Breezy to locally windy trades will weaken slightly Friday into Monday and will then hold at moderate strengthen through the remainder of the week. Showers will favor windward and mauka areas, with little rainfall over most leeward sections.
Locally windy trades are in place this afternoon and should persist tonight. A robust 1034 mb surface high centered about 1,000 miles north of the islands is driving the strong trade wind flow, and little change is expected overnight. Meanwhile, mid level ridging will continue to produce stable conditions and cause the trades to become accelerated over and downwind of prominent terrain. As a result, a Wind Advisory remains in place for portions of Maui County and Big Island through tonight. Even though the atmosphere is stable and precipitable water is near to below seasonal average, showers have been somewhat active over some windward areas, especially on Big Island. Expect the trades to continue to focus rainfall over windward and mauka areas, as well as over the Kona slopes of the Big Island each afternoon. Other leeward sections should see little rainfall.
Modest changes are expected on Friday. The surface high will start to slowly weaken, leading to borderline Wind Advisory conditions. Given uncertainty, we will leave it to the night shift to decide whether or not to extend the advisory, which currently expires at 6 AM. Little change in the the rainfall pattern is expected, with showers generally light to moderate and focused windward.
Trades will drop a notch during the weekend but will still remain breezy through the Memorial Day holiday. The surface high driving the winds will weaken slightly but remain at around 1029 mb, strong enough to produce breezy trades. Stable conditions will continue, and modest windward rainfall and a few afternoon showers over the Kona slopes are expected. Moderate trade winds will prevail Tuesday through the middle of next week.
A tight pressure gradient back across the islands from high pressure located far northeast of the state will produce fresh to near gale-in-gust trade winds the next couple of days. Greater stability from mid to upper level ridging expanding in from the north and west, along with drier air moving in around the eastern edge of this ridging, will result in less frequent showers. Most light precipitation will impact windward exposures and high terrain, especially during the overnight evening and early morning hours.
AIRMET Tango remains in place to account for low level turbulence over and downwind of terrain. This AIRMET will remain in place the next couple of days in response to high winds and stability.
The strong high pressure ridge north of the Hawaiian Islands will maintain easterly trade winds in the strong to gale range through Friday morning. A Gale Warning remains in effect for the Alenuihaha and Pailolo Channels, and Maalaea Bay. The Gale Warning may need to be extended through the day Friday as there does not seem to be much change in the strength of the high pressure. The Small Craft Advisory (SCA) for all remaining island waters has been extended through the day Saturday. Expect SCA to continue into the first half of next week for all or portions of the state.
A high surf advisory (HSA) remains in effect for all east facing shores through Friday afternoon due to strong trade wind swell holding into the weekend. Winds may ease a touch tonight allowing surf to drop below advisory levels Friday afternoon through the weekend but conditions will remain borderline and thus will continue to monitor in case there is a need to extend the HSA.
Surf along north facing shores will remain small into Friday. The next small north- northwest (330 degree) swell will move into the Hawaii region Friday afternoon, gradually increasing surf heights along north and west- facing shores through the weekend.
A series of small, long-period south swells will support near- average surf along south-facing shores over the next several days.
High Surf Advisory until 6 PM HST Friday for Olomana-Kahoolawe- Maui Windward West-Kauai North-Kauai East-East Honolulu-Koolau Windward-Molokai Windward-Molokai Southeast-Windward Haleakala- Kipahulu-South Haleakala-Big Island Southeast-Big Island East- Big Island North.
Wind Advisory until 6 AM HST Friday for Lanai Mauka-Kahoolawe- Maui Windward West-Maui Leeward West-Kohala-Molokai-Lanai Windward-Lanai Leeward-Lanai South-Maui Central Valley North- Maui Central Valley South-South Haleakala-Big Island South-Big Island Southeast-Big Island North.
Small Craft Advisory until 6 PM HST Saturday 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-Big Island Windward Waters-Big Island Leeward Waters-Big Island Southeast Waters.
Gale Warning until 6 AM HST Friday for Maalaea Bay-Pailolo Channel-Alenuihaha Channel.
