West Side

Today: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Haze. Highs 72 to 83. Light winds becoming east up to 10 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Lows 63 to 72. Light winds.

Tuesday: Mostly sunny in the morning then becoming partly sunny. Highs 73 to 83. Light winds becoming east up to 10 mph in the afternoon.

South Side

Today: Mostly sunny in the morning then becoming partly sunny. Haze. Highs 74 to 84. Light winds.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Lows 64 to 69. Light winds.

Tuesday: Mostly sunny in the morning then becoming partly sunny. Highs 74 to 85. Light winds becoming west up to 10 mph in the afternoon.

North Shore

Today: Partly sunny with scattered showers. Haze. Highs 78 to 83 near the shore to around 65 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Lows 66 to 72 near the shore to around 52 near 5000 feet. Southeast winds up to 10 mph.

Tuesday: Mostly sunny. Isolated showers in the morning. Highs 77 to 82 near the shore to around 65 near 5000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Central Maui

Today: Mostly sunny in the morning then becoming partly sunny. Haze. Highs 79 to 84. Northeast winds up to 10 mph.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Lows around 66. East winds up to 10 mph in the evening becoming light.

Tuesday: Mostly sunny in the morning then becoming partly sunny. Highs 80 to 85. East winds up to 10 mph.

Upcountry

Today: Mostly cloudy with scattered showers. Highs 51 to 66. East winds up to 10 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Lows around 44 at the visitor center to around 41 at the summit. East winds up to 10 mph.

Tuesday: Mostly sunny in the morning then becoming partly sunny. Highs 52 to 66. East winds up to 10 mph.

East Maui

Today: Partly sunny with scattered showers. Haze. Highs 78 to 83 near the shore to around 65 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Lows 66 to 72 near the shore to around 52 near 5000 feet. Southeast winds up to 10 mph.

Tuesday: Mostly sunny. Isolated showers in the morning. Highs 77 to 82 near the shore to around 65 near 5000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Lanai City

Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Haze through the day. Highs 68 to 78. Light winds. Chance of rain 30 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Lows 59 to 65. Light winds.

Tuesday: Mostly sunny in the morning then becoming partly sunny. Highs 68 to 78. Light winds.

Kaunakakai

Today: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Haze. Highs 68 to 85. Light winds. Chance of rain 40 percent.

Tonight: Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Lows 55 to 71. Light winds. Chance of rain 20 percent.

Tuesday: Mostly sunny. Highs 68 to 85. Light winds.

Detailed Forecast

Synopsis

An approaching weak cold front will stall out near Kauai on Wednesday and continue to keep the high pressure ridge entrenched directly over the Hawaiian Islands. Large scale stability under this ridge and drier southeasterly wind flow will minimize shower activity into Tuesday. Clouds and showers along the frontal band may stall over Kauai by Wednesday, potentially increasing shower activity over the Garden Isle. Trade winds will build back into the region and strengthen from Thursday onward, bringing back periods of passing showers to windward and mountain areas, favoring the typical overnight to early morning hours.

Discussion

Looking into the big picture satellite imagery this morning, a band of fairly stable stratocumulus clouds are moving up from the southeast into the Big Island and east Maui. Local radar imagery shows passing showers over the southeast slopes of both islands. Farther to the northwest, another weakening cold front approaches the Hawaii Region. A high pressure ridge remains locked in place over the island chain, producing stable conditions and light southeasterly winds. The subsidence temperature inversion heights, as measured by weather balloon observations from Lihue and Hilo at 2 AM HST (12Z) this morning, are showing two temperature inversion levels around 3,000 and 6,000 feet elevation.
These two temperature inversions will continue to serve as a stable capping force for cloud development, reducing shower potential statewide. Additional stable dry trends are also due in part to southeasterly wind flow that places the smaller islands in a drier rain shadow of the Big Island with clouds tracking more parallel to island mountain ranges, limiting orographic lifting of clouds over windward mountains. Lighter large scale winds will also keep daytime onshore sea breezes going for most areas through Tuesday. VOG (Volcanic smOG) from the Kilauea Volcano will also ride into all islands on these drier southeasterly winds. This VOG will appear as haze affecting all islands today, with some improving trends from today onward as the low level steering winds begin to change.
This dry southeasterly wind pattern will continue for most areas through Tuesday or Wednesday. On Wednesday, medium range model solutions continue to show changes in our local weather pattern as a weakening cold front moves near Kauai and stalls. Shower activity will likely increase over Niihau and Kauai for 12 to 24 hours, until this front breaks apart and drifts westward away from the islands. Differences between the main operational American (GFS) and European (ECMWF) remain, with the ECMWF model showing wetter trends for the islands in Kauai County.
A high pressure system will build in north of the state for the second half of the week, increasing easterly trade winds across the region. Expect some southeasterly winds to linger on Thursday morning, with winds becoming more easterly and stronger from Thursday night into next weekend. As the ridge over the islands lifts northward, our typical trade wind shower activity returns with brief passing showers forecast along windward and mountain areas, favoring the typical overnight to early morning hours.

Aviation

Light southeasterly flow will continue through Tuesday before becoming light and variable. Local sea breezes will occur each day with land breezes developing overnight. Expect mostly VFR conditions with brief MVFR conditions along exposed southeast coasts and slopes of the Big Island and Maui early this morning as a band of low level band of clouds with embedded light to moderate showers moves through. A thin veil of high clouds will build over head from west to east through the day.
No AIRMETs are in effect and none are expected.

Marine

A weak surface ridge will remain over the area through Tuesday and maintain light to moderate southeast background flow. This pattern will allow for daytime sea breezes and nighttime land breezes along waters adjacent to the coasts. A slowly declining large northwest swell will generate seas above Small Craft Advisory (SCA) levels for exposed waters today and a SCA remains in effect until noon. Oahu leeward waters were already removed during this package, due the lowering seas. A cold front is projected to approach Kauai from the northwest on Wednesday, but models quickly weaken it into a trough as it retrogrades back westward, away from the islands. Moderate to locally strong easterly trade winds will finally return Friday into the weekend as surface high pressure builds northeast of the area.
The current, large, long-period northwest (320 degree) swell will slowly decline through the remainder of today. Waimea Bay Buoy 51201 continues to report swell heights in the 10 to 12 foot range and the High Surf Warning will remain in effect through noon today for exposed north and west facing shores of most islands. Surf is then expected to drop to advisory levels by this afternoon as the swell energy eases. Another large, long period northwest swell (310-330 degree) is forecast to fill in on Wednesday, peak Thursday, then slowly subside on Friday. Surf may once again approach warning levels.
East shore surf will remain small through Thursday due to weak winds, then become choppier as trade winds increase Friday through the weekend. Expect small background swell and surf for south facing shores.

Fire weather

Rather dry conditions are expected to persist through at least Tuesday. Winds will be light and variable under a stable land and sea breeze pattern, keeping weather conditions below critical fire weather thresholds. Two temperature inversion heights will remain in place over Maui and the Big Island today, with the lowest inversion height in the 2,500 to 3,000 foot elevation range and the higher inversion height in the 6,000 to 6,500 foot elevation range.

HFO Watches/Warnings/Advisories

High Surf Warning until noon HST today for north and west facing shores of Niihau, Kauai, Oahu, Molokai, north facing shores of Maui, and west facing shores of the Big Island.
Small Craft Advisory until noon HST today for Hawaiian coastal waters and channels exposed to the large northwest swell.

Data Courtesy of NOAA.gov