Photo Credit: Tyler Rooke

West Side

Today: Breezy. Mostly sunny with isolated showers. Highs 75 to 81. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows 61 to 68. East winds 10 to 20 mph. Chance of rain 40 percent.

Monday: Mostly sunny with isolated showers. Highs 75 to 81. East winds 10 to 15 mph. Chance of rain 20 percent.

South Side

Today: Sunny. Highs around 81. Northeast winds 10 to 15 mph.

Tonight: Mostly clear. Lows around 62. Northeast winds 10 to 15 mph.

Monday: Sunny. Highs around 81. Northeast winds 10 to 15 mph.

North Shore

Today: Breezy. Partly sunny with scattered showers. Highs 73 to 78 near the shore to around 60 near 5000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 59 to 65 near the shore to 44 to 49 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Monday: Breezy. Mostly sunny with scattered showers. Highs 73 to 78 near the shore to around 59 near 5000 feet. East winds 10 to 20 mph. Chance of rain 40 percent.

Central Maui

Today: Breezy. Mostly sunny with isolated showers. Highs 77 to 82. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers after midnight. Lows 60 to 65. East winds 10 to 15 mph. Chance of rain 20 percent.

Monday: Mostly sunny with isolated showers. Highs 77 to 82. East winds 10 to 15 mph. Chance of rain 20 percent.

Upcountry

Today: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 55 at the visitor center to around 51 at the summit. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly clear with scattered showers. Lows around 42 at the visitor center to around 37 at the summit. East winds 15 to 20 mph. Chance of rain 50 percent.

Monday: Breezy. Sunny with isolated showers. Highs around 53 at the visitor center to around 49 at the summit. East winds 15 to 20 mph. Chance of rain 20 percent.

East Maui

Today: Breezy. Partly sunny with scattered showers. Highs 73 to 78 near the shore to around 60 near 5000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 59 to 65 near the shore to 44 to 49 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Monday: Breezy. Mostly sunny with scattered showers. Highs 73 to 78 near the shore to around 59 near 5000 feet. East winds 10 to 20 mph. Chance of rain 40 percent.

Lanai City

Today: Breezy. Mostly sunny with isolated showers. Highs 71 to 78. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Lows around 62. Northeast winds 10 to 15 mph.

Monday: Mostly sunny with isolated showers. Highs 71 to 78. East winds 10 to 15 mph. Chance of rain 20 percent.

Kaunakakai

Today: Mostly sunny. Breezy. Isolated showers in the morning. Highs 69 to 79. East winds 10 to 25 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers after midnight. Lows 54 to 66. East winds 15 to 25 mph. Chance of rain 20 percent.

Monday: Breezy. Mostly sunny with isolated showers. Highs 69 to 79. East winds 15 to 25 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

The high pressure ridge will build north of the islands for the next few days allowing moderate to locally breezy trade winds to return to the region through Tuesday. An upper level low just east of the Big Island will produce enough instability for passing trade wind showers mainly over windward and mountain areas of each island, favoring the overnight to early morning hours. A cold front approaching the state from the northwest on Wednesday will push the ridge over the islands, producing a stable and dry light wind pattern shift lasting through Friday. Moderate to breezy trade winds return next weekend as a high pressure system passes by just north of the island chain. The approaching cold front will stall out and fade just north of Kauai on Friday with a few remnant cloud bands briefly increasing trade wind shower activity next weekend.

Discussion

Satellite imagery this morning continues to show an upper level low just east of the Big Island with a weakening surface trough just northwest of Kauai. Cloud bands drifting through the region appear somewhat unstable, especially over the eastern islands and periods of overnight to early morning windward shower activity remain in the short range forecast. Local radar imagery continues to show passing shower bands drifting into the islands.
The subtropical ridge north of the state will strengthen today, allowing moderate to breezy trade winds to blow across the region through Tuesday. Instability from the upper level low east of the Big Island will generate a few unstable cloud bands for passing showers over windward and mountain areas of each island. These showers will tend to favor the typical overnight to early morning hours. Isolated thunderstorms also remain in the forecast each afternoon for the upper slopes of the leeward Big Island through Monday.
On Wednesday the pattern changes again, as a cold front approaching the islands from the northwest will drive the subtropical ridge over the region and weaken the trade winds. Decreasing trade winds will last into Friday with local scale land and sea breezes forming over all islands. Cloud cover will shift to island mountain and interior sections each afternoon due to converging sea breeze winds and island surface heating. Clouds will diminish after sunset, with clear skies through the early morning hours, as diverging land breezes stabilize the atmosphere and push any lingering clouds from the land into the sea. Increasing large scale subsidence under this ridge will also dry out the atmosphere, enhance radiational cooling at night, and produce cooler low temperatures trends across the state. The approaching cold front will stall and dissipate just north of Kauai on Friday.
By next Saturday, a high pressure system moving eastward, just north of the Hawaiian Islands, will produce moderate to breezy trade winds just in time for next weekend. This shifting wind pattern will bring a return to trade wind weather with brief passing showers possible over windward and mountain sections.

Aviation

Locally breezy trades will focus showers over windward and mauka areas through the period, particularly overnight and during the early morning. High stability will limit shower intensity for most locations, but deeper moisture and a weaker inversion in the vicinity of the Big Island will favor a greater coverage and intensity of windward showers there. Brief periods of MVFR will be possible. An upper low positioned immediately east of the state will once once again set the stage for isolated afternoon thunderstorms over upslope sections of Leeward Big Island during peak heating today.
AIRMET Tango for lee turbulence will likely be needed over the eastern end of the state by this afternoon as locally breezy trades gradually strengthen.

Marine

A strengthening surface ridge N of the islands will support fresh to locally strong trade winds the next couple of days. A Small Craft Advisory (SCA) is in effect for many zones, either due to winds near 25 kt, or for combined seas near 10 feet. Seas should diminish below 10 feet over all zones by this evening, but winds near 25 kt will continue over Maui and Big Island waters through at least Monday. Wind speeds will gradually diminish Tuesday through Thursday as an approaching front pushes the ridge back toward the islands, with the ridge expected to be near Kauai by Thursday.
A High Surf Advisory (HSA) remains posted for exposed N and W facing shores for an ongoing NW swell, see the Coastal Hazard Message (CFWHFO) for additional details. Swell heights at buoys 51001/51101 NW of Kauai are now slowly trending down after peaking above guidance (at 9-11 feet) over the previous 12 hours. This swell will peak in island waters today, then gradually diminish tonight through Monday, with surf dropping below HSA heights. Yet another WNW swell is expected to arrive Monday night and Tuesday, potentially getting to HSA levels. This swell will slowly drop below HSA levels Wednesday into Thursday, with a small to moderate WNW swell persisting into next weekend. A slightly elevated short-period E swell will continue to bring some surf to E facing shores the next day or two, while a S swell provides some surf to S facing shores the next couple of days.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST this evening for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kauai North, Molokai Windward, Molokai North, Molokai West, Windward Haleakala.
Small Craft Advisory until 6 PM HST Monday 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 Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Oahu Windward Waters, Kaiwi Channel, Maui County Windward Waters.

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Data Courtesy of NOAA.gov