Photo Credit: Leosan Miguel

West Side

Today: Breezy. Partly sunny with scattered showers and isolated thunderstorms in the morning, then mostly sunny with isolated showers and thunderstorms in the afternoon. Highs 75 to 81. East winds up to 25 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Breezy. Isolated showers after midnight. Lows 64 to 70. East winds 10 to 25 mph. Chance of rain 20 percent.

Monday: Partly sunny in the morning then becoming mostly sunny. Breezy. Isolated showers. Highs 77 to 83. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

South Side

Today: Mostly sunny with scattered showers and isolated thunderstorms in the morning, then partly sunny with isolated thunderstorms in the afternoon. Highs around 81. Northeast winds up to 15 mph. Chance of rain 30 percent.

Tonight: Partly cloudy. Lows around 65. Northeast winds up to 15 mph.

Monday: Mostly sunny. Highs around 83. Northeast winds up to 15 mph.

North Shore

Today: Mostly cloudy. Breezy. Widespread showers and isolated thunderstorms in the morning, then scattered showers and isolated thunderstorms in the afternoon. Highs 73 to 78 near the shore to around 60 near 5000 feet. East winds 10 to 25 mph. Chance of rain 90 percent.

Tonight: Breezy. Cloudy with scattered showers. Lows 62 to 68 near the shore to around 49 near 5000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Monday: Mostly cloudy. Breezy. Showers in the morning, then scattered showers in the afternoon. Highs 75 to 80 near the shore to around 61 near 5000 feet. East winds 10 to 25 mph. Chance of rain 80 percent.

Central Maui

Today: Breezy. Partly sunny with scattered showers and isolated thunderstorms in the morning, then mostly sunny with isolated showers and thunderstorms in the afternoon. Highs 77 to 82. East winds 10 to 25 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening. Lows 63 to 68. East winds 10 to 25 mph. Chance of rain 20 percent.

Monday: Partly sunny in the morning then becoming mostly sunny. Breezy. Isolated showers. Highs 79 to 84. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

Upcountry

Today: Breezy. Mostly cloudy with scattered showers and isolated thunderstorms. Highs around 56 at the visitor center to around 52 at the summit. East winds up to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 45 at the visitor center to around 39 at the summit. East winds 10 to 25 mph. Chance of rain 50 percent.

Monday: Breezy. Mostly sunny with scattered showers in the morning, then partly sunny with isolated showers in the afternoon. Highs around 56 at the visitor center to around 52 at the summit. East winds up to 25 mph. Chance of rain 50 percent.

East Maui

Today: Mostly cloudy. Breezy. Widespread showers and isolated thunderstorms in the morning, then scattered showers and isolated thunderstorms in the afternoon. Highs 73 to 78 near the shore to around 60 near 5000 feet. East winds 10 to 25 mph. Chance of rain 90 percent.

Tonight: Breezy. Cloudy with scattered showers. Lows 62 to 68 near the shore to around 49 near 5000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Monday: Mostly cloudy. Breezy. Showers in the morning, then scattered showers in the afternoon. Highs 75 to 80 near the shore to around 61 near 5000 feet. East winds 10 to 25 mph. Chance of rain 80 percent.

Lanai City

Today: Mostly sunny with isolated showers and thunderstorms in the morning, then partly sunny with scattered showers and isolated thunderstorms in the afternoon. Highs 70 to 77. Northeast winds up to 15 mph. Chance of rain 40 percent.

Tonight: Partly cloudy. Isolated showers after midnight. Lows around 64. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Monday: Breezy. Mostly sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs 71 to 78. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Kaunakakai

Today: Mostly sunny. Breezy. Isolated showers and thunderstorms in the morning, then isolated thunderstorms in the afternoon. Highs 70 to 80. East winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers after midnight. Lows 56 to 68. East winds 10 to 20 mph. Chance of rain 20 percent.

Monday: Breezy. Partly sunny with isolated showers. Highs 71 to 81. East winds 10 to 20 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

An upper low over the state will maintain an unstable and moist airmass which will generate showers and isolated thunderstorms, with locally heavy rainfall, into this evening. Drier and more stable conditions will filter across the state to begin the work week, with trade winds focusing showers mainly across windward areas into next weekend.

Discussion

Current radar shows showers across the islands again this morning, with the largest concentration of showers focused along windward areas as locally breezy trade winds continue. Radar estimates suggest locally enhanced rainfall rates remaining embedded within some of the showers this morning. Lightning data shows a few strikes in the vicinity of the Big Island, over 200 miles north to northeast of Hilo, in an area of enhanced instability (Showalter Index (SW) around -2c). A few isolated strikes were also noted over interior Oahu earlier this morning.
Today through tonight…High pressure centered well northeast of the state will maintain moderate to locally breezy trades through tonight. An upper low centered across the state this morning, will slowly move eastward and become centered across the Big Island tonight through early Monday, while an upper ridge builds in across the western end of the state. This pattern will maintain deep layered moisture (PWs greater than 1.50″) and modest instability (SW around 0 to -1c) across the state this morning. This unstable airmass will then shift eastward and become mainly concentrated across the eastern end of the state this evening into early Monday. Corresponding thunderstorm probabilities show the best chance for isolated storms, remains around the Big Island along with windward zones and surrounding waters into this afternoon. Otherwise, drier and more stable conditions will begin to push in across the western end of the state later this afternoon. Overall, will maintain the current forecast trends, with showers and isolated thunderstorms lingering across a majority of the islands this morning/afternoon. Have also introduced a diminishing trend in the precipitation pattern this afternoon/evening across the western islands, to reflect drier and more stable conditions expanding into the region.
Monday and Tuesday…the transition toward stable and dry conditions will continue, as the upper low weakens and exits eastward of the state. High pressure drifting well north of the region will further reinforce the trade wind weather pattern across the islands to begin the work week. Current data solutions suggest enough moisture lingering around the islands (modeled PW values 1.25 to 1.35″, moisture depths 9k-13k ft) to maintain increased areal coverage of showers across windward locations into early Tuesday. Showers will remain focused across mainly windward areas. However the airmass will quickly stabilize through the beginning of the week, which will greatly reduce the threat of locally heavy rainfall.
Wednesday into next weekend…the airmass continues to become more dry and more stable through the period, with forecast PW values falling to under 1.00″ while modeled moisture depths fall to around 8k ft or less. This pattern will greatly reduce the intensity and areal coverage of showers across the islands. Lingering trade wind flow will maintain showers to mainly favored windward locations, with the most persistent shower coverage at night through early morning.

Aviation

Breezy easterly trade winds will prevail through the 24-hr forecast period, with clouds and showers favoring windward areas. Showery conditions will continue through the morning hours today, with some becoming heavy and spilling into leeward areas due to plenty of moisture and an upper trough in the area. The added instability associated with the upper trough will also support a few thunderstorms today. A return of drier air and more stable trade wind conditions is expected tonight into Monday.
AIRMET Sierra for tempo mountain obscuration for most windward areas will persist through the morning hours.
AIRMET Tango for moderate low-level turbulence will continue over and downwind of island mountains.

Marine

A strong high pressure system north of the Hawaii region will continue to drift eastward producing fresh to locally strong trade winds over the coastal waters through the week. An upper level low over the eastern islands will continue to slowly drift eastward today. This low will enhance shower activity mainly over southern and eastern waters today before drifting away from the region on Monday. A Small Craft Advisory (SCA) was cancelled for most leeward waters and all waters around Kauai this morning. The SCA remains in effect for most waters around Maui and Hawaii Counties due to strong winds. Weather conditions will become more stable today, although isolated thunderstorms may linger into the evening hours.
A medium period north-northwest swell (340-350 degrees) will decline today lowering surf heights along north and west facing shores. On Monday, the next long period northwest swell (310-320 degrees) will slowly fill in, and peak on Tuesday and Wednesday. On Thursday, two overlapping swells will build into the region. A new long period northwest (320-330 degree) swell will arrive by Thursday morning, while a trailing medium period north (350-360 degree) swell fills in by Thursday night. These two swells may boost surf heights to near advisory levels for exposed north and west facing shores on Thursday and Friday. Surf along east facing shores will remain choppy and small through the week as a belt of fresh to strong easterly trades continues to blow across the region. Surf along south facing shores will also remain on the small side.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Monday for Oahu Windward Waters, Kaiwi Channel, Maui County Windward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov