Photo Credit: Brendan Stephen

West Kaua’i

Today: Breezy. Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 87 near the shore to around 74 above 3000 feet. East winds 15 to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 67 to 73 near the shore to around 60 above 3000 feet. East winds 15 to 25 mph with gusts to 45 mph. Chance of rain 50 percent.

Sunday: Breezy. Mostly sunny with isolated showers. Highs around 86 near the shore to around 74 above 3000 feet. East winds 15 to 20 mph. Chance of rain 20 percent.

South Kaua’i

Today: Mostly cloudy. Breezy. Scattered showers in the morning, then showers likely in the afternoon. Highs 79 to 86. East winds around 25 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Windy. Occasional showers in the evening, then scattered showers after midnight. Lows around 72. East winds 25 to 30 mph. Chance of rain 80 percent.

Sunday: Breezy. Partly sunny with scattered showers. Highs 78 to 86. East winds 20 to 25 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Breezy. Partly sunny with scattered showers in the morning, then cloudy with occasional showers in the afternoon. Highs 72 to 82 in the valleys to around 64 above 4000 feet. East winds 20 to 25 mph with gusts to 45 mph. Chance of rain 90 percent.

Tonight: Mostly cloudy. Windy. Occasional showers in the evening, then scattered showers after midnight. Lows 62 to 69 in the valleys to around 58 above 4000 feet. East winds 20 to 30 mph. Chance of rain 90 percent.

Sunday: Breezy. Scattered showers in the morning, then occasional showers in the afternoon. Highs 71 to 82 in the valleys to around 63 above 4000 feet. East winds 15 to 25 mph. Chance of rain near 100 percent.

North Kaua’i

Today: Mostly cloudy. Breezy. Scattered showers in the morning, then occasional showers in the afternoon. Highs 74 to 87. East winds 15 to 25 mph. Chance of rain 90 percent.

Tonight: Mostly cloudy. Breezy. Occasional showers in the evening, then scattered showers after midnight. Lows 63 to 73. East winds 15 to 25 mph. Chance of rain 90 percent.

Sunday: Breezy. Mostly sunny with scattered showers in the morning, then partly sunny with numerous showers in the afternoon. Highs 74 to 86. East winds 15 to 25 mph. Chance of rain 70 percent.

East Kaua’i

Today: Breezy. Partly sunny with scattered showers in the morning, then cloudy with occasional showers in the afternoon. Highs 71 to 84. East winds 20 to 25 mph. Chance of rain 90 percent.

Tonight: Mostly cloudy. Windy. Occasional showers in the evening, then scattered showers after midnight. Lows 64 to 75. East winds 15 to 30 mph. Chance of rain 90 percent.

Sunday: Mostly cloudy. Breezy. Scattered showers in the morning, then numerous showers in the afternoon. Highs 70 to 83. East winds 15 to 25 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Gusty trade winds are expected to prevail through the remainder of the weekend. By Sunday night, a slow moving, upper-level low develops northeast of the islands, resulting in periods of heavy rain, thundershowers, and the potential for a wintry mix along the summits of the Big Island. Thereafter, a new weather regime will develop, leading to light and variable winds, and occasional light showers through the remainder of the outlook period.

Discussion

The quasi-stationary high pressure NNE of the islands continues to be the dominating weather factor, resulting in prevailing gusty winds, especially across wind-prone locations including valleys and channels where downsloping and funneling effects are most prominent, leaving the Wind Advisory unaltered through Sunday morning. Furthermore, these gusty winds are accompanied by mostly dry conditions, continuing the Red Flag Warning to persist through the afternoon for the leeward side of all islands.
As the weekend comes to an end and the work week returns, latest model guidance suggests a change of weather factors, with the development of an upper-level low settling directly over the Big Island and persisting for the next several days. This will play a vital role in reducing winds across the islands and increasing the instability, with 500 mb temperatures in the -12C vicinity; a key component to expanding the clouds and showers to the windward side of all islands. Precipitable water varies slightly between the Euro and the GFS (1.3-1.4 vs 1.2-1.3, respectively) but nevertheless showcasing potentially heavy downpours as early as Sunday night into Monday with periods of isolated thundershowers.
Adequate moisture and sufficient instability over the Big Island will result in more widespread enhanced rainfall that may result in a wintry mix or a light dusting of snow across the summits of Mauna Kea and Mauna Loa; however, confidence remains low on timing and accumulation amounts, if any.
Model guidance indicates the aforementioned upper-level low will exit the region to the east by Tuesday, reducing winds across the island to generally light and variable. This will open the doors to another weather regime change, evolving into land-sea breezes beginning Wednesday. Periods of light showers may develop; yet, the general consensus is much drier conditions are expected through the remainder of the week and into the outlook period.

Aviation

Strong high pressure northeast of the islands should keep strong and gusty trades for the next couple of days. Low cigs and SHRA should mainly impact windward and mauka areas. A few SHRA could make it to leeward sides. While brief MVFR conds are possible with any SHRA, VFR conds will prevail.
AIRMET Tango for mod low-level turb over and downwind of island terrain for the next several days.

Marine

Strong high pressure will remain stationary today far northeast of the islands. The high should gradually weaken Sunday as the pressure gradient slowly weakens through the beginning of next week. A Gale Warning remains in effect through Sunday night for the windier waters and channels around Maui County and the Big Island. A Small Craft Advisory remains in effect for all remaining coastal waters through Sunday night for strong winds and seas greater than 10 feet.
Surf along north facing shores will remain small through the weekend as the short period north swell levels off. A small, medium period northwest swell is expected to fill in Sunday night and linger through the first half of the week. A moderate, short to medium period north swell will build over the second half of next week although uncertainty remains as the system has yet to develop.
Surf along east facing shores will continue to remain large, rough, and choppy through Sunday night coinciding with the strong trade winds. The High Surf Advisory remains in effect through Sunday night for all east facing shores. Next week, surf along east facing shores look to drop as the trade winds ease through the week.
Surf along south facing shores, is expected to remain tiny to flat through the forecast period. Shorelines exposed to the easterly wind wave on south and north facing shores may continue to see an uptick over the weekend.
Peak monthly tides are forecasted in the early morning hours through Monday morning. These high tides combined with elevated seas from strong trade winds may increase coastal inundation impacts for vulnerable locations during the morning high tides. This has prompted a Coastal Flood Statement which will continue through early Monday morning.

Fire weather

A combination of strong, gusty winds, relative humidity values falling below 45%, and vast amounts of dry fuels will contribute to the threat of extreme fire behavior. Given this, a Red Flag Warning will continue to remain in effect through this afternoon.

HFO Watches/Warnings/Advisories

Red Flag Warning until 4 PM HST this afternoon for Niihau, Kauai South, Kauai Southwest, East Honolulu, Honolulu Metro, Ewa Plain, Waianae Coast, Oahu North Shore, Waianae Mountains, Molokai West, Molokai Leeward South, Lanai Windward, Lanai Leeward, Lanai South, Lanai Mauka, Maui Leeward West, Maui Central Valley North, Maui Central Valley South, South Maui/Upcountry, South Haleakala, Big Island South, Big Island Southeast, Kohala, Big Island Interior.
High Surf Advisory until 6 AM HST Monday for Olomana, Maui Windward West, Kauai East, Koolau Windward, Molokai Southeast, Windward Haleakala, Kipahulu, South Haleakala, Big Island Southeast, Big Island East, Big Island North.
Wind Advisory until 6 AM HST Sunday for Lanai Mauka, Kahoolawe, Maui Windward West, Maui Leeward West, Kohala, Big Island Interior, Molokai North, Molokai West, Molokai Leeward South, 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 AM HST Monday 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 AM HST Monday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov