Photo Credit: James Grenz

Hilo

Today: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 83 near the shore to 69 to 74 at 4000 feet. North winds up to 15 mph. Chance of rain 70 percent.

Tonight: Cloudy. Numerous showers in the evening, then frequent showers after midnight. Lows around 67 near the shore to around 53 at 4000 feet. Northwest winds up to 15 mph. Chance of rain 90 percent.

Tuesday: Cloudy with numerous showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 82 near the shore to around 71 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Kona

Today: Sunny with isolated showers in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 82 to 87 near the shore to around 69 near 5000 feet. West winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 68 to 74 near the shore to around 54 near 5000 feet. Light winds. Chance of rain 50 percent.

Tuesday: Mostly sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 82 to 87 near the shore to around 69 near 5000 feet. Southwest winds up to 10 mph shifting to the northwest in the afternoon. Chance of rain 50 percent.

Waimea

Today: Windy. Partly sunny with scattered showers. Highs around 81 near the shore to 69 to 79 near 3000 feet. East winds up to 30 mph increasing to 10 to 30 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows around 67 near the shore to 55 to 61 near 3000 feet. East winds 10 to 25 mph. Chance of rain 70 percent.

Tuesday: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 81 near the shore to 69 to 79 near 3000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Kohala

Today: Windy. Partly sunny with scattered showers. Highs around 81 near the shore to 69 to 79 near 3000 feet. East winds up to 30 mph increasing to 10 to 30 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows around 67 near the shore to 55 to 61 near 3000 feet. East winds 10 to 25 mph. Chance of rain 70 percent.

Tuesday: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 81 near the shore to 69 to 79 near 3000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

South Big Island

Today: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs around 86 near the shore to around 73 near 5000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 69 near the shore to around 52 near 5000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny. Scattered showers in the afternoon. Highs around 86 near the shore to around 73 near 5000 feet. East winds up to 15 mph. Chance of rain 30 percent.

Puna

Today: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 83 near the shore to 69 to 74 at 4000 feet. North winds up to 15 mph. Chance of rain 70 percent.

Tonight: Cloudy. Numerous showers in the evening, then frequent showers after midnight. Lows around 67 near the shore to around 53 at 4000 feet. Northwest winds up to 15 mph. Chance of rain 90 percent.

Tuesday: Cloudy with numerous showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 82 near the shore to around 71 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Waikoloa

Today: Sunny in the morning then becoming partly sunny. Breezy. Isolated showers. Highs around 86 near the shore to 70 to 76 above 4000 feet. Northeast winds up to 25 mph with gusts to 45 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows 69 to 74 near the shore to 50 to 57 above 4000 feet. Southeast winds up to 25 mph. Chance of rain 20 percent.

Tuesday: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 86 near the shore to 70 to 76 above 4000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Strong trade winds will continue today, with clouds and showers favoring windward and mauka locations. A transition period is expected Tuesday through midweek as an upper disturbance and surface trough approach and move in from the east. Diminishing trade winds along with increasing moisture may be enough to trigger a few showers over our dry leeward areas through the afternoon hours where sea breezes form Wednesday through the second half of the week.

Discussion

Despite a strong upper ridge in place and subsidence inversion, added low-level moisture that has moved into the smaller islands this morning combined with breezy trades has led to showery conditions for some windward and mauka locations. Some of these showers have made it over to leeward areas periodically on Oahu, which will likely persist through the early morning hours. Satellite data showed a surge in northeast winds trailing this area of moisture, that supports the gusty trades lingering for another day (Wind Advisory has been extended for the windier areas over the eastern end of the state).
Trade winds will begin to ease tonight through midweek as an upper low moves in from the east and the gradient begins to relax. An increase in deep layer moisture combined with the added instability and surface trough could fuel localized heavy showers, and a thunderstorm or two can't be ruled out over the eastern end of the state Tuesday night through Wednesday. Once the surface trough moves through, the low-level flow will shift out of the east-southeast Wednesday into the second half of the week. This pattern shift will translate to a land and sea breeze regime setting up, which will drive rainfall chances up over our leeward areas through the afternoon and evening periods.

Aviation

Breezy to locally strong trade winds will continue today and tonight. A broken band of low clouds and showers will move southward through the islands today, bringing some MVFR cigs/vsbys to windward areas as it moves through. AIRMET Sierra remains in effect for mountain obscuration across windward sections of Kauai, Oahu, Molokai, and Maui. Conditions should improve later this morning over the smaller islands. AIRMET Sierra could be required for windward Big Island later today.
AIRMET TANGO remains in effect for moderate low level turbulence over and downwind of the terrain of all islands. This AIRMET will continue today, and possibly through much of tonight.

Marine

A strong high pressure system far north of the Hawaiian Islands will keep fresh to strong trade winds blowing through Monday. The trade winds will weaken starting tonight through Thursday as a weak trough moves into the region. A Small Craft Advisory (SCA) remains in effect portions of central and eastern Hawaiian waters through this afternoon. This SCA will decrease in coverage to the typical windier waters around Maui and the Big Island by tonight. Lighter winds are expected from Wednesday through Thursday night with near shore land and sea breezes developing. More unstable conditions arrive with an upper level disturbance potentially producing isolated thunderstorms over the Big Island waters from Tuesday night into Wednesday.
A south swell currently moving into the region will elevate south shore surf through Tuesday. Only small background south swells are then expected from Wednesday through the weekend, keeping lower surf heights along south facing shores.
Surf along east facing shores will hold steady through Tuesday due to strong trades over and upstream of the islands. Wind waves will decrease on Wednesday as trades diminish, however distant tropical activity in the Eastern Pacific will send a small, medium period, east swell into the region from Tuesday night through Friday, producing a slight boost to east shore surf. Surf along north facing shores will remain nearly flat this week.

Fire weather

The Red Flag Warning remains in effect through the day today. A transition from the showery conditions this morning will shift back to dry and stable by midday, with the likelihood of reaching Red Flag conditions becoming high this afternoon. Winds will trend down Tuesday through the rest of the week.

HFO Watches/Warnings/Advisories

Red Flag Warning until 6 PM HST this evening for Niihau, Kauai Leeward, Oahu South Shore, Waianae Coast, Molokai Leeward, Lanai Makai, Lanai Mauka, Kahoolawe, Maui Windward West, Maui Leeward West, Maui Central Valley, Leeward Haleakala, Kona, South Big Island, Kohala, Big Island Interior.
Wind Advisory until 6 PM HST this evening for Lanai Mauka, Kahoolawe, Kohala, Lanai Windward, Lanai Leeward, Big Island North.
Small Craft Advisory until 6 AM HST Tuesday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.
Small Craft Advisory until 6 PM HST this evening for Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters.

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Data Courtesy of NOAA.gov