Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Breezy. Mostly sunny with isolated showers. Highs around 82 near the shore to around 71 above 3000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows 68 to 74 near the shore to around 61 above 3000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Saturday: Breezy. Mostly sunny with isolated showers. Highs around 82 near the shore to around 70 above 3000 feet. East winds 10 to 25 mph. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 80. East winds 20 to 25 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 70. East winds 15 to 20 mph. Chance of rain 50 percent.

Saturday: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 77 to 82. Northeast winds 20 to 25 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Mostly cloudy. Breezy. Showers in the morning, then numerous showers in the afternoon. Highs 70 to 77 in the valleys to around 61 above 4000 feet. East winds 10 to 25 mph. Chance of rain 80 percent.

Tonight: Mostly cloudy. Breezy. Numerous showers in the evening, then showers after midnight. Lows 62 to 69 in the valleys to around 59 above 4000 feet. East winds 10 to 25 mph. Chance of rain 90 percent.

Saturday: Mostly cloudy. Breezy. Showers in the morning, then scattered showers in the afternoon. Highs 69 to 76 in the valleys to around 61 above 4000 feet. East winds 15 to 25 mph. Chance of rain 80 percent.

North Kaua’i

Today: Breezy. Partly sunny with scattered showers. Highs 73 to 82. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 64 to 72. East winds 10 to 20 mph. Chance of rain 50 percent.

Saturday: Breezy. Partly sunny with scattered showers. Highs 73 to 82. East winds 10 to 20 mph. Chance of rain 50 percent.

East Kaua’i

Today: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 72 to 81. East winds 15 to 20 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 64 to 74. East winds 15 to 20 mph. Chance of rain 70 percent.

Saturday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 72 to 80. East winds 15 to 20 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Two strong high pressure systems moving through the weather pattern far north of the islands will continue to produce strong trade winds for the next seven days. Strong winds will exceed advisory thresholds in windier zones over the eastern half of the state today. Upper level troughing will lift cloud heights and keep periods of wet trade wind showers in the forecast into next week. An upper level low drifting east of the Big Island this weekend and much of next week will bring enhanced shower activity along windward slopes of the Big Island and East Maui.

Discussion

The water vapor satellite imagery this morning continues to show a few upper level lows embedded along a narrow trough over the Hawaiian Islands. Divergence aloft associated with this upper level troughing are keeping trade wind temperature inversion heights elevated in the 8,000 to 10,000 foot range. Upper air balloon soundings at 12Z this morning over Lihue and Hilo show inversion heights around 8,000 and 10,000 feet respectively. Strong trade winds under this inversion will continue to lift the moisture up the windward mountain slopes of each island and produce numerous showers over windward and mountain areas. These elevated inversion heights will allow windward and mountain showers to spread into leeward areas into the weekend.
Two strong high pressure systems will move through the regional weather pattern far north of the state over the next seven days, keeping strong and gusty trade winds in the forecast. Surface wind speeds will likely exceed wind advisory thresholds during this breezy to windy trade wind time period. The Wind Advisory was extended into the windier areas of most islands in Maui County, while this advisory remains in effect for the North Kohala area of the Big Island lasting through this afternoon. This advisory may be extended in time as strong and gusty trade winds remain in the forecast into Saturday. A brief decrease in trade wind speeds are anticipated late Saturday into Sunday, as the first high pressure center weakens far north of the island chain and another strong high quickly builds in to take its place. Wind speeds will increase back into the breezy to windy range from late Sunday through much of next week.
An upper level trough with embedded cold core lows, will also linger over the Hawaii region through next week. This upper trough will keep periods of trade wind showers over the islands most days. Trade wind inversion heights will likely range from 7,000 to 10,000 feet into the weekend. Slightly higher trade wind heights in the 10,000 to 12,000 foot range are forecast for the windward Big Island this weekend as a passing upper low drifts in a few hundred miles east of Hilo. Shower activity will favor windward and mountain regions with higher coverage in the overnight to early morning hours.
A slight decrease in shower trends may develop from Kauai to Maui starting on Monday and lasting through Thursday, as the upper trough axis shifts south of the island chain producing more stable convergent flow aloft for most of the smaller islands. The windward Big Island might be the exception as it remains closest to another upper low setting up just a few hundred miles east of Hilo from Tuesday through Thursday.

Aviation

High pressure to the northeast will maintain fresh to strong trade winds into the weekend, with low clouds and showers favoring windward sections of the islands. MVFR ceilings and visibility in SHRA will be confined to windward slopes through the early morning hours, with some decrease in shower activity during the day. VFR conditions will prevail across leeward areas. Meanwhile, a few high cirrus clouds will continue to stream over the state today as a low aloft weakens west of the islands.
AIRMET Sierra for tempo mountain obscuration remains in effect for windward sections of Kauai, Oahu, and the Big Island. Improving conditions are expected over the smaller islands later this morning, but conditions may linger over the Big Island today.
AIRMET Tango is in effect for low level mechanical turbulence downwind of the terrain on all islands. Expect this AIRMET to remain posted into the weekend.

Marine

Strong high pressure to the northeast will remain the driving force for strong to near-gale force trades over the coastal waters through the forecast period. A new high replacing the existing one this weekend may cause a brief, and slight, decline in wind speeds. As the new high builds, expect another uptick in wind speeds. A Small Craft Advisory remains in effect for all coastal waters for the winds and the seas generated by the winds. Expect this to continue through the weekend, and likely into next week.
The upper level low west of the region continues to produce some thunderstorms in the western offshore waters. The potential for thunderstorms remains in the forecast there through the weekend as the low continues to move west.
The strong trades upstream of the islands will maintain the large and rough trade wind swell into next week. The current High Surf Advisory for east facing shores is out through early Saturday morning. Its possible that surf will drop a little this weekend with winds decreasing just a bit, but as the winds increase again early next week, surf will once again increase in response. A small northwest swell (310-320) will maintain below normal surf along north and west facing shores before essentially fading entirely by the middle of next week. South swell will hold at background levels.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Saturday for east facing shores.
Wind Advisory until 6 PM HST this evening for portions of Maui County and northern Big Island.
Small Craft Advisory until 6 PM HST Monday for all Hawaiian waters,

Data Courtesy of NOAA.gov