Photo Credit: Braden Jarvis

West Kaua’i

Today: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 87 near the shore to around 77 above 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy in the evening, then mostly cloudy with scattered showers after midnight. Lows 70 to 75 near the shore to around 61 above 3000 feet. East winds around 10 mph. Chance of rain 50 percent.

Monday: Partly sunny. Breezy. Isolated showers in the morning. Highs around 87 near the shore to around 77 above 3000 feet. East winds 10 to 25 mph. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 86. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 68 to 74. East winds 10 to 20 mph. Chance of rain 50 percent.

Monday: Partly sunny. Windy. Scattered showers in the morning. Highs around 86. East winds 10 to 30 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Breezy. Partly sunny with scattered showers. Highs 73 to 81 in the valleys to around 70 above 4000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 61 to 66 in the valleys to around 56 above 4000 feet. East winds 10 to 25 mph. Chance of rain 70 percent.

Monday: Mostly cloudy. Breezy. Numerous showers in the morning. Highs 73 to 81 in the valleys to around 70 above 4000 feet. East winds 10 to 25 mph. Chance of rain 70 percent.

North Kaua’i

Today: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 76 to 86. East winds 10 to 15 mph. Chance of rain 40 percent.

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

Monday: Partly sunny. Breezy. Scattered showers in the morning. Highs 76 to 86. East winds 10 to 20 mph. Chance of rain 50 percent.

East Kaua’i

Today: Partly sunny with scattered showers. Highs 75 to 86. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 62 to 75. East winds 10 to 15 mph. Chance of rain 70 percent.

Monday: Mostly cloudy. Numerous showers in the morning. Highs 75 to 86. East winds 10 to 15 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Moderate trade winds will prevail through today. Showers may increase later today, with the highest rainfall chances remaining over windward areas. Expect windy, very gusty, and dry conditions Monday into Wednesday.

Discussion

High pressure far northeast and far northwest of the islands will drive moderate trade winds across the region today and tonight. An upper trough dropping down toward the state will stall near Kauai today, potentially increasing shower activity, especially across the western end of the state. The upper trough will weaken tonight and be pushed away by strong upper ridging moving in from the east. This will lead to rebuilding trade winds and increased stability from Monday onward.
Expect a significant change in our winds Monday through Wednesday. High pressure will build to our north as Hurricane Dora, currently about 1150 miles southeast of Hilo, passes westward about 500 miles south of the islands. The resultant tightening of the pressure gradient over the islands, combined with a drier airmass, will drive a strong and gusty wind pattern. Models show a very low and strong subsidence inversion developing as early as Monday, along with winds of 40 to 50 kt around the inversion level. Under this stable and strong flow, winds over and downwind of terrain should exceed the Wind Advisory threshold, and localized damaging wind gusts to High Wind Warning levels are a real possibility. Expect advisory level winds on the summits of Maui and the Big Island Monday morning, and possibly across adjacent lower elevations. Warning level winds would be possible by Monday afternoon for the summits, with additional lower elevation areas reaching advisory levels. A High Wind Watch is in effect from Monday morning through late Tuesday night.

Aviation

Surface high pressure well to the northeast of the state will continue to help generate moderate trades across the islands through the day today. Some low level moisture caught up in the flow will bring scattered to numerous showers to the windward sides of the islands. Brief periods of MVFR ceilings and visibility may accompany this activity. Elsewhere, expect isolated showers.
There are currently no AIRMETs in effect.

Marine

Trade wind speeds will strengthen today through Tuesday as the high pressure ridge builds north of the islands and Hurricane Dora passes south of the Hawaiian Islands from Monday afternoon through Wednesday morning on a high confidence westward track. Wind speeds will peak on Tuesday as Dora passes well to the south, with gales expected over the windier channels and waters around Maui County and the Big Island from Monday through Wednesday morning where a Gale Watch is posted. Seas will become rough and quickly exceed the Small Craft Advisory thresholds over exposed waters from Monday into Monday night.
Surf along east facing shores will be small today, then quickly ramp up and become rough later tonight through Wednesday due to a combination very strong trades, large seas and a moderate size long period easterly swell generated from Dora. The largest surf is expected over the eastern end of the state, where surf heights may reach warning levels from late Monday through Tuesday night. A downward trend is expected from Wednesday through Thursday as a more typical trade wind pattern returns and seas lower.
Surf along south facing shores will remain small today with mainly a combo of background south and south-southwest swell energy rolling through. A short to medium period southeast swell is expected to fill in Tuesday through midweek as Dora passes far to the south. This will be a short-lived event with a peak occurring late Tuesday into early Wednesday. A long period south- southwest swell originating from the South Pacific will arrive by Wednesday morning and lead to rising south shore surf height trends to near advisory thresholds lasting into Thursday. CDIP buoy readings yesterday at the American Samoa station were reporting from 7 to 8 feet, which would yield at least a 3 foot long period south swell.

Fire weather

There are no significant fire weather concerns today and tonight, but critical fire weather conditions are looking highly likely beginning Monday. Dry, stable, and breezy to windy trades are expected as deep high pressure to the north moves in tandem with Hurricane Dora, which is forecast to pass south of the islands. Conditions could develop as early as Monday, but Tuesday has the greatest potential as the Keetch Byram Drought Index (KBDI) is expected to reach the critical 600 mark and models show leeward relative humidity falling below 45 percent. A Fire Weather Watch is now in effect from Monday morning through late Tuesday night for leeward portions of the islands, where critical fire conditions are most likely to develop.

HFO Watches/Warnings/Advisories

Fire Weather Watch from Monday morning through late Tuesday night for Kauai Leeward, Oahu South Shore, Waianae Coast, Oahu North Shore, Olomana, Central Oahu, Waianae Mountains, Molokai Leeward, Lanai Makai, Lanai Mauka, Maui Leeward West, Maui Central Valley, Leeward Haleakala, Kona, South Big Island, Kohala.
High Wind Watch from Monday morning through late Tuesday night for Lanai Mauka, Haleakala Summit, Big Island Interior, Big Island Summits, Maui Central Valley North, Maui Central Valley South, South Maui/Upcountry.
Gale Watch from Monday morning through late Tuesday night for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov