Photo Credit: Jason Weingardt

West Kaua’i

Today: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 87 near the shore to around 74 above 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows around 71 near the shore to around 61 above 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tuesday: Breezy. Mostly cloudy with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 85 near the shore to around 72 above 3000 feet. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

South Kaua’i

Today: Partly sunny. Breezy. Showers likely in the morning, then scattered showers in the afternoon. Highs 82 to 88. East winds 15 to 20 mph. Chance of rain 70 percent.

Tonight: Breezy. Scattered showers in the evening, then occasional showers after midnight. Lows around 71. Northeast winds 15 to 25 mph. Chance of rain near 100 percent.

Tuesday: Breezy. Occasional showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 80 to 86. Northeast winds 20 to 25 mph. Chance of rain near 100 percent.

Kaua’i Mountains

Today: Mostly cloudy. Breezy. Occasional showers in the morning, then scattered showers in the afternoon. Highs 73 to 82 in the valleys to around 65 above 4000 feet. East winds 10 to 25 mph. Chance of rain 90 percent.

Tonight: Breezy. Occasional showers. Lows 63 to 69 in the valleys to around 59 above 4000 feet. East winds 10 to 25 mph. Chance of rain near 100 percent.

Tuesday: Breezy. Occasional showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 71 to 80 in the valleys to around 63 above 4000 feet. Northeast winds 20 to 25 mph. Chance of rain near 100 percent.

North Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 76 to 87. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Breezy. Showers likely in the evening, then occasional showers after midnight. Lows 65 to 72. East winds 10 to 15 mph increasing to 10 to 25 mph after midnight. Chance of rain near 100 percent.

Tuesday: Breezy. Occasional showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs 73 to 84. East winds 15 to 25 mph. Chance of rain near 100 percent.

East Kaua’i

Today: Breezy. Mostly cloudy with showers likely in the morning, then mostly sunny with scattered showers in the afternoon. Highs 73 to 85. East winds 10 to 20 mph. Chance of rain 70 percent.

Tonight: Breezy. Showers likely in the evening, then occasional showers after midnight. Lows 65 to 75. Northeast winds 10 to 25 mph. Chance of rain near 100 percent.

Tuesday: Breezy. Occasional showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 71 to 83. Northeast winds 20 to 25 mph. Chance of rain near 100 percent.

Detailed Forecast

Synopsis

Breezy trade winds will push showers mainly across windward areas through today. Strengthening northeasterly winds will drive a front down the island chain tonight and Tuesday, bringing a period of increased clouds and showers. A cool and relatively dry air mass will move over the islands after the front passes. Expect gradually diminishing trade winds and warmer conditions by the end of the week.

Discussion

Trade winds continue to strengthen this morning as a strong high builds north northwest of the islands. Models show that surging northeast winds will push a front over the islands tonight and Tuesday. Showers accompanying the front will move rather quickly through the island chain, focusing rainfall across windward areas. Significant rainfall totals are not expected. A Wind Advisory that is in effect for portions of Maui and Hawaii Counties through tonight may need to be extended and/or expanded as conditions warrant.
Expect very windy and relatively dry conditions to develop for a day or two after frontal passage early Tuesday, lowering dew points and temperatures. Strong winds and a dry air mass will combine to increase potential for hazardous fire weather. However, relative humidity may not reach critically low levels to warrant the issuance of a Red Flag Warning.
Models show a trough passing northeast of the islands later this week, possibly increasing trade wind showers Wednesday and Thursday. Otherwise, only a few windward showers are expected. The high north of the islands will weaken Thursday and Friday, causing trade winds to weaken while veering to the east. Another front may move over the islands Sunday.

Aviation

Breezy to locally strong trades will continue today, then strengthen to strong levels for most areas tonight through Tuesday as a front moves through the area from the northeast. Brief periods with MVFR conditions are possible in passing showers, mainly over windward and mauka areas. A band of low clouds and showers accompanying the front tonight into Tuesday could lead to more widespread MVFR conditions with mountain obscuration for most windward/mauka areas.
AIRMET Tango remains in effect for low-level moderate turbulence over and downwind of the mountains on all islands due to breezy trade winds. This will continue through at least mid-week.
AIRMET Sierra is now in effect for mountain obscuration on Maui and the Big Island. This will likely persist through daybreak before improving later this morning.

Marine

Strong surface high pressure far north of the area will remain stationary over the next few days, keeping fresh to locally strong trade winds over the nearshore waters. A surge of strong to locally gale force easterly trade winds will increase winds across all local waters, as a cold front pushes down the island chain Monday night into Tuesday. A Small Craft Advisory is in effect for all coastal waters zones through Tuesday afternoon except for Paiolo and Alenuihaha Channel which has a Gale Watch starting from this afternoon through Tuesday afternoon. The SCA will likely need to be extended through at least Wednesday as the trades remain strong and a northeast swell helps to keep wave heights above 10 feet. Trades look to weaken slightly into the moderate to locally strong range by Thursday and Friday.
Surf along east-facing shores will remain rough and elevated through the forecast period. Strengthening trades, coinciding with a large, short period northeast (040 degrees) swell will likely push east shore surf to High Surf Advisory levels early Tuesday through Wednesday. The trade wind and northeast swell combo will also wrap into exposed north-facing shores. This could lead to moderate surges in harbors such as Hilo and Kahului during this time. However, the angle of the northeast swell may have enough of an easterly component to prevent significantly unsafe conditions for Kahului Harbor, so the buoys will be closely monitored as the event unfolds.
A small, medium-period northwest swell will hold through the day today, then decline through mid-week. No significant northwest swells are expected thereafter, until a small, long-period northwest swell is slated to arrive late Friday.
Small mainly background south swell energy is expected through middle of next week. A small, long-period south swell could boost south shore surf from Thursday night through Friday.

Fire weather

As mentioned above, the combination of dry air and strong winds behind a passing front will increase the possibility of hazardous fire weather conditions Tuesday afternoon. However, forecast relative humidities (RH) remain slightly too high to issue Fire Weather Watches or Red Flag Warnings at this time. We will monitor conditions closely as this situation may change quickly.

HFO Watches/Warnings/Advisories

Wind Advisory until 6 AM HST Tuesday for Lanai Mauka, Kahoolawe, Maui Windward West, Maui Leeward West, Kohala, Big Island Interior, Molokai Windward, Molokai North, Lanai Windward, Lanai Leeward, Lanai South, Maui Central Valley North, Maui Central Valley South, South Haleakala, Big Island South, Big Island Southeast, Big Island North.
Small Craft Advisory until 6 PM 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, Maalaea Bay, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.
Small Craft Advisory until 6 PM HST this evening for Pailolo Channel, Alenuihaha Channel.
Gale Watch from this evening through Tuesday afternoon for Pailolo Channel, Alenuihaha Channel.

Data Courtesy of NOAA.gov