Hilo

Today: Partly sunny with scattered showers. Highs around 85 near the shore to 70 to 75 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 70 near the shore to around 56 at 4000 feet. North winds up to 15 mph. Chance of rain 50 percent.

Wednesday: Partly sunny with scattered showers. Highs around 85 near the shore to 70 to 75 at 4000 feet. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Kona

Today: Mostly sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs 83 to 88 near the shore to around 70 near 5000 feet. Light winds. Chance of rain 20 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 71 to 76 near the shore to around 57 near 5000 feet. Light winds. Chance of rain 20 percent.

Wednesday: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 83 to 88 near the shore to around 70 near 5000 feet. Light winds becoming west up to 10 mph in the afternoon. Chance of rain 20 percent.

Waimea

Today: Partly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 83 near the shore to 70 to 80 near 3000 feet. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 70 near the shore to 58 to 64 near 3000 feet. East winds up to 25 mph. Chance of rain 50 percent.

Wednesday: Partly sunny. Windy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 83 near the shore to 70 to 80 near 3000 feet. East winds up to 30 mph increasing to 10 to 30 mph in the afternoon. Chance of rain 50 percent.

Kohala

Today: Partly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 83 near the shore to 70 to 80 near 3000 feet. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 70 near the shore to 58 to 64 near 3000 feet. East winds up to 25 mph. Chance of rain 50 percent.

Wednesday: Partly sunny. Windy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 83 near the shore to 70 to 80 near 3000 feet. East winds up to 30 mph increasing to 10 to 30 mph in the afternoon. Chance of rain 50 percent.

South Big Island

Today: Breezy. Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 87 near the shore to around 74 near 5000 feet. East winds up to 25 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening. Lows around 72 near the shore to around 55 near 5000 feet. Northeast winds up to 25 mph. Chance of rain 20 percent.

Wednesday: Windy. Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 87 near the shore to around 74 near 5000 feet. East winds 10 to 30 mph. Chance of rain 20 percent.

Puna

Today: Partly sunny with scattered showers. Highs around 85 near the shore to 70 to 75 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 70 near the shore to around 56 at 4000 feet. North winds up to 15 mph. Chance of rain 50 percent.

Wednesday: Partly sunny with scattered showers. Highs around 85 near the shore to 70 to 75 at 4000 feet. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Waikoloa

Today: Breezy. Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 87 near the shore to 71 to 77 above 4000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening. Lows around 74 near the shore to 53 to 60 above 4000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny. Breezy. Highs around 87 near the shore to 71 to 77 above 4000 feet. Northeast winds up to 20 mph.

Detailed Forecast

Synopsis

The trades will strengthen today, with breezy to locally windy conditions then expected through Thursday as a weak low or surface trough slides by to the south of the state. The trades will ease back to moderate and locally breezy levels Friday through early next week. Fairly dry trade wind weather will prevail during the next 7 days, with showers favoring windward and mauka areas mainly at night and during the early morning hours. A stray shower may reach leeward areas at times, but most areas should remain dry.

Discussion

Currently at the surface, a 1030 mb high is centered around 1800 miles north-northeast of Honolulu, while a broad trough of low pressure is located around 700 miles south-southeast of the Big Island. The resulting gradient is producing moderate to locally breezy trade winds across the island chain early this morning. Radar imagery shows scattered showers moving into windward areas, with very little if any rain reaching leeward locales. Main short term focus revolves around trade winds trends and rain chances.
High pressure to the distant north-northeast will shift southward and closer to the islands during the next few days, while a weak area of low pressure, or surface trough, slides by around 300-400 miles south of the state. This should lead to a strengthening of the trades today, with breezy to locally windy conditions then continuing through Thursday, with a peak in trade wind speeds on Wednesday. The trades should ease to moderate and locally breezy levels Friday through early next week, as the high northeast of the state weakens, and the low/trough shifts further west and away from the island chain.
As for the remaining weather details, a fairly dry trade wind pattern should prevail through the forecast period. Showers will focus primarily over windward and mauka areas during the overnight and early morning hours. A stray shower may occasionally drift into leeward areas, although most areas will remain dry. There remains the potential for an increase in showers over the Big Island Wednesday night and Thursday as the weak low or surface trough slides by to the south, but the latest trends suggest the deepest moisture associated with this feature should remain to the south of the state.

Aviation

High pressure far northeast of the islands will maintain breezy to locally windy trade winds across the state. AIRMET Tango remains in effect for low-level mechanical turbulence leeward of mountains from Oahu to the Big Island. An upper level disturbance west of Kauai and Niihau could bring some tempo moderate turbulence above FL360 as it moves north, but conditions at the moment look to stay below AIRMET criteria.
Satellite imagery continues to show an area of enhanced moisture drifting west across the state. This has resulted in occasional MVFR cigs along windward areas from Oahu to the Big Island. AIRMET Sierra for tempo mountain obscuration will remain in effect for these areas through at least the morning hours. Otherwise, expect mainly VFR conditions at most locations as trades focus clouds and showers along windward and mauka areas.

Marine

The typical pressure gradient caused by high pressure over the northeast Pacific is being enhanced by a broad area of low pressure well southeast of the islands. This is now driving locally strong trades in the rest of the waters around Maui County and leeward Oahu waters, in addition to the typical windier locations around Maui and the Big Island. Therefore, the Small Craft Advisory has been expanded to include those additional areas. The SCA has also been extended in time for the typical windy areas. A further expansion of the SCA may be required by late tonight or early Wednesday, especially if wind speeds increase further in response to any strengthening within this trough.
No significant swells are expected through the forecast period. However, strengthening trades will build short-period wind waves over east-facing shores through mid-week, peaking near or slightly above the seasonal average Wednesday into Thursday. A very small, long-period south swell arrives today, fading by Thursday.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Thursday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.
Small Craft Advisory until 6 AM HST Thursday for Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Big Island Windward Waters.

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Data Courtesy of NOAA.gov