Trade winds will strengthen Sunday into Monday, then persist through much of the week, bringing periods of showers to mainly windward and mauka locations. A Wind Advisory has been issued for the typically windier higher terrain areas, passes, and areas immediately south through west of mountains across all islands for Sunday through Sunday night.
Radar and satellite imagery this afternoon show isolated showers moving into most windward areas on moderate to breezy trade winds, with a slightly higher concentration of low clouds and showers affecting windward portions of the Big Island and Maui. The motion of these clouds and showers indicates the low-level steering flow has taken on a subtle southeasterly component, a pattern that is expected to persist over the next several days even as surface trade winds remain generally easterly. In addition, patches of high-level cirrus continue to stream overhead from the west, which could make for a particularly dynamic sunset this evening.
Looking ahead, a robust 1045 mb surface high far north of the state will drift south-southeastward through the weekend, positioned between two areas of low pressure - one north of Midway and another off the California coast. As this pattern evolves, the pressure gradient across the main Hawaiian Islands will tighten, leading to strengthening trade winds. The moderate to breezy trades observed today are expected to become windy and gusty on Sunday, especially as a band of enhanced moisture moves through the area. This moisture plume, currently evident on satellite imagery roughly 400 miles to the east, is forecast to arrive tomorrow on the strengthening trade wind flow. Its arrival will likely increase windward and mauka cloud cover and shower activity, while also enhancing the potential for stronger gusts to mix down within showers.
Given the combination of a strengthening pressure gradient and the added contribution from convective mixing within showers, the main short-term concern is whether winds will reach Wind Advisory criteria. Recent high-resolution model guidance continues to support advisory-level winds (sustained speeds near or above 30 mph and/or gusts exceeding 50 mph) particularly across the typically windier areas. As a result, a Wind Advisory has been issued for these zones beginning tomorrow and continuing through tomorrow night, though an extension may be needed. The strongest gusts are expected across the eastern end of the state.
Breezy to locally windy trade winds are expected to persist through at least midweek, bringing periodic increases in clouds and showers to windward and mauka locations.
For the latter half of the week into the weekend, discrepancies between the GFS and ECMWF gradually increase. Regardless, a trade wind pattern looks to persist across the state with windward and mauka focused showers, and trade wind speeds are expected to ease slightly.
Easterly moderate to breezy trade winds continue through today, bringing showers and clouds primarily to windward and mountain areas across the state. The trade winds are expected to slightly strengthen tomorrow, and are expected to persist over the next several days. A band of moisture is expected to move into the state from the east early tomorrow morning. This will increase MVFR conditions across windward and mountain areas for most islands. VFR will prevail elsewhere.
AIRMET Tango remains in effect for moderate turbulence downwind of island terrain due to the breezy trade winds. AIRMET Sierra for mountain obscuration is currently in effect for N through E sections of Kauai, Oahu, Molokai, and Maui. AIRMET Sierra is also in effect for mountain obscuration for the Big Island from Laupahoehoe to Cape Kumukahi to Apua Point. Conditions for Oahu and Molokai are expected to improve this evening, while conditions on Kauai, Maui, and the Big Island, will likely linger into tonight.
A strong high far north of the state will produce windy and rough conditions across all area waters through at least the middle of next week. The current strong trade winds will strengthen another notch on Sunday with widespread strong to near gales expected across the coastal and offshore waters. The windier channels around Maui County should see wind speeds increasing during the day tomorrow to gale force speeds. A Gale Warning has been issued for Sunday and Sunday night for the Alenuihaha and Pailolo channels. Elsewhere, a Small Craft Advisory (SCA) remains in effect due to a combination of winds and seas. Winds may ease slightly by Monday, but overall strong to near gales will continue across the state through the middle of next week.
Nearshore buoys such as the Mokapu buoy has been showing a steady rise over the past 12 hours. Surf along east facing shores have now reached advisory thresholds and will continue to build through Sunday night as the trade winds strengthen another notch. High Surf Advisory is now in effect for east facing exposures of Kauai, Oahu, Molokai, Maui and the Big Island through Monday night. This advisory could very well get extended through the middle of next week due to the strong trade winds persisting across the state.
The current small medium period northwest to north-northwest swell will steadily decline this evening through Sunday. Minimal energy is expected from the northwest during the first half of next week, although select exposures should see some wind swell. A small northwest bump is possible towards the second half of next week. Surf along south shores will remain small but a slight increase is expected for areas exposed to the trade wind swell.
Wind Advisory from 6 AM Sunday to 6 AM HST Monday for Kauai Leeward-Kauai Mountains-Waianae Coast-Waianae Mountains-Lanai Mauka-Kahoolawe-Maui Windward West-Maui Leeward West-Kohala-Big Island Interior-Kauai North-Kauai South-East Honolulu-Honolulu Metro-Koolau Leeward-Molokai-Lanai Windward-Lanai Leeward-Maui Central Valley North-Maui Central Valley South-Windward Haleakala-Kipahulu-South Haleakala-Big Island South-Big Island Southeast-Big Island North.
High Surf Advisory until 6 AM HST Tuesday for Olomana-Maui Windward West-Kauai East-Kauai South-East Honolulu-Koolau Windward-Molokai Windward-Molokai Southeast-Windward Haleakala- Kipahulu-Big Island Southeast-Big Island East-Big Island North.
Small Craft Advisory until 6 AM HST Monday 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- Big Island Windward Waters-Big Island Leeward Waters-Big Island Southeast Waters.
Small Craft Advisory until 6 AM HST Sunday for Pailolo Channel- Alenuihaha Channel.
Gale Warning from 6 AM Sunday to 6 AM HST Monday for Pailolo Channel-Alenuihaha Channel.
