Strong and gusty trade winds are expected into Thursday as high pressure builds south toward the state. Windward and mauka shower chances increase later tonight and Thursday as a band of moisture accompanying a decaying frontal boundary moves from north to south across the state. Moderate to locally breezy trades will return Friday.
A high building far north of the state has strengthened the trade winds today. Gusts have not been overly impressive nor persistent, but peak gusts of 45 to 50 mph have been measured in the typical windy areas around Maui County and the Big Island. Have left the Wind Advisory in place until 6 AM Thursday with the potential for a further uptick this evening. Winds will be strongest through gaps and over and downslope of ridges, where gusts of 50 to 55 mph are possible. The combination of strong trade winds and dry conditions has elevated fire weather concerns today.
A weakening frontal boundary will bring somewhat deeper moisture south through the islands tonight into Thursday. Increased shower coverage is expected over mostly windward and mauka areas, but a few may make it into leeward areas too.
The strong trade winds should begin to ease some Friday down to breezy to locally strong speeds. Another high pressure ridge will slide east well to the north of the state this weekend. Some increase in the trades is possible again Saturday night and Sunday before the high stalls to our northeast early next week. A reduced pressure gradient should allow trades to relax some by that time. Brief pulses of better moisture in the trades will keep typical trade wind showers over windward and mauka areas mostly during the overnight and early morning hours through the period.
Locally strong trade winds will continue tonight before gradually weakening through the second half of the week. A dying frontal boundary will push through the island chain tonight into Thursday, providing an increase in shower activity. Windward and mountain areas will see most of the showers, but leeward areas could see some spillover showers as well. MVFR conditions are expected within showers while VFR prevails elsewhere.
AIRMET Tango is in effect for low level moderate turbulence downwind of terrain, upper level moderate turbulence between FL260 and FL380, and for strong surface winds 30 kt or greater over Maui County and the Big Island. Expect the strong surface winds to weaken by tomorrow morning, and the upper level moderate turbulence to diminish by early tonight. AIRMET Tango will likely remain in effect for low level moderate turbulence through tomorrow.
Mountain obscurations are likely across windward sections of the islands as the frontal boundary moves down the island chain later tonight.
Strong high pressure north of Hawaii will maintain fresh to locally gale force winds across the marine areas through tonight. A Gale warning is in effect through tonight for the windier waters and channels around Maui County and the Big Island. Guidance may allow for a Gale warning extension through Thursday or to bring it down to a Small Craft Advisory. The current Small Craft Advisory (SCA) has been extended for all other coastal water zones through Thursday. A front will drop south from the northern offshore waters to reach the central waters as it weakens tonight. This disturbance will bring increased shower activity to the area through Thursday. Through the weekend, the trade winds will trend down slightly to fresh to locally strong speeds across all waters.
PacIOOS Buoy 51201 near Waimea Bay has begun to observe long period forerunners as the swell has begun to rise on north and west facing shores. This large long period north-northwest swell (340 deg) will peak late tonight into early Thursday morning before declining through Friday. A High Surf Advisory (HSA) is in effect for north facing shores of Kauai, Oahu and Molokai and Maui and west facing shores of Kauai and Oahu through Thursday afternoon. Seas are also forecast to exceed 10 feet late tonight into Thursday so the Small Craft Advisory will also include large seas. Surf will decrease Friday followed by a north swell this weekend which could push surf back to advisory levels on Sunday.
Surf along east facing shores will remain rough and choppy due to the strong trade winds through Friday, then may diminish slightly this weekend. A small, long-period south swell may bring a small bump to south shore surf today into Thursday. Surf becomes tiny again Friday into the weekend for south- facing shores.
High Surf Advisory until 6 PM HST Thursday for Kauai North-Maui Central Valley North-Maui Windward West-Molokai North-Molokai West-Molokai Windward-Niihau-Oahu North Shore-Waianae Coast- Windward Haleakala.
Wind Advisory until 6 AM HST Thursday for Big Island North-Big Island South-Big Island Southeast-Kahoolawe-Kohala-Lanai Leeward- Lanai Mauka-Lanai Windward-Maui Central Valley North-Maui Central Valley South-Maui Leeward West-Molokai Leeward South- Molokai North-Molokai Southeast-Molokai West-Molokai Windward- South Haleakala.
Small Craft Advisory until 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.
Gale Warning until 6 AM HST Thursday for Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters-Maalaea Bay- Pailolo Channel.
