmosphere coupled with increasing forcing aloft from an upper level subtropical jet stream will cause heavy rain and thunderstorms to fill in along this low level band through the overnight hours and through Saturday. Some caution here additional heavy rain bands may yet develop any other island. As this current convergence band continues to drift eastward the primary heavy rain threats in the short term will increase over the islands of Maui County into Saturday. Saturday night through Sunday the large scale flooding threats increase over the Big Island of Hawaii. Hourly rainfall rates of 2 to 3 inches are likely, even higher hourly rainfall rates are possible under developing thunderstorms. Confidence is growing on this forecast solution as the latest satellite imagery trends supports this conclusion.

This is a dangerous life threatening weather pattern evolving across the state of Hawaii through Sunday. Flash flooding is the primary threat with damaging wind gusts possible. We will closely monitor these small scale heavy shower and thunderstorm bands as they develop for flooding potential across the state. Island by island forecast impacts of these rapidly developing small scale features are typically more predictable on an hour by hour basis.
Longer range forecasts of these smaller scale bands are extremely challenging. Overall additional widespread rainfall amounts in the larger scale through Sunday statewide remains in the 3 to 8 inch range with the understanding that these smaller scale convective cloud bands can double or sometimes triple these ranges for some localized areas of each island.

PREVIOUS DISCUSSION
Issued at 342 PM HST Fri Mar 20 2026

This afternoon radar (as of 3:40 PM HST) shows a large area of moderate to heavy showers over Maui County, and scattered showers over Kauai and Oahu. Light showers are expected to move into northwest Big Island this evening. Winds were generally out of the south at speeds averaging 10 to 20 mph with gusts 20 to 30 mph.
Flood warnings are still in effect on Oahu, with flood advisories on Maui County. Rainfall amounts on Oahu in the past 6 hours were generally in the 2 to 6 inch range, with a maximum of 8.58 inches at Wahiawa.

The forecast remains largely unchanged, with a flood watch in effect for all areas except the peaks on the Big Island through Sunday. Periods of showers, heavy at times, will continue to move through the islands. Southwest flow aloft will remain in place thanks to an upper level trough to our west. Smaller "pieces" of energy will move through this trough and occasionally boost the shower activity, possibly leading to isolated thunderstorms. The exact location of these increased showers is impossible to know ahead of time (beyond the state of modeling science out here in the middle of the ocean). Therefore, folks should be aware that flooding will continue to be possible in all areas where the flood watch has been issued.

Forecast models are reasonably consistent in keeping the axis of heaviest rainfall over the central islands tonight and Saturday, then shifting it slowly eastward Saturday night into Sunday. This will slowly take the risk of flooding eastward with it.
Some drying will occur from Monday into Wednesday as trade winds become established over the state, but windward areas will see numerous light to moderate showers. Winds are expected to be a little weaker both Saturday and Sunday (in most areas) than they have been today. The exception will be the peaks on the Big Island, where winds will approach wind advisory criteria Saturday evening through Sunday morning. Several inches of snow are likely to fall on the summits Saturday night into early next week.

The long range forecast shows the possibility of another trough moving into the area from the northwest late next week. At this time, the setup is not a kona low system, but could push a cold front through the state. Details will become available as we get closer in time.

AVIATION
Bands of rain with embedded heavy showers and storms are expected to continue over Oahu and Maui County through the night. These rainbands are producing periods of IFR to LIFR CIGS/VSBYS, which will persist into the weekend as an upper level trough approaches from the west. Kauai and Big Island are expected to be mostly VFR through tonight, with MVFR conditions possible within an occasional shower.

Low-level winds continue to be out of the S-SSW, and may veer more SW over the western half of the state on Saturday. Winds are strongest over Maui county, with gusts reported up to 39 kt at PHOG. These winds may result in localized mechanical turbulence leeward of terrain. Winds will remain gusty through the evening, but gradually weaken through the weekend.

AIRMET Sierra for mountain obscuration is in effect across all islands except Kauai and the Big Island, and will likely continue into the weekend. AIRMET Tango is in effect for moderate turbulence downwind of terrain for Oahu and Maui county below 090.
AIRMET Zulu for light icing in the 140-FL260 layer will continue to be a concern within deeper cloud layers associated with the upper level disturbance.

MARINE
Issued at 342 PM HST Fri Mar 20 2026

Light to moderate S winds may strengthen tonight as surface low pressure west of Kauai deepens. Moderate to locally strong S/SW prevail through Saturday, and periods of heavy showers and thunderstorms are expected. The low will lift north on Sunday allowing moderate N winds to develop around Kauai which will then veer to NE and spread south. Fresh to strong NE winds may require a Small Craft Advisory over most waters.

N swell will increase into Saturday in maintenance of moderate swell through the weekend along N facing shores. A small, overlapping WNW swell then arrives late Saturday and holds through Monday. Surf along E shores remain well below average through the weekend. NE trades then develop early next bringing increase NE fresh swell and an increase in short period choppy surf which may approach the High Surf Advisory threshold.

A moderate S swell slowly diminishes through today followed by a small reinforcing SSW swell this weekend into Monday. Smaller surf is expected along south facing shores through the remainder of the week.

HFO WATCHES/WARNINGS/ADVISORIES
Flood Watch through Sunday afternoon for all Hawaiian Islands.

Winter Storm Watch from Saturday evening through Sunday afternoon for Big Island Summits.