West Kaua’i

Tonight: Mostly clear. Lows around 75 near the shore to around 64 above 3000 feet. Northeast winds up to 15 mph.

Tuesday: Mostly sunny with isolated showers. Highs 87 to 93 near the shore to around 77 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Tuesday Night: Partly cloudy with isolated showers. Lows around 75 near the shore to around 64 above 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

South Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows around 74. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Tuesday: Mostly sunny. Isolated showers in the morning. Highs 82 to 90. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tuesday Night: Partly cloudy with isolated showers. Lows 71 to 76. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Kaua’i Mountains

Tonight: Mostly cloudy with scattered showers. Lows 68 to 73 in the valleys to around 62 above 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 77 to 86 in the valleys to around 74 above 4000 feet. East winds up to 10 mph. Chance of rain 30 percent.

Tuesday Night: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 67 to 73 in the valleys to around 62 above 4000 feet. East winds 10 to 15 mph. Chance of rain 30 percent.

North Kaua’i

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 69 to 76. East winds up to 15 mph. Chance of rain 40 percent.

Tuesday: Mostly sunny. Isolated showers in the morning. Highs 80 to 89. East winds up to 15 mph. Chance of rain 20 percent.

Tuesday Night: Partly cloudy with isolated showers. Lows 69 to 76. East winds around 10 mph. Chance of rain 20 percent.

East Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 68 to 76. Northeast winds 10 to 15 mph decreasing to up to 10 mph after midnight. Chance of rain 50 percent.

Tuesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 78 to 87. East winds 10 to 15 mph. Chance of rain 30 percent.

Tuesday Night: Partly cloudy with isolated showers. Lows 68 to 76. East winds 10 to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Trade winds will continue through much of the week with high pressure system far to the northeast. A potential area for tropical development remains about 1100 miles east-southeast of the islands. Conditions remain favorable for tropical development and we will continue to closely monitor how this could impact the islands.

Discussion

No changes to the forecast with the afternoon package.
High pressure remains far to the northeast of the state and will continue to bring trades to the region this week. Dewpoints remain in the low to mid 70s across the state, so despite the breezy trade winds, it feels muggier than normal. A brief drop in dewpoint temperatures is expected Wednesday, with a return to low 70s on Thursday and Friday. Expect clouds and showers to be focused over the typical windward and mauka slopes in the trade wind flow. Additional clouds and shower are also expected over the Kona slopes of the Big Island during the afternoon and evening hours.
The main concern is related to the area of potential tropical development about 1100 miles east-southeast of the islands. The National Hurricane Center continues to report that the area is conducive for additional tropical development over the next several days. As no system has yet developed, there remain a lot of questions as to where any such system will form and move. As such, the forecast for Hawaii could change significantly once any such system develops. Stay tuned for the latest updates on this developing tropical cyclone from the National Hurricane Center online at www.hurricanes.gov. When and should a system form, the forecast will be updated to reflect the impacts on Hawaii.

Aviation

Moderate to breezy trade winds are expected over the next several days. Showers will focus mostly over windward and mountain areas, with some lower ceilings over windward and mountain areas this afternoon and tonight. Some heavy showers that developed over upslope Big Island should decrease tonight. Conditions should improve early tomorrow morning as slightly drier air moves in.
AIRMET Sierra is in effect for mtn obsc for windward areas of Kauai and Big Island as well as leeward and upslope Big Island due to persistent showers and low clouds. This AIRMET could continue some of the night as moisture lingers but will likely be cancelled for leeward Big Island as land breezes take hold.

Marine

High pressure to the far northeast will remain nearly stationary through midweek as moderate to locally strong trade winds persist through Wednesday. The Small Craft Advisory (SCA) has been extended through Tuesday afternoon for the windier waters and channels around Maui County and the Big Island. The SCA may need to be extended through Wednesday. Later in the week, the focus will shift to the deep tropics southeast of the state. Latest guidance from the National Hurricane Center has a medium chance in 2 days for a tropical cyclone to form southeast of the islands. Depending on the track, it will have differing effects on local winds, seas and weather as early as Thursday. Northeasterly winds appear likely to strengthen as the cyclone approaches during the latter half of the week, but impacts will be highly track- dependent and there is significant forecast uncertainty at this time.
Surf along south facing shores will continue to remain elevated as overlapping south swells continue to impact the islands. A slightly bigger swell will build in Tuesday as another moderate, long period south swell is expected to arrive late Tuesday, fill in Wednesday, and remain elevated through Friday. Surf may approach advisory levels at the peak of the swell.
Surf along east facing shores will continue to remain moderate and rough due to moderate to locally strong trade winds. Later in the week, the track of a developing tropical cyclone will dictate the potential for a swell from the southeast to east. Aside from wrapping trade wind energy, surf along north-facing shores will remain flat to tiny through the week.
Due to a combination of peak monthly high tides and water levels running higher than predicted in a few locations, a Coastal Flood Statement is in effect for minor coastal flooding around the afternoon high tide through at least Tuesday. Tides will be decreasing on Wednesday, but coastal flooding may continue to be possible around high tide for locations where water levels are running highest.

Fire weather

Fire weather conditions this week will remain just below critical thresholds this week due to the lack of stronger wind speeds. Minimum humidity levels will briefly reach criteria each day over the driest leeward areas and the lower sustained wind speeds will be the limiting factor. Temperature inversion heights near Maui and the Big Island will range from 5,500 to 6,500 feet elevation tonight.

HFO Watches/Warnings/Advisories

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

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Data Courtesy of NOAA.gov