Hilo

Today: Partly sunny with scattered showers. Highs around 77 near the shore to 62 to 67 at 4000 feet. North winds up to 10 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 61 near the shore to around 47 at 4000 feet. Light winds. Chance of rain 50 percent.

Tuesday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs around 78 near the shore to 62 to 67 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Kona

Today: Mostly sunny. Scattered showers in the afternoon. Highs 77 to 82 near the shore to around 68 near 5000 feet. Northwest winds up to 10 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Isolated showers in the evening. Lows 61 to 67 near the shore to around 48 near 5000 feet. Light winds. Chance of rain 20 percent.

Tuesday: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 77 to 82 near the shore to around 68 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Today: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs around 76 near the shore to 68 to 75 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows around 60 near the shore to 46 to 54 near 3000 feet. East winds up to 10 mph. Chance of rain 40 percent.

Tuesday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 77 near the shore to 68 to 75 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Kohala

Today: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs around 76 near the shore to 68 to 75 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows around 60 near the shore to 46 to 54 near 3000 feet. East winds up to 10 mph. Chance of rain 40 percent.

Tuesday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 77 near the shore to 68 to 75 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

South Big Island

Today: Mostly sunny. Scattered showers in the afternoon. Highs around 80 near the shore to around 69 near 5000 feet. East winds up to 15 mph. Chance of rain 40 percent.

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 63 near the shore to around 47 near 5000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Tuesday: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 80 near the shore to around 69 near 5000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Puna

Today: Partly sunny with scattered showers. Highs around 77 near the shore to 62 to 67 at 4000 feet. North winds up to 10 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 61 near the shore to around 47 at 4000 feet. Light winds. Chance of rain 50 percent.

Tuesday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs around 78 near the shore to 62 to 67 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Waikoloa

Today: Mostly sunny. Scattered showers in the afternoon. Highs around 79 near the shore to 63 to 70 above 4000 feet. Northeast winds up to 10 mph shifting to the northwest in the afternoon. Chance of rain 40 percent.

Tonight: Mostly clear. Isolated showers in the evening. Lows around 65 near the shore to 43 to 51 above 4000 feet. Southeast winds up to 10 mph. Chance of rain 20 percent.

Tuesday: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 79 near the shore to 63 to 70 above 4000 feet. Light winds becoming north up to 10 mph in the afternoon. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A high pressure ridge far north of the islands will keep light to moderate trade winds in the forecast through Tuesday as a surface trough north of the islands keeps the trade winds weaker than normal. An upper level low lingering northeast of the island chain will produce passing showers for windward and mountain areas, especially over the eastern islands of Maui and the Big Island. The upper low will move over the islands from Wednesday onward as trade winds strengthen increasing wind speed and producing wet weather trends across the state lasting through the weekend.

Discussion

Comparing infra-red and water vapor satellite imagery this morning we see a large upper low northeast of the island chain and a low level circulation north of the islands associated with this upper level system. This upper low will help lift the trade wind inversion heights in the short term near Maui and the Big Island keeping passing showers in the forecast for both islands. Thunderstorms are developing around the upper low with a few forming just 150 miles east of Hilo. A slow moving cold front is also located west of Kauai near 170W longitude.
In the short term forecast, a high pressure system far north of the Hawaiian Islands will produce trade winds over the region. However, a surface trough associated with the upper level low northeast of the state will serve to weaken these wind speeds keeping them in the light to moderate range through Tuesday. The upper low will also help to raise the height of the trade wind inversion over the eastern islands allowing higher cloud tops and deeper convection to form. This weather pattern will produce more trade wind showers over the eastern islands through Tuesday with more stable conditions and less windward showers over the islands of Kauai, Niihau, Oahu and Molokai. The upper low will slowly drift westward over the next few days setting up near Molokai on Wednesday as a high pressure ridge strengthens north of the state.
The weather pattern changes from Wednesday onward as the upper low drifts over the island chain with strengthening trade winds and significant wet weather trends. Most of the passing showers will affect windward and mountain areas, however some of the stronger showers will drift into typically drier leeward sections. Enough instability over the region and surface heating over mountain slopes will produce isolated thunderstorms over the Big Island each afternoon from Wednesday through Friday. Medium to long range forecast guidance continues to show upper level troughing over the state lasting through the weekend. A positive signal for an extended period of wet trade wind weather.

Aviation

Moderate trades from the NNE are focusing limited clouds and showers over the windward slopes of the smaller islands this morning while heavier showers over Windward Big Island have largely been pushed offshore by the land breeze. As trades weaken today, a modified sea breeze pattern will emerge. This will support an increase in clouds and showers over the most leeward and sheltered zones. Evolution of convection on the Big Island will be similar to Sunday with robust afternoon shower development tending to focus over southeast-facing slopes.
AIRMET Sierra for mountain obscuration remains in effect for Windward Big Island. Conditions are expected to improve during the next few hours.

Marine

Winds will ease to light to locally moderate and shift out of an easterly direction beginning this morning. The islands will remain in a weak wind area between surface highs to the northwest and northeast through Tuesday. Trades will slowly rebuild Tuesday night and Wednesday as high pressure strengthens far north of the state. A Small Craft Advisory (SCA) will likely be needed then for the typically windy waters around the Big Island and Maui, and an expansion to additional waters is possible late in the week.
Surf is at a minimum on all shores currently, but swells from around the compass are expected during the next few days. The latest in a series of west-northwest swells will arrive late today and likely push north and west shore surf above High Surf Advisory (HSA) levels during the peak Tuesday and Wednesday. Due to the significant initial west component, west facing shores of the Big Island could see surf nearing High Surf Warning levels (12 feet for that area) late Tuesday. In addition, seas mainly around Kauai could reach 10 ft and require an SCA Tuesday into Wednesday. Though probably smaller, another pulse of west- northwest swell will arrive Thursday or Friday, followed by a decline over the weekend. An out of season south-southwest swell will arrive late today, cause south shore to peak near the summertime average late Tuesday, then lower through the work week. A short period north-northeast swell will briefly boost east shore surf to near seasonal average today and Tuesday. As winds build over and east of the islands later in the week, rough trade wind swell could lead to surf near the HSA level along east-facing shores.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov