Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Partly sunny with isolated showers. Highs around 82 near the shore to around 70 above 3000 feet. Southeast winds up to 15 mph shifting to the south in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy. Isolated showers after midnight. Lows around 69 near the shore to around 59 above 3000 feet. South winds around 10 mph. Chance of rain 20 percent.

Tuesday: Mostly cloudy with isolated showers. Highs around 82 near the shore to around 69 above 3000 feet. South winds 10 to 15 mph. Chance of rain 20 percent.

South Kaua’i

Today: Breezy. Partly sunny with isolated showers. Highs 79 to 84. Southwest winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy. Scattered showers after midnight. Lows around 68. Southwest winds 10 to 15 mph. Chance of rain 40 percent.

Tuesday: Mostly cloudy with scattered showers. Highs 78 to 83. South winds 10 to 15 mph. Chance of rain 40 percent.

Kaua’i Mountains

Today: Breezy. Partly sunny with isolated showers. Highs 73 to 79 in the valleys to around 63 above 4000 feet. Southwest winds up to 20 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 61 to 67 in the valleys to around 58 above 4000 feet. Southwest winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday: Breezy. Mostly cloudy with scattered showers. Highs 73 to 79 in the valleys to around 63 above 4000 feet. South winds 10 to 20 mph. Chance of rain 50 percent.

North Kaua’i

Today: Breezy. Mostly sunny with isolated showers. Highs 73 to 82. South winds up to 25 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy. Isolated showers after midnight. Lows 62 to 70. South winds 10 to 15 mph. Chance of rain 20 percent.

Tuesday: Partly sunny with scattered showers. Highs 73 to 82. South winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Breezy. Isolated showers. Highs 72 to 82. Southwest winds 10 to 25 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy. Scattered showers after midnight. Lows 62 to 73. Southwest winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday: Mostly cloudy with scattered showers. Highs 72 to 82. South winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

A stationary front cloud band remains just north and west of Kauai this morning as the subtropical ridge remains locked in place over the Hawaii region. Expect light to moderate southerly winds over the islands through Tuesday with hybrid sea breezes each day along terrain sheltered north slopes of each island. Stable conditions aloft will keep mostly dry weather with just a few isolated light showers mainly along sea breeze wind convergence boundaries. A cold front will move into the smaller islands from Wednesday morning near Kauai to Maui County by Thursday. Drying trends and southerly flow will return from Friday to Saturday. The next round of rainfall will likely arrive by Sunday as another cold front drifts into the western islands.

Discussion

Satellite imagery this morning continues to show pillow like stable stratocumulus clouds developing across the Hawaii region. Upper air balloon soundings show subsidence inversion heights around 5,000 feet at both Lihue, Kauai and Hilo, Hawaii as of 2 AM HST. This means only limited light shower activity in the short range forecast is possible. The approaching short wave trough roughly 600 miles northwest of Kauai is on a collision course with the lingering stationary front. The steering flow aloft associated with this short wave trough will push the front eastward into the islands from Wednesday through Thursday. Satellite imagery shows this process is right on track with global model solutions.
Rain and wind threats with this passing cold front appear to be fairly minor at this point in time. While gusty winds are possible near any showers and along north and east facing shores of island mountains. We do not expect these wind gusts to reach Wind Advisory thresholds for most locations. However, the highest summits on Maui and the Big Island will likely see strong winds at or above advisory thresholds. Expect rainfall for all areas from Kauai to Maui during this event, however the flood threat is low with only water ponding on area roads and elevated stream levels are forecast with this system.
The humid, warm and fairly dry weather conditions will rapidly change over Kauai County starting late Tuesday around midnight HST where south winds will strengthen and veer from a more southwesterly direction by late Wednesday morning. These stronger southwesterly winds will produce gusty winds in some areas, typically along north and east slopes of island mountains. Numerous showers will develop over Kauai around sunrise on Wednesday morning. Showers and clouds will diminish for Kauai by Thursday morning as the front drifts eastward with cool westerly winds.
Stronger southerly winds and showers trends will develop over Oahu by Wednesday morning ahead of the approaching cold front that will move over Oahu by late Wednesday afternoon. Expect numerous showers as the frontal band lingers over Oahu into Wednesday night. As was the case for Kauai wind speeds will increase a bit in the afternoon hours with some stronger gusts near showers and along north and east slopes of island mountains. Clouds and showers will diminish over Oahu by Thursday morning as the cold front drifts eastward with cooler temperatures.
The islands in Maui County will start to see increasing southwesterly winds, clouds and showers starting Wednesday afternoon as the cold front approaches. Scattered to numerous showers are forecast as the cold front stalls and weakens over Maui on Thursday. Expect cooler conditions for Maui County by Thursday night with decreasing clouds and showers. However, stronger winds aloft may produce wind speeds at the summit of Haleakala in the solid wind advisory range.
The Big Island will miss out on much of the rainfall as the front will diminish before reaching the eastern edge of the state. However stronger winds aloft will produce High Wind Advisory to Warning levels for the highest summits of Mauna Kea and Mauna Loa from Wednesday night into Friday.
The stable subtropical ridge pattern returns on Friday and Saturday with light to moderate southerly winds, hybrid sea breezes along terrain sheltered northern slopes of each island, and limited rainfall. The next round of rainfall will likely arrive by next Sunday as another cold front drifts into the western islands. Stay tuned.

Aviation

Sluggish southerly background flow will allow a land breeze/sea breeze pattern to persist through today. After a rather clear morning, expect increased cloud cover this afternoon through early evening. VFR will prevail at the TAF sites, but MVFR ceilings may occur during afternoon sky cover maximum across mauka areas. No AIRMETS are in effect now, but AIRMET Sierra may be needed this afternoon if MVFR conditions develop within increased mauka cloud cover.

Marine

A series of large west to west-northwest (280-310 deg) swells is expected this week, which will keep exposed waters and beaches under a Small Craft and High Surf Advisory through at least midweek. The first and largest west swell has peaked and will continue to slowly ease today. Recent observations at the offshore buoys to the northwest reflect this trend and show the spectral peak down into the 12-15 second bands while holding out of the west-northwest (280-300 degrees). As a result, the High Surf Warning for exposed beaches has been lowered to an advisory this morning. The next westerly pulse is expected to fill in tonight through Tuesday, then again Wednesday night through Thursday. The westerly component will allow some wrap into southern exposures and, combined with increasing south-southwest winds, support increasing surf for south facing shores. In addition to the dominant westerly swells, a small northerly (360 deg) swell has filled in overnight and will peak today before moving out tonight.
Expect the local winds to hold out of the south to southwest over the smaller islands and out of the southeast around the Big Island through the first half of the week. Wind speeds will near SCA levels Tuesday night through Wednesday as a currently-stalled front approaches and begins to move through the island chain. Wind directions will shift out of the west to west-northwest following its passage late Wednesday through Thursday, with speeds easing into the light to moderate range.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Wednesday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kona, Kohala, Kauai North, Molokai Windward, Molokai North, Molokai West, Lanai Leeward, Maui Central Valley North, Windward Haleakala, Big Island South.
Small Craft Advisory until 6 AM HST Wednesday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters.

Data Courtesy of NOAA.gov