As the remnants of Fausto exit the region today, trade winds will increase to breezy levels this afternoon, then strong to locally windy levels Friday and Saturday. Trades then ease back to the usual breezy levels early next week as the high weakens. Typical summertime showers are expected for windward and mountain areas.
A band of light to moderate showers will transit through the western half of the state this morning as the remnant circulation and moisture of Fausto exits the area to the west. East to southeast winds can still be expected for Oahu and Kauai for the morning before the typical breezy easterly trade winds fill in during the afternoon. Showers then will focus over the usual windward and mountain areas through the weekend and next week.
Trade winds are then forecast to ramp up Friday and Saturday to strong levels as high pressure to the north strengthens. Model cross sections show the inversion staying around 5,000 ft and mid level temperatures increasing. These factors will increase the chances of strong downsloping winds under an increasingly stable airmass, and could get to wind advisory levels. A wind advisory for parts of the state is being considered and more details will follow as confidence increases. The time period for the strongest winds at this time appears to be Friday night through Saturday afternoon. Dewpoint temperatures are also forecast to decrease as drier air moves in with the strengthening trades. The lower humidity, decrease in showers, and increased winds will elevate the fire weather threat. We will continue to monitor all available guidance and observations.
Sunday into early next week trades will weaken to moderate to locally breezy levels as Hurricane Genevieve tracks far northeast of the state, disrupting the trade wind flow.
Moderate to locally breezy trades will spread from east to west across the island chain today as former tropical cyclone Fausto passes further to the northwest of the state. Meanwhile, an area of enhanced low level moisture will bring clouds and showers to mainly windward portions of Oahu and Kauai. Some MVFR ceilings and visibility in SHRA may accompany this band as it moves westward over the region. Trades will remain moderate to locally breezy tonight with showers and clouds once again favoring windward locations.
AIRMET SIERRA remains in effect for north through east sections of Oahu above 2000 ft due the passing showers and low clouds. AIRMET TANGO will likely be needed by the end of the day as breezier trades fill in.
Variable to light northerly winds will yield to east-southeast to easterly trades building in from east to west across the state today as Fausto's remnant low exits off to the northwest. A Small Craft Advisory (SCA) is in effect through Friday night for strong trade winds throughout the windier waters of Maui County and the Big Island. Trades strengthen through the weekend, which could necessitate an expansion of the SCA to the rest of the coastal waters later on. A weakness in the ridge of high pressure develops on Sunday, which will cause trade winds to weaken again for early next week.
A medium period south swell peaking today will bring south shore surf around the summer average (5-6ft). Surf then fades gradually through the weekend while a mix of small south swells maintains surf slightly below the seasonal average.
Surf along east shores will trend up tonight into the weekend due to a combination of building short period trade wind swell and renewed medium to long period east swell emanating from Hurricane Genevieve in the East Pacific. North shores will see flat to tiny surf through early next week as a weakening Post-Tropical Cyclone Fausto moves away from the islands and no significant north swells are forecast.
Small Craft Advisory until 6 AM HST Saturday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters.
