A high pressure system drifting slowly from west to east far north of the Hawaiian Islands over the next few days will increase easterly trade winds into the moderate to breezy range lasting into the middle of next week. Brief pulses of enhanced showers are forecast with three passing easterly waves favoring the windward mountain areas in the overnight to early morning hours starting Friday night and lingering into Tuesday morning.
Moderate trades will strengthen to breezy levels Thursday as a ridge builds north of the islands. An area of moisture moving east to west across the state will bring clouds and showers to the windward and mauka areas. Brief MVFR ceilings may occur within better organized showers, but mostly VFR conditions should prevail.
AIRMET Sierra has been issued for windward areas of the Big Island as the above mentioned area of clouds and showers move in. Maui may need to added overnight as the clouds and showers spread to this AIRMET later this evening.
Surface high pressure far northwest of the islands will move closer tonight and Thursday, then build as it moves to the north then northeast of Hawaii on Friday. As a result, trade winds will gradually increase to fresh to locally strong levels over the next couple of days. A Small Craft Advisory (SCA) has been issued for the typically windy waters around Big Island and Maui starting Thursday. A stronger surface high will pass far north of the islands late Saturday and Sunday, likely increasing trade winds and possibly necessitating an expansion of the SCA to additional waters. Elevated trade winds will persist into early next week.
The current northwest swell will continue a gradual decline through Thursday, followed by a moderate north-northwest swell Friday through the weekend. The current swell has lowered to around 4 ft at 12 seconds this evening and will slowly fall through Thursday. The next swell will be from the north-northwest and will arrive Friday. Surf along north and west facing shores should top out around seasonal average during the peak of the swell Friday afternoon and Saturday, then slowly decline late Saturday and Sunday as the dropping swell shifts more northerly and a smaller overlapping northwest swell arrives. Both swells will fade early next week.
Surf along south facing shores will briefly fall near or just below seasonal average as the current south swell continues a slow decline tonight. A new long-periond south swell will build Thursday and may push south shore surf back above seasonal average through Friday. The swell will slowly decline Saturday through early next week.
Surf along east facing shores will remain small through Thursday and will steadily increase Friday as trade winds strengthen over the region. Rough trade wind swell will produce east shore surf above seasonal average Saturday through early next week.
Small Craft Advisory from 6 AM Thursday to 6 PM HST Saturday for the typical windier waters and channels near Maui and the Big Island.
