Hawaii County Climate Forecast is April 04, 2021

Hilo

Today: Occasional showers. High near 76. East winds at 10 miles an hour. The risk of precipitation is 80%. New rainfall levels of less than a tenth of an inch are possible.

Tonight: Occasional showers. Low around 64. Light west-southwest wind. The risk of precipitation is 80%. New rainfall between a quarter and a half inch is possible.

Monday: Showers likely, mostly before noon. Mostly cloudy with a high of nearly 78. East winds at 11 miles per hour. The risk of precipitation is 70%. New levels of rainfall between a tenth and a quarter of an inch are possible.

Kona

Today: isolated showers and thunderstorms after 1 p.m. Increasing clouds with a high of nearly 79. West winds at 7 miles per hour. The risk of precipitation is 50%. New rainfall less than a tenth of an inch, except during thunderstorms greater amounts.

Tonight: isolated showers and thunderstorms before 1am, then isolated showers. Cloudy, then gradually cloudy, with a low of 62. West winds of 8 miles per hour turns east-southeast in the evening. The risk of precipitation is 50%. New rainfall less than a tenth of an inch, except during thunderstorms greater amounts.

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Monday: isolated showers before 7 a.m., then isolated showers after 1 p.m. Increasing clouds with a high wind of nearly 79. East-southeast winds at 9 miles per hour going west in the morning. The risk of precipitation is 40%. New rainfall levels of less than a tenth of an inch are possible.

Waimea

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Today: Showers likely, mostly before noon. Partly sunny, with a high of nearly 74. East-northeast winds at 14 mph, with gusts as high as 18 mph. The risk of precipitation is 60%. New rainfall between a quarter and a half inch is possible.

Tonight: Showers likely. Mostly cloudy, with a low of 53. Breezy, with an easterly wind of 15 mph, with gusts as high as 21 mph. The risk of precipitation is 60%. New rainfall between a quarter and a half inch is possible.

Monday: a few showers. Partly sunny, with an altitude of nearly 75. Airy, with an east-northeast wind at 17 mph, with gusts as high as 24 mph. The risk of precipitation is 50%. New rainfall between a quarter and a half inch is possible.

Kohala

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Today: Showers likely. Cloudy, with a high of nearly 70. Northeasterly winds at 13 mph. The risk of precipitation is 70%. New levels of rainfall between a tenth and a quarter of an inch are possible.

Tonight: Showers likely. Mostly cloudy, with a low of around 46. Breezy, with an easterly wind around 15 mph, with gusts as high as 21 mph. The risk of precipitation is 70%. New rainfall between a quarter and a half inch is possible.

Monday: Occasional showers. High near 71. Breezy, with a northeast wind at 15 mph, with gusts as high as 21 mph. The risk of precipitation is 80%. New rainfall between a quarter and a half inch is possible.

South Big Island

Today: Sunny, with a high of almost 76. Windy, with an east-northeast wind at 24 mph, with gusts of up to 31 mph.

Tonight: isolated showers. Partly cloudy, with a low of 71. Windy, with east-northeast winds of 25 mph, with gusts as high as 32 mph. The probability of precipitation is 20%.

Monday: Sunny, with a high near 76. Windy, with an east-northeast wind at 26 mph, with gusts as high as 34 mph.

Feedback

Today: Occasional showers. High near 75. East northeast winds at 9 miles per hour. The risk of precipitation is 80%. New rainfall between a quarter and a half inch is possible.

Tonight: Occasional showers. Low around 62. Light west-northwest wind. The risk of precipitation is 80%. New rainfall between a quarter and a half inch is possible.

Monday: Showers likely. Mostly cloudy with a high of nearly 75. East northeast winds at 13 miles per hour. The risk of precipitation is 70%. New rainfall between a quarter and a half inch is possible.

Waikoloa

Today: 20 percent chance of showers and thunderstorms after noon. Mostly sunny, with a high of nearly 80. Northwest winds at 7 miles per hour.

Tonight: A slight chance of showers and thunderstorms. Partly cloudy with a low of 62. East-northeast winds of 8 miles per hour. The probability of precipitation is 20%.

Monday: Mostly sunny, with a high of nearly 81. Northwest winds at 9 miles per hour.

Summary

High pressure buildings far north of the state will gradually increase the trade winds. An upper trough moving across the islands will bring some high clouds and improve the trade winds today, especially for Maui and the Big Island. The trade winds will decrease on Wednesday and remain moderately strong until next weekend, making for more typical trade wind weather.

discussion

Some changes to the grids with the morning package, but the general forecasting philosophy remains the same. Today lowered the PoPs for some areas of Kauai and Oahu in line with some of the higher resolution model guidelines. The QPF values ​​increased for windward areas, particularly Maui and the Big Island, given the total overnight rainfall and a mix of models showing up tomorrow night. Also lowered the wind speeds a bit from the middle to the end of the week, which is in line with a trend in the models showing that the winds are not quite as strong as previously forecast, but still expect moderate trades towards the end of the week.
High pressure to the north will maintain the flow of trade winds. The almost stationary surface in the northeast will remain in place for the next few days. As the high slowly moves eastward and intensifies, the resulting pressure gradient over the islands is expected to intensify, which will cause our winds to rise slightly. Frontal remains riding the Trades have reached the windward sides of the islands, with the main overnight focus being on Maui, with some making it to Oahu.
An upper trough axis that is roughly northeast to southwest over the western end of the state overnight will continue to affect our weather until tonight. High clouds pour over the islands from the southwest and west on the east side of the trough. The trough also brings colder temperatures to the upper levels of the islands. Both Lihue and Hilo night readings had 500 mb temperatures close to -12 ° C (below normal). Rainwater (PW) in Lihue was about 1 inch (almost normal for April) while in Hilo it was 1.43 inches (slightly above normal). The trough is expected to be east of the islands tomorrow morning. There is a chance that a thunderstorm or two may hit the Big Island this afternoon / evening and as mentioned above, total rainfall levels are likely to be higher than normal trade winds, especially in windward areas. Along with all of this, there is a chance that any precipitation that reaches the Big Island peaks will come in the form of freezing rain and / or snow.
Lower PW values ​​are expected to propagate across the islands from the north past this upper trough, and temperatures of 500MB are expected to return to near normal. Both of these will help induce a drier and more stable mass of air. This should lead to a downward trend in shower activity at the start of the new work week. Expect airy trades to last at least through Tuesday as the high pressure continues in the north. Apart from the typical afternoon showers on the Kona slopes, the showers should again concentrate on windward slopes with predominantly dry leeward conditions.
The trade winds are likely to subside a notch on Wednesday and will remain at moderate strength until next weekend. The JRC and ECMWF have a slow moving middle to upper trough east of the state and a ridge to the west. The islands should stay just far enough away from the trough to create a stable trade wind flow and typical trade wind weather. However, there is currently some uncertainty.

aviation

Boosting trade has resulted in the issuance of AIRMET Tango for Lee Turbulence for the Big Island through Maui. There is potential for additional expansion in the forecast period, especially as trade reversal increases from north to south. In the near future, MVFR will still take precedence over Windward Big Island and Maui, where AIRMET Sierra will remain in effect. As trading initiates greater coverage of low clouds and showers this afternoon through tonight, MVFR for Molokai through Kauai is becoming increasingly likely.
AIRMET Sierra for Mountain Darkening applies to Windward Big Island and Maui.
AIRMET Tango for Lee Turbulence applies to Big Island and Maui.

marine

The high pressure north of the state will keep the strong to strong trade winds up until Wednesday. Trades will dip into the moderate to fresh range by the end of the week as the far north of the islands weakens. A Small Craft Advisory (SCA) is now in effect for the typically windy waters around Maui and the Big Island until 6:00 p.m. Tuesday. The SCA will likely need to expand to include most, if not all, of the ocean zones tonight through Tuesday as trade peaks.
The current north swell will intensify over the next few days and gradually shift in a northeasterly direction. Surfing on the north and east facing shores will follow in a steady increase, with surf likely hitting the High Surf Advisory (HSA) thresholds on the east facing shores by late Monday and then staying at the advisory level through Thursday. This swell will then slowly decrease on Friday until the next weekend. A series of small south swell will move through the islands over the next 7 days, keeping the surf on the south coast near the seasonal average for early spring.

HFO watches / warnings / notices

Small Craft Advisory until 6:00 p.m. HST Tuesday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, and Big Island Southeast Waters.

Data courtesy of NOAA.gov

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