A weakening cold front dissipate over the Big Island today. Expect much drier and cooler conditions for the state except for the Big Island where remnants of the front will linger. Winds will veer southerly tonight and Wednesday as the next front approaches from the northwest. Expect breezy to locally windy south southwesterly wind Wednesday. The front is forecast to quickly slide down the island chain Wednesday night into Thursday and bring a line of moderate locally heavy rainfall with it. The week should end cool and fairly dry with trades re- established.
Latest satellite and radar imagery show the main frontal band dissipating over the Big Island early this morning. Peak rainfall totals from the frontal passage so far range from over 1.0 inch of rainfall from North Kohala to North Hilo to 0.10 inches of an inches over the South Kohala and North Kona districts. Elsewhere, post frontal subsidence aloft made for a dry and cool evening. Dewpoints range from low 50s to low 60s across the state this morning. Winds have also relaxed to light to moderate breezy northerly winds. Expect mostly dry and sunny conditions today as dry subsident air aloft settles in and winds veer to a northeasterly flow. Parts of the Big Island and Maui will likely see clouds and showers linger through the day due to remnant moisture around the Big Island that will keep isolated to scattered light showers around for windward areas as trades redevelop and for upslope Kona as the afternoon seabreeze develops.
Winds will veer southerly tonight as the next cold front approaches the islands from the northwest. Winds speeds will gradually strengthen to breezy to windy by mid- day Wednesday out of the south southwest. Wind speeds may meet or exceed wind advisory criteria along ridgetops and areas downslope of elevated terrain in a predominate southwesterly flow during this time. This is so far the most concerning hazard with the next system where winds could be strong enough to uproot trees in saturated soils especially downslope of ridges. Winds may also meet or exceed advisory levels for the summits of the Big Island. Both the GFS and ECMWF show moisture lifting northward over the western half of the state, ahead of the front, which will be conducive for pockets of prefrontal showers to develop within this flow. For the eastern half of the state, dry conditions prevail tonight into Wednesday.
The main rainband associated with the next front will quickly move through Kauai beginning late afternoon Wednesday and Oahu Wednesday evening. The rainband will then sweep across Maui County early Thursday morning before pushing through the Big Island Thursday. Latest guidance depicts this system to be similar, but more robust, than the one experienced yesterday with moderate to locally heavy rain embedded within the rainband. Thunderstorms appear to remain northeast of the coastal waters at this time. The threat of flash flooding remains limited due to how quickly this front will move over the state.
Breezy northerly winds will immediately fill in behind the front and once again bring noticeably drier and cooler weather with dewpoints dropping in the low 50's to low 60's. These northerly winds will shift easterly over the weekend as a surface high quickly passes northeast of the state. Upper level ridging will keep mostly dry and stable tradewind weather through the weekend. In the extended forecast another potentially robust front will move over the state early next week, however there is still some significant difference in the timing and strengthen between the GFS and ECMWF deterministic models and will continue to monitor.
A cold front will weaken and dissipate over the Big Island today. Gentle to breezy northerly winds have filled in behind the front ushering in drier and more stable air. Expect mostly VFR conditions today, except for the Big Island where lingering clouds and showers will create brief MVFR conditions. MVFR conditions are possible later tonight over the western half of the state as prefrontal showers develop in veering southeasterly flow, while drier conditions settle in over the eastern half of the state.
Breezy to locally windy south southwesterly winds are expected Wednesday along with an increase in clouds and showers as a robust front approaches the state from the northwest.
AIRMET Sierra for mountain obscuration is in effect for the windward portions of the Big Island.
AIRMET TANGO is in effect over the entire state due moderate turb between FL220/320.
The forward motion of a diminishing cold front has stalled out near the Big Island this morning. This front will fade into a trough later today and then drift westward across the islands, ahead of the next approaching cold front. This next strong cold front will sweep from west to east through the western islands on Wednesday morning, and once again stalling out near the Big Island by Thursday afternoon. A passing high pressure system far north of the islands will bring back easterly trade winds across Hawaiian Waters from Friday through Sunday. Winds weaken and veer from a more southeasterly direction over northwestern waters by next week Monday as another cold front approaches the islands from the northwest.
The current extra large long to medium period northwest (310-330 degree) swell will continue to produce warning level surf along exposed north and west facing shores today. A High Surf Warning (HSW) remains in effect through the afternoon hours for these shorelines, and a High Surf Advisory (HSA) remains in effect for west facing shores of the Big Island. The northwest swell energy will fall below warning thresholds later tonight, and the HSW will transition to a HSA with the afternoon forecast package for the same north and west facing shores lasting through Wednesday. A Small Craft Advisory remains in effect today for most coastal waters exposed to the large northwest swell and some waters exposed to stronger winds.
Another extra large long period northwest (310-330 degree) swell will build into the region by Thursday, likely producing another round of warning level surf along exposed north and west facing shores lasting through Friday, and lingering near advisory levels Saturday before another reinforcing northwest swell briefly boosting surf heights back above warning levels on Sunday and Sunday night.
Surf along east facing shores will remain small through most of this week due shifting wind directions from the passing fronts, while no significant swells are expected to impact the state from the south.
High Surf Warning until 6 PM HST this evening 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.
High Surf Advisory until 6 PM HST this evening for Kona-Kohala.
Small Craft Advisory until 6 PM HST this evening for Kauai Northwest Waters-Kauai Windward Waters-Kauai Leeward Waters- Kauai Channel-Oahu Windward Waters-Oahu Leeward Waters-Kaiwi Channel-Maui County Windward Waters-Maui County Leeward Waters- Maalaea Bay-Pailolo Channel-Alenuihaha Channel-Big Island Windward Waters-Big Island Southeast Waters.
