Hilo

Today: Scattered showers. Partly sunny, with a high near 80. Light and variable wind becoming east northeast 5 to 8 mph in the afternoon. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Showers likely, mainly after midnight. Mostly cloudy, with a low around 67. East northeast wind 5 to 8 mph becoming calm. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

Friday: Scattered showers. Partly sunny, with a high near 81. Calm wind becoming east 5 to 8 mph in the afternoon. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Kona

Today: Isolated showers after 1pm. Mostly sunny, with a high near 80. Calm wind becoming southwest 5 to 8 mph in the afternoon. Chance of precipitation is 20%.

Tonight: Isolated showers before 1am. Partly cloudy, with a low around 66. South wind 5 to 9 mph becoming calm after midnight. Chance of precipitation is 20%.

Friday: Isolated showers after 1pm. Mostly sunny, with a high near 80. Light and variable wind becoming west 5 to 10 mph in the morning. Chance of precipitation is 20%.

Waimea

Today: Scattered showers. Partly sunny, with a high near 74. Windy, with a northeast wind 17 to 22 mph increasing to 23 to 28 mph in the afternoon. Winds could gust as high as 40 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 57. Windy, with a northeast wind 21 to 24 mph, with gusts as high as 34 mph. Chance of precipitation is 40%. New precipitation amounts between a tenth and quarter of an inch possible.

Friday: Scattered showers. Partly sunny, with a high near 76. Breezy, with a northeast wind 16 to 18 mph, with gusts as high as 25 mph. Chance of precipitation is 40%. New precipitation amounts between a tenth and quarter of an inch possible.

Kohala

Today: Showers likely. Mostly cloudy, with a high near 68. Very windy, with an east wind around 31 mph, with gusts as high as 45 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Showers likely. Mostly cloudy, with a low around 56. Very windy, with an east wind around 31 mph, with gusts as high as 45 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

Friday: Showers likely. Mostly cloudy, with a high near 69. Windy, with an east wind 16 to 24 mph, with gusts as high as 34 mph. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

South Big Island

Today: Isolated showers before noon. Sunny, with a high near 83. Windy, with an east wind 28 to 30 mph, with gusts as high as 39 mph. Chance of precipitation is 20%.

Tonight: Isolated showers. Partly cloudy, with a low around 72. Windy, with an east northeast wind 26 to 29 mph, with gusts as high as 37 mph. Chance of precipitation is 20%.

Friday: Sunny, with a high near 83. Windy, with an east wind 23 to 26 mph, with gusts as high as 34 mph.

Puna

Today: Showers likely, mainly before noon. Mostly cloudy, with a high near 75. Northwest wind 9 to 14 mph becoming northeast in the afternoon. Winds could gust as high as 18 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 64. Northeast wind 8 to 13 mph becoming northwest after midnight. Chance of precipitation is 70%. New precipitation amounts between a tenth and quarter of an inch possible.

Friday: Showers likely, mainly before noon. Partly sunny, with a high near 76. Northwest wind 7 to 9 mph becoming east northeast in the afternoon. Chance of precipitation is 60%. New precipitation amounts between a tenth and quarter of an inch possible.

Waikoloa

Today: Sunny, with a high near 83. Windy, with a southeast wind 5 to 10 mph becoming east northeast 18 to 23 mph in the afternoon. Winds could gust as high as 32 mph.

Tonight: Mostly clear, with a low around 65. Windy, with an east northeast wind 16 to 24 mph, with gusts as high as 34 mph.

Friday: Increasing clouds, with a high near 83. East wind 8 to 11 mph becoming north in the afternoon.

Detailed Forecast

Synopsis

Gusty trade winds will persist through Friday, but the trades will weaken slightly this weekend. Low clouds and brief trade showers will continue along windward facing sections, especially during nights and mornings. Leeward areas of the smaller islands will be mostly dry, but upslope sections of the leeward Big Island will continue to have isolated showers each afternoon and evening. The trade winds are expected to gradually strengthen again early next week.

Discussion

A 1031 mb surface high pressure system is centered near 36N 164W, or about 1000 miles north-northwest of Honolulu. The very tight pressure gradient south of this feature is maintaining locally windy trade winds across the main Hawaiian Islands early this morning. Aloft, mid-tropospheric ridging is also keeping stable atmospheric conditions over the region. Loops of satellite imagery and radar reflectivity data show the robust low-level trade wind flow is transporting broken low clouds with embedded scattered showers into most of the windward facing slopes and coastal sections of the islands.
The latest model output shows no big changes to the current forecast. Expect the typical June breezy trade wind weather pattern to persist over the Hawaiian Islands. Little significant rainfall accumulation is expected since the atmosphere over the state will remain strongly capped below 7 thousand feet. Low clouds and brief showers will continue along windward sections, especially during nights and mornings. Mostly clear skies will persist over most leeward sections of the smaller islands, but there might be a stray shower or two. The upslope sections of the leeward Big Island will continue to have clouds and isolated showers each afternoon and evening. Note that the global models indicate that the remnant moisture from a former frontal band, which is currently near 23N 150W, may bring a slight increase in trade showers to portions of Kauai and Oahu on Friday.
By this weekend, the forecast models show a complex low pressure system developing over the northeast Pacific. This is supposed to cause the surface high, which is currently far north-northwest of the islands, to weaken. At the same time a weak surface ridge is expected to move down to near latitude 25N. This scenario will likely weaken the trade wind speeds this weekend. However, it appears that the lightest winds will be east-northeast of the islands, with light to moderate trade winds persisting across most of the state.
Looking ahead to early next week, the surface high will build far north of the state, which will once again tighten the pressure gradient across the region. Therefore, the trade winds will gradually strengthen starting Monday night or Tuesday. The forecast models also show a ragged band of low clouds and showers associated with a weakening frontal boundary pushing south toward the islands early next week. This may potentially result in an increase in trade showers over portions of Kauai, and possibly Oahu, next Tuesday and Wednesday.

Aviation

A large high pressure ridge N of the islands will keep breezy gusty trade winds in the forecast through this evening. These stronger trade winds will produce clouds and brief passing showers over windward and mountain sections of each island. Cloud and shower trends will increase in the overnight to early morning hours where brief periods of MVFR conditions are possible along these favored windward slopes.
AIRMET Sierra in effect for Mountain Obscuration over the N and E slopes of Kauai, Oahu, Molokai, Maui and Big Island. This AIRMET will likely decrease in coverage after sunrise.
AIRMET Tango remains in effect for Moderate Turbulence over and SW through NW of island mountains due to strong winds flowing over higher terrain features. This AIRMET will likely continue into Friday.

Marine

Fresh to strong easterly trade winds will continue into Friday as the gradient remains tight over the region. A weakness in the ridge is expected to form to the northeast Friday into the weekend as a front dips southward over the northeast Pacific. Easterly trades will respond and ease into the moderate to fresh category, potentially enough to relax the Small Craft Advisory for all areas by Saturday.
Surf along east facing shores will remain rough today due to the strong trades in place. A downward trend is expected Friday through the weekend due to the upstream trades being disrupted from the aforementioned front dipping southward over the northeast Pacific.
Surf along north facing shores will remain near flat levels through the weekend, with the exception being along the typical areas exposed to trade wind energy wrapping in. A small, low/medium- period, north-northeast swell will be possible early next week due to broad low pressure setting up over the Gulf of Alaska.
Surf along south facing shores will remain small through the weekend with mainly small, background, southerly swells rolling through. Favorable pattern unfolding within Hawaii’s swell window across the southern hemisphere this weekend could translate to an upward trend locally by the third week of June.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Friday for Kaiwi Channel, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.
Small Craft Advisory until 6 PM HST this evening for Kauai Northwest Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Maui County Windward Waters, Maui County Leeward Waters, Big Island Windward Waters.

Data Courtesy of NOAA.gov