West Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Isolated showers. Highs around 90 near the shore to around 76 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 72 to 77 near the shore to around 62 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Saturday: Mostly sunny with isolated showers. Highs around 89 near the shore to around 76 above 3000 feet. East winds around 10 mph. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 81 to 90. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 74. East winds 10 to 15 mph. Chance of rain 40 percent.

Saturday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 82 to 90. East winds 10 to 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Mostly cloudy with scattered showers. Highs 76 to 88 in the valleys to 64 to 69 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 67 to 72 in the valleys to around 60 above 4000 feet. East winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 50 percent.

Saturday: Partly sunny with scattered showers. Highs 75 to 87 in the valleys to 64 to 69 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

North Kaua’i

Today: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 80 to 89. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 67 to 75. East winds up to 15 mph. Chance of rain 40 percent.

Saturday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 80 to 89. East winds 10 to 15 mph. Chance of rain 40 percent.

East Kaua’i

Today: Partly sunny with scattered showers. Highs 76 to 88. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 67 to 79. East winds 10 to 15 mph. Chance of rain 50 percent.

Saturday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 76 to 87. East winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

A broad subtropical ridge will linger across the Central Pacific basin into the middle of next week, producing moderate to locally breezy trade winds each day. Two wrinkles in the forecast will increase shower trends through this morning as an easterly wave passes through Oahu and Kauai. Brief passing showers over windward and mountain areas will return later this afternoon and last through Monday evening. Another low level wave in the easterlies will drift through the islands from Tuesday to Wednesday; increasing shower trends.

Discussion

The infrared satellite imagery shows a weak easterly wave drifting westward through the island of Kauai this morning. Expect continued enhanced cloud and shower coverage across the western islands of Oahu, Kauai and Niihau through the early morning hours. Drier trends are already returning to the eastern islands with more stable stratocumulus clouds developing east of the island chain as the high pressure ridge builds stable subsidence (downward vertical motions) back into the region. Bands of high level cirrus clouds, made of ice crystals, will drift over the islands through Sunday. These high level cirrus clouds will likely enhance sunrise and sunset colors for all islands.
A typical summer forecast with little changes to our day to day moderate to locally breezy easterly trade wind weather regime remains in the forecast through Monday evening. Only brief passing showers are possible with temperature inversion heights in the 5,000 to 7,000 foot range, favoring windward and mountain areas in the overnight to early morning hours. Dry trends will continue for leeward areas that are west of island mountains.
The latest medium range models continue to show another wrinkle in the force developing by early Tuesday morning, as a wave in the easterlies drifts from east to west across the island chain. Low level forcing from this passing low level trough will push subsidence inversion heights into the 8,000 to 9,000 foot range, deepening moisture levels, and increasing cloud and shower trends from early Tuesday morning near the Big Island and Maui, then spreading westward to the islands of Oahu and Kauai by Tuesday night into Wednesday morning. One challenge with this forecast will be in how far north the trough tracks through the islands. If the trough passes farther south of the state, then these shower trends will be more limited for the western half of the state. We have higher confidence that the eastern Hawaiian Islands will see enhanced shower activity, especially in the early Tuesday morning hours.
Long range model solutions are hinting at yet more chances for enhanced shower trends by the end of next week. Stay tuned.

Aviation

A weak trough moving through Kauai this morning will enhance clouds and showers over Oahu and Kauai through around 18Z today. Otherwise moderate to locally breezy trade winds will linger through the week. Brief passing showers will favor windward and mountain areas in the overnight to early morning hours. VFR conditions will prevail outside of showers.
No AIRMETs are in effect. AIRMET Sierra for mountain obscuration over select windward areas is possible through Saturday.

Marine

High pressure will remain far northeast of the state through this weekend and allow moderate to locally strong trades to prevail across the local coastal waters. Thus, a Small Craft Advisory will remain in place for the typically windy channels and waters of Maui County and the Big Island through at least Sunday morning. Winds may weaken slightly late Sunday into early next week, then strengthen once again by midweek.
A small, medium to long period, south swell will continue to fill in today and help bump up south shore surf to near or slightly above September averages. This swell will then slowly decline by late Saturday into Sunday. Small south swell/surf expected through the remainder of the forecast period.
Surf along north facing shores will be slightly elevated over the next several days as a small, moderate period, north northwest swell holds. Beyond Sunday, however, north shore surf will drop back into the tiny to small range. East facing shores will see typical trade wind generated energy throughout the forecast period.

Fire weather

Humidity levels will remain dry into next week with increasing humidity and shower trends from Tuesday into Wednesday as a weak low level trough drifts from east to west across the island chain. Wind speeds will likely remain below critical fire weather thresholds for the next seven days. Temperature inversion heights near the Big Island and Maui today will range from 5,500 to 6,500 feet.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Sunday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.