Photo Credit: Randy Alona Gallegos

West Side

Today: Breezy. Mostly sunny with isolated showers. Highs 76 to 87. Northeast winds 10 to 25 mph increasing to 20 to 25 mph in the afternoon. Chance of rain 20 percent.

Tonight: Breezy. Mostly clear with isolated showers. Lows 68 to 74. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

Monday: Sunny and breezy. Isolated showers in the morning. Highs 76 to 87. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

South Side

Today: Breezy. Sunny with isolated showers. Highs around 89. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Breezy. Isolated showers after midnight. Lows 67 to 75. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Monday: Sunny and breezy. Highs around 88. Northeast winds 10 to 20 mph.

North Shore

Today: Breezy. Mostly cloudy with showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs 76 to 84 near the shore to around 66 near 5000 feet. East winds up to 20 mph. Chance of rain 80 percent.

Tonight: Breezy. Partly cloudy with scattered showers. Lows around 71 near the shore to 49 to 55 near 5000 feet. Southeast winds up to 20 mph. Chance of rain 50 percent.

Monday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 75 to 83 near the shore to around 66 near 5000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Central Maui

Today: Breezy. Mostly sunny with isolated showers. Highs 81 to 87. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Mostly clear with isolated showers. Lows 67 to 73. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Monday: Sunny and breezy. Highs 80 to 88. Northeast winds 10 to 20 mph.

Upcountry

Today: Breezy. Mostly sunny with scattered showers. Highs around 62 at the visitor center to around 58 at the summit. East winds 10 to 25 mph decreasing to up to 25 mph in the afternoon. Chance of rain 50 percent.

Tonight: Breezy. Mostly clear with isolated showers. Lows around 46 at the visitor center to around 43 at the summit. East winds up to 25 mph. Chance of rain 20 percent.

Monday: Sunny and breezy. Highs around 62 at the visitor center to around 58 at the summit. East winds up to 20 mph.

East Maui

Today: Breezy. Mostly cloudy with showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs 76 to 84 near the shore to around 66 near 5000 feet. East winds up to 20 mph. Chance of rain 80 percent.

Tonight: Breezy. Partly cloudy with scattered showers. Lows around 71 near the shore to 49 to 55 near 5000 feet. Southeast winds up to 20 mph. Chance of rain 50 percent.

Monday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 75 to 83 near the shore to around 66 near 5000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Lanai City

Today: Breezy. Mostly sunny with isolated showers. Highs 73 to 82. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

Tonight: Breezy. Mostly clear with isolated showers. Lows 63 to 68. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Monday: Sunny and breezy. Highs 72 to 81. Northeast winds 10 to 20 mph.

Kaunakakai

Today: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 66 to 89. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly clear with isolated showers. Lows 58 to 74. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Monday: Sunny and breezy. Highs 66 to 88. Northeast winds 10 to 20 mph.

Detailed Forecast

Synopsis

Showers will remain focused over windward and mauka areas through mid-morning followed by improving conditions late this morning and early this afternoon. Locally breezy trades will weaken to moderate and may become light during mid-to-late week. Drier than normal conditions are forecast through the week.

Discussion

The depth of incoming trade wind showers has decreased over the last couple of hours as they succumb to the resident stable airmass. Per the morning upper air observations, the inversion currently slopes downward from around 6kft at Hilo to 4.5kft at Lihue. As a consequence, satellite estimates suggest even the tallest cloud tops struggling to exceed 7,000 ft in depth. Showers are therefore expected to remain mostly confined to windward areas with any leeward precipitation likely to be quite light and may not even be measurable. Conditions will improve during mid- to- late morning in response to diurnal forcing and as the incoming moisture axis shifts west of the area. Breezy trades will then hold through Monday.
Consensus exists among the global models that an amplifying mid- level trough will establish between about 160W and 150W from mid- week onward, Hawaii residing along the southern periphery of cyclonic flow aloft. Sandwiched between subtropical riding on either side, an emerging col in the surface pressure pattern will cause a reduction in trades as early as Tuesday that will continue through the week. The net effect on local sensible weather will be drier weather, warmer afternoons and, if the gradient sufficiently diminishes, the emergence of land/sea breezes – most likely over the western end of the state.

Aviation

High pressure north of the islands will support locally breezy trade winds into Monday, and AIRMET Tango will remain posted for moderate low-level turbulence to the lee of the terrain. The island atmosphere will remain stable, with VFR conditions prevailing. However, some increase in low-level moisture will bring a few brief showers to windward areas this morning, producing brief MVFR conditions.

Marine

Fresh to strong easterly trade winds will continue through Monday, then ease into the light to moderate range Monday night through midweek as a weakness in the ridge forms in response to a passing front to the north. As a result, the Small Craft Advisory will remain in place for the typically windier waters and channels from Oahu to the Big Island through Monday. Seas should hover just below the 10 ft advisory-level over these windier waters into Monday, then lower Tuesday through midweek. For the extended period (midweek through next weekend), guidance depicts the progressive pattern continuing across the northern Pacific, which suggests an increasing likelihood for the lighter winds to stick around.
Surf along north facing shores will remain up through the last week of October with overlapping north-northeast to north-northwest swells moving through due to the aforementioned active pattern across the northern Pacific. The north swell that quickly ramped up and peaked Friday night is on its way down this morning per the latest buoy observations. This downward trend will be short- lived with the next long-period, northerly swell arriving and building later today through tonight. Expect a peak Monday through Tuesday below the advisory-level of 15 ft (faces) for north facing shores. This will be followed by a north-northwest swell arriving late Tuesday from the developing hurricane-force low currently racing northeastward toward the Date Line/Aleutians today. Guidance suggest the peak from this source occurring Tuesday night, then easing Wednesday through Thursday. A medium- period, north-northwest swell arriving late Thursday should keep the surf up through Friday.
Surf along south facing shores will trend up by midweek as a late season, south-southwest swell arrives and moves through. Otherwise, mainly background, south swells and short-period, southeast trade wind energy moving through are expected.
Surf along east facing shores will remain small and choppy through Monday, then lower Tuesday through midweek as the local winds ease. The exception will be along east facing shores exposed to northerly swell moving through.

HFO Watches/Warnings/Advisories

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

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Data Courtesy of NOAA.gov