Photo Credit: Brendan Stephen

West Kaua’i

Today: Breezy. Partly sunny with scattered showers. Highs around 81 near the shore to around 69 above 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 70 near the shore to around 59 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Monday: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs around 80 near the shore to around 68 above 3000 feet. Northeast winds up to 20 mph. Chance of rain 50 percent.

South Kaua’i

Today: Breezy. Mostly cloudy with showers likely. Highs around 80. Northeast winds 15 to 20 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Breezy. Showers likely in the evening, then scattered showers after midnight. Lows 66 to 71. Northeast winds 15 to 20 mph. Chance of rain 70 percent.

Monday: Mostly cloudy in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs around 79. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Breezy. Mostly cloudy with occasional showers. Highs 68 to 76 in the valleys to around 63 above 4000 feet. East winds 10 to 25 mph. Chance of rain 90 percent.

Tonight: Breezy. Mostly cloudy with occasional showers. Lows 59 to 64 in the valleys to around 53 above 4000 feet. Northeast winds 10 to 25 mph. Chance of rain 90 percent.

Monday: Mostly cloudy. Breezy. Occasional showers in the morning, then showers likely in the afternoon. Highs 67 to 75 in the valleys to around 62 above 4000 feet. Northeast winds 10 to 25 mph. Chance of rain 80 percent.

North Kaua’i

Today: Mostly cloudy. Occasional showers in the morning, then showers likely in the afternoon. Highs 73 to 80. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 90 percent.

Tonight: Mostly cloudy. Breezy. Occasional showers in the evening, then scattered showers after midnight. Lows 62 to 71. East winds 10 to 20 mph. Chance of rain 90 percent.

Monday: Breezy. Partly sunny with scattered showers. Highs 72 to 79. East winds 10 to 20 mph. Chance of rain 50 percent.

East Kaua’i

Today: Mostly cloudy. Breezy. Occasional showers in the morning, then showers likely in the afternoon. Highs 73 to 80. Northeast winds 10 to 20 mph. Chance of rain 90 percent.

Tonight: Mostly cloudy. Occasional showers in the evening, then scattered showers after midnight. Lows 60 to 72. Northeast winds 10 to 15 mph. Chance of rain 90 percent.

Monday: Breezy. Mostly cloudy with scattered showers. Highs 72 to 79. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

High pressure north of the state will keep breezy to locally windy conditions in place today. The trades will ease a bit each day Monday and Tuesday, with breezy conditions continuing. Typical trade wind weather featuring windward and mauka showers and the occasional leeward spillover will continue through early next week. Winds will diminish and and rain chances will decrease around mid week as a cold front approaches from the northwest. The cold front could bring an increase in showers Thursday night into next weekend.

Discussion

Currently at the surface, a 1030 mb high is centered around 1400 miles north-northeast of Honolulu, while a trough of low pressure is positioned around 1000 miles west of Kauai. These features are producing a rather tight pressure gradient across the island chain early this morning, with breezy to locally windy conditions statewide. Infrared satellite imagery shows partly to mostly cloudy conditions, with coverage the greatest over the western end of the state and windward sections of the eastern islands. Radar imagery shows scattered to numerous showers moving into windward areas, with some of these showers spreading into leeward communities as well. Main short term focus revolves around trade wind trends during the next few days.
High pressure north-northeast of the state will gradually weaken as it edges slowly east-southeast today and tonight. A new strong high will build far north of the state through the first half of the work week. Breezy to locally windy conditions are expected today, and a Wind Advisory remains posted for the typically windier areas of Maui County and the Big Island through 6 PM this evening. The trades will gradually ease a bit each day Monday through Tuesday, although breezy conditions are expected to continue. A more noticeable decrease in the trades is expected on Wednesday as a front approaches from the northwest. The wind forecast becomes highly uncertain toward the end of the week as model consistency and run to run continuity has been poor to say the least. Overall, lighter winds should prevail Thursday, with the potential for westerly winds to develop Friday into next weekend.
As for the remaining weather details, fairly typical trade wind weather will prevail through Tuesday, with bands of clouds and showers moving through from time to time. Showers will favor windward and mauka areas, but some will also reach leeward areas due to the strength of the trades. We could see the coverage and intensity of showers increase tonight through Tuesday, particularly over the eastern end of the state, as some upper level energy rotates southward through the islands and lifts inversion heights. Shower coverage should decrease Wednesday through Thursday as the trades become disrupted with the approach of a cold front. As mentioned in the previous paragraph, considerable uncertainty remains in the forecast late in the week, so will take a blended forecast approach for now until details become more clear. Overall, it appears that chances for rainfall will increase Thursday night and possibly remain elevated into next weekend.

Aviation

Breezy to locally strong trade winds will persist today and beyond, as a robust high pressure system remains far north of the islands. AIRMET Tango is posted for tempo moderate low-level turbulence for leeward sides of the mountains on all islands due to the strong winds and stable conditions.
Brief MVFR conditions due to lower ceilings and visibilities in passing showers will mainly affect windward and mauka sections across the island chain. AIRMET Sierra is in effect for tempo mountain obscuration along windward sides of Kauai and Oahu above 2500 feet this morning due to more extensive low clouds and showers arriving in with the trade wind flow. Expect this AIRMET to continue through the morning with fewer clouds and showers statewide this afternoon.

Marine

High pressure north of the islands will drive strong trade winds across the local waters during the next few days. Gale force winds will continue through this afternoon in the windier waters around Maui and the Big Island, with Small Craft Advisory (SCA) level winds expected elsewhere. Wind speeds may ease slightly tonight, but at a minimum, SCA level winds will continue for most marine zones through Tuesday. An approaching front will cause trades to decrease below SCA threshold around the middle of the week.
Strong trade winds will keep east shore surf elevated through Tuesday but will remain well below the advisory threshold of 10 feet. Surf along east facing shores will lower to near or below normal levels around the middle of next week as the trades back off.
Surf along north and west facing shores will remain small and well below normal through the remainder of the weekend. A small northwest and a small north swell will give surf a boost along north and west facing shores Monday through Wednesday. The potential for a new large northwest swell could bring near warning level surf to north and west facing shores late in the week although forecast confidence remains low.
Surf along south facing shores will remain small with only background south swell energy through the middle of the week. A new small south swell could give south shore surf a slight boost late in the week.

HFO Watches/Warnings/Advisories

Wind Advisory until 6 PM HST this evening for Lanai Mauka, Kahoolawe, Maui Windward West, Maui Leeward West, Kohala, Big Island Interior, Molokai Windward, Molokai Southeast, 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 until 6 PM HST this evening 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.
Gale Warning until 6 PM HST this evening for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov