Photo Credit: Braden Jarvis

West Kaua’i

Today: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs around 84 near the shore to around 71 above 3000 feet. East winds 15 to 25 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers after midnight. Lows 66 to 72 near the shore to around 58 above 3000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Saturday: Mostly sunny. Breezy. Highs around 85 near the shore to around 73 above 3000 feet. East winds 10 to 20 mph.

South Kaua’i

Today: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 79 to 86. East winds 20 to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 69. East winds around 20 mph. Chance of rain 50 percent.

Saturday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 80 to 87. East winds 15 to 20 mph. Chance of rain 40 percent.

Kaua’i Mountains

Today: Windy. Partly sunny with scattered showers. Highs 70 to 78 in the valleys to around 62 above 4000 feet. East winds 20 to 30 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 60 to 66 in the valleys to around 56 above 4000 feet. East winds 15 to 25 mph. Chance of rain 50 percent.

Saturday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 72 to 79 in the valleys to around 63 above 4000 feet. East winds 15 to 25 mph. Chance of rain 40 percent.

North Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 73 to 84. East winds 15 to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 61 to 71. East winds 15 to 20 mph. Chance of rain 50 percent.

Saturday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 74 to 85. East winds 15 to 20 mph. Chance of rain 40 percent.

East Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 70 to 82. East winds 15 to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 61 to 72. East winds 15 to 20 mph. Chance of rain 50 percent.

Saturday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 71 to 82. East winds 15 to 20 mph. Chance of rain 40 percent.

Detailed Forecast

Synopsis

A strong high pressure system centered far north of the Hawaiian Islands will continue to produce strong trade winds across the state through tonight then decreasing to more breezy trades from Saturday into Tuesday. These strong winds will build clouds over mountain areas and produce periods of showers mainly over windward and mountain areas with drier conditions over all island leeward sections through the weekend. The weather pattern may change dramatically from Wednesday onward as a kona low sets up just north or northwest of the island chain with unstable weather conditions possible by the end of next week.

Discussion

The satellite imagery this morning shows low level clouds drifting into the islands on the strong trade wind flow with a few bands of high level cirrus clouds drifting through the region. Local radar imagery shows isolated to scattered showers passing through windward and mountain areas of most islands with drier conditions over leeward areas. This pattern will likely continue through the weekend. Strong easterly trade winds are producing vog (Volcanic smOG) over the leeward slopes of the Big Island today. Haze was introduced into the weather grid today and tonight to cover this vog plume spreading westward from the Big Island. Most of the vog will remain south of the smaller islands.
A strong high pressure system centered far north of the Hawaiian Islands will continue to produce breezy to strong trade winds across the region into the weekend. These strong winds will keep wind advisories up for portions of Maui and Hawaii Counties through tonight. A High Wind Warning remains in effect through this afternoon for the Kohala area of the Big Island. The Wind Advisories will probably be dropped by Saturday as wind speeds begin to decrease below Wind Advisory thresholds. However, breezy trade winds will still linger into the first half of next week.
An upper level ridge over the islands will tend to limit rainfall activity into the upcoming weekend with temperature inversion heights ranging from 5,000 to 7,000 feet. Normally this is a drier weather pattern, however in this case shower activity will be driven by the strong trade winds pushing clouds up and over island mountains. Periods of showers remain in the forecast for windward and mountain areas. Downward moving air (subsidence) over leeward areas will create more stable conditions and keep drier weather in the forecast. These conditions will continue through Saturday with a slight increase in showers expected on Sunday as the upper level ridge weakens and a low level cloud band moves through the islands.
Wetter trade winds will develop on Monday and Tuesday as clouds associated with a weak low level trough pass through the islands and the high pressure system north of the state drifts eastward. A cold frontal system moves into the Central Pacific basin late Tuesday will produce a large shift to our weather pattern from Wednesday onward.
In the long range forecast outlook, cold air behind this front will become cut off and long range models are consistently showing a kona low forming just north or northwest of the Hawaiian Islands by next week Thursday and Friday. Much of our future rainfall forecasting will depend on exactly where the low center anchors relative to the islands. However, if the American GFS and European models are close with their current forecasts, then we may see a period of unstable kona weather over a portions of the state by late next week. Stay tuned to the latest forecast updates as these predicted weather conditions will likely evolve over time.

Aviation

Moderate to locally strong trade winds will guide light showers off the Pacific towards north and east facing slopes and coasts of the Hawaiian Islands. Brief MVFR conditions are to be expected in these passing showers. Mountain obscuration could become an issue for Windward Big Island or East Maui later today.
AIRMET Tango remains in effect for occasional moderate turbulence over and immediately south through west of mountains. Conditions are likely to persist through the remainder of the week due to a combination of strong winds in the lower levels and a sharp inversion aloft.

Marine

High pressure north of the islands will keep strong trade winds blowing through early next week, with the trades expected to remain particularly strong through tonight. Gale force winds will continue in the windier waters around Maui and the Big Island, with Small Craft Advisory (SCA) level winds elsewhere through 6 AM Saturday. The trades will ease slightly this weekend, but SCA level winds will likely continue for most marine zones through Tuesday. An approaching cold front is forecast to decrease the trades below SCA levels around the middle of next week.
Strong trade winds will keep east shore surf elevated and well above normal through early next week. A High Surf Advisory remains in effect through 6 PM this evening. Surf along east facing shores will lower to near or below normal levels around the middle of next week as the trades back off.
Surf along north and west facing shores will remain small and well below normal through the weekend. A moderate size northwest and a moderate size north swell will give surf a boost along north and west facing shores Monday through Wednesday with a decline expected on Thursday. A new very large northwest swell could move in next Friday, bringing warning level surf to north and west facing shores.
Surf along south facing shores will remain small with only background south swell energy for the next week.

Fire weather

The Fire Weather Watch was cancelled for all islands this morning as minimum humidity levels will likely remain above critical fire weather thresholds.

HFO Watches/Warnings/Advisories

High Wind Warning until 6 PM HST this evening for Kohala.
Wind Advisory until 6 AM HST Saturday for portions of Maui and Hawaii Counties.
Gale Warning until 6 AM HST Saturday for Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.
Small Craft Advisory until 6 AM HST Saturday for all waters and channels outside of the Gale Warning.
High Surf Advisory until 6 PM HST this evening for east facing shores of Kauai, Maui, Molokai, Oahu and the Big Island.

Data Courtesy of NOAA.gov