Photo Credit: James Grenz

Hilo

Today: Scattered showers, mainly before noon. Partly sunny, with a high near 83. Calm wind becoming east northeast 5 to 7 mph in the afternoon. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Isolated showers. Mostly cloudy, with a low around 64. East wind 5 to 8 mph becoming west in the evening. Chance of precipitation is 20%.

Saturday: Isolated showers. Mostly sunny, with a high near 84. West southwest wind 5 to 10 mph becoming east southeast in the morning. Chance of precipitation is 20%.

Kona

Today: Scattered showers after noon. Partly sunny, with a high near 80. Light and variable wind becoming west northwest 5 to 9 mph in the afternoon. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers, mainly before midnight. Mostly cloudy, with a low around 63. Northwest wind 5 to 7 mph becoming calm after midnight. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Saturday: Isolated showers after noon. Partly sunny, with a high near 80. Light west wind becoming west northwest 6 to 11 mph in the morning. Chance of precipitation is 20%.

Waimea

Today: Scattered showers. Partly sunny, with a high near 79. Breezy, with a northeast wind 14 to 18 mph, with gusts as high as 26 mph. Chance of precipitation is 30%. New precipitation amounts between a tenth and quarter of an inch possible.

Tonight: Scattered showers, mainly before 7pm. Partly cloudy, with a low around 56. Northeast wind around 14 mph, with gusts as high as 20 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Saturday: Scattered showers, mainly after 1pm. Partly sunny, with a high near 79. Northeast wind 6 to 11 mph becoming west in the afternoon. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Kohala

Today: Scattered showers. Partly sunny, with a high near 65. Breezy, with an east wind 8 to 18 mph, with gusts as high as 26 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers, mainly before midnight. Partly cloudy, with a low around 51. East northeast wind 5 to 8 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Saturday: Scattered showers, mainly after noon. Partly sunny, with a high near 65. Calm wind becoming southwest around 6 mph. Chance of precipitation is 30%.

South Big Island

Today: Isolated showers after noon. Mostly sunny, with a high near 85. Windy, with an east wind 20 to 23 mph, with gusts as high as 30 mph. Chance of precipitation is 20%.

Tonight: Isolated showers before midnight. Partly cloudy, with a low around 72. Breezy, with an east northeast wind 17 to 20 mph, with gusts as high as 25 mph. Chance of precipitation is 20%.

Saturday: Isolated showers after noon. Mostly sunny, with a high near 85. Breezy, with an east northeast wind 11 to 21 mph, with gusts as high as 28 mph. Chance of precipitation is 20%.

Puna

Today: Scattered showers. Partly sunny, with a high near 82. North northwest wind 6 to 11 mph becoming east northeast 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 62. East northeast wind 5 to 8 mph becoming calm. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Saturday: Scattered showers, mainly before noon. Mostly sunny, with a high near 83. West wind 5 to 11 mph becoming east southeast in the morning. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Waikoloa

Today: Scattered showers after noon. Partly sunny, with a high near 85. East wind 5 to 10 mph becoming west in the afternoon. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Partly cloudy, with a low around 64. West wind 5 to 14 mph becoming east in the evening. Winds could gust as high as 18 mph.

Saturday: Isolated showers after noon. Mostly sunny, with a high near 85. West northwest wind 6 to 11 mph becoming light and variable in the afternoon. Chance of precipitation is 20%.

Detailed Forecast

Synopsis

Moderate trade winds will prevail today with passing showers favoring windward and mauka areas. A series of fronts approaching from the northwest will disrupt the trade wind flow over the Holiday weekend, bringing a land and sea breeze pattern to the smaller islands, while light to moderate east-southeasterly winds prevail near the Big Island. Showers will favor interior and leeward areas during the afternoon and early evening hours, with a few showers possible near the coast at night. The lighter winds will will also make it feel more like summer with hot and increasingly more muggy weather expected as the Holiday weekend progresses. More typical trade wind weather will return Tuesday through late next week.

Discussion

Currently at the surface, a 1026 mb high is centered around 1500 miles east-northeast of Honolulu, with a ridge axis extending westward to around 400 miles north of Kauai. The resulting pressure gradient is producing light to moderate trade winds across the island chain early this morning. Infrared satellite imagery shows clear to partly cloudy conditions in most areas, with a bit more substantial cloud cover in some windward locales as well as portions of leeward Big Island. Radar imagery shows scattered showers moving into windward areas, with a stray shower reaching leeward locales from time to time. Main short term concern revolves around trade wind trends during the next couple days.
The ridge of high pressure north of the islands will keep moderate trades in place today, before the trades begin ease tonight as the ridge settles southward. A series of cold fronts approaching from the northwest will suppress the ridge axis further south and closer to the island chain over the Holiday weekend, with the low level boundary layer flow shifting around to the east-southeast. As a result, we should see a land and sea breeze pattern develop over the smaller islands by Saturday afternoon, with this pattern then holding through Memorial Day. Meanwhile light to moderate east- southeasterly winds are expected to prevail near the Big Island. Model solutions show high pressure north and northeast of the state becoming more dominant by Tuesday, and this should bring a return of moderate trade winds to the island chain, with moderate to locally breezy trades then prevailing through late next week.
As for the remaining weather details, no significant rainfall is expected during the next 7 days, with relatively stable conditions holding over the entire island chain. A typical trade wind pattern should hold in place through early Saturday, with a few passing showers affecting mainly windward areas, particularly at night and during the early morning hours. A land and sea breeze pattern is expected over the Holiday weekend, and this should allow for the development of a few showers over interior and leeward areas during the afternoon and early evening hours, while showers remain confined to immediate coastal locales favored in an east-southeasterly boundary layer flow during the overnight and early morning hours. The light east-southeasterly boundary layer flow will also make it feel more like summer with hot and increasingly more muggy weather expected as the Holiday weekend progresses. A more typical trade wind pattern should resume Tuesday through late next week, and while the humidity levels may linger for a day or two, we should see a return to more comfortable conditions by Wednesday or Thursday of next week.

Aviation

A weak high pressure ridge north of the region will continue to produce light to moderate trade winds for most areas through this afternoon. Terrain sheltered airfields, such as western slopes of each island and Lanai, will see more variability in the wind directions. Stable conditions aloft will limit cloud and shower activity with brief passing showers favoring windward and mountain areas. Trade winds will weaken across the region starting later tonight.
No AIRMET’s in effect and none are expected.

Marine

A surface ridge northeast of the state is maintaining moderate trade winds early this morning. A large surface low developing far north of the area from tonight through this weekend will force the surface ridge to move down closer to the state. This will cause the background flow to weaken and veer out of the east-southeast from Saturday through Monday. A new surface high is expected to build north of the area as the low departs on Tuesday. This will likely cause the trade winds to strengthen again from Tuesday through the middle of next week.
Surf is expected to remain below the High Surf Advisory (HSA) criteria along all shorelines through early next week. Several swells arriving from the Southern Hemisphere will maintain small to moderate surf along south facing shores through the Memorial Day Holiday Weekend. Surf heights may briefly drop along south facing shores next Tuesday, but will likely be small to moderate again starting mid-week. The current small northwest swell will gradually lower through Saturday. A new medium period northwest swell arriving early Sunday will cause surf to increase to small to moderate heights along most north and west facing shores from late Sunday through Tuesday. This swell will gradually lower from next Wednesday into Friday. Surf along east facing shores will gradually diminish from tonight into early next week due to the light background flow. As the trade winds return next Tuesday, expect surf to increase slightly along east facing shores around the middle of next week.
See the Coastal Hazard Message (CFWHFO) for information regarding minor coastal flooding during the time of peak high tides this evening.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov