Photo Credit: Jason Weingardt

West Kaua’i

Today: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 83 near the shore to around 73 above 3000 feet. East winds 10 to 15 mph shifting to the northeast in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy with scattered showers. Lows 66 to 71 near the shore to around 57 above 3000 feet. Northeast winds 10 to 15 mph decreasing to up to 15 mph after midnight. 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: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 81. Northeast winds around 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with numerous showers. Lows 64 to 70. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Tuesday: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 80. Northeast winds 15 to 20 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Cloudy. Showers in the morning, then scattered showers in the afternoon. Highs around 76 in the valleys to around 65 above 4000 feet. East winds 10 to 15 mph. Chance of rain 90 percent.

Tonight: Cloudy and breezy. Numerous showers in the evening, then showers after midnight. Lows around 60 in the valleys to around 52 above 4000 feet. East winds 10 to 20 mph. Chance of rain 90 percent.

Tuesday: Mostly cloudy. Breezy. 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 20 mph. Chance of rain 80 percent.

North Kaua’i

Today: Mostly cloudy with scattered showers. Highs 76 to 82. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with numerous showers. Lows 60 to 69. East winds 10 to 15 mph. Chance of rain 70 percent.

Tuesday: Partly sunny with scattered showers. Highs 75 to 81. East winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 74 to 80. East winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with numerous showers. Lows 58 to 71. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Tuesday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 73 to 79. East winds 15 to 20 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

An upper level low over the islands this morning will weaken on Tuesday. Trade winds have also returned to the region. Expect a wet trade wind weather pattern today with isolated thunderstorms for some areas into the Monday morning hours. Thunderstorms will continue over the Big Island each afternoon through Tuesday. Expect showers in this wet trade wind pattern to slowly decrease in coverage into Wednesday with showers favoring windward and mountain areas. Decreasing trade wind showers are forecast on Thursday, then increasing shower activity again from Friday into next weekend as another upper low sets up northeast of the state.

Discussion

Satellite imagery this morning shows clouds and showers continuing to develop across the region. However, both satellite and local radar imagery show these convective clouds appear less intense compared to the heavier showers and thunderstorms that developed last night. More stable trade winds have also returned at the surface. This means the upper low is likely weakening and the enhanced showers should be less intense today with shower coverage slowly decreasing into Wednesday. Isolated thunderstorms remain in the forecast through the afternoon hours, then only popping up near the Big Island on Tuesday afternoon. The Winter Weather Advisory for the Big Island Summits was extended until this evening due to continued snow showers. These snow showers are forecast to decrease in frequency through the afternoon hours.
Upper air balloon observations from 2 AM HST this morning at Lihue and Hilo show a weak trade wind temperature inversion setting up around the 7,000 foot elevation level. This weak inversion will likely strengthen over the next 24 hours as stability increases and will allow for periods of showers to continue into Wednesday. The highest shower coverage will occur along windward and mountain areas with the highest rainfall amounts favoring the overnight to early morning hours.
Wednesday will likely start a brief transition period to a drier trade wind weather pattern as a weak upper level ridge develops over the islands. Trade wind temperature inversion heights will range from 5,000 to 7,000 feet limiting shower activity. Only brief passing showers are expected mainly over windward areas in the overnight hours. These more typical trade winds will last through Thursday night.
Trade winds continue from Friday into next weekend as an upper level low develops northeast of the Hawaiian Islands. This upper low will lift the trade wind inversion heights and produce periods of showers across the state.

Aviation

A disturbance aloft will shift east of the islands early this morning, allowing conditions to gradually improve over the eastern end of the state. A return of more typical trade wind weather is expected as the day progresses, although it may be a bit more showery than normal, particularly over windward slopes and coasts.
AIRMET Sierra remains in effect for mountain obscuration across Maui County and the Big Island. Conditions should improve in these area later this morning. AIRMET Tango remains in effect for moderate upper level turbulence over the entire state. Conditions should improve over the western islands later this morning, but the turbulence could linger through the day over the eastern end of the state. Finally, a mention of light icing remains in AIRMET Zulu over the eastern end of the state.

Marine

Although trade winds have returned and should hold through the week, added instability associated with an upper disturbance supports locally heavy showers and a few thunderstorms over the next day or two. The best chance of for this activity will transition to windward coasts and waters. Small Craft Advisory level winds (25 kt) will persist through the first half of the week over the windier channels and waters around Maui County and the Big Island. Winds may weaken slightly by next weekend as the ridge settles southward.
Surf along east facing shores will steadily rise through the first half of the week as the easterly trades return locally and upstream across the eastern Pacific (1036 mb high building off west coast today thru Tuesday). Guidance shows this holding into the second half of the week before easing next weekend as the trades upstream trend down.
The quiet conditions across the northern Pacific continues through the first week of April, with minimal swell anticipated. This will translate to the nearly flat conditions continuing for north and west facing shores. The exception will be for north facing shores exposed to trade wind energy wrapping in, which could generate some small surf for the typical standout locations this week, especially starting by Tuesday. For the extended, there is a potential for a short/medium period northerly swell associated with a decent sized area of north-northwest winds setting up and expanding southward from the Aleutians around the Date Line Friday through Saturday. If this materializes, this swell would arrive locally early next week and linger through midweek.
For south facing shores, guidance supports the small conditions continuing well into April with mainly background energy moving through. The European solution does depict a gale setting up south-southeast of New Zealand within our swell window later this week with seas climbing to 30 ft, which could produce a small south-southwest source by mid April.

HFO Watches/Warnings/Advisories

Winter Weather Advisory until 6 PM HST this evening for Big Island Summits.
Small Craft Advisory until 6 AM HST Tuesday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov