Swell Matrix

Area Forecast Discussion

National Weather Service Honolulu Hi

358 am hst Mon apr 13 2026

Synopsis

Light to moderate rain continues across the western portion of the state, as the rain band gradually meanders away from the islands. Light and variable winds will favor some onshore sea breezes through midweek. By the latter half of the weak, light trades and quiet weather return to the forecast for the latter end of the week.

Discussion

Latest radar imagery continues to show remnant showers developing across the smaller Hawaiian Islands. These showers have been showing predominately less than a tenth of an inch per hour across the state, with some locally higher amounts across leeward Big Island. Despite this, opting to cancel the remaining Flood Watch for Kauai through Maui as a result. The threat for widespread flash flooding has decreased across the Hawaiian Islands, therefore, the Flood Watch has been cancelled. However, due to lingering moisture and saturated grounds, some minor flooding may still occur in areas affected by heavy showers.

Winds across the state are anticipated to be light and variable beginning tomorrow, favoring onshore sea breezes each afternoon, which may result in some showers as the lingering airmass over the islands remains moisture-rich. Moreover, dewpoints are expected to remain in the upper-60s throughout the week, maintaining high humidity levels that will persist until trades return. As the low pressure system, once anchored north of the islands, finally dislodged and moved northeastward away from the Hawaiian Islands by mid-week -- and with it, the band of rainfall. A broad area of high pressure quickly builds in its wake, opening the door for light trades to make a return by the latter half of the week. Trades remain quite light and are not expected to make much of a profound effect on the local humidity levels. However, for the first time in several weeks, there is no potential event forthcoming for the Hawaiian Islands.

Aviation

Low cigs and SHRA will continue over the islands today. MVFR conds possible in heavier SHRA. Winds should remain light.

AIRMET Sierra is in effect for mtn obsc for Kauai to Maui.

AIRMET Tango is in effect for mod turb btn 120-FL280. Conds should slowly improve into tomorrow.

Marine

A weak surface trough remains draped over the central islands, extending from a low pressure system far north-northwest of the area. Moderate to fresh easterly winds will persist to the east of the trough, while light to moderate southerly winds occur to the west. This weak surface boundary along with an upper level disturbance moving over the region will continue to bring showers and the potential for isolated thunderstorms through mid-week. The surface trough lifts northwest in the latter half of the week and high pressure to the northeast will begin to take over at the surface, causing gentle to moderate easterly trades to gradually develop across the Hawaiian coastal waters by this weekend.

A small, medium-period northwest swell will diminish today. However, small surf will be maintained along north and west facing shores by a reinforcing pulse on Tuesday. Following this, northwest swell energy declines through the rest of the week.

A medium-period south swell will continue to decline today as well. A new south swell arrives on Tuesday, once again providing a boost to surf along south facing shores through mid week before gradually subsiding into the weekend.

Surf along east facing shores will remain below seasonal average with lighter than average trade winds near and upstream of the islands forecast through next week.

Watches, Warnings, Advisories

None.

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