Photo Credit: Jason Weingardt

West Kaua’i

Rest Of Today: Mostly sunny. Breezy. Highs around 85 near the shore to around 75 above 3000 feet. East winds up to 20 mph.

Tonight: Breezy. Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows around 75 near the shore to around 64 above 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Monday: Mostly cloudy. Breezy. Scattered showers in the morning, then numerous showers in the afternoon. Highs around 83 near the shore to around 73 above 3000 feet. Northeast winds up to 25 mph with gusts to 45 mph. Chance of rain 70 percent.

South Kaua’i

Rest Of Today: Mostly sunny. Breezy. Highs around 84. East winds 15 to 25 mph.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows around 75. Northeast winds 15 to 25 mph. Chance of rain 70 percent.

Monday: Windy. Mostly cloudy with occasional showers. Highs around 82. Northeast winds 15 to 30 mph. Chance of rain 90 percent.

Kaua’i Mountains

Rest Of Today: Partly sunny. Breezy. Highs 73 to 79 in the valleys to around 68 above 4000 feet. East winds 10 to 25 mph.

Tonight: Mostly cloudy. Windy. Numerous showers in the evening, then occasional showers after midnight. Lows around 68 in the valleys to around 60 above 4000 feet. East winds 10 to 30 mph. Chance of rain 90 percent.

Monday: Windy. Cloudy with occasional showers. Highs 71 to 77 in the valleys to around 66 above 4000 feet. East winds 10 to 30 mph. Chance of rain 90 percent.

North Kaua’i

Rest Of Today: Mostly sunny. Highs 75 to 84. East winds up to 15 mph.

Tonight: Mostly cloudy. Numerous showers in the evening, then occasional showers after midnight. Lows 68 to 76. East winds up to 15 mph. Chance of rain 90 percent.

Monday: Breezy. Mostly cloudy with occasional showers. Highs 73 to 82. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 90 percent.

East Kaua’i

Rest Of Today: Partly sunny. Highs 75 to 85. East winds 10 to 15 mph.

Tonight: Mostly cloudy. Numerous showers in the evening, then occasional showers after midnight. Lows 66 to 77. Northeast winds 10 to 15 mph. Chance of rain 90 percent.

Monday: Breezy. Cloudy with occasional showers. Highs 73 to 83. Northeast winds 10 to 25 mph. Chance of rain 90 percent.

Detailed Forecast

Synopsis

Strengthening trade winds will become windy today through Monday before easing slightly Tuesday through late next week. A dry and stable air mass will prevail today with only a few brief windward showers. Moisture associated with a dissipating front will bring an increase in showers to the smaller islands beginning tonight on Kauai, shifting southward to Oahu Monday, and to Maui County late Monday or Monday night. Typical trade wind weather will then prevail through Tuesday. A decrease in showers is then possible Wednesday and Thursday as troughing develops northwest of the state and pulls the old frontal remnants northward. High pressure building in to the distant north looks to bring a resurgence of trade wind showers beginning Thursday night and continuing through next weekend.

Discussion

Currently at the surface, a stationary front is located around 75 miles north of Kauai, while a strong 1036 mb high is centered to the distant northwest. The gradient across the islands continues to drive moderate to breezy trade winds across the island chain early this morning. Infrared satellite imagery shows clouds favoring windward and mauka areas, with lesser cloud cover in most leeward locales. Radar imagery shows a few light showers moving into windward slopes and coasts, with a few sprinkles or some light mist reaching leeward communities at times. Main short term focus remains on the strengthening trades and fire weather concerns.
Strong high pressure to the distant northwest will build southeastward and closer to the islands during the next couple days, resulting in strengthening trade winds across the state. The trades will strengthen to breezy and locally windy levels today, then strengthen further tonight and Monday, with windy conditions expected statewide. A Wind Advisory has been issued for portions of Kahoolawe, Lanai, Maui and the Big Island beginning at noon today and continuing through 6 PM Monday. The advisory may need to be expanded to include additional zones with the afternoon forecast package. The trades will gradually ease Monday night and Tuesday, then hold generally at moderate to breezy levels through the remainder of the work week and into next weekend.
As for the remaining weather details, a few light showers will move move into windward slopes and coasts this morning, with some mist or a few sprinkles possibly reaching leeward areas at times. Dry conditions will prevail statewide this afternoon, with very little shower activity expected. A band of moisture associated with a decaying front will bring some showery weather as it moves into Kauai tonight, possibly reaching Oahu prior to daybreak Monday. The band of moisture will then approach Maui County by late Monday, with rather showery weather expected for at least windward Kauai and Oahu. The moisture band appears to stall out over the smaller islands Monday night and Tuesday, but doesn't appear to ever make it south into the Big Island. As a result, showery weather will continue for windward sections of the smaller islands with a few showers reaching leeward locales as well.
An upper level low will cut off to the northwest of the state Wednesday and Thursday, inducing surface troughing to the west of the island chain. The models show this feature lifting the band of moisture back northward and reducing shower coverage across Maui County and Oahu, with showery conditions quite possibly continuing across windward Kauai. The upper level low begins to fill and surface troughing dampens out Thursday night and Friday, with a new building high to the distant north bringing a resurgence of trade wind showers to the islands that appears to continue through next weekend.

Aviation

Light to moderate trades will steadily strengthen to become windy later today and tomorrow. This flow will bring low level turbulence over and lee of island terrain and cause clouds and showers to favor windward and mauka areas over the next couple of days.
Taking a look at infrared satellite imagery, a large area of stable cumulus with ceilings around 5000-6000 ft is currently upstream of the Hawaiian Islands and moving into windward portions of the eastern end of the state. Extensive mountain obscuration is not expected to develop, but will continue to monitor in case AIRMET Sierra is needed. Another feature-of-note is a cold front that is currently north of the state. This front will slowly sag south today, bringing increasing clouds and showers to Kauai tonight, then impacting Oahu heading into Monday.
Overall, VFR conditions will prevail today, with only brief MVFR conditions possible in passing light showers. Greater shower coverage over Kauai tonight may bring longer periods of MVFR conditions, and an AIRMET Sierra may be needed for mountain obscuration.
AIRMET Tango for low-level mechanical turbulence over and in the lee of island terrain will remain in effect for the next couple of days, due to the strengthening trade winds.

Marine

A strong surface high pressure located approximately 1,700 nautical miles northwest of the islands will track east over the next couple of days, strengthening trades from fresh to locally strong levels to strong to gale force for the typically windier areas. A Gale Warning is now in effect from tonight through Monday evening for the typical windier waters. For all other waters, a Small Craft Advisory is in effect through Monday evening for area wide strong to near gale force winds and seas building to 12 feet.
Tiny surf along north facing shores will see a small boost later today as a small, medium period north- northwest swell fills in. This swell will peak tonight and slowly subside as it shifts out of the north through the first half of the week. Another small, medium period northwest swell is expected to fill in during the second half of next week to help revive surf heights once more.
Surf along east- facing shores will trend up over the next couple of days in direct response to strengthening trades. Expect elevated, rough, choppy surf conditions to peak Monday before easing towards typically rough, choppy conditions Tuesday through midweek as winds over and upstream relax slightly.
Surf along south facing shores will trend down today and Monday as a small, medium period south- southwest swell fades. A small, long period south- southwest swell may fill in late Tuesday night and Wednesday, providing a small boost in surf along south facing shores through the middle of the week.

Fire weather

Increasing trade wind speeds are expected, while KBDI well over 600 speaks to the dryness of fuels. With a dry and stable air mass building over the state, critical fire weather conditions are expected today and Monday, especially when relative humidity reaches its minimum in the afternoon. As a result, a Red Flag Warning remains in effect for primarily leeward portions of the islands.

HFO Watches/Warnings/Advisories

Red Flag Warning from 10 AM this morning to 6 PM HST Monday for Niihau, Kauai Leeward, Oahu South Shore, Waianae Coast, Oahu North Shore, Oahu Koolau, Central Oahu, Waianae Mountains, Molokai Leeward, Lanai Makai, Lanai Mauka, Maui Leeward West, Maui Central Valley, Leeward Haleakala, Kona, South Big Island, Kohala, Big Island Interior.
Wind Advisory from noon today to 6 PM HST Monday for Lanai Mauka, Kahoolawe, Maui Windward West, Maui Leeward West, Kohala, Big Island Interior, Lanai Windward, Lanai Leeward, Maui Central Valley North, Maui Central Valley South, South Haleakala, Big Island South, Big Island Southeast, Big Island North.
Small Craft Advisory from 6 AM this morning to 6 AM HST Tuesday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Big Island Windward Waters.
Small Craft Advisory until 6 PM HST this evening for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.
Gale Warning from 6 PM this evening to 6 AM HST Tuesday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov