West Kaua’i

Today: Sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 83 to 89 near the shore to around 71 above 3000 feet. Northeast winds up to 10 mph in the morning becoming light. Chance of rain 50 percent.

Tonight: Partly cloudy. Lows around 69 near the shore to around 58 above 3000 feet. Light winds.

Tuesday: Mostly sunny. Isolated showers in the afternoon. Highs 83 to 88 near the shore to around 72 above 3000 feet. Light winds. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 79 to 87. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 68. Northeast winds around 10 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers. Highs 80 to 87. Northeast winds around 10 mph. Chance of rain 20 percent.

Kaua’i Mountains

Today: Partly sunny with scattered showers. Highs 73 to 82 in the valleys to around 64 above 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 63 to 68 in the valleys to around 56 above 4000 feet. Northeast winds around 10 mph in the evening becoming light. Chance of rain 30 percent.

Tuesday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 73 to 82 in the valleys to around 64 above 4000 feet. East winds around 10 mph. Chance of rain 50 percent.

North Kaua’i

Today: Partly sunny with scattered showers. Highs 76 to 84. East winds up to 10 mph. Chance of rain 40 percent.

Tonight: Partly cloudy. Isolated showers in the evening. Lows 63 to 71. East winds around 10 mph in the evening becoming light. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers. Highs 76 to 84. Northeast winds around 10 mph. Chance of rain 20 percent.

East Kaua’i

Today: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 74 to 85. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Isolated showers in the evening. Lows 63 to 73. Northeast winds around 10 mph in the evening becoming light. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers. Highs 74 to 85. Northeast winds around 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

The high pressure ridge north of the Hawaiian Islands will weaken over the next several days, decreasing trade wind speeds down to more moderate levels through Friday. More stable weather conditions are expected with only brief passing showers over windward and mountain areas through the rest of the week. A minor increase in shower trends may develop from Tuesday afternoon through Wednesday morning over the western islands. Locally breezy trade winds return from Saturday into early next week as the ridge builds in far north of the island chain.

Discussion

The satellite imagery this morning tells the tale of a narrow west to east oriented upper trough with embedded weak lows drifting along the trough axis. The subtropical jet stream lingers just south of this upper trough and begins to strengthen in response to convective thunderstorm development along the Inter Tropical Convergence Zone near The Equator. Far north of the state, cold fronts continue to dig into and weaken the subtropical ridge, this weaker ridge pattern will continue through Friday.
Overall mostly stable conditions will prevail across the island chain through Friday due to large scale subsidence (stable downward vertical motions). One wrinkle in this stable force may develop from Tuesday afternoon through Wednesday morning as a weak upper low briefly deepens near Kauai and the strengthening subtropical jet stream builds northward over the islands. Colder air and divergence aloft surrounding this upper low will briefly lift inversion heights and increase shower trends favoring the western islands. Expect increasing shower coverage into the scattered range for this time period, favoring the typical overnight to early morning hours. Otherwise more isolated shower activity will prevail through Friday.
The subtropical ridge will build north of the state from Saturday into the first half of next week. Trade wind speeds will increase into the moderate to breezy range with brief passing showers mainly over windward and mountain areas. A typical summer weather pattern for Hawaii Nei.

Aviation

VFR conditions will prevail across the state into Tuesday. One exception will be brief periods of MVFR conditions with showers and low cloud ceilings near Kauai this morning.
AIRMET Sierra remains in effect for mountain obscurations along N thru SE sections of the Garden Isle. These conditions will diminish later this morning.

Marine

High pressure to the far north-northwest will drift west over the next several days as easterly trade winds across the coastal waters gradually ease into the gentle to locally fresh range through the week.
Surf along south facing shores will remain small today with a tiny to small long-period reinforcement will expected late tonight followed by another long-period south-southwest swell Wednesday into Thursday. This mid-week swell will bring another boost to south shore surf.
East shore surf will gradually decline through mid-week as the trades weaken slightly. Surf along north facing shores will remain tiny through the next several days. Gale force winds associated with a surface low moving near the Aleutians this weekend are expected to send a small, medium period north- northwest swell towards the islands during the latter half of the week.
Through Wednesday, it is possible that higher than normal tides could lead to some coastal flooding during the peak of high tides in the early afternoon hours. However, since the elevated tides are generally expected between the peaks of the aforementioned south swells, this event should have minimal impacts.

HFO Watches/Warnings/Advisories

None.