Photo Credit: Brendan Stephen

West Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Isolated showers. Highs around 84 near the shore to around 69 above 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 68 near the shore to around 58 above 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny with isolated showers. Highs around 84 near the shore to around 69 above 3000 feet. East winds around 10 mph. Chance of rain 20 percent.

South Kaua’i

Today: Cloudy with numerous showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 75 to 82. East winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 68. East winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday: Partly sunny with scattered showers. Highs 76 to 83. East winds 10 to 15 mph. Chance of rain 40 percent.

Kaua’i Mountains

Today: Breezy. Cloudy with showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 70 to 81 in the valleys to around 61 above 4000 feet. East winds 10 to 20 mph. Chance of rain 80 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows around 66 in the valleys to around 55 above 4000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Tuesday: Breezy. Partly sunny with scattered showers. Highs 70 to 81 in the valleys to around 61 above 4000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

North Kaua’i

Today: Mostly cloudy with scattered showers. Highs 73 to 84. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 62 to 70. East winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday: Partly sunny with scattered showers. Highs 74 to 83. East winds 10 to 15 mph. Chance of rain 40 percent.

East Kaua’i

Today: Cloudy with numerous showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 70 to 80. East winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows 63 to 72. East winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday: Partly sunny with scattered showers. Highs 70 to 81. East winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Breezy easterly trade winds will continue through the morning hours, decreasing to moderate levels by this afternoon. A passing weak upper level disturbance will drift over the islands today enhancing passing showers with a few thunderstorms possible over the Big Island. An unstable band of clouds and showers will drift into the islands on the trade winds, bringing another round of wet weather for all islands from Wednesday into Thursday. An upper trough moving into the region from the north will keep wet weather in the forecast lasting into the weekend.

Discussion

Local island radar imagery shows numerous showers riding into the windward and mountain slopes of all islands this morning. Some of the stronger showers are drifting over drier leeward areas. Satellite water vapor channel imagery continues to show a weakening upper level low slowly drifting from west to east across the island chain. This upper low will produce enough instability to keep wet trade winds in the forecast today with isolated thunderstorms over the Big Island as it tracks eastward across the state.
A 1030 mb high pressure system remains far north of the island chain and will continue to produce breezy easterly trade winds across the state through the morning hours. By this afternoon we will transition to more moderate wind speeds as the high pressure system drifts eastward away from the Hawaiian Islands. Expect light to moderate easterly trade winds to continue through the rest of the week with a hybrid wind pattern of trade wind and sea breezes over terrain sheltered leeward areas.
Wetter than normal conditions remain in the forecast for all islands through much of this week. Enhanced showers will continue into Monday as a weakening upper level disturbance drifts from west to east across the island chain. Tuesday will trend a bit drier. An unstable band of clouds and showers, remnants of an old East Pacific cold front, will drift into the islands on the trade winds producing wet weather for all islands from Wednesday into Thursday. An upper level trough sweeping in from north on Thursday and Friday will likely keep enhanced showers in the forecast into next weekend.

Aviation

Breezy easterly trade winds will persist today, with clouds and showers favoring windward and mauka locations. MVFR conditions will be possible in showers, especially across windward areas overnight through the early morning hours. VFR conditions will prevail elsewhere. Although confidence is low, added instability associated with an upper low in the area could lead to an isolated thunderstorm over the Big Island this afternoon.
AIRMET Sierra for tempo mountain obscuration will persist over windward portions of each island through the morning hours.
AIRMET Tango is in effect for moderate turbulence below 8000 feet downwind of island terrain due to the winds. Additionally, moderate turbulence aloft (FL280-FL380) is expected today.

Marine

A high pressure system north of the state has shifted east overnight easing the fresh to strong breezes over some zones. Thus the Small Craft Advisory (SCA) for all waters has been scaled back to typically windy waters around the Big Island and Maui County through today. SCA conditions may drop late Tuesday into Wednesday as the high continues to track east and weaken. Expect gentle to locally fresh trade winds to prevail Wednesday through Friday as a trough develops north of the state and lingers. In addition, a few heavy showers will be possible today.
Pulses of south to southwest swell are due this week, with High Surf Advisory (HSA) conditions expected by Thursday. The PacIOOS buoy off of Lanai is still showing some inconsistent energy in the 16 to 18 second range so have keep surf numbers elevated this morning but with a gradually down trend later today through Wednesday. Forerunners from a larger and longer lived south- southwest swell will arrive Wednesday, and surf is expected rise to the HSA level during the peak of the swell Thursday and Friday.
A pair of small northwest swells will move through over the next several days. The Hanalei PacIOOS buoy shows some northwest energy in the 14 to 18 second range filling in early this morning. Expect this swell to continue to spread down the island chain today, peaking Tuesday, and declining late Tuesday and Wednesday. Wind- driven waves of 8 to 9 feet at 9 seconds will maintain rough east shore surf above the May average through today. As trade winds decline over the next few days, these seas will gradually decline to around May average by Tuesday, then drop to below average for the rest of the week.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST early this morning 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 AM HST Tuesday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov