Photo Credit: Tyler Rooke

West Side

Today: Breezy. Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 83 to 90. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 68 to 75. East winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 83 to 90. East winds 10 to 15 mph. Chance of rain 40 percent.

South Side

Today: Breezy. Mostly sunny with isolated showers. Highs 87 to 92. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Breezy. Isolated showers in the evening. Lows around 69. North winds 10 to 20 mph. Chance of rain 20 percent.

Tuesday: Sunny and breezy. Highs 87 to 92. North winds 10 to 20 mph.

North Shore

Today: Mostly cloudy. Breezy. Showers likely in the morning, then scattered showers in the afternoon. Highs 82 to 88 near the shore to 62 to 68 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Occasional showers in the evening, then showers likely after midnight. Lows 65 to 72 near the shore to around 53 near 5000 feet. East winds 10 to 15 mph. Chance of rain 90 percent.

Tuesday: Partly sunny. Numerous showers in the morning, then isolated showers in the afternoon. Highs 82 to 88 near the shore to 61 to 66 near 5000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

Central Maui

Today: Mostly sunny. Breezy. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 90. Northeast winds 10 to 20 mph. Chance of rain 30 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 67 to 73. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny. Breezy. Isolated showers in the morning. Highs around 90. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Upcountry

Today: Breezy. Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 60 at the visitor center to around 56 at the summit. East winds 10 to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Partly cloudy with scattered showers. Lows around 48 at the visitor center to around 44 at the summit. East winds 15 to 25 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 58 at the visitor center to around 54 at the summit. East winds 15 to 25 mph. Chance of rain 50 percent.

East Maui

Today: Mostly cloudy. Breezy. Showers likely in the morning, then scattered showers in the afternoon. Highs 82 to 88 near the shore to 62 to 68 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Occasional showers in the evening, then showers likely after midnight. Lows 65 to 72 near the shore to around 53 near 5000 feet. East winds 10 to 15 mph. Chance of rain 90 percent.

Tuesday: Partly sunny. Numerous showers in the morning, then isolated showers in the afternoon. Highs 82 to 88 near the shore to 61 to 66 near 5000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

Lanai City

Today: Breezy. Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 75 to 84. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 68. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday: Sunny. Isolated showers in the afternoon. Highs 75 to 84. East winds 10 to 15 mph. Chance of rain 20 percent.

Kaunakakai

Today: Mostly sunny. Breezy. Scattered showers in the afternoon. Highs 79 to 89. Northeast winds 10 to 20 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy with scattered showers. Lows 63 to 74. East winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny. Isolated showers in the morning. Highs 79 to 89. East winds around 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Locally breezy trade winds will deliver an area of showery low clouds today into tonight, fueling an increase in windward showers. Trades will diminish slightly on Tuesday, and may ease further later in the week, delivering periodic clouds and showers to windward areas.

Discussion

In summary, moderate to locally breezy trade winds will persist for most of the upcoming week as high pressure prevails to the distant N. The trades will deliver patches of low-level moisture that will fuel periodic showers over windward areas, with showers most active during nights and mornings. A trend toward lighter winds is expected toward the end of the week as the high moves to the distant NE Pacific.
After a fairly dry night statewide, yet another area of increased low-level moisture will be moving in from the E today and tonight, bringing showers mainly to windward areas. The leading edge of this particular batch of moisture is now moving into windward Big Island, with model guidance indicating that it will spread to windward portions of Maui County by mid-morning, Oahu in the late afternoon/early evening, and Kauai this evening/overnight. The subsidence inversion will continue to weaken and rise up to 12,000 ft, which will allow for moderate showers to develop, with a few heavier rain cores possible, especially over leeward Big Island this afternoon and evening. With the inversion elevated, showers will periodically spread to leeward areas elsewhere. Overall, rainfall totals are not expected to be significant as showers will not remain over any one area for very long.
Trade winds will drop slightly by Tuesday as the moisture clears the islands to the W, with winds changing little through Thursday as the surface high reorganizes further N. The island atmosphere will be fairly stable and typical shower activity will be focused over windward areas, as well as leeward Big Island slopes. Model guidance differs on the details of the the large scale pattern across the Pacific later in the week, and of importance to Hawaii, the position of the surface high. Generally speaking however, we expect a trend toward lighter trade winds. The weaker winds will likely allow afternoon sea breezes to drive cloud and shower development over leeward areas of the islands, while also delivering a few windward showers. A nearby upper level troughing may enhance shower intensity toward the end of the week.

Aviation

Moderate to locally breezy trade winds will continue for at least the next 24 hours. A low level trough moving through the Big Island this morning will sweep westward across the state, spreading clouds and enhanced showers across the eastern islands this morning, and then spreading westward into Molokai, Lanai, Oahu and Kauai from the afternoon to evening hours. Low cloud cover may trigger mountain obscurations and heavier showers that will lead to periods of MVFR conditions, especially over windward airfields.
AIRMET Sierra in effect this morning for mountain obscuration over the windward areas of the Big Island. This AIRMET will expand to Maui later this morning and may continue to expand westward to other islands through the afternoon to evening hours.

Marine

Surface high pressure positioned north of the state will keep the pressure gradient down across the state tight enough to support moderate to locally strong trade winds. A Small Craft Advisory is in effect for the typically windier waters around Maui County and Big Island through this afternoon. North Pacific systems look to become more progressive in their eastward treks as high pressure to the west travels into the northeastern Pacific late this week and weakens the regional gradient and subsequent winds.
High swell from storm and gale force wind fetch regions near New Zealand and the Tasman Sea will be directed towards the islands. These swells are timed to reach our local waters next weekend and will likely produce increased surf heights along many south-facing shores. A series of small, medium period north swells from a couple of systems northwest of the state will provide a minor bump to late week north shore surf. Near term east wind wave chop will remain slightly elevated under these generally moderate to fresh east trades over and upstream of the islands. East swell generated from eastern Pacific Tropical Cyclone Kay may also arrive over the weekend.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST this evening for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov