Hawaii County climate forecast is March 30, 2021

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Photo credit: James Grenz


Today: a few showers. Partly sunny with a high near 77. Light and changeable winds blowing from 5 to 9 miles per hour from the east in the afternoon. The probability of precipitation is 50%. New rainfall levels of less than a tenth of an inch possible.

Tonight: A few showers. Mostly cloudy with a low of about 64. East winds 5 to 8 mph, calm after midnight. The probability of precipitation is 30%. New rainfall levels of less than a tenth of an inch possible.

Wednesday: A few showers. Partly sunny with a high near 77. Light and changeable wind blowing 5 to 11 miles per hour from the northeast in the afternoon. The probability of precipitation is 50%. New rainfall levels of less than a tenth of an inch possible.








Southern big island









Light to moderate trade winds will persist today, with conditions over the islands, particularly on Kauai, remaining somewhat volatile. The showers will favor windward areas this morning and spread to the leeward and interior areas this afternoon. A more typical trade wind pattern will return tonight and will continue until early next week. During this time, showers in windward and mauka areas are preferred, with occasional stray showers spreading downwind. Trades will gradually pick up from Wednesday, with moderate to breezy trades on Thursday and Friday rising to breezy and locally windy levels this weekend through early next week.


Currently, at the surface, a high of 1039 mb is located about 2000 miles northeast of Honolulu, while a low of 1010 mb is located about 950 miles west-northwest of Kauai. The local gradient is prevented from reaching its full potential by a trough about 1050 miles north of the state. As a result, trades across the country generally hold up at light to moderate levels, with land breezes being present in some of the more protected areas. Infrared satellite imagery shows partially to mostly cloudy conditions across the state, with cloud cover being greatest in windward areas. Meanwhile, radar images show scattered showers moving into windward areas, some showers over the Big Island under the wind, and very little shower activity in other areas under the wind. The top short-term concern revolves around the potential for heavy rainfall on Kauai this afternoon.
There will be light to moderate trade over the islands today as the low pressure area northwest of the state remains nearly stationary. The slope will be light enough to allow sea breezes to develop in some of the more protected areas this afternoon. That low in the far northwest of the state will recede west tonight and Wednesday, allowing moderate trade winds to return to the entire chain of islands. Trades will strengthen to moderate and locally breezy levels on Thursday and Friday as a new strong high builds north of the islands. Trades are then expected to intensify to airy and locally windy levels over the weekend through early next week as the strong high slowly settles south and closer to the island chain.
As for the remaining weather details, the showers this morning will favor the windward and mauka areas and spread to the leeward and inland areas this afternoon as local sea breezes support the shower development. The most unstable weather will be over the far western end of the state, so the Flash Flood Watch will remain in effect for Kauai. Elsewhere, the potential for flash floods appears to be low.
A truer east-northeast trade wind pattern is expected to take hold tonight and continue until early next week. Fairly typical trade winds will prevail throughout the period, with showers favoring windward and mauka areas, especially during the night and early morning hours, with an occasional shower spreading downwind from time to time.


Light to moderate, low-level trade winds will continue across the state through tonight. Expect brief showers of trade along east to southeast facing sections of the islands today. This can lead to short term MVFR conditions in some windward and mauka sections of the state. The weaker trade wind regime will likely allow local sea wind circulations to become established on most of the islands by this afternoon. As a result, clouds and showers are expected to form over the leeward and interior parts of the state later today. This may result in short-term MVFR conditions this afternoon, especially in areas with heavier rainfall.
AIRMET Sierra remains in effect for mountain darkening over the northeast to the southeast of the Big Island. This AIRMET might later be needed for some of the smaller islands when extensive cloud cover and precipitation develop, especially on Kauai.


Two weak surface pressure systems northwest and north-northeast of the Hawaiian Islands will keep weaker trade winds in the forecast today. The Small Craft Advisory was canceled this morning due to these lighter winds. From Wednesday a high pressure ridge will build up in the region. Trade winds will intensify in the fresh to strong area by the weekend.
Expect a little surf for all banks on the weekend. A few small north to northwest swells will continue to penetrate the area through Thursday. Surfing along the north and west coasts will continue to decrease from Friday through the weekend. Trade winds will continue to keep the surf stable along the east-facing coasts through Friday. The surf on the east coast will trend a little higher from Saturday through early next week as trades over and upstream of the islands get stronger. Surfing along the south-facing coastlines will remain elevated through Wednesday before dropping closer to the seasonal average from Thursday through early next week.

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Flash Flood Watch for Kauai by this afternoon.

Data courtesy of NOAA.gov

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