Photo Credit: James Grenz

Hilo

Today: Scattered showers. Partly sunny, with a high near 79. East southeast wind 5 to 9 mph becoming light southeast in the afternoon. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 60. Light and variable wind. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Saturday: Scattered showers. Partly sunny, with a high near 79. Light and variable wind becoming east 5 to 9 mph in the afternoon. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Kona

Today: Scattered showers after noon. Mostly sunny, with a high near 81. North wind 7 to 11 mph becoming west southwest in the afternoon. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers before midnight. Partly cloudy, with a low around 61. West southwest wind 5 to 7 mph becoming calm in the evening. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Saturday: Scattered showers after noon. Mostly sunny, with a high near 81. Calm wind becoming west northwest around 5 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Waimea

Today: Isolated showers. Mostly sunny, with a high near 77. Breezy, with an east wind 7 to 15 mph, with gusts as high as 21 mph. Chance of precipitation is 20%.

Tonight: Scattered showers, mainly after 7pm. Mostly cloudy, with a low around 46. Breezy, with a north northeast wind 14 to 17 mph, with gusts as high as 24 mph. Chance of precipitation is 40%. New precipitation amounts between a tenth and quarter of an inch possible.

Saturday: Scattered showers, mainly before 1pm. Mostly sunny, with a high near 77. Breezy, with a northeast wind 14 to 17 mph, with gusts as high as 24 mph. Chance of precipitation is 40%. New precipitation amounts between a tenth and quarter of an inch possible.

Kohala

Today: Scattered showers. Partly sunny, with a high near 75. Windy, with an east northeast wind 13 to 18 mph increasing to 21 to 26 mph in the afternoon. Winds could gust as high as 38 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 41. Very windy, with an east northeast wind 24 to 33 mph, with gusts as high as 48 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Saturday: Scattered showers. Partly sunny, with a high near 74. Very windy, with an east wind 28 to 33 mph decreasing to 22 to 27 mph in the morning. Winds could gust as high as 48 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

South Big Island

Today: Sunny, with a high near 80. Windy, with an east wind 17 to 24 mph, with gusts as high as 31 mph.

Tonight: Mostly clear, with a low around 70. Windy, with an east northeast wind 22 to 25 mph, with gusts as high as 32 mph.

Saturday: Sunny, with a high near 79. Windy, with an east wind around 25 mph, with gusts as high as 32 mph.

Puna

Today: Scattered showers. Partly sunny, with a high near 78. East northeast wind 6 to 9 mph. Chance of precipitation is 50%. New precipitation amounts between a tenth and quarter of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 58. East northeast wind around 6 mph becoming light and variable. Chance of precipitation is 50%. New precipitation amounts between a tenth and quarter of an inch possible.

Saturday: Scattered showers. Partly sunny, with a high near 78. North northwest wind 5 to 14 mph becoming northeast in the morning. Winds could gust as high as 18 mph. Chance of precipitation is 50%. New precipitation amounts between a tenth and quarter of an inch possible.

Waikoloa

Today: Sunny, with a high near 82. North northwest wind 3 to 6 mph.

Tonight: Mostly clear, with a low around 58. Light and variable wind becoming east 5 to 10 mph after midnight.

Saturday: Sunny, with a high near 82. North northeast wind 7 to 10 mph.

Detailed Forecast

Synopsis

A low pressure system far north of the state will lift northeastward away from the islands today. A high pressure ridge will build in north of the islands, allowing trade winds to return and strengthen through the weekend. Passing shower activity will shift to windward and mountain areas through Sunday. The weather pattern for next week remains less certain, as trade winds become disrupted by a frontal system approaching from the northwest.

Discussion

The large scale satellite picture remains unchanged this morning, as a large low pressure system far north of the state continues to drift northeastward away from the region. A weakening trough near Kauai will diminish and drift westward today as the trade winds return to the region. Enough instability will linger near Kauai for isolated thunderstorm potential along the trough axis near Kauai. The subtropical jet stream continues to produce high level cirrus ice clouds over the region, enhancing sunrise and sunset colors into Saturday.
Shower activity will gradually trend lower today, with showers favoring windward and mountain areas in a developing trade winds pattern. High pressure building in north of the region will strengthen trade winds into the moderate to breezy range this weekend. A low level convergent cloud band, likely associated with an old dissipated cold front, will drift in on the trades from Sunday afternoon into Monday. This surface feature is supported by an upper level trough forming over the islands. Both the surface and upper level features will combine forces to enhance shower activity through Monday night.
Tuesday through Thursday…A frontal low pressure system approaches the islands from the northwest, weakening the ridge north of the islands, and decreasing our trade winds. East to southeast winds are likely to develop over the state during this time period. Shower activity will typically trend lower in the southeasterly wind regime due to rain shadowing effects over the smaller islands located on the lee side of the Big Island. Southeastern slopes of the Big Island will see some enhancement to shower activity during the day.
Long range global weather model solutions continue to diverge significantly from Wednesday onward. Differences revolve around the location and intensity of the next frontal low approaching the state from the northwest. The American (GFS) model continues to bring this frontal system closer to the islands as compared to the European (ECMWF) model with a wetter forecast over the islands, with heavier showers potentially favoring the western islands. In previous forecast battles between these two global models, the GFS has been more successful in the longer time ranges. Therefore, we are blending both models a bit to reduce errors, leaning more towards the GFS for the best rain and wind solution at this point. Stay tuned to next week’s forecast, as our wind and weather impacts will likely change in this low confidence solution.

Aviation

Early this morning, a band of showers and low clouds continues near Kauai ahead of a weakening surface trough. Satellite imagery also depicts a smaller band of low clouds near Molokai that is gradually moving west. Periodic MVFR conditions will be possible for Kauai for the the remainder of the morning but conditions are expected to improve throughout the day as easterly trade winds return to the state. For now, AIRMET Sierra remains in effect for mountain obscuration for both Kauai and Molokai, but could be cancelled for Molokai later this morning as conditions improve.
With an easterly trade wind regime returning to the state later today, VFR conditions will prevail and isolated to scattered showers will favor east facing slopes and coasts.
AIRMET Tango remains in effect for moderate turbulence from FL250 and FL400 from Oahu to the Big Island early this morning. Model data suggest that moderate turbulence will wane and push well east of the Hawaiian Islands over the next couple of hours, though upper turbulence could return once again this evening.

Marine

A trough of low pressure near Kauai will weaken and shift westward over the next couple days, allowing high pressure to the distant northeast to become more dominant. As a result, light winds will gradually transition over to trade winds from east to west across the island chain today and tonight, with the trades strengthening to fresh to strong levels this weekend. A Small Craft Advisory (SCA) remains in effect for the windier waters around Maui and the Big Island from noon today through 6 AM Monday. The windward Big Island waters have been added to the SCA with the morning package due to strong winds expected here as well. Additionally, the SCA may need to be expanded to include more zones over the weekend as the trades strengthen. Early next week the trades will ease into the light to moderate range as a storm system develops several hundred miles west of the state, with the lightest winds expected over the western islands.
Surf along north facing shores will gradually lower today through early Saturday, as the current northwest swell declines. A new moderate northwest swell will boost north shore surf late Saturday through Monday, with a peak expected on Sunday. After a very small day along north facing shores on Tuesday, a new small to moderate size west-northwest swell is expected to bring another boost to north shore surf Wednesday through late next week.
Surf along east facing shores will hold fairly steady through Saturday, with a small increase expected over the weekend as the trades strengthen. East shore surf will then lower a notch Monday as the trades ease slightly, then hold at fairly typical levels through the remainder of next week.
Several overlapping south swells will keep some surf in place along south facing shores through the weekend. A larger long- period south swell will fill in late Sunday and Sunday night, giving a bit of a boost to south shore surf Monday through Wednesday, with smaller surf expected for the tail end of next week.
Surf is expected to remain below advisory levels along all shores during the next 7 days.

HFO Watches/Warnings/Advisories

Small Craft Advisory from noon today to 6 AM HST Monday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov