Photo Credit: Braden Jarvis

West Kaua’i

Today: Partly sunny. Breezy. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 80 near the shore to around 66 above 3000 feet. East winds up to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows around 66 near the shore to around 56 above 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tuesday: Breezy. Mostly sunny with isolated showers. Highs around 81 near the shore to around 67 above 3000 feet. East winds up to 25 mph. Chance of rain 20 percent.

South Kaua’i

Today: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 75 to 80. Northeast winds 15 to 25 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 65. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

Tuesday: Breezy. Partly sunny with scattered showers. Highs 76 to 81. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Breezy. Mostly cloudy with occasional showers. Highs 69 to 75 in the valleys to around 58 above 4000 feet. East winds 10 to 25 mph. Chance of rain 90 percent.

Tonight: Mostly cloudy. Breezy. Numerous showers in the evening, then occasional showers after midnight. Lows 58 to 64 in the valleys to around 53 above 4000 feet. East winds 10 to 25 mph. Chance of rain 90 percent.

Tuesday: Mostly cloudy. Breezy. Occasional showers in the morning, then numerous showers in the afternoon. Highs 69 to 75 in the valleys to around 59 above 4000 feet. East winds 10 to 25 mph. Chance of rain 80 percent.

North Kaua’i

Today: Mostly cloudy. Breezy. Occasional showers in the morning, then numerous showers in the afternoon. Highs 70 to 81. East winds 10 to 20 mph decreasing to up to 20 mph in the afternoon. Chance of rain 90 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 58 to 67. East winds 10 to 20 mph decreasing to up to 15 mph after midnight. Chance of rain 70 percent.

Tuesday: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 70 to 81. East winds up to 15 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 70 percent.

East Kaua’i

Today: Mostly cloudy. Breezy. Occasional showers in the morning, then numerous showers in the afternoon. Highs 68 to 78. East winds 10 to 20 mph. Chance of rain 90 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 59 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 68 to 78. East winds 10 to 20 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

High pressure to the north of Hawaii will maintain breezy trade winds through the week. Clouds and showers will favor windward and mauka areas, with the gusty winds carrying some showers over leeward areas at times.

Discussion

The forecast was modified with the morning package to align the PoPs and associated grids towards the NBM. Overall the changes are minor. Through midweek, the PoPs were increased a bit over some windward areas. During the end of the week, the forecast was made a little wetter.
A robust strong surface high remains far north of Oahu continues to drive breezy trades over the area. Mid-level ridging over the islands is helping to maintain a stable airmass overnight. Overnight soundings showed little change, with an inversion based between 6000 to 8000 ft, and precipitable water running slightly below the seasonal normal. As a result, breezy trades will continue, and will carry passing moderate showers over windward slopes. Expect some spotty showers over the Kona slopes of the Big Island this afternoon. The gusty trades could still carry some of the showers to leeward areas on the smaller islands.
Expect little change through much of the week. The surface high will weaken slightly Monday and Tuesday, but the pressure gradient over Hawaii will hold firm as the high sinks a little southward. As a result we are expecting the breezy and gusty trade winds to change little. Another high will move north of Hawaii by Wednesday, and maintain breezy trades through at least Friday. Random patches of moisture in the trade wind flow will bring periodic boosts in mainly windward rainfall over the next several days, with the next area passing through late tonight and Monday morning. Chances for more widespread rainfall and a few heavier showers will increase on Thursday and Friday as an upper-level trough digs to the west of the islands and moves to the east over the islands.

Aviation

Breezy trade winds will remain in place through at least midweek. Clouds and light showers will favor windward coasts and slopes, and be most active in the late night and morning hours. AIRMET Sierra for mountain obscuration will likely become necessary for northeast slopes of Kauai and the Big Island later this morning with conditions expected to last trough mid-afternoon. VFR conditions are expected to prevail elsewhere.
In the afternoon and early evening, lee-side sea breezes and daytime heating will encourage cumulus build-ups along south and west facing slopes of the Big Island, but a strong inversion aloft around 07 kft will limit their growth.
AIRMET Tango remains in effect for moderate low-level turbulence, and will likely be needed through midweek. Additionally, the proximity of a passing upper level jet streak may trigger isolated moderate upper-level turbulence this morning.

Marine

An area of large high pressure centered approximately 1,300 nautical miles north of the islands is producing a tight enough pressure gradient back toward the state to maintain fresh to locally strong trade winds. Little overall change in the near term Central Pacific weather pattern will occur in the coming days as the high remains anchored north of the area and maintains these stronger winds the next several days. A Small Craft Advisory (SCA) remains in effect for all Hawaiian nearshore waters primarily due to these winds but also for relatively higher seas produced by a passing northeast swell. Little change in the overall nature of these strengthened trades and agitated seas has the all-water SCA now in effect through (at least) Tuesday night. Winds may trend down a touch going into the middle of next week as the high gets replaced by another slightly weaker high to the northwest and moves closer to the islands.
The only show in town swell-wise will be a new moderate size, short to medium period northeast (40-60 degree) swell originating from a close proximity gale low. As evidenced by the swell being observed at Buoy 51000 around midnight, it will be filling into the nearshore waters later this morning, peaking during the afternoon and evening hours. A High Surf Advisory (HSA) is in effect for all east-facing shores through early Tuesday morning. The HSA may need to be extended in time on Tuesday. Days of fresh to locally strong trades has produced a rough, short period wind wave and, with no substantial break in the trades, rough conditions are expected to continue along eastern shores. East-facing shore surf trends will have to be closely monitored through the day. The northeast swell mixed in with elevated trade wind waves does create a low probability that rough east surf could briefly reach 15 foot warning thresholds. Weekend eastern passing southern hemispheric gale lows have produced swell energy that will eventually make it into our local waters Thursday. Thus, south-facing shore surf may increase by another foot or two later this week with the arrival of these small, longer period south swells.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Tuesday for Olomana, Maui Windward West, Kauai East, Kauai South, Koolau Windward, Molokai Windward, Molokai Southeast, Windward Haleakala, Kipahulu, Big Island East, Big Island North.
Small Craft Advisory until 6 AM HST Wednesday for all Hawaiian waters,

Data Courtesy of NOAA.gov