West Kaua’i

Today: Mostly sunny. Breezy. Isolated showers in the morning. Highs 86 to 91 near the shore to around 78 above 3000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 68 to 73 near the shore to around 60 above 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 85 to 91 near the shore to around 78 above 3000 feet. East winds 10 to 15 mph. Chance of rain 40 percent.

South Kaua’i

Today: Partly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 81 to 89. Northeast winds 15 to 20 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy with scattered showers. Lows 69 to 74. Northeast winds around 15 mph. Chance of rain 50 percent.

Wednesday: Partly sunny with scattered showers. Highs 81 to 90. East winds around 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Breezy. Partly sunny with scattered showers. Highs 74 to 85 in the valleys to around 67 above 4000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 63 to 68 in the valleys to around 57 above 4000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Wednesday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 76 to 85 in the valleys to around 68 above 4000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

North Kaua’i

Today: Partly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 77 to 88. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 40 percent.

Tonight: Mostly cloudy with scattered showers. Lows 63 to 73. East winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 78 to 88. East winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Partly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 74 to 86. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 62 to 75. East winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 74 to 87. East winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

A strong high pressure ridge north of the Hawaiian Islands will keep breezy to windy trade winds in the forecast for one more day today. The strongest winds will develop over the windier areas of Maui and Hawaii Counties. Dry weather conditions will combine with these strong gusty winds to produce elevated fire danger across the state each afternoon, mainly over the drier leeward slopes. Wind speeds will decrease from Wednesday onward. A slight increase in shower trends remains in the forecast from Wednesday night onward.

Discussion

The satellite picture this morning shows bands of fairly stable clouds moving into the windward mountain slopes of each island. A ridge aloft will produce enough downward motions (subsidence) to limit vertical cloud growth and thereby produce only brief passing light showers across the Hawaii Region. Temperature inversion heights today will range from 5,000 to 6,000 feet today due to the stronger subsidence. These temperature inversion heights will lift into the 7,000 to 8,000 foot range from Wednesday onward as the high pressure ridge weakens, slightly increasing shower trends statewide. An upper level low just southwest of the island chain will produce bands of high level cirrus ice crystal clouds across the state, enhancing sunrise and sunset colors.
The main weather story today will continue to focus on the breezy to windy easterly trade winds blowing across the state. A Wind Advisory remains in effect until this evening for windier areas of Maui and Hawaii Counties; including the summits of Mauna Kea and Mauna Loa on the Big Island. The pattern will begin to change on Wednesday as the high pressure ridge north of the state weakens. These strong trade wind speeds will start to decrease to more moderate to breezy levels for the rest of the week.
Relatively dry humidity levels will combine with these breezy to windy conditions to elevate fire weather conditions across the state, mainly over drier and windier leeward areas. Please refer to the Fire Weather section below for more details.

Aviation

Stable conditions with breezy to windy trade winds will continue across the state today. Passing showers will favor windward and mountain areas in the overnight to early morning hours, bringing the potential for brief MVFR conditions. Otherwise, VFR conditions will prevail.
AIRMET Tango remains in effect for moderate low-level turbulence over and downwind of island terrain. This AIRMET will likely persist as strong trade winds remain in the forecast.

Marine

High pressure will remain nearly stationary far north of the islands through today, which will support continued fresh to strong trades across the area. The Small Craft Advisory remains in effect for all Hawaiian coastal waters through 6 PM HST Tuesday. The surface high will move eastward and weaken slightly during the second half of the week, but winds are likely to remain breezy to locally strong in the windier channels and waters of Maui County and the Big Island. Therefore, the SCA will likely need to be extended for these areas. Additionally, seas may also approach 10 feet at times in the Alenuihaha Channel over the next couple of days.
South shore surf is expected to slowly decline as the current small south swell fades. The next small, long- period south swell is expected to arrive this evening and peak on Wednesday. This swell may boost south-facing shore surf heights slightly from Tuesday night through Wednesday before gradually easing again through Friday. Guidance shows that another, smaller long-period reinforcement could arrive Friday night into the first half of the weekend.
Surf along east-facing shores will be rough and choppy for the next couple of days in response to the gusty easterly trade winds. As the trades ease a bit during the latter portion of the week, surf along east-facing shores will also trend down.

Fire weather

Breezy to windy trade winds with stable and relatively dry conditions will persist today. Minimum relative humidity at lower leeward elevations will likely fall to around 45 percent this afternoon, and with the temperature inversion dropping to as low as 5,000 feet, winds will become gusty over and downwind of island mountains. This will result in near critical fire weather conditions over dry leeward areas in the afternoon hours, though no headlines (watches or warnings) are due since the Keetch Byram Drought Index will remain below the 600 threshold at Honolulu.

HFO Watches/Warnings/Advisories

Wind Advisory until 6 PM HST this evening for windier areas of Maui and Hawaii Counties, including the highest summits of the Big Island.
Small Craft Advisory until 6 PM HST this evening for all Hawaiian waters.