Moderate to locally breezy trade winds today will be on the increase tonight, with locally strong winds Wednesday through Thursday as a new high builds north of the state. Clouds and showers will be focused over windward and mauka areas, with some spilling over to leeward areas. Additional windward showers are expected late in the week as a band of moisture moves from north to south across the state. Moderate to locally breezy trades will return over the weekend.
The forecast has been nudged to the latest National Blend of Models (NBM), but the overall forecast remains the same. There is increased confidence in an uptick in winds starting tonight, with advisory level winds possible. Several models suggest some areas like the Kohala mountains on the Big Island could see warning level winds tomorrow. The NBM is the model showing the highest winds, but other models also suggest high end advisory or low end warning level.
A high pressure system far to the northwest of the islands is moving to the east. Although the GFS and ECMWF don't strengthen the high, the pressure gradient still tightens as a result of the high moving north of the islands. Winds will be strongest through gaps, and over and downslope of ridges, and the models show the winds strongest over Maui and the Big Island. The global models are showing the strongest winds on the Big Island summits tonight and tomorrow.
A cold and stationary front to the north through northwest of the islands will be partly responsible for an uptick in shower activity later in the week. The boundary will move to the east, and weaken, and the moisture associated with the boundary will then get caught up in the trade wind flow.
Tropical Storm Pena is nearly 800 miles southwest of the islands this morning and continues to move the west, away from the state for the next week.
Moderate to locally breezy trade winds today will increase to locally strong trade winds tonight. Showers focused over windward and mauka areas will bring passing MVFR conditions, mainly during the overnight hours and early in the morning.
AIRMET Tango remains in effect for moderate turbulence below 7000 feet within the lee of higher terrain. This AIRMET will likely continue through the next several days as locally breezy trade winds persist.
High pressure will build north of Hawaii through Wednesday. Fresh to locally strong trade winds will become strong across all Hawaiian waters tonight. As a result, the Small Craft Advisory expands in area to cover all coastal waters after 6 PM and has been extended through Wednesday night. Seas are also forecast to exceed 10 feet beginning Wednesday with the arrival of a large north-northwest swell. Meanwhile, a front drops south into the northern offshore waters tonight and weakens to a trough. The trough reaches the central waters by Wednesday night and leads to increased shower activity into Thursday. High pressure will gradually weaken heading into the weekend, and trades will gradually diminish back to fresh to locally strong levels.
A moderate, medium-period bump to northwest swell will fade through Tuesday night. Moderate surf this morning will subside to small levels along north and west facing shores today into tonight. A much larger northwest to north-northwest swell generated by the dynamic fetch of a gale force low near Kamchatka will arrive on Wednesday and may bring warning level surf heights to exposed north and west facing shores as it builds through the day and peaks Wednesday night. Surf will decrease to advisory levels on Thursday as the swell begins to fade and then fall below advisory levels by Friday. A northwest reinforcement is expected to arrive this weekend which could push surf back to advisory levels.
Surf along east facing shores will increase for Wednesday as trade winds strengthen tonight. East shore surf remains elevated and choppy through Friday, then may diminish slightly this weekend. A small, long-period south swell may bring a small bump to south shore surf on Wednesday.
Small Craft Advisory from 6 PM this evening to 6 AM HST Thursday for Big Island Windward Waters-Kaiwi Channel-Kauai Channel-Kauai Leeward Waters-Kauai Northwest Waters-Kauai Windward Waters-Maui County Leeward Waters-Maui County Windward Waters-Oahu Leeward Waters-Oahu Windward Waters.
Small Craft Advisory until 6 AM HST Thursday for Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters- Maalaea Bay-Pailolo Channel.
