Swell Matrix

Area Forecast Discussion

National Weather Service Honolulu Hi

404 am hst Mon aug 17 2026

Synopsis

Tropical Storm Lala is continuing to move west of the state. Some lingering showers remain over Kauai and will continue to taper off today. Trade wind pattern returns Tuesday with windward and mauka showers. Later this week winds may veer slightly southeast.

Discussion

Radar and satellite show some showers along windward Oahu and some leftover bands of rain from Tropical Storm Lala moving over Kauai and Niihau. Showers will continue to dissipate as trade wind weather returns.

Tropical Storm Lala continues to move away to the west, well southwest of Kauai. Tropical storm warnings are cancelled. The Flash Flood watch has also be cancelled. With the departure of Lala winds will ease into the moderate category. Inversion depth and PWATs will remain a little higher than normal through the upcoming week, leading to relatively wet trades. Showers can be expected over windward and mauka locations with some isolated spillover into leeward areas. These trades will veer to the east- southeast Thursday night, and remain that way through next weekend.

Aviation

Categories will gradually improve from tempo IFR to prevailing MVFR to overall VFR through the period. Tropical Storm Lala, currently located about 250 miles southwest of Lihue, Kauai continues to move westward at 10 mph. This will institute a return to generally light trade winds that will pull a drier air mass across the region. The result will be less SHRA and lifted ceilings from occasional MVFR to prevailing VFR this afternoon.

AIRMET SIERRA will be in effect this morning for mountain obscuration for both windward Big Island and Kauai.

Marine

Tropical Storm Lala early this morning is approaching the far western edge of the offshore waters as it continues to move west. Fresh to locally strong easterly trade winds will gradually build through the day from the east to west. As the associated strong winds from Lala are now outside of the coastal waters, the Small Craft Advisory (SCA) has been trimmed back for all zones except for the windier waters and channels around Maui County and the Big Island through tonight. By midweek trade winds look to ease through the forecast period to gentle to fresh speeds across all coastal waters.

Surf along south facing shores will remain elevated today from a moderate medium to long period swell that has filled in overnight. Surf will likely peak today before slowly declining through midweek. Another long period south swell generated from gales just south and east of New Zealand will begin arriving late this week.

Surf along east facing shores will continue to decline today as Lala progresses further west of the state. East facing shores will remain small to moderate through the forecast period. North facing shores will remain tiny with only wind wave-driven chop in tandem with the declining east swell wrap.

Watches, Warnings, Advisories

Small Craft Advisory until 6 AM HST Tuesday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters.

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