Area Forecast Discussion

SYNOPSIS

A light land and sea breeze pattern will produce afternoon clouds and spotty showers over land and partial clearing at night. Trade winds will redevelop late Wednesday and strengthen Thursday and Friday focusing rainfall over windward and mauka areas.

SHORT TERM UPDATE

Issued at 945 AM HST Wed Apr 22 2026

Minor update this morning to alter the chance of rain on Big Island for this afternoon. Sea breeze should develop precipitation patterns much like yesterday, so forecast was changed to be closer to yesterday's observed shower regime. This lowered the chance of rain at the highest elevations, and increased it on the southeast coast (mainly Kau District and to a lesser extent the Puna District).

PREV DISCUSSION

Issued at 341 AM HST Wed Apr 22 2026

No significant changes to the forecast with the morning package. Changes were confined to incorporate the latest National Blend of Model data to the forecast.

A trough to the west of the islands is helping to keep light winds over the region. Light winds over night resulted in land breezes that have helped to clear most of the skies over the islands. This afternoon we anticipate some afternoon sea breezes that will bring some clouds and showers to the interiors of the islands.

The trough is expected to dissipate over the next day, which will allow a surface ridge to set up north of the islands. This in turn will allow trade winds to build back over the region. A mid to upper ridge will limit shower activity for Thursday and Friday. Over the weekend, moisture currently upstream the islands will be carried in on the trade wind flow. This will bring a return to more typical trade wind showers over the weekend.

AVIATION

Issued at 341 AM HST Wed Apr 22 2026

Land breezes this morning will become sea breezes today with cloud and shower buildups over interior areas. Northeasterly trade winds will then fill in by the evening. Once the trade winds return, showers will return to focusing over windward and mountain areas. VFR conditions will prevail with brief MVFR conditions any in showers.

No AIRMETs in effect.

MARINE

Issued at 945 AM HST Wed Apr 22 2026

Light coastal sea breezes will develop later this morning with light trades gradually returning this evening into Thursday as a ridge of high pressure builds north of the state. Moderate to locally fresh trades will be the dominant wind from Thursday through the weekend. Brief periods of locally strong winds will be possible over the windier areas around Maui County and the Big Island during this time.

A small, medium period, west northwest to northwest swell has leveled out this morning and will gradually decline the next few days.

A moderate size, medium period north northeast swell is arriving this morning and will peak later today with surf heights above advisory thresholds for east facing shores. This swell will also produce above above average surf along select west facing shores along Maui and the Big Island near Kua Bay. This swell will slowly decline through the remainder of the week. Strengthening trades later this week will support closer to seasonal average surf for eastern exposures this weekend.

Small westerly energy from former Super Typhoon Sinlaku is expected to come through the next couple of days. This swell may lift surf along better western exposures from today through the end of the week.

HFO WATCHES / WARNINGS / ADVISORIES

High Surf Advisory until 6 AM HST Thursday for Big Island East- Big Island North-Big Island Southeast-Kipahulu-Koolau Windward- Molokai Southeast-Molokai Windward-Olomana-Windward Haleakala.