Breezy trades weaken slightly during midweek then restrengthen by late in the week. Potential tropical development threatens to bring heavy rainfall to eastern portions of the state during the latter half of the week, though uncertainty remains higher than usual at this time.
Issued at 301 AM HST Mon Sep 21 2026
Trades will remain breezy through today, but are expected to slightly weaken by midweek. Showers will primarily impact windward and mountain areas, with possibly a higher frequency over windward Big Island today. Kona slopes of the Big Island could also see some afternoon showers. MVFR conditions are expected within showers while VFR prevails elsewhere.
AIRMET Tango for moderate low level turbulence downwind of island terrain will remain in effect through today due to the breezy trade winds. An upper level trough positioned NW of Kauai, which is currently advecting high clouds over the the state, could also cause some moderate upper level turbulence over Kauai by midday.
AIRMET Sierra is not currently in effect, but could be issued later today due to upstream clouds and showers.
Issued at 301 AM HST Mon Sep 21 2026
Fresh to locally strong trade winds expected through tonight before decreasing slightly through midweek. A Small Craft Advisory is in effect for the typical windy waters of Maui County and the Big Island through Tuesday evening. Wind speeds will restrengthen during the latter half of the week as a trough or potential tropical disturbance moves near the islands. Shower coverage will also increase, along with the potential for isolated thunderstorms, particularly across the eastern waters.
Surf along south facing shores will remain above average over the next couple of days as a long period SSW swell holds relatively steady. This swell will then gradually fade heading into mid week. A slightly smaller, long-period south-southwesterly swell will fill in late this week into next weekend generated by a series of lows near New Zealand. West facing shores will experience a bit of the southerly wrap through most of the week.
Breezy trade winds will maintain moderate surf along east facing shores for the next several days. Surf along north facing shores will remain flat to tiny through Monday, but will see a slight bump Tuesday into Wednesday as a small, medium-period northwest swell fills in from an Aleutian low. Then a small, long-period west-northwest swell generated by Tropical Storm Dujuan as it curves northeast near Japan and potentially strengthens into a hurricane will build locally Friday into next weekend, increasing surf along north and west facing shores.
Small Craft Advisory until 6 PM HST Tuesday for Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters- Maalaea Bay-Pailolo Channel.
