Photo Credit: Jason Weingardt

West Kaua’i

Today: Mostly sunny with isolated showers. Highs around 89 near the shore to around 77 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 70 to 75 near the shore to around 62 above 3000 feet. Northeast winds up to 15 mph shifting to the east after midnight. Chance of rain 20 percent.

Wednesday: Breezy. Mostly sunny with isolated showers. Highs around 89 near the shore to around 77 above 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

South Kaua’i

Today: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 84 to 89. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 70 to 75. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Wednesday: Breezy. Mostly cloudy with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 86. Northeast winds 10 to 25 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 75 to 84 in the valleys to around 66 above 4000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 60 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 63 to 69 in the valleys to around 58 above 4000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Wednesday: Breezy. Partly sunny with scattered showers. Highs 75 to 84 in the valleys to around 66 above 4000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

North Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 79 to 88. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 65 to 74. Southeast winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 79 to 88. East winds 10 to 20 mph. Chance of rain 50 percent.

East Kaua’i

Today: Partly sunny with scattered showers. Highs 77 to 87. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 64 to 77. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Breezy. Partly sunny with scattered showers. Highs 77 to 87. East winds 10 to 20 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

A high pressure system far north of the Hawaiian Islands will continue to keep moderate to locally breezy trade winds in the forecast through at least Saturday. Southeasterly winds may develop by the first half of next week. Passing windward and mountain showers will develop during the overnight to early morning hours through the weekend. More isolated showers are possible over leeward areas. A slight increase in these shower trends may develop from Thursday night into the weekend.

Discussion

The big picture moderate to locally breezy trade wind weather pattern continues this morning with bands of fairly stable clouds drifting in on the trade winds. These clouds will produce periods of rain showers mainly along windward and mountain slopes of each island through the early morning hours. Shower activity will diminish around 9 AM HST and then return later this evening. A weakening cold front remains stalled out around 700 miles north to northeast of the state. Unstable clouds in this band may break up and be captured by the trade winds, moving into the islands later this weekend. Cirrus clouds associated with a subtropical jet stream are moving from west to east spreading high level cirrus clouds across the island chain over the next several days. These cirrus clouds are made of ice crystals and will enhance sunrise and sunset colors.
Upper air balloon soundings from 2 AM HST (12Z) this morning are suggesting some stability trends over the western half of the state with trade wind temperature inversion heights at Lihue and Hilo around 4,000 feet and 8,000 feet respectively. The Lihue sounding is much drier and more stable as compared to a wetter looking sounding at Hilo, a big reason for this large difference is due to a band of clouds riding into the eastern half of the Big Island this morning. We will have to see if the drier and more stable trends at Lihue persist into the afternoon hours at the 2 PM HST (00Z) sounding time. This low inversion height may indicate more limited shower activity over the western half of the state in the short range forecast.
A weak trough moving through the trade winds shows up in the 700 MB model streamlines this morning just east of the Big Island around 152W longitude. This trough is hard to see on satellite imagery and much of the dynamics associated with this weak atmospheric wave will pass south of the islands. However, continued cloud and shower enhancement will favor the eastern slopes of Maui and the Big Island through tonight.
The next disturbance in the force is expected to move into the islands late Thursday through Friday night. This trough is associated with the remnants of former Tropical Depression 14E. Expect decent moisture moving across the state with the passage of this system. Hot and muggy feeling weather may develop along with a subtle enhancement to cloud and shower activity statewide. This wet trade wind weather pattern will continue through Monday morning as windward and mountain showers will be enhanced by unstable cloud remnants of the dissipated frontal boundary as these clouds are captured by the trade winds and advected over the island mountains. These weekend showers will mainly affect windward and mountain areas, favoring the typical overnight to early morning time period.
Extended range models continue to hint at a cold front moving into the Central Pacific near the International Date Line early next week. The cold air associated with this trough will break down the ridge north to northwest of Hawaii, placing the islands in a southeasterly wind flow pattern. Changes in weather are expected with wetter trends along the southeastern slopes, Kau and Puna Districts, of the Big Island. Cloud and shower trends will decrease over the rest of the state as the ridge aloft will likely increase subsidence (downward motions in the atmosphere) lowering trade wind temperature inversion heights and the southeasterly winds will cause the smaller islands, from Maui to Kauai, to fall into the leeward rain shadow of Mauna Kea and Mauna Loa.

Aviation

Surface high pressure well north of the islands will allow for moderate trades to persist trough the remainder of today. Scattered showers will mainly affect windward locations with isolated showers elsewhere. There may be brief periods of MVFR ceilings and visibility associated with any heavier activity, but not expecting anything widespread.
AIRMET TANGO remains in effect for tempo moderate turbulence below 9000 feet for areas south through west of mountainous terrain.

Marine

Fresh to strong easterly trades will continue through the week, which supports the Small Craft Advisory (SCA) in place for the windy waters around Maui County and the Big Island. This advisory may need to be expanded to other waters on Wednesday as the ridge strengthens north of the state. Guidance shows the trades backing down slightly over the weekend as a weakness forms in the ridge.
Surf along south facing shores will slowly trend down today, as a south-southwest swell eases. Surf will drop below average on Wednesday, then remain small through Friday. Guidance does depict an upward trend due to a small southeast swell arriving over the weekend.
Surf along north facing shores will trend up today, then remain up through much of this week due a series of small north to north-northeast swells. Early morning observations from buoy 51000 reflect this northerly swell energy centered around the 10-12 second band, which has been trending up overnight. This will be followed by a similar north-northeast swell Thursday through Friday. For the extended, guidance is hinting at similar activity for north and west exposures next week beginning around Monday, but from the north-northwest.
Surf along east facing shores will remain small today, then potentially trend up around Wednesday as the trades increase.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov