Weather Forecast

Hawaii County Weather Forecast for April 18, 2021

April 18, 2021, 7:16 AM HST
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Photo Credit: James Grenz

Hilo

Today: Scattered showers, mainly before noon. Partly sunny, with a high near 82. Light and variable wind becoming east 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 after midnight. Mostly cloudy, with a low around 63. East wind 5 to 7 mph becoming southwest after midnight. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Monday: Scattered showers, mainly before noon. Partly sunny, with a high near 83. Southwest wind 6 to 13 mph becoming east southeast in the afternoon. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Kona

Today: Isolated showers after noon. Partly sunny, with a high near 83. Light and variable wind becoming southwest around 6 mph in the morning. Chance of precipitation is 20%.

Tonight: Isolated showers. Partly cloudy, with a low around 63. Light and variable wind becoming north around 6 mph. Chance of precipitation is 20%.

ARTICLE CONTINUES BELOW AD

Monday: Isolated showers after noon. Mostly sunny, with a high near 83. Light and variable wind becoming west 5 to 7 mph. Chance of precipitation is 20%.

Waimea

ARTICLE CONTINUES BELOW AD

Today: Scattered showers, mainly before noon. Partly sunny, with a high near 74. Northeast wind 10 to 14 mph, with gusts as high as 18 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers, mainly after midnight. Partly cloudy, with a low around 52. Northeast wind 5 to 14 mph becoming southwest after midnight. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Monday: Scattered showers after noon. Mostly sunny, with a high near 74. West wind around 6 mph becoming calm in the afternoon. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Kohala

ARTICLE CONTINUES BELOW AD

Today: Scattered showers. Partly sunny, with a high near 67. Breezy, with an east wind 9 to 18 mph, with gusts as high as 25 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers, mainly after midnight. Partly cloudy, with a low around 44. Breezy, with an east wind 16 to 21 mph becoming east southeast 5 to 10 mph after midnight. Winds could gust as high as 30 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Monday: Scattered showers after noon. Mostly sunny, with a high near 67. Southwest wind 5 to 8 mph becoming east northeast in the afternoon. Chance of precipitation is 30%.

South Big Island

Today: Mostly sunny, with a high near 83. Breezy, with an east northeast wind 18 to 22 mph, with gusts as high as 28 mph.

Tonight: Isolated showers after midnight. Partly cloudy, with a low around 69. Windy, with an east northeast wind 20 to 23 mph, with gusts as high as 29 mph. Chance of precipitation is 20%.

Monday: Isolated showers. Mostly sunny, with a high near 83. Breezy, with an east wind 16 to 22 mph, with gusts as high as 29 mph. Chance of precipitation is 20%.

Puna

Today: Scattered showers. Partly sunny, with a high near 79. Light and variable wind becoming east northeast 5 to 8 mph in the afternoon. 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 61. East northeast wind 5 to 7 mph becoming calm. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Monday: Scattered showers, mainly before noon. Partly sunny, with a high near 81. Southwest wind 6 to 10 mph becoming southeast in the afternoon. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Waikoloa

Today: Mostly sunny, with a high near 80. East wind 6 to 9 mph becoming northwest in the afternoon.

Tonight: Partly cloudy, with a low around 62. North wind 5 to 8 mph becoming light and variable.

Monday: Isolated showers after noon. Mostly sunny, with a high near 80. West northwest wind 5 to 8 mph becoming calm in the afternoon. Chance of precipitation is 20%.

Detailed Forecast

Synopsis

Moderate trade winds will hold on through tonight, with a few showers primarily affecting windward and mauka areas. The trades will become disrupted Monday, setting up a land and sea breeze pattern that will last through Wednesday. Rather dry weather will continue with a few showers affecting areas near the coast at night and over interior areas during the afternoon and early evening hours. Moderate trade winds should return Thursday and linger into next weekend, bringing more typical but drier than normal trade wind weather.

Discussion

Currently at the surface, a 1025 mb high is centered around 1650 miles northeast of the Big Island, with ridging extending westward to a location around 600 miles due north of Kauai. Meanwhile a dissipating surface trough is located a few hundred miles northeast of Hilo. Light to moderate trades prevail in most areas early this morning, although land breezes have developed in many leeward locales as well as windward sections of Kauai. Infrared satellite imagery shows a mix of high and low clouds producing variably cloudy conditions, with cloud coverage highest in windward areas and over much of Kauai. Radar imagery shows scattered showers affecting windward sections of Maui County, with very little shower activity elsewhere at the moment. Main short term concern revolves around trade wind trends during the next couple days.
The surface trough northeast of the islands will continue to dissipate today, while the high northeast of the state steadily strengthens. This will allow the trades to ramp back up to moderate speeds. This will be short lived however, as a new cold front will be approaching from the northwest Sunday night and Monday, easing the trades and shifting winds around to the east- southeast. The east-southeast winds will hold in place through mid week, with terrain blockage bringing a land and sea breeze set up to the smaller islands Monday through Wednesday. A new surface ridge is forecast to develop north of the islands Wednesday night, bringing a return of moderate trades Thursday into next weekend.
As for the remaining weather details, fairly dry conditions are expected statewide during the next 7 days. A cloud band associated with an old front currently in the vicinity of Maui County will begin to shift westward overnight. Scattered showers are expected over windward areas this morning, with a stray shower possibly spilling over into leeward areas. Shower coverage should diminish quickly late this morning into early this afternoon, with only a few isolated showers possible mainly in windward locales and over the leeward Big Island slopes.
Tonight a few windward showers can be expected as the low level boundary layer flow tips east-southeasterly. A land breeze and sea breeze pattern will set up Monday through Wednesday, with a few showers possible in coastal areas favored in an east-southeasterly flow at night, and over interior areas during the afternoon and early evening hours. Models are showing a bit of an increase in deep moisture overspreading the western islands from the south Tuesday and Wednesday, which could bring a few more showers to Kauai and Oahu during this time. A more typical but drier than normal trade wind pattern appears to return Wednesday night and linger into next weekend.

Aviation

A weak high pressure ridge north of the region will keep stable light to moderate trade winds in the forecast today. A few passing showers are possible in this stable pattern with VFR conditions forecast over the next 24 hours.
No AIRMETs in effect and none are expected.

Marine

Moderate to fresh northeast to east trade winds will persist into tonight, then shift out of the southeast and diminish through the first half of the week as a weakness in the ridge develops to the north. This pattern shift will translate to a land and sea breeze regime developing along the coasts for most areas beginning early Monday. The exception will be over the windward waters of the Big Island along the Hamakua coast and around South Point where moderate to fresh southeast winds will continue. A return of moderate to fresh easterly trades will be possible for all waters late Wednesday through the second half of the week.
Surf along north facing shores will hold steady through Monday due to a persistent short-to-medium period mix of north- northwest to north-northeast energy moving through. As this energy eases into Tuesday, a medium-period, moderate northwest swell from a nearby source should arrive and begin to build down the island chain Tuesday night through Wednesday. This will be a long- lived event that should hold into next weekend.
Surf along south facing shores will remain up into Monday as the Tasman swell that arrived Saturday moves through. A gradual downward trend is anticipated Tuesday through midweek. A similar south-southwest swell will be possible late in the week.
Surf along east facing shores will remain small through the week.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov

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