Photo Credit: James Grenz

Hilo

Today: Frequent showers. High near 76. Light and variable wind becoming east 5 to 9 mph in the afternoon. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Frequent showers. Low around 61. Light north northeast wind. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Sunday: Frequent showers, with thunderstorms also possible after noon. High near 76. North northeast wind 3 to 8 mph. Chance of precipitation is 80%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Kona

Today: Scattered showers. Widespread haze. Partly sunny, with a high near 78. Light and variable wind becoming west southwest 5 to 7 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers. Widespread haze. Mostly cloudy, with a low around 59. Light and variable wind. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Sunday: Scattered showers, with thunderstorms also possible after 1pm. Widespread haze. Increasing clouds, with a high near 78. Light and variable wind. Chance of precipitation is 40%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Waimea

Today: Showers likely. Mostly cloudy, with a high near 73. Breezy, with a northeast wind 15 to 22 mph, with gusts as high as 31 mph. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Showers likely. Mostly cloudy, with a low around 50. Breezy, with an east wind around 15 mph, with gusts as high as 21 mph. Chance of precipitation is 70%. New precipitation amounts between a tenth and quarter of an inch possible.

Sunday: Showers likely, with thunderstorms also possible after noon. Cloudy, with a high near 73. Breezy, with an east northeast wind around 17 mph, with gusts as high as 24 mph. Chance of precipitation is 70%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Kohala

Today: Frequent showers. High near 69. Windy, with an east wind 22 to 26 mph, with gusts as high as 55 mph. Chance of precipitation is 90%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Frequent showers. Low around 43. Breezy, with an east wind 18 to 21 mph, with gusts as high as 29 mph. Chance of precipitation is 90%. New precipitation amounts of less than a tenth of an inch possible.

Sunday: Frequent showers, with thunderstorms also possible after noon. High near 69. Breezy, with an east wind around 18 mph, with gusts as high as 25 mph. Chance of precipitation is 100%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

South Big Island

Today: Scattered showers. Widespread haze. Mostly sunny, with a high near 78. Windy, with an east northeast wind around 23 mph, with gusts as high as 30 mph. Chance of precipitation is 50%.

Tonight: Scattered showers. Widespread haze. Mostly cloudy, with a low around 67. Windy, with an east northeast wind around 24 mph, with gusts as high as 31 mph. Chance of precipitation is 50%.

Sunday: Scattered showers. Widespread haze. Increasing clouds, with a high near 78. Windy, with an east northeast wind around 26 mph, with gusts as high as 34 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Puna

Today: Frequent showers. High near 75. Northwest wind 8 to 14 mph becoming east northeast in the morning. Winds could gust as high as 18 mph. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Frequent showers. Low around 59. North northeast wind around 10 mph. Chance of precipitation is 90%. New precipitation amounts between a tenth and quarter of an inch possible.

Sunday: Frequent showers, with thunderstorms also possible after noon. High near 75. Breezy, with a north northeast wind 11 to 15 mph, with gusts as high as 21 mph. Chance of precipitation is 80%. New rainfall amounts between a quarter and half of an inch possible.

Waikoloa

Today: Scattered showers, mainly after noon. Mostly sunny, with a high near 79. Light and variable wind becoming north northeast 8 to 13 mph in the afternoon. Chance of precipitation is 30%.

Tonight: Scattered showers, mainly before midnight. Partly cloudy, with a low around 59. East northeast wind 6 to 8 mph. Chance of precipitation is 30%.

Sunday: Isolated showers, with thunderstorms also possible after noon. Partly sunny, with a high near 79. Northeast wind around 10 mph. Chance of precipitation is 20%.

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