Photo Credit: Brendan Stephen

West Kaua’i

Today: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs around 83 near the shore to around 73 above 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows 66 to 71 near the shore to around 57 above 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny with isolated showers. Highs around 82 near the shore to around 72 above 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

South Kaua’i

Today: Breezy. Mostly sunny with isolated showers. Highs around 81. Northeast winds 20 to 25 mph. Chance of rain 20 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 64 to 70. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

Tuesday: Breezy. Partly sunny with scattered showers. Highs around 80. East winds 15 to 20 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Breezy. Partly sunny with scattered showers. Highs around 76 in the valleys to around 65 above 4000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with numerous showers. Lows around 60 in the valleys to around 52 above 4000 feet. East winds 10 to 25 mph. Chance of rain 70 percent.

Tuesday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 75 in the valleys to around 64 above 4000 feet. East winds 15 to 25 mph. Chance of rain 60 percent.

North Kaua’i

Today: Breezy. Mostly sunny with scattered showers. Highs 75 to 82. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 40 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 60 to 69. East winds 10 to 20 mph. Chance of rain 50 percent.

Tuesday: Breezy. Partly sunny with scattered showers. Highs 74 to 81. East winds 15 to 20 mph. Chance of rain 50 percent.

East Kaua’i

Today: Mostly sunny. Breezy. Isolated showers in the morning, then scattered showers in the afternoon. Highs 74 to 80. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 58 to 71. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Tuesday: Breezy. Partly sunny with scattered showers. Highs 73 to 79. East winds 15 to 20 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Trade winds will continue to strengthen, becoming breezy and gusty through Wednesday as a strong high develops north of the state. An upper trough may produce periods of locally enhanced rainfall. Showers will favor windward slopes. Expect afternoon rainfall across leeward and interior Big Island areas. Trade winds will ease to moderate strength Thursday into next weekend.

Discussion

A strong high far northwest of Kauai will build eastward and drive strengthening trade winds for the next few days. A weakening front north of the islands will work to counteract the high's trade-strengthening impact, but trades will slowly increase anyway. Expect breezy and gusty trade winds through Wednesday. The high far north of the state will strengthen to about 1040 mb on Tuesday as the intervening front dissipates, making local trade winds quite strong. Upper troughing will linger and, while conditions are not expected to be significantly unstable, models suggest that the inversion will be weak or absent. This will work to enhance showers. Rainfall will favor windward areas, with enhanced afternoon clouds and shower activity becoming more extensive over leeward and interior Big Island. Periods of thin high clouds will continue.
Trades will ease Thursday as the high to the north weakens. Models suggest a simultaneous but brief instability boost. This could raise chances of thunderstorms, mainly on the Big Island slopes, and shower activity in the trade flow could become enhanced. Moderate trade winds and more stable conditions are expected Friday into next weekend.

Aviation

A high pressure ridge far north of the state will produce moderate to locally breezy trade winds across the Hawaii region through Monday. An upper level trough will enhance shower activity mainly in the windward and mountain areas, favoring the overnight to early morning hours. Periods of MVFR conditions are forecast over windward airfields with prevailing VFR over most leeward sites.
AIRMET Sierra for mountain obscuration remains in effect for north through east sections from Kauai to Maui. These conditions will likely continue through the early morning hours.
AIRMET Tango remains in effect for moderate low level turbulence over and south through west of mountains for all islands. AIRMET Tango is also in effect for moderate to isolated severe turbulence over the islands as a subtropical jet stream approaches from the west.
Occasional light icing in layered clouds will also remain in the forecast. Conditions are mostly likely across Kauai and Oahu.

Marine

High pressure north of the state will build eastward and drive the increasing trades through mid- week, peaking at near- gales in the windiest zones Tuesday into Wednesday, then gradually weakening from Thursday onward. A Small Craft Advisory (SCA) remains in effect for the typical windy zones and has expanded over waters around Kauai and Oahu. The SCA may need to be expanded as trade winds strengthen across the waters.
A small to moderate north (350 deg) swell has begun to rise slightly over the offshore buoys, resulting in building surf for north- facing shores this afternoon with a peak on Tuesday. Surf levels are forecast to approach but not reach the High Surf Advisory (HSA) threshold on Tuesday. East facing shores will have short period trade wind swell from building trades and may also see a slight rise for selective spots exposed to the north swell. A small medium period northwest (320 deg) swell is possible at the end of the week. South-facing exposures will continue to have minimal surf due to long period south swells throughout the week.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Tuesday for Kauai Northwest Waters, Kauai Leeward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Leeward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov