Marine Weather and Tide Forecast for Maunaloa, HI

SHORT TERM UPDATE
With the shortwave aloft moving east of the islands, convection over the area has ceased, and the forecast was updated to remove thunderstorms on the Big Island this evening and make minor changes to tonight's forecast. The forecast looks good for the rest of the week.

PREV DISCUSSION
Issued at 345 PM HST Mon Apr 20 2026 The shortwave trough that passed through the islands earlier today has moved to the east. Some thunderstorms formed over the Big Island slopes around midday, but have died off this afternoon.
Another stray thunderstorm is possible through the evening hours.

A low pressure system north of the islands is helping to keep winds light, and that is expected to continue into Wednesday. The lighter winds will result in some localized land and sea breezes.
This in turn will lead to some clearing overnight, with some afternoon clouds and showers forming over the interior of the islands.

The second half of the week should see the low move to the far northeast of the islands, and that will allow a new ridge to build north of the region. This will allow trade winds to build across the area during the latter part of the week. A ridge aloft will help to provide a stable airmass over the region with limited shower activity. Moisture upstream of the islands will be carried in on the returning trade wind flow and will likely reach the islands over the weekend, bringing a return to more typical trade wind shower activity by the end of the weekend.

AVIATION
Generally light winds continue across all terminals this evening, expected to persist through the next couple of days. Onshore sea breezes will bring interior clouds and light showers, followed by overnight clearing with emerging offshore land breezes. Expect low-MVFR/IFR due to low cloud ceilings. Otherwise, VFR conditions prevail.

No AIRMETs in effect.

MARINE
Issued at 345 PM HST Mon Apr 20 2026 A series of lows and troughs northwest and north of the islands will act to keep weak to locally moderate east southeast flow in place across the local waters through early Wednesday. Light wind flow should allow for afternoon sea breeze development near the shores. By Late Wednesday through this weekend, surface high pressure building north of the area will bring a return of moderate to locally strong trades.

Forerunners from a small, medium- period, northwest swell are still on track to arrive late tonight, with this swell forecast to build Tuesday and peak on Wednesday. This should bring an uptick in surf along north facing shores.

A moderate, medium- period north- northeast swell arrives on Tuesday and peaks also on Wednesday, bringing moderate surf to north and northeast facing shores, before slowly declining through the end of the week. East facing shores will see an increase in surf with wrap from the aforementioned north-northeasterly swell despite below- seasonal average trades. Strengthening trades late this week will also give east facing shores a bump in surf.

Surf will continue to be small along south facing shores through the period.

HFO WATCHES/WARNINGS/ADVISORIES
None.