Borderline moderate to strong gusty trades are expected on today, with drier air across the state now that a weak front has passed through the state overnight. Trades should ease slightly on Tuesday, but breezy to locally strong trades will likely persist through rest of the week. Passing showers will ride in with the breezy trades throughout the week and will mainly be focused over windward and mauka areas, and should be most numerous at night.
Radar showed scattered showers moving into most windward and mauka areas on all islands this morning, with a few making over to leeward areas, especially on Oahu. Satellite indicated mostly cloudy skies. Winds were brisk, with northeast winds averaging 10 to 20 mph, with the usual windy sites gusting generally 20 to 35 mph. Morning soundings showed a developing trade inversion ranging from 7500 feet at Lihue to 8000 feet at Hilo, with moisture lower than yesterday (PW values ranging from 1.30 inches at Lihue to 1.73 at Hilo).
A persistent surface high pressure system to our north will remain more or less in place through Wednesday before being replaced by a new high building in from the west into the weekend. This will help keep trade winds blowing. Winds will be strongest today as the initial high builds in behind a departing front. Winds will be moderate to strong, but apart from an occasional gust on exposed ridges, wind advisory criteria are not expected to be met over land.
Showers will move in occasionally, mainly windward and mauka, and most numerous at night as is so often the case with trade winds. Wind speeds are forecast to weaken slightly Tuesday, then maintain moderate speeds through the end of the week.
We continue to watch, along with NHC, for the potential development of a tropical system to our southeast this week. As of this writing, the chance for development is at 70%. At this time, the chance of a system directly impacting the islands is low.
Remnants of a frontal boundary have moved east through the eastern end of the state as drier air moves in from the west. Enough moisture remains for isolated to scattered light showers, where brief MVFR conditions are expected. Showers have become focused over windward and mountain areas. Strengthening NE trade winds will become breezy to strong statewide overnight.
Airmet Sierra is in effect for mountain obscuration for Kauai, Oahu, Molokai, and Maui, and for the Big Island from Upolu Point to Cape Kumukahi to South Cape, for clouds and showers above 2000 feet.
AIRMET Tango is in effect for moderate turbulence between FL210 and FL350 over Kauai, Oahu, Molokai, Lanai, and Maui due to an upper level disturbance. This AIRMET will likely expand to the Big Island today. AIRMET Tango is also in effect to cover moderate turbulence downwind of terrain statewide below 8000 feet.
High pressure north of Hawaii will bring fresh to strong northeast winds to the region today and little easing is forecast through midweek. Therefore, the Small Craft Advisory (SCA) has been extended into Tuesday for the combination of winds for most waters and seas above 10 feet for areas exposed to a moderate north-northwest swell. Fresh to locally strong northeast trade winds are expected through most of the week.
Surf along north- and west-facing shores will remain at High Surf Advisory level conditions through this evening as the current moderate, north-northwest swell begins to slowly drop today. Offshore NDBC buoy 51101 continues to show northwest swell energy at 7 feet, 15 seconds early this morning. Surf will fall below advisory level by tonight and become small by Wednesday. Another moderate, long period northwest swell arrives Wednesday night and will likely push north and west shore surf back to advisory levels Thursday into Friday. A medium- period swell fills in on Saturday, likely prolonging moderate to large surf action into the weekend.
The current moderate, medium period south swell will continue a gradual decline through Tuesday. South shore surf will be tiny through much of the week with little southerly background energy reaching the islands. East-facing shores will see an increase in trade wind swell as strong northeast winds fill in today. Surf along east-facing shores will stay choppy as trades sustain through much of the week.
High Surf Advisory until 6 PM HST this evening for Kauai East- Kauai North-Kauai Southwest-Koolau Windward-Maui Central Valley North-Maui Windward West-Molokai North-Molokai Windward-Niihau- Oahu North Shore-Waianae Coast-Windward Haleakala.
Small Craft Advisory until 6 PM HST Tuesday for Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters- Big Island Windward Waters-Kaiwi Channel-Kauai Channel-Kauai Leeward Waters-Kauai Northwest Waters-Kauai Windward Waters- Maalaea Bay-Maui County Leeward Waters-Maui County Windward Waters-Oahu Leeward Waters-Oahu Windward Waters-Pailolo Channel.
