Photo Credit: James Grenz

Hilo

Today: Scattered showers. Partly sunny, with a high near 80. East southeast wind 6 to 9 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 62. South southwest wind around 6 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Friday: Scattered showers. Partly sunny, with a high near 79. Southeast wind 5 to 8 mph. Chance of precipitation is 40%. 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. Light west southwest wind. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Isolated showers before midnight. Partly cloudy, with a low around 62. Light and variable wind. Chance of precipitation is 20%.

Friday: Isolated showers after noon. Mostly sunny, with a high near 81. North wind around 6 mph becoming calm in the afternoon. Chance of precipitation is 20%.

Waimea

Today: Scattered showers, mainly after 1pm. Mostly sunny, with a high near 77. Light west wind. Chance of precipitation is 40%. New precipitation amounts between a tenth and quarter of an inch possible.

Tonight: Scattered showers, mainly after 1am. Partly cloudy, with a low around 47. Light and variable wind. Chance of precipitation is 40%. New precipitation amounts between a tenth and quarter of an inch possible.

Friday: Scattered showers. Mostly sunny, with a high near 77. East wind 3 to 7 mph. Chance of precipitation is 40%. New precipitation amounts between a tenth and quarter of an inch possible.

Kohala

Today: Showers likely, mainly after noon. Partly sunny, with a high near 74. Light and variable wind. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 41. East wind 5 to 7 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Friday: Showers likely, mainly after noon. Partly sunny, with a high near 75. Breezy, with an east wind 11 to 21 mph, with gusts as high as 29 mph. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

South Big Island

Today: Scattered showers, mainly before noon. Mostly sunny, with a high near 80. Breezy, with an east wind 14 to 17 mph, with gusts as high as 22 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers, mainly before midnight. Partly cloudy, with a low around 70. Breezy, with an east northeast wind 13 to 16 mph, with gusts as high as 21 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Friday: Isolated showers. Mostly sunny, with a high near 80. Breezy, with an east wind 16 to 21 mph, with gusts as high as 26 mph. Chance of precipitation is 20%.

Puna

Today: Scattered showers. Partly sunny, with a high near 79. Southeast wind 6 to 8 mph. Chance of precipitation is 40%. New precipitation amounts between a tenth and quarter of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 60. South southeast wind around 5 mph becoming light and variable after midnight. Chance of precipitation is 50%. New precipitation amounts between a tenth and quarter of an inch possible.

Friday: Showers likely, mainly before noon. Partly sunny, with a high near 78. East northeast wind around 9 mph. Chance of precipitation is 60%. New precipitation amounts between a tenth and quarter of an inch possible.

Waikoloa

Today: Isolated showers after noon. Mostly sunny, with a high near 82. West wind 3 to 7 mph. Chance of precipitation is 20%.

Tonight: Mostly clear, with a low around 60. Light southeast wind.

Friday: Isolated showers after noon. Sunny, with a high near 82. Light and variable wind. Chance of precipitation is 20%.

Detailed Forecast

Synopsis

A strong low pressure system north to northwest of the Hawaiian Islands with a stalled cold front just northwest of Kauai will keep light southerly winds in the forecast today. A cloud boundary over the Kauai channel near Oahu and instability aloft will enhance shower activity over the western islands through tonight. The low north of the state will drift slowly northeastward away from the islands allowing trade winds to return by Friday. Trade winds will strengthen into the moderate to breezy range this weekend as high pressure builds over the region. Passing showers will favor windward and mountain areas from Friday into the first half of next week.

Discussion

Satellite imagery this morning continues to show a strong low pressure system roughly 800 miles north to northwest of the Hawaiian Islands. A weakening stationary front associated with this low remains stalled just 100 miles northwest of Kauai. Light southerly winds will continue southeast of the front today with unstable showers developing over the western islands. Brief passing showers are forecast over the eastern half of the state today under the influence of a high pressure ridge. South of the state, a subtropical jet stream with upper level cirrus ice clouds will linger near the Big Island for the next few days.
The low pressure system located far north of the islands will slowly weaken and drift toward the northeast over the next few days. Expect unsettled weather conditions with periods of enhanced showers over the western islands of Niihau, Kauai and Oahu through tonight. Most of the heavier shower activity will develop along the convergence boundary near west Oahu, this boundary will drift slowly westward and diminish over the next 24 hours. The stalled cold front northwest of Kauai will also weaken and begin to move westward away from the state.
The subtropical ridge will build in north of the island chain by Friday, as the low north of the islands departs the pattern. Trade winds will increase into the moderate to breezy range lasting through the weekend. Passing shower activity will shift back towards a typical trade wind pattern, favoring windward and mountain areas of each island with the highest coverage in the overnight to early morning hours. More isolated to scattered shower activity remains in the forecast over leeward locations.
This returning trade wind weather pattern will hold into the first half of next week. Global weather forecast models remain in good agreement with this short to medium range solution. Differences between the latest American (GFS) model and the European (ECMWF) model show up in our passing shower activity from Sunday onward. Blended both models a bit, leaning heavier on the GFS model in the long range, to reduce errors in precipitation chances and weather.
Monday through Wednesday…Longer range forecast guidance is hinting at a convergence band of moisture, likely from an old dissipated frontal boundary will move into the islands from east to west on the trade winds early Monday morning through Tuesday. This unstable cloud band may enhance shower activity mainly along windward and mountain slopes. By Wednesday, another low pressure system and cold front approach the islands from the northwest. Models are suggesting some prefrontal convergence bands will show up ahead of the front.
Unsurprisingly, there are rather large differences between the GFS and ECMWF forecasts with both the strength and timing of this next frontal system as it approaches the state. Both model solutions diverge from Wednesday onward with the location of the frontal band near the islands. Please stay tuned for updates in next week’s weather forecast, as rainfall coverage with this next frontal system may change significantly over time.

Aviation

Early this morning, a surface front is located near Kauai with a pre-frontal convergence band in the Kauai Channel near west Oahu. The pre-frontal convergence is supporting showers and low clouds within this band, as seen in latest satellite and radar imagery. Showers and MVFR conditions will continue to favor Oahu and Kauai as the front and convergence band temporarily stall. AIRMET Sierra for mountain obscuration remains in effect for Kauai and Oahu, and this is expected to persist through at least the rest of the morning.
Today, the front will merge with the convergent band, weaken, and then drift west of the area on Friday as a surface trough. Showers and tempo MVFR conditions will continue to favor the western islands throughout the day but conditions should gradually improve, especially by this evening and tonight. Elsewhere, showers will favor east and southeast facing slopes and coasts under a weak southerly flow regime with prevailing VFR conditions. Additionally, an upper jet passing near the Big Island today could create some moderate upper level turbulence, especially for the southern half of the state before weakening and moving east of the area tonight.

Marine

A slow-moving cold front just NW of Kauai has an associated convergence band near Kauai and Oahu that is acting as a focus for cloud and shower development. Meanwhile, a surface ridge extends over Maui and the Big Island from the ENE, where mostly dry conditions prevail. Little overall change is expected today, with showers persisting between Kauai and Oahu, occasionally moving ashore. The front will gradually dissipate tonight and Friday, leaving a weak surface trough near Kauai before the trough moves W of the islands by the weekend. In the meantime, SE flow near the Big Island turns to the SW near Kauai as the flow rounds the surface ridge, but winds will become variable in most areas by tonight. High pressure will build N of the islands over the next couple of days, supporting strengthening trade winds statewide, with trade winds building from E to W Friday and Friday night. A Small Craft Advisory (SCA) will likely be required in the typically windy zones as trade winds build.
Surf will be elevated (and close to High Surf Advisory (HSA) levels) along N and W facing shores today, before gradually diminishing into Saturday. A moderate NNW swell on Sunday is expected to peak below HSA-levels, with a WNW swell possible around Wednesday. Surf along E facing shores will remain below HSA levels, but elevated in the short term due to a large area of fresh to strong trade winds upstream of the islands. A downward trend is expected over the weekend. Surf along S facing shores will trend up today, then remain elevated (but below HSA levels) into next week as overlapping, long-period SSW swells arrive from the S Pacific.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov