Photo Credit: Allen Tate

West Side

Today: Isolated showers before 1pm. Mostly sunny, with a high near 80. Light and variable wind becoming south southwest 5 to 8 mph in the morning. Chance of precipitation is 20%.

Tonight: Scattered showers and thunderstorms after 1am. Partly cloudy, with a low around 65. Northwest wind 5 to 9 mph becoming northeast after midnight. Chance of precipitation is 30%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Tuesday: Scattered showers and thunderstorms, mainly before 1pm. Mostly cloudy, with a high near 78. Breezy, with a north northeast wind 8 to 18 mph, with gusts as high as 26 mph. Chance of precipitation is 30%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

South Side

Today: Isolated showers before 1pm. Mostly sunny, with a high near 80. Southeast wind 6 to 9 mph becoming southwest in the afternoon. Chance of precipitation is 20%.

Tonight: Partly cloudy, with a low around 64. Light and variable wind becoming north northeast 8 to 13 mph in the evening.

Tuesday: A 20 percent chance of showers and thunderstorms after 7am. Mostly cloudy, with a high near 78. Windy, with a north wind 13 to 18 mph increasing to 20 to 25 mph in the afternoon. Winds could gust as high as 37 mph.

North Shore

Today: Mostly sunny, with a high near 78. South southwest wind 6 to 9 mph.

Tonight: Scattered showers and thunderstorms after 1am. Partly cloudy, with a low around 65. Calm wind becoming north 5 to 8 mph. Chance of precipitation is 40%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Tuesday: Scattered showers and thunderstorms before 7am, then showers likely and possibly a thunderstorm between 7am and 1pm, then scattered showers and thunderstorms after 1pm. Mostly cloudy, with a high near 76. Breezy, with a northeast wind 5 to 15 mph, with gusts as high as 21 mph. Chance of precipitation is 60%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Central Maui

Today: Mostly sunny, with a high near 78. South southwest wind 5 to 7 mph.

Tonight: Scattered showers and thunderstorms after 1am. Partly cloudy, with a low around 63. Calm wind becoming north northwest 5 to 9 mph after midnight. Chance of precipitation is 30%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Tuesday: Scattered showers and thunderstorms. Mostly cloudy, with a high near 76. Breezy, with a north northeast wind 6 to 15 mph, with gusts as high as 21 mph. Chance of precipitation is 50%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Upcountry

Today: Isolated showers after noon. Mostly sunny, with a high near 66. Breezy, with a south wind 10 to 17 mph, with gusts as high as 24 mph. Chance of precipitation is 20%.

Tonight: A 20 percent chance of showers and thunderstorms after midnight. Partly cloudy, with a low around 52. West southwest wind 5 to 10 mph becoming light and variable.

Tuesday: Scattered showers and thunderstorms, mainly before noon. Mostly cloudy, with a high near 62. Breezy, with a north northeast wind 5 to 10 mph increasing to 13 to 18 mph in the afternoon. Winds could gust as high as 25 mph. Chance of precipitation is 30%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

East Maui

Today: Isolated showers before noon. Mostly sunny, with a high near 76. South wind 6 to 11 mph becoming light and variable. Chance of precipitation is 20%.

Tonight: Isolated showers, with thunderstorms also possible after midnight. Partly cloudy, with a low around 61. Northwest wind 8 to 14 mph, with gusts as high as 20 mph. Chance of precipitation is 20%.

Tuesday: Showers likely and possibly a thunderstorm. Mostly cloudy, with a high near 74. Breezy, with a northwest wind 14 to 16 mph becoming north northeast in the afternoon. Winds could gust as high as 22 mph. Chance of precipitation is 60%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Lanai City

Today: Isolated showers. Mostly sunny, with a high near 72. Southeast wind 9 to 14 mph becoming west in the afternoon. Winds could gust as high as 18 mph. Chance of precipitation is 20%.

Tonight: Scattered showers and thunderstorms after midnight. Mostly cloudy, with a low around 61. West wind 7 to 13 mph becoming east northeast after midnight. Chance of precipitation is 30%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Tuesday: Scattered showers and thunderstorms before noon. Mostly cloudy, with a high near 71. Windy, with a northeast wind 13 to 18 mph increasing to 24 to 29 mph in the morning. Winds could gust as high as 41 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Kaunakakai

Today: Isolated showers before noon. Mostly sunny, with a high near 77. Light and variable wind becoming west southwest 5 to 9 mph in the afternoon. Chance of precipitation is 20%.

Tonight: Scattered showers and thunderstorms, mainly after midnight. Mostly cloudy, with a low around 65. West wind 6 to 11 mph becoming northeast after midnight. Chance of precipitation is 40%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Tuesday: Scattered showers and thunderstorms before noon. Mostly cloudy, with a high near 76. Windy, with a north northeast wind 11 to 16 mph increasing to 18 to 23 mph in the morning. Winds could gust as high as 33 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Detailed Forecast

Synopsis

A cold front will move through Kauai this afternoon, Oahu and Maui County tonight, and then through the Big Island on Tuesday. The front will bring scattered showers and a slight chance of thunderstorms to the island chain as it moves through. Cool, breezy, and rather dry north winds will build in behind the front, followed by returning trade winds on Wednesday. The trades will persist through the remainder of the work week, as the airmass slowly modifies and trade wind showers increase closer to seasonal normals. Trade winds may shift out of the east-southeast next weekend, with an upper level disturbance possibly bringing more unsettled weather to windward areas, particularly over the eastern end of the state.

Discussion

Currently at the surface, a high pressure ridge axis is centered over the central islands early this morning, while an approaching cold front is located around 275 miles west-northwest of Kauai. Light land breezes are present across the entire island chain. Infrared satellite imagery shows clear to partly cloudy skies across the state. Radar imagery shows a few isolated showers in the vicinity of Oahu and Maui County, with rain free conditions elsewhere. Main short term concern revolves around the shower and thunderstorm chances associated with the incoming cold front.
High pressure will prevail this morning, as the cold front northwest of the state makes steady progress southeastward. Rather dry conditions will persist through midday, with only a few isolated showers possible over Maui County and Oahu this morning. The leading edge of the front is expected to reach Kauai this afternoon, progress to Oahu and Maui County tonight, then pass over the Big Island on Tuesday. Both the GFS and ECMWF suggest that a somewhat shallow band of moisture along the front will focus rainfall primarily along north facing terrain. However, the upper-level trough driving the front will produce significant instability aloft with 500 mb temperatures declining to an exceptionally cold -17C. This will bring a threat of thunderstorms along the front, allow showers to briefly spread over all areas of most islands, and could lead to a short-lived spell of winter weather across the summits of the Big Island as well as Haleakala. The models seem to be converging on the front moving over the Big Island Tuesday afternoon, which could lead to higher thunderstorm chances here as the daytime heating combines with increased moisture and instability.
Cool, dry and breezy north winds will fill in behind the front, then shift to a more typical east-northeast trade wind direction on Wednesday as surface high pressure passes by north of the state. Dew points will drop into the 50s again, and precipitable water will plummet to around 1/2 an inch. As a result, expect little shower activity and a crisp feel to the air as temperatures run several degrees below normal and winds remain breezy.
Moderate trade winds will prevail Thursday and Friday as the airmass over the islands gradually modifies, returning temperatures and windward shower activity closer to seasonal normals. A weak cutoff low to the east of the islands may send more shower activity into windward areas, particularly across Maui and the Big Island over the weekend. Trade winds will likely weaken and shift out of the east-southeast over the weekend as well, which may allow for a few afternoon showers in leeward areas which linger into the evening hours.

Aviation

This morning, an approaching frontal system to the northwest of Kauai will help to maintain light and variable flow. Expect mainly dry weather with VFR conditions, though a few passing light showers may push over Oahu, Molokai, and Maui. By late this afternoon and this evening, the aforementioned front will begin to quickly push across the islands from west to east and bring showers and isolated thunderstorms with brief MVFR ceilings and visibility.
There are no AIRMETS currently in effect.

Marine

Winds will shift rapidly out of the west, then northwest today as a front approaches from the northwest and pushes the high off to the east of the area. The front will reach the Kauai waters this afternoon, move through the Oahu and Maui County waters tonight, then shift through the Big island on Tuesday. Locally strong north winds behind the front will shift to northeast trade winds by Tuesday night.
The current northwest and north swells will continue to subside today. A new, large northwest swell is expected to build late tonight and peak Tuesday, with surf likely reaching HSA heights along north and west facing shores. Another, even larger northwest swell is expected Friday night, with a still larger northwest swell possible early Sunday. East and south shore surf will remain small through the forecast period.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov