Moderate to breezy northeast trade winds will become more northerly as Tropical Storm Fausto tracks north of the state for the western half of the state today. Expect an increase in cloud and shower activity along northern and windward exposed slopes with some spillage over the leeward areas. Winds will weaken becoming light and variable in the wake of the Tropical Storm Fausto starting over the eastern half of the state by the evening then the western half Wednesday afternoon and evening. In this lighter wind regime, land/sea breeze pattern will develop. Localized heavy showers will remain possible through Wednesday. A stable and drier breezy trade wind weather pattern will filter in across the state from Thursday onward as Fausto dissipates and remnant moisture moves west of the islands.
Satellite and radar imagery reveals numerous to scattered low clouds and showers along windward and mauka locations with some showers making into leeward spots. Showers have been mostly light to moderate with hourly rainfall totals ranging between .05 to .20 inches with some standout spots receiving less than .5 inches in the wetter areas. As Tropical Storm Fausto passes north of the state the trades will be diminished and allow for the development of a sea breeze regime for the Big Island and possibly Maui County later this afternoon and evening. Breezy northeast trade winds are more likely to persist ahead of the cyclone for Oahu and Kauai, which will keep a more typical windward and mauka shower pattern. With the more saturated air, heavy rain showers will be possible in the afternoon/evening for locations where the synoptic-scale winds weaken enough to give way to the sea breeze.
On Wednesday, winds will weaken across the state allowing for afternoon sea breezes and localized heavy rain showers to develop over leeward and interior areas. Confidence in the flooding threat from Fausto remains low but will continue to monitor and update as necessary.
Subtle shifts in the forecast track are still possible which would affect the specific island by island impacts from Fausto. We strongly encourage the public to pay close attention to this passing storm system as weather impacts over the Hawaiian Islands will evolve as Fausto gets closer.
By Wednesday night, Fausto continues on a west- northwest track and begins to gain distance from the islands, which will reintroduce moderate to breezy southeast to easterly winds into the forecast. From Thursday onward, a drier and more stable breezy trade wind pattern will return.
Showers embedded within the N-NE flow continue to bring MVFR conditions to windward areas of all islands, and occasionally spill over into leeward areas. Isolated IFR conditions are possible in heavier showers. Expect this to continue through today with gradual improvement in ceilings.
As Tropical Storm Fausto draws closer (but remains north of the islands), trade winds will weaken and become more northerly over the eastern end of the state, followed by Oahu and Kauai tonight. Afterwards, light southeast to south winds will develop and spread over the state from east to west, allowing sea-breeze induced showers to increase during the afternoon and evening hours. Aviation interests near the Hawaiian Islands should monitor updates to TC SIGMET Sierra, which covers Fausto, as the system passes north of the islands over the next few days.
AIRMET Sierra is in effect for mountain obscurations for windward sections of Kauai, Oahu, Molokai, and Maui. Mountain obscurations may return to the Big Island later today due to windward showers or afternoon showers over upslope areas.
Moderate to fresh north-northeast winds will prevail today as Hurricane Fausto enters the far northeast offshore waters. Winds will become more north and decrease tonight as Fausto moves through the northern offshore waters. As Fausto passes by, winds will be light and variable over the coastal waters, then shift out of the south, then immediately southeast in its wake. As Fausto moves off to the northwest and high pressure builds to the north, east- northeast trades will build back in on Thursday, then strengthen to fresh to locally strong levels Friday into the weekend. A Small Craft Advisory (SCA) is in effect for the windward waters and channels due to the east swell through tonight.
Nearshore buoys on the eastern side of the islands have shown a considerable uptick with the medium- and long-period energy from Fausto. The surf is expected to peak this morning before dropping off through Wednesday. A High Surf Warning for east facing shores remains in effect through Wednesday afternoon. East shore surf will trend back up Friday into the weekend due to a combination of rising trade wind swell and a new long-period east swell generated by Hurricane Genevieve.
A series of south swells will keep south shore surf near the summer average (5-6ft) through the week.
Surf along N shores could also see some brief increase as Fausto (or its remnants) pass near the region through Wednesday, then return to typical flat to tiny levels late Wednesday into the weekend.
High Surf Warning until 6 PM HST Wednesday for Big Island East- Big Island North-Big Island Southeast-East Honolulu-Kauai East- Kipahulu-Koolau Windward-Maui Windward West-Molokai Southeast- Molokai Windward-Olomana-Windward Haleakala.
Small Craft Advisory until 6 AM HST Wednesday for Alenuihaha Channel-Big Island Southeast Waters-Big Island Windward Waters- Kaiwi Channel-Kauai Channel-Kauai Northwest Waters-Kauai Windward Waters-Maui County Windward Waters-Oahu Windward Waters- Pailolo Channel.
