Photo Credit: Allen Tate

West Side

Today: Scattered showers. Mostly sunny, with a high near 79. Windy, with an east northeast wind 13 to 18 mph increasing to 20 to 25 mph. Winds could gust as high as 36 mph. Chance of precipitation is 30%.

Tonight: Isolated showers. Mostly clear, with a low around 66. East northeast wind around 14 mph, with gusts as high as 18 mph. Chance of precipitation is 20%.

Sunday: Scattered showers. Mostly sunny, with a high near 80. East northeast wind around 14 mph, with gusts as high as 18 mph. Chance of precipitation is 30%.

South Side

Today: Scattered showers. Increasing clouds, with a high near 79. Light and variable wind becoming east northeast 8 to 13 mph in the afternoon. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Isolated showers. Mostly clear, with a low around 64. East northeast wind around 14 mph, with gusts as high as 18 mph. Chance of precipitation is 20%.

Sunday: Scattered showers. Mostly sunny, with a high near 80. East northeast wind around 14 mph, with gusts as high as 18 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

North Shore

Today: Scattered showers. Mostly sunny, with a high near 77. Windy, with an east wind 13 to 23 mph, with gusts as high as 32 mph. Chance of precipitation is 40%.

Tonight: Scattered showers. Partly cloudy, with a low around 65. Breezy, with an east wind around 17 mph, with gusts as high as 24 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Sunday: Scattered showers. Mostly sunny, with a high near 78. Windy, with an east wind 18 to 26 mph, with gusts as high as 40 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Central Maui

Today: Scattered showers. Mostly sunny, with a high near 77. Breezy, with a north wind 5 to 10 mph becoming east northeast 15 to 20 mph in the afternoon. Winds could gust as high as 28 mph. Chance of precipitation is 40%.

Tonight: Scattered showers. Partly cloudy, with a low around 63. Breezy, with an east wind around 15 mph, with gusts as high as 21 mph. Chance of precipitation is 40%.

Sunday: Scattered showers. Mostly sunny, with a high near 78. Windy, with an east wind 16 to 23 mph, with gusts as high as 32 mph. Chance of precipitation is 40%.

Upcountry

Today: Scattered showers. Mostly sunny, with a high near 63. Breezy, with a light and variable wind becoming east 11 to 16 mph in the afternoon. Winds could gust as high as 22 mph. Chance of precipitation is 40%.

Tonight: Scattered showers, mainly before midnight. Mostly clear, with a low around 52. Breezy, with an east wind around 17 mph, with gusts as high as 24 mph. Chance of precipitation is 30%.

Sunday: Scattered showers. Mostly sunny, with a high near 65. Breezy, with an east wind 18 to 20 mph, with gusts as high as 28 mph. Chance of precipitation is 50%.

East Maui

Today: Showers likely, mainly before noon. Partly sunny, with a high near 75. Breezy, with an east wind around 15 mph, with gusts as high as 21 mph. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Frequent showers. Low around 61. East wind around 14 mph, with gusts as high as 18 mph. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Sunday: Showers likely, mainly before noon. Cloudy, with a high near 76. East wind around 14 mph, with gusts as high as 18 mph. Chance of precipitation is 70%. New precipitation amounts between a tenth and quarter of an inch possible.

Lanai City

Today: Scattered showers. Partly sunny, with a high near 72. Breezy, with a northeast wind 14 to 22 mph, with gusts as high as 31 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers. Mostly clear, with a low around 60. Breezy, with an east northeast wind 14 to 16 mph, with gusts as high as 22 mph. Chance of precipitation is 30%.

Sunday: Scattered showers. Mostly sunny, with a high near 72. Breezy, with an east northeast wind around 18 mph, with gusts as high as 25 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Kaunakakai

Today: Scattered showers. Mostly sunny, with a high near 76. Windy, with an east wind 17 to 23 mph, with gusts as high as 32 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers. Mostly clear, with a low around 66. Windy, with an east wind around 23 mph, with gusts as high as 32 mph. Chance of precipitation is 40%.

Sunday: Scattered showers. Mostly sunny, with a high near 77. Windy, with an east northeast wind around 26 mph, with gusts as high as 38 mph. Chance of precipitation is 30%.

Detailed Forecast

Synopsis

A high to the north will maintain breezy trade winds over the area through the next several days. In the near-term, the most active showers will be over windward areas of Kauai, Oahu and Maui County. Starting late Sunday, heavier showers will move over the Big Island, then spread west through mid-week.

Discussion

As of 2 AM, the surface analysis showed a strong 1039 mb high far north of the main Hawaiian Islands. This high will maintain breezy trade winds over the area through the middle of next week. The trade winds are carrying remnants of a front over mainly windward areas from Kauai to Maui. A trough aloft is making the atmosphere over the islands a bit unstable, so the frontal remnants are taller than typical trade-wind clouds. The clouds are tall enough, and the trade winds are strong enough, for the showers to spread leeward on the smaller islands.
The trough aloft is forecast to deepen over the next few days. That will make the atmosphere more unstable and help pull deeper moisture over the islands from the southeast starting on Sunday. It is too soon to know the details of this developing pattern, but it looks as if rainfall will become more active, starting on the Big Island by late Sunday, then spreading northwest. Heavy rain and thunderstorms will be possible on the Big Island with ice and snow over the upper elevations. As this pattern develops, a Flash Flood Watch and a Winter Weather Watch may need to be issued.
There have been large differences from model run to model run and between the GFS and ECMWF models next week. That reduces the confidence we have in the long-term forecasts.

Aviation

High pressure to the north-northwest and frontal remnants to the east will continue to bring clouds and showers to the islands today. Over the last couple of hours, clouds and showers have thinned some, and so AIRMET SIERRA has been canceled for mountain obscuration. Its possible that it may be needed again, if clouds and showers build up again over the islands. However VFR conditions prevail over most of the islands, with passing MVFR conditions.
AIRMET TANGO continues for low level mechanical turbulence to the lee of the mountains on Kauai, due to winds remaining elevated in both observations and the VAD wind profile. Winds are expected to trend down a bit today which could allow the AIRMET to be canceled.

Marine

A strong high pressure system far north of the Hawaiian Islands will drift slowly southeastward over the next few days. Trade wind speeds will remain in the fresh to strong range today, and then increase into the strong to near gale range from Sunday through Wednesday. Gale conditions may develop over the windier eastern waters and channels next week.
The current Small Craft Advisory (SCA) includes most island waters due to a combination of strong trade winds and elevated seas. The SCA will expand on Sunday to include all coastal waters through Monday morning and will likely continue into much of next week due to increasing trade winds.
A north swell continues to elevate surf heights along exposed shores. This north swell may produces surges in north facing harbors, including Hilo and Kahului harbors. Swell heights will slowly decrease through Sunday and the High Surf Advisory for north facing shores of the eastern islands was cancelled this morning. The forerunners of the next northwest swell are expected to arrive on Sunday, with overlapping northwest and north swells producing medium size surf along north and west facing shores through Monday, and then decreasing to smaller size surf from Tuesday through Thursday.
Strengthening trade winds will increase surf along east facing shores through the first half of next week with a building trade wind swell. Surf may reach HSA levels along exposed east facing shores on Tuesday and Wednesday.
Background south swells will provide small surf to south facing shores through Thursday.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM Sunday for all Hawaiian waters except Maui County Leeward waters and Oahu Leeward waters.
Small Craft Advisory from 6 AM Sunday through 6 AM Monday for all Hawaiian waters.

Data Courtesy of NOAA.gov