Photo Credit: Brendan Stephen

West Kaua’i

Today: Mostly sunny with isolated showers. Highs around 88 near the shore to around 76 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 61 above 3000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers. Highs around 88 near the shore to around 76 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

South Kaua’i

Today: Mostly cloudy in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs around 85. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 68 to 74. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday: Breezy. Mostly cloudy with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 85. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Partly sunny with scattered showers. Highs 75 to 82 in the valleys to around 66 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 61 to 66 in the valleys to around 56 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tuesday: Mostly cloudy with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 75 to 82 in the valleys to around 66 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

North Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 78 to 87. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 64 to 74. East winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 78 to 87. East winds up to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Partly sunny with scattered showers. Highs 78 to 86. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 62 to 75. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 78 to 86. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

A high pressure system far northwest of the Hawaiian Islands will continue to keep moderate to locally breezy trade winds in the forecast through the weekend. Passing windward and mountain showers will develop during the overnight to early morning hours in this pattern. More isolated showers are possible over leeward areas. A slight increase in these shower trends may develop from Thursday night into the weekend.

Discussion

Satellite imagery this morning continues to show a fairly stable cloud pattern in the trade wind flow just upstream of island chain with less shower coverage last night as compared to the previous two nights. Farther north of the Hawaii Region a cold front is approaching from the north. This front will stall north of the islands and weaken with perhaps a slight increase in island showers next weekend as remnant clouds from this band sneaks into the trade wind flow. Far east of the state a circulation associated with former Tropical Depression 14E will bring subtle increases in cloud and shower trends into the state from Thursday night to Friday night. Upper air balloon soundings from 12Z this morning at Lihue and Hilo show temperature inversion heights around the 8,000 foot elevation level. This stable layer aloft will tend to keep scattered to numerous showers in the forecast over the windward and mountain slopes of most islands.
The forecast remains fairly consistent from day to day with only slight changes in cloud and shower trends in the forecast mainly over windward and mountain areas. A high pressure ridge north of the islands will keep moderate to locally breezy trade winds in the forecasts into next weekend with a slight decrease in shower coverage through Wednesday. Additional moisture will produce a subtle increase in cloud and shower trends later this week. The first round in moisture increases is associated with the remnants of former Tropical Depression 14E reaching the islands late Thursday into Friday. The next round of shower enhancement will be from cloud bands associated with a former cold front that stalled out north of the state and then was captured by the trade winds is expected to move into the islands by Saturday.
In the extended range forecast for next week Monday onward, another cold frontal trough moving into the Central Pacific near the International Date Line will break down and move the ridge axis over the islands, producing more stable southeasterly wind flow over the state, and increasing clouds and showers moving up the southeastern slopes over the Kau and Volcano regions 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) decreasing 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 northwest of the islands will allow for moderate trades to persist trough the forecast period. 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, though trades will weaken slightly later today.

Marine

Fresh to strong easterly trades will persist through most of the week, which supports the small craft advisory continuing for the windy waters around Maui County and the Big Island. This advisory may need to be expanded to other waters by Wednesday as the ridge strengthens north of the state. Guidance shows the trades backing down slightly Friday through the weekend as a weakness forms in the ridge.
Surf along south facing shores will remain up through Tuesday due to a fresh, long-period south-southwest swell filling in (200-210 degrees). The nearshore PacIOOS buoy at Barbers Point reflects this new energy centered around the 18 second band this morning. Surf will drop below average around 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 slightly Tuesday, then remain up through much of this week due to a system that skirted the Aleutians from west to east over the past few days and is now parked in the Gulf of Alaska. The initial phase will arrive Tuesday out of the north and linger through midweek, before transitioning out of the north-northeast Thursday and Friday. For the extended, guidance is hinting at similar activity for north and west exposures next week beginning around Tuesday, but from swell energy out of a more typical northwest direction.
Surf along east facing shores will remain small and rough into Tuesday, then potentially trending up around midweek as the trades pick up.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov