Moderate to breezy trade winds produced by strong high pressure far northwest of the Hawaiian Islands will increasingly back northeast ahead of an approaching Hurricane Fausto tonight into Tuesday. Shower activity should also experience an uptick, but continue to favor windward mountain areas through early Tuesday. As Fausto passes north of the Hawaiian Islands on Tuesday and Wednesday as a tropical storm, diminishing winds for the islands could allow for sea breezes and heavy afternoon rain showers. A drier, breezy trade wind weather pattern will return across the state from Thursday onward as Fausto drifts westward away from the Hawaiian Islands.
Satellite imagery and radar reveals bands of showers entering the coastal waters from the northeast as increased moisture associated with Hurricane Fausto begins to move into the Hawaiian Islands. These showers will begin to move onshore this evening, increasing precipitation for windward and mauka locations through Tuesday morning. Total rainfall amounts could amount to up to half an inch to one inch of rain for localized mauka areas. Dew points are already increasing into the lower to mid 70s this afternoon, which will make for muggy conditions through Wednesday whilst Fausto passes north of the islands as a tropical storm.
Fausto's passage to the north will also act to actually reduce winds for the islands, which should allow for the development of a sea breeze regime for the Big Island and possibly Maui County as well on Tuesday. 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. Backed northeasterly 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.
Tuesday night, fairly weak winds and the potential for land breezes should actually lead to more limited shower activity despite the increased moisture and proximity of the tropical storm. Southwesterly shear will tend to push the heavier precipitation associated with the weakening storm north and east of the center, away from Hawaii. On Wednesday, another day of relatively weak winds will lead to further potential for sea breezes and heavy rain showers, this time including Oahu and Kauai.
At this stage, subtle shifts in forecast track may still occur that 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 the closer Fausto gets.
High confidence Fausto impacts include: warning-level high surf warning for east facing shores through Tuesday. A High Surf Warning is already in effect for east facing shores through Wednesday. Lesser confidence impacts include: strong winds to around 40 mph near and north of the low center and possible heavy rain threats from Tuesday through Wednesday.
No time like the present to review your family hurricane preparedness plans, and ensure every household has at least a 14 day supply of food and water available if needed during this years active hurricane season.
By Wednesday night, the cyclone continues on a west- northwest track and begins to gain distance from the islands, which will induce moderate to breezy southeast to easterly winds. From Thursday onward, a drier and more stable breezy trade wind pattern is set to return.
As Fausto draws closer (but remains north of the islands), trades will weaken and back (become more northeasterly) tonight and Tuesday over the eastern end of the state. This weakening and backing will occur Tuesday night over Oahu and Kauai. By Tuesday night over the eastern end, light southeast to south winds will develop. Showers will increase as trade winds die off and sea- breezes kick in. MVFR conditions are likely in heavier showers, but otherwise we will see VFR. TC SIGMET Sierra covers Fausto.
No AIRMETs are currently in effect.
Moderate to fresh NNE winds will be in place tonight as Hurricane Fausto enters the far northeast offshore waters. Winds will become more north and decrease tonight into Tuesday as Fausto moves through the northeast and northern offshore waters. As Fausto passes by, winds will be light and variable over the coastal waters, followed by south, then southeast immediately 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 on Friday into the weekend. A Small Craft Advisory (SCA) remains in effect for the winder waters and channels around Maui County and the Big Island through the remainder of the afternoon. Additionally a SCA is now in effect for the windward waters due to the east swell through Tuesday night.
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 continue building through the evening and then peak tomorrow before dropping off Wednesday afternoon. A High Surf Warning for east facing shores is currently in effect through Wednesday afternoon. East shore surf will then 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 summertime 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 Tuesday and 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 Northwest Waters-Kauai Windward Waters-Maui County Windward Waters-Oahu Windward Waters-Pailolo Channel.
