Photo Credit: Tyler Rooke

West Side

Today: Mostly sunny with isolated showers. Highs 79 to 85. Light winds. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 64 to 69. Light winds. Chance of rain 20 percent.

Tuesday: Partly sunny with scattered showers. Highs 79 to 85. Light winds becoming east 10 to 15 mph in the afternoon. Chance of rain 30 percent.

South Side

Today: Mostly sunny with isolated showers. Highs around 84. Light winds. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows around 65. Light winds. Chance of rain 20 percent.

Tuesday: Partly sunny with scattered showers. Highs around 85. Light winds becoming north 10 to 15 mph in the afternoon. Chance of rain 30 percent.

North Shore

Today: Partly sunny with scattered showers. Highs 77 to 82 near the shore to around 64 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with isolated showers. Lows 62 to 68 near the shore to around 50 near 5000 feet. Southeast winds 10 to 15 mph. Chance of rain 20 percent.

Tuesday: Breezy. Mostly cloudy with scattered showers. Highs 77 to 82 near the shore to around 62 near 5000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Central Maui

Today: Mostly sunny with isolated showers. Highs around 83. Northeast winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 63 to 68. Southeast winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Tuesday: Breezy. Partly sunny with scattered showers. Highs 81 to 86. East winds 10 to 20 mph. Chance of rain 30 percent.

Upcountry

Today: Partly sunny with scattered showers. Highs around 59 at the visitor center to around 55 at the summit. Southeast winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 46 at the visitor center to around 41 at the summit. Southeast winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday: Breezy. Partly sunny with scattered showers. Highs around 57 at the visitor center to around 53 at the summit. East winds 10 to 20 mph. Chance of rain 50 percent.

East Maui

Today: Partly sunny with scattered showers. Highs 77 to 82 near the shore to around 64 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with isolated showers. Lows 62 to 68 near the shore to around 50 near 5000 feet. Southeast winds 10 to 15 mph. Chance of rain 20 percent.

Tuesday: Breezy. Mostly cloudy with scattered showers. Highs 77 to 82 near the shore to around 62 near 5000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Lanai City

Today: Partly sunny with scattered showers. Highs 73 to 80. Light winds. Chance of rain 40 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 65. Light winds. Chance of rain 40 percent.

Tuesday: Partly sunny with scattered showers. Highs 73 to 80. Light winds. Chance of rain 30 percent.

Kaunakakai

Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 73 to 83. Light winds. Chance of rain 40 percent.

Tonight: Mostly cloudy with scattered showers. Lows 58 to 68. Light winds becoming southeast around 10 mph after midnight. Chance of rain 40 percent.

Tuesday: Partly sunny with scattered showers. Highs 74 to 84. East winds around 10 mph. Chance of rain 30 percent.

Detailed Forecast

Synopsis

A developing low far northwest of the islands will move southward today, then shift west and away from the state thereafter. This low will shift our winds to southerlies and southeasterlies today, bringing deeper moisture over the western islands during the first half of the week. Breezy to windy trades and more typical weather should return for the second half of the week.

Discussion

Winds are veering to southeasterlies, as expected, as a developing low far northwest of the islands moves southward and adjusts the wind field this morning. Cloud cover across the smaller islands decreased dramatically overnight, with broken low clouds persisting across windward Big Island areas. Broken to overcast low clouds also persist across waters southwest of Maui County. Radar shows scattered showers within residual cloud areas. Winds will continue to veer through today.
Models shows the low will move to the south today, then move west away from the state afterwards. Confidence is high that the associated front will remain just west of Kauai, which should keep the main area of instability to the west as well. However, enough additional moisture and instability east of the front will reach Kauai to prompt the addition of thunderstorms to the forecast there from this afternoon into Tuesday. Spotty heavy rainfall is possible as far east as Oahu tonight into Tuesday.
Overnight soundings show a thermal inversion around 10,500 feet. We expect this inversion to remain in place for another day, but it may become weaker on Tuesday. As moisture increases near the Big Island Tuesday, we will look more closely at the possibility for thunderstorm development over the slopes, with the eruption helping to provide some of the instability needed. A transition back to a more typical trade wind pattern is expected to spread from east to west across the state late Tuesday night and Wednesday as a new high builds north of the islands.

Aviation

As a low develops far northwest of the islands, light to locally moderate winds will shift more to the southeast and south through today. Moisture moving up from the south and southwest will mainly affect the western part of the state, with Kauai and Oahu likely seeing the most lower cloudiness and showers, and accompanying MVFR conditions. And with lighter winds, afternoon sea breezes may also affect the isles, with convective buildups over leeward and interior sections.
No AIRMETs in effect.

Marine

Latest surface analysis and satellite imagery show a low that has developed roughly 475 nm NW of Kauai along a cold front and surface ridge to the north. This low will move SW today and develop into a storm- force kona low today. Gentle to fresh east to southeast winds will continue to veer out of the south today as these features approach the area today and strengthen to moderate to locally strong. Low- level convergent flow on the SE side of the low could prompt the development of heavy showers and possibly a thunderstorm over Kauai waters, later today and tomorrow.
The kona low is expected to move steadily W by tomorrow through the week, with high pressure strengthening to the N. The tightening low- level pressure gradient will support strong SE winds by tomorrow, backing to the E by Wednesday, and remaining strong to near-gale force through the end of the week. Winds and seas will likely increase to the point that a Small Craft Advisory (SCA) will be required for most (if not all) zones by tomorrow.
Mid- to short-period NE swell continues to be the primary wave energy early this morning according to near shore PacIOOS buoy data, as the ongoing WNW swell fades out. Some modest NE swell reinforcements are expected tonight, with this swell then gradually diminishing over the next several days. Surf along E facing shores will increase by midweek as trade winds increase near and upstream of the islands, and may lead to high surf. While most of the strong winds associated with the kona low will not be aimed directly at the islands, the proximity and strength of the low is expected to send NW swell toward the islands today and Tuesday, with the swell largest on the W end of the island chain. Offshore buoys have yet to pick up on this swell which is why it was decided to hold off on issuing an advisory with this package. Latest model guidance has also come in lower on the predicted peak surf heights, thus confidence in this swell peaking up to warning levels is still uncertain but not totally out of the question, especially for Kauai. After this swell peaks and diminishes, little in the way of NW swell is expected into next weekend.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov