A cold front currently moving across Kauai this afternoon will progress down the island chain tonight, finally stalling out and diminishing near the Big Island by Tuesday afternoon. Southwesterly winds will remain in the breezy to strong range with higher gusts through tonight ahead of the front. Briefly breezy northwesterly winds with cool and dry conditions will follow behind the frontal passage. A stronger weather system may produce more significant weather impacts across from late Friday onward with the potential for periods of heavy rain and thunderstorms.
Satellite imagery this afternoon shows bands of cumulus clouds with embedded showers streaming northeastward across the state from the southwest, out ahead of a cold front currently moving across Kauai. Strong to locally gusty southwest winds have firmly increased to Wind Advisory levels across all Hawaiian Islands, with sustained speeds generally in the 20 to 30 mph range and gusts frequently reaching 40 to 50 mph this afternoon. The strongest winds continue to favor higher terrain and areas north and east of island terrain features. A Wind Advisory remains in effect through tonight to address these conditions, though winds are expected to ease below advisory levels as the front passes and winds shift out of the northwest. Even stronger winds are expected across the highest summits on the Big Island, where speeds will increase to warning levels later this afternoon and evening. A High Wind Warning remains in effect for the summits of Mauna Kea and Mauna Loa through Wednesday.
The cold front is currently crossing Kauai this afternoon and remains on track to reach Oahu this evening, Maui County late tonight, and the Big Island Tuesday morning, though with noticeably weaker shower activity by the time it reaches the eastern end of the state. The most significant rainfall is expected to occur during a four to six hour window as the main frontal band moves through each island. Cooler and drier northwesterly winds will follow the front, allowing overnight and early morning temperatures to dip into the 60s as clearer skies and drier air promote more efficient radiational cooling.
Lighter winds are expected to return from Tuesday night through Thursday as a weak high pressure system settles just north of the islands and drifts eastward. By Thursday night into Friday, winds will shift back out of the southwest ahead of the next cold front approaching from the northwest. Current guidance suggests this front may stall near Kauai and Oahu from Saturday night into Sunday as the associated cold pool aloft evolves into a cutoff low near the islands.
Forecast uncertainty remains high regarding the impacts of this cutoff low heading into the weekend. Recent model trends show the front slowing sooner and stalling farther north than earlier forecasts suggested, with the upper low also trending westward over time. If this system sets up close enough to the islands, it could produce periods of heavy rain and thunderstorms, with an increased risk for flooding from Saturday through Monday. At this time, the highest potential for significant impacts appears to be across the western islands, including Niihau, Kauai, and Oahu. However, impacts will depend heavily on the eventual placement and evolution of the upper low. This system will continue to be closely monitored as forecast confidence improves over the coming days.
Gusty southwesterly winds continue for the islands ahead of an advancing cold front that is expected to bring a round of showers through early morning Tuesday. These showers may bring MVFR conditions, primarily due to degraded cigs, with isolated IFR conditions possible. This front is currently impacting Kauai, and is expected to move southeast through Oahu and Maui County this evening and overnight, before weakening as it reaches the Big Island by early morning Tuesday. Winds will shift more north and northwesterly behind the front for during the day Tuesday.
AIRMET Sierra is in effect for mountain obscuration across Kauai, Maui, and Lanai. This may need to be expanded as the front moves southeast across the island chain.
AIRMET Tango remains in effect for moderate with isolated severe low level turbulence below 5000 feet over and downwind (north and east) of mountain terrain across all islands. The strongest turbulence will be felt surface to 2000 feet in these areas. Conditions are expected to improve overnight as winds weaken behind the front.
A front that is currently over the northwest coastal waters near Kauai this afternoon will continue moving moving across the state through Tuesday. A Small Craft Advisory (SCA) remains in effect for all waters due to strong southwesterly winds as the front approaches and moves through tonight. The front will swiftly move through Kauai this evening, with moderate to strong northwesterly winds filling in behind. The front will then weaken, and winds will gradually ease to moderate to fresh speeds as it progresses through the eastern half of the island chain overnight through Tuesday. Winds will shift out of the east on Wednesday as a weak high quickly moves from west to east over the state. Light to gentle southerly winds will return Thursday as another front approaches the state from the northwest. Southerly winds will gradually strengthen to moderate to fresh speeds Friday ahead of the next front with moderate to locally strong northerly winds filling in behind the front as the front moves southeast over the state Friday into the weekend.
Surf heights are expected to rapidly build along north and west facing shores this evening and peak Tuesday well above High Surf Warning levels along most north and west facing shores as an extra large northwest swell builds in. While northwest Hawaii buoy 51001 is still showing predominantly short period wind-generated swell this afternoon, there have been upward trends in the medium to long period 13 to 17 second bands throughout the day, indicating forerunners of the incoming northwest extra large swell energy. Though the swell will peak on Tuesday, overlapping pulses will keep surf elevated through Wednesday before subsiding below High Surf Advisory levels Thursday night into Friday. With this afternoon's forecast updates, a High Surf Warning has been issued for north and west facing shores of Niihau, Kauai, Oahu, Molokai, and the Big Island, and for north facing shores of Maui. This swell will also push combined seas well above the 10 foot SCA threshold in many areas. Another extra large swell is possible late Friday and Saturday.
Rough choppy surf along south facing shores will hold through tonight as southerly winds remain strong ahead of the front. Surf along east facing shores will remain tiny through much of the week due to lack of strong trades near and upstream of the state. An increase surf is possible along east shores this weekend.
The Coastal Flood Statement will remain in effect through Tuesday morning, as peak monthly tides coincide with much higher than predicted ocean levels. Expect minor flooding of low-lying coastal infrastructure as well as some some beach erosion during peak high tides through the morning hours again early Tuesday. Thereafter, mean higher high water (MHHW) levels at the daily high tides are expected to be lower, and the Coastal Flood Statement will likely be cancelled or allowed to expire.
High Surf Warning until 6 PM HST Wednesday for Niihau-Kauai Leeward-Waianae Coast-Oahu North Shore-Maui Windward West-Kona- Kohala-Kauai North-Molokai Windward-Molokai North-Molokai West- Maui Central Valley North-Windward Haleakala-Big Island East-Big Island North.
Wind Advisory until 6 AM HST Tuesday for Niihau-Kauai Leeward- Kauai Mountains-Waianae Coast-Oahu North Shore-Olomana-Central Oahu-Waianae Mountains-Lanai Mauka-Kahoolawe-Maui Windward West- Maui Leeward West-Kona-Kohala-Big Island Interior-Kauai North- Kauai East-Kauai South-East Honolulu-Honolulu Metro-Ewa Plain- Koolau Windward-Koolau Leeward-Molokai-Lanai Windward-Lanai Leeward-Lanai South-Maui Central Valley North-Maui Central Valley South-Windward Haleakala-Kipahulu-South Maui/Upcountry- South Haleakala-Big Island South-Big Island Southeast-Big Island East-Big Island North.
High Wind Warning until 6 PM HST Wednesday for Big Island Summits.
Small Craft Advisory until 6 PM HST Wednesday for all Hawaiian waters except Maalaea Bay-
Small Craft Advisory until 6 AM HST Tuesday for Maalaea Bay.
