Photo Credit: Braden Jarvis

West Kaua’i

Today: Cloudy and breezy. Highs around 85 near the shore to around 73 above 3000 feet. East winds up to 20 mph.

Tonight: Cloudy. Isolated showers after midnight. Lows around 70 near the shore to around 60 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Saturday: Mostly cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 85 near the shore to around 73 above 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

South Kaua’i

Today: Cloudy and breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 78 to 85. East winds 10 to 20 mph. Chance of rain 30 percent.

Tonight: Cloudy with scattered showers. Lows around 71. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Saturday: Mostly cloudy with scattered showers. Highs 78 to 85. East winds 10 to 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 72 to 81 in the valleys to around 64 above 4000 feet. East winds up to 15 mph. Chance of rain 40 percent.

Tonight: Cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 63 to 68 in the valleys to around 58 above 4000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

Saturday: Cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 72 to 80 in the valleys to around 64 above 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

North Kaua’i

Today: Cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 75 to 86. East winds up to 15 mph. Chance of rain 40 percent.

Tonight: Cloudy with scattered showers. Lows 64 to 72. East winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 50 percent.

Saturday: Cloudy with scattered showers. Highs 75 to 86. East winds up to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 71 to 82. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 40 percent.

Tonight: Cloudy with scattered showers. Lows 64 to 74. East winds 10 to 15 mph. Chance of rain 50 percent.

Saturday: Cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 71 to 82. East winds 10 to 15 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

A high pressure ridge north of the islands will keep moderate to breezy easterly trade winds over the islands, peaking today and then decreasing slightly into the middle of next week. Clouds and showers will favor typical windward and mountain areas, trending higher in the overnight to early morning hours.

Discussion

Satellite imagery this morning continues to show a large band of high level cirrus clouds produced by the subtropical jet stream are spreading over the Hawaii region from west to east today. Fairly stable low level clouds are drifting over the islands in moderate to breezy easterly trade winds. These high level cirrus clouds may enhance sunrise and sunset colors through the weekend.
Trade winds will continue to blow across the Hawaiian Islands at moderate to breezy levels through much of next week. Breezy wind speeds will peak today as the high pressure ridge builds in slightly, and then decrease slightly by this weekend as the surface pressure gradient weakens a bit. Trade winds will drive clouds up and over windward island mountains into the middle of next week. Brief periods of showers remain in the forecast mainly over these windward and mountain areas, trending higher in the overnight to early morning hours. Drier leeward areas will see less clouds and only isolated showers due to the subsidence caused by the down sloping trade winds immediately leeward of the eastern mountain ranges of each island. Drying and warming effects produced by this small scale atmospheric compression tends to keep leeward areas more stable and dry in typical trade wind weather patterns.
Only subtle changes are expected in the day to day weather forecast for each island in a fairly stable trade wind weather pattern. Weak upper level troughing north and west of the island chain will bring a slight increase in passing shower activity this weekend, mainly over windward areas in the overnight to early morning time periods. The highest chances for clouds and showers statewide will linger over eastern Maui near Hana, and over the eastern slopes of the Big Island from the Hamakua Coast to Hilo to the Puna District.

Aviation

Moderate to breezy easterly trade winds will persist across the Hawaiian Islands into the weekend. Isolated to scattered showers will favor windward coasts and slopes, with greater coverage expected during the overnight hours. Brief MVFR conditions are possible in moderate showers. Otherwise, VFR conditions will prevail.
AIRMET Sierra for mountain obscuration remains in effect for windward areas of Kauai, Oahu and the Big Island this morning. Conditions may improve later today, but an uptick in windward showers tonight may require AIRMET Sierra once again. No other AIRMETS are in effect and none are expected.

Marine

High pressure will gradually build westward well to the north of the state today and tonight, keeping fresh to strong trade winds in place across the island chain. A Small Craft Advisory (SCA) remains in effect for most waters around Maui County and the Big Island as well as the northwest Kauai waters through 6 AM Saturday. For the windiest waters around Maui and the Big Island the SCA extends through 6 PM Saturday. A trough of low pressure will amplify and linger west of the islands this weekend into early next week, resulting in a slight easing of the trades and a shift to a more east-southeasterly direction over the western end of the state. Moderate to locally strong easterly trades will prevail over the eastern waters.
South shore surf will remain small and below the summer average through the middle of next week, with only small and inconsistent pulses of southwest swell expected. The next significant south- southwest swell (200 deg) appears to move in toward the end of next week. East shore surf will remain near the seasonal average through Friday, followed by a slight decrease this weekend through the middle of next week as the trades ease over and upstream of the islands. Surf along north shores will remain very small with a slight bump possible late Sunday through Monday.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov