Photo Credit: Braden Jarvis

West Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Breezy. Isolated showers. Highs around 89 near the shore to around 74 above 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 72 near the shore to around 61 above 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Sunday: Breezy. Mostly sunny with isolated showers. Highs around 89 near the shore to around 76 above 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

South Kaua’i

Today: Breezy. Partly sunny with scattered showers. Highs 79 to 87. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 72. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Sunday: Breezy. Partly sunny with scattered showers. Highs 80 to 87. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 73 to 87 in the valleys to 61 to 66 above 4000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with numerous showers. Lows 66 to 72 in the valleys to around 58 above 4000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Sunday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 74 to 87 in the valleys to 62 to 67 above 4000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

North Kaua’i

Today: Mostly cloudy in the morning then becoming mostly sunny. Scattered showers. Highs 77 to 90. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 65 to 74. East winds up to 15 mph. Chance of rain 70 percent.

Sunday: Partly sunny with scattered showers. Highs 78 to 90. East winds up to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 73 to 85. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 66 to 76. East winds 10 to 15 mph. Chance of rain 70 percent.

Sunday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 74 to 86. East winds 10 to 15 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

A high pressure system north of the Hawaiian Islands will continue to gradually weaken and drift slowly west over the next several days. Trade wind speed trends will remain in the moderate to breezy range through Sunday, and then lower to moderate levels from Monday onward. Strong and stable subsidence aloft will limit shower potential for most days into next week. However, a slight increase in cloud and shower trends will continue through the day today as a weak easterly wave moves from east to west down the island chain.

Discussion

Looking into the satellite picture this morning we see an upper level cold core low and an area of thunderstorms roughly 700 to 800 miles northwest of Kauai. High level cirrus clouds are streaming up from the south over the western islands, riding in along an upper level subtropical jet stream. We also see a slight counter clockwise (cyclonic) rotation in the low level cumulus cloud field associated with a weak trough in the trade winds. This weak easterly wave will continue to slowly move through the islands today, pushing up on the trade wind temperature inversion, and increasing cloud and shower trends into the evening hours. Most of the enhanced showers will form during the typical diurnal rainfall maximum in the overnight to early morning hours.
In the larger scale, a strong high pressure system north of the Hawaiian Islands will continue to produce moderate to breezy trade winds across the region today. The high center will continue to weaken and drift slowly westward, with decreasing wind speed trends into the moderate to breezy range from Saturday to Sunday, and then further weakening to more moderate levels from Monday on through much of next week.
Through much of next week expect fairly stable conditions under an upper level ridge will continue to limit vertical cloud heights and shower development into much of next week. One wrinkle in this forecast was mentioned above with the low level trough adding some short range instability to the mix through tonight. Otherwise stable and mostly dry weather with trade wind thermal inversion heights in the 4,000 to 6,000 foot height range will prevail across the state.

Aviation

Breezy trade winds will hold in place today and tonight, strongest and most gusty from mid morning through late afternoon. Low clouds and showers will favor windward and mauka areas through the period, bringing MVFR cigs/vsbys at times.
AIRMET Sierra remains in effect for mountain obscuration over windward sections of most islands. Conditions should improve by mid morning.
AIRMET Tango remains in effect for moderate low-level turbulence over and downwind of the terrain of all islands. This AIRMET will likely continue through the day.

Marine

Strong surface high pressure far northeast of the state will maintain fresh to locally strong trades through the weekend. A Small Craft Advisory has been extended for the typical windier areas around Maui County and the Big Island through Sunday. By early next week, the aforementioned high is forecast to drift west and allow trades to ease into the gentle to fresh range.
Overlapping small, medium to long period south swells will continue to provide small surf along south facing shores today. Surf along east facing shores will remain choppy with short period wind waves. Local wind swell may wrap into select north and south facing shores. Surf along north facing shores will remain nearly flat, typical of this time of year.

Fire weather

Breezy trade winds and low relative humidity will keep elevated fire weather concerns over leeward areas through Sunday. Locations such as West Maui and leeward Kohala on the Big Island are of particular concern. Trade winds will remain in the moderate to breezy range through Sunday, and then down to moderate levels from Monday onward as the pressure gradient over the state relaxes.
Most leeward areas will remain dry. Brief periods of showers will move into windward areas mainly in the overnight hours. Humidity levels will see good to excellent overnight recoveries. Exceptions to this humidity rule will be for elevations in the 4,000 to 8,000 foot range, which may see periods of warmer temperatures with much drier conditions, within and above the subsidence temperature inversion level.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Sunday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov