A front will push through Kauai and Oahu this morning then move through Maui County this afternoon and then Big Island this evening. Breezy northerly winds behind the front will bring in cooler and drier air. Northerly winds will veer southerly Tuesday night into Wednesday as another front arrives Wednesday night into Thursday. Expect another round of moderate to heavy showers and even stronger winds associated with this second frontal passage. Pre- frontal southerly winds Wednesday afternoon could be quite gusty. The week should end cool and fairly dry with trades re- established.
Satellite and radar imagery show a thick cloud band associated with a passing cold front center over Kauai County early this morning. Moderate to occasionally heavy showers can been see within the frontal band orientated from the southwest to northeast over the Kauai channel. Breezy westerly winds within and ahead of the cloud band will quickly become breezy northerly winds as the front passes each island today and tonight. The front is expected to pass through Kauai early this morning then Oahu rest of this morning. The front will then push over Maui County this afternoon before moving on to the Big Island later this afternoon and evening.
Drier and stable air will settle across the state Tuesday morning allowing low temperatures to be around 5 degrees below normal. By Tuesday afternoon, winds will veer rapidly around to easterly and then southerly Tuesday evening as a stronger front approaches the state from the northwest. Remnant moisture around the Big Island will then shift back west over the state within the strengthening southerly flow, increasing low level clouds and chance of showers across the state. Rainfall is expected to be light to moderate as mid levels remain stable.
Wednesday, a new front will approach from the northwest generating a prefrontal convergent zone with moderate to occasionally heavy showers developing over the western portion of the island chain. In addition, strong south to southwest surface winds will develop over the smaller islands. Gusts of 25 to 35 mph are expected Wednesday afternoon, especially over higher terrain and just downwind (what is normally windward will briefly become leeward during this period of southwest surface winds). Headlines for wind may be needed as we get closer in time. The front is forecast to get to Kauai County around sunset, Oahu in the evening, Maui County before sunrise, and Big Island by noon Thursday. This will bring another round of showers, some possibly heavy. Fast movement through the state should limit the risk of flooding.
Friday and Saturday will be cool as relatively dry air moves in behind this second front. Trades will build back in, pushing the remnants of the front south of the state. Showers should be limited as this prevents the moisture from passing back over the state as with the first front earlier in the week.
A cold front is currently moving over Kauai and pushing through Oahu rest of this morning. The front will move through Maui County this afternoon and Big Island this evening. Moderate to locally heavy showers are expected along and head of the frontal boundary, with prevailing MVFR conditions as the front moves through. Brief IFR conditions could be possible within heavier showers. Behind the front, breezy northerly winds will fill in, along with drier conditions.
AIRMET Sierra is in effect for IFR conditions over Lanai and MVRF mountain obscuration due to clouds and showers for all other islands west of Maui County.
AIRMET TANGO is in effect for NE through SE section of Kauai due to strong westerly winds but will likely be cancelled as the front passes Kauai and breezy winds become northerly.
A strong cold front moves down the island chain from west to east today, stalling out near the Big Island by tonight. An extra large long period northwest swell will quickly build surf heights along exposed north and west facing shores above warning levels through the day. By Wednesday an even stronger cold front will quickly move through the islands, spreading fresh to strong winds across the northwestern coastal waters into Thursday. A Small Craft Advisory was issued for most coastal waters exposed to the large northwest swell and increasing winds.
A dangerous extra large long period northwest (310-330 degree) swell will quickly build into Hawaiian Waters through the day. Offshore buoy 51001 was reporting a 12 foot 18 second period swell just after midnight HST. Surf heights will swiftly rise above High Surf Warning (HSW) levels as this next northwest swell builds into the region. Warning level surf will spread eastward with the swell energy propagation, and that means islands such as Molokai and Maui may see a brief delay in the higher warning level surf until later this morning . A HSW was issued this morning for all exposed north and west facing shores of Niihau, Kauai, Oahu, Molokai, and north facing shores of Maui which remains in effect through Tuesday afternoon. This northwest swell energy may also bring advisory level surf to west facing shores of the Big Island starting late tonight into Tuesday.
Yet another extra large northwest (310-330 degree) swell will build into the region by Thursday, potentially producing another round of warning level surf along exposed north and west facing shores lasting through Friday. This northwest swell energy will diminish into next weekend.
Surf along east facing shores will remain small through the first half of this week due to a continued disruption in the trade wind flow. Surf heights will remain very small along south facing shores through the forecast period.
High Surf Warning until 6 PM HST Tuesday for Niihau-Kauai Leeward-Waianae Coast-Oahu North Shore-Maui Windward West-Kauai North-Molokai Windward-Molokai North-Molokai West-Maui Central Valley North-Windward Haleakala.
Small Craft Advisory until 6 PM HST Tuesday for Kauai Northwest Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel- Oahu Windward Waters-Oahu Leeward Waters-Kaiwi Channel-Maui County Windward Waters.
Small Craft Advisory from 6 PM this evening to 6 PM HST Tuesday for Maui County Leeward Waters-Maalaea Bay-Pailolo Channel- Alenuihaha Channel-Big Island Windward Waters.
