West Kaua’i

Today: 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.

Tonight: Partly cloudy with isolated showers. Lows around 74 near the shore to around 61 above 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Sunday: Mostly sunny. Isolated showers in the afternoon. Highs around 89 near the shore to around 76 above 3000 feet. Northeast winds up to 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 82 to 90. East winds 10 to 15 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy with isolated showers. Lows around 73. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Sunday: Partly sunny in the morning then becoming mostly sunny. Isolated showers. Highs 82 to 90. East winds 10 to 15 mph. Chance of rain 20 percent.

Kaua’i Mountains

Today: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 75 to 87 in the valleys to 64 to 69 above 4000 feet. East winds 10 to 15 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy with isolated showers. Lows 66 to 72 in the valleys to around 59 above 4000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Sunday: Partly sunny with isolated showers. Highs 77 to 87 in the valleys to 64 to 69 above 4000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

North Kaua’i

Today: 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.

Tonight: Partly cloudy with isolated showers. Lows 66 to 74. East winds 10 to 15 mph decreasing to up to 15 mph after midnight. Chance of rain 20 percent.

Sunday: Mostly sunny with isolated showers. Highs 80 to 89. East winds up to 15 mph. Chance of rain 20 percent.

East Kaua’i

Today: 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 40 percent.

Tonight: Mostly cloudy with isolated showers. Lows 67 to 78. East winds 10 to 15 mph. Chance of rain 20 percent.

Sunday: Partly sunny in the morning then becoming mostly sunny. Isolated showers. Highs 77 to 88. East winds 10 to 15 mph. Chance of rain 20 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. Brief passing showers over windward and mountain areas will return later this afternoon and last through Monday evening. One wrinkle in the forecast will develop from Tuesday into Wednesday as an easterly wave passes through the Hawaiian Islands increasing clouds and shower trends.

Discussion

This mornings satellite imagery shows fairly stable stratocumulus clouds drifting into the islands on the easterly trade winds. This mornings upper air balloon soundings from Hilo and Lihue show subsidence inversion heights at the 6,000 and 7,000 foot level respectively. At these heights clouds will deepen enough for only isolated to scattered shower coverage favoring windward mountain slopes of all islands exposed to the easterly trade winds. 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 continue to hint at additional enhanced shower trends by the end of next week. Stay tuned.

Aviation

Moderate to locally breezy trade winds will hold for the next few days as high pressure to the northeast remains in place. 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.

Marine

Weak surface high pressure will remain anchored north of the islands the next several days. This will support moderate to locally strong trade winds across the nearshore waters. A Small Craft Advisory (SCA) remains in effect for the typically windy bays and channels surrounding Maui County and Big Island through Sunday afternoon. Winds may briefly fall below SCA criteria Sunday morning but are expected to restrengthen by the afternoon hours. Moderate trades will prevail through the middle of next week before once again picking back up to SCA levels across the typically windy areas Thursday and Friday.
The recent small, medium period north swell is currently on the decline today but should still have enough energy to keep north- facing shore surf up to near head high heights into this afternoon. This swell will significantly fall off Sunday and produce waist high surf by late Sunday afternoon. Another medium period north swell arrival Thursday may cause a slight bump in late week surf along north-facing shores.
Surf along south-facing shores will remain near or slightly above late summer norms the next couple of days. This morning's elevated south surf will fall through the day as the small, medium period south swell that peaked yesterday drops off through this afternoon. A small long period reinforcement arriving tonight will hold south shore surf to around waist high Sunday.
Typical short period wind wave chop will occur along east-facing shores under moderate trades this weekend.

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 PM HST Sunday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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