Photo Credit: Brendan Stephen

West Kaua’i

Today: Breezy. Mostly sunny with isolated showers. Highs around 79 near the shore to around 67 above 3000 feet. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Gusts up to 45 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows around 68 near the shore to around 57 above 3000 feet. East winds up to 25 mph. Gusts up to 45 mph in the evening. Chance of rain 50 percent.

Sunday: Breezy. Mostly sunny with isolated showers. Highs around 78 near the shore to around 66 above 3000 feet. East winds up to 25 mph. Chance of rain 20 percent.

South Kaua’i

Today: Mostly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 78. East winds 15 to 25 mph. Chance of rain 70 percent.

Tonight: Breezy. Partly cloudy with scattered showers. Lows 64 to 69. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

Sunday: Breezy. Partly sunny with numerous showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs around 77. Northeast winds 15 to 25 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Partly sunny. Breezy. Occasional showers in the morning, then numerous showers in the afternoon. Highs 66 to 74 in the valleys to around 61 above 4000 feet. East winds 10 to 25 mph with gusts to 45 mph. Chance of rain 80 percent.

Tonight: Mostly cloudy. Breezy. Numerous showers in the evening, then occasional showers after midnight. Lows 57 to 62 in the valleys to around 51 above 4000 feet. East winds 10 to 25 mph. Chance of rain 90 percent.

Sunday: Partly sunny. Windy. Occasional showers in the morning, then numerous showers in the afternoon. Highs 65 to 73 in the valleys to around 60 above 4000 feet. East winds 10 to 30 mph. Chance of rain 80 percent.

North Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 71 to 78. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Numerous showers in the evening, then scattered showers after midnight. Lows 60 to 69. East winds up to 20 mph. Chance of rain 70 percent.

Sunday: Breezy. Partly sunny with scattered showers. Highs 70 to 77. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

East Kaua’i

Today: Breezy. Partly sunny with numerous showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs 71 to 78. East winds 10 to 20 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with numerous showers. Lows 58 to 70. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Sunday: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 70 to 77. Northeast winds 10 to 25 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Strong high pressure north of the state will keep breezy to windy trades in place through late next week. Scattered to numerous showers can be expected over windward slopes and coasts, with a few showers reaching leeward communities as well due to the strength of the trades.

Discussion

Currently at the surface, a 1038 mb high is centered around 1100 miles north of Honolulu, with another 1048 mb high located 1600 miles north-northwest of Kauai. The pressure gradient produced by these features is keeping breezy trade winds in place across the island chain early this morning. Infrared satellite imagery shows low clouds moving in from the east with the trades, while scattered high clouds are streaming overhead from the west. Variably cloudy conditions are present over the islands, with cloud coverage the greatest over windward areas. Radar imagery shows scattered to numerous showers moving into windward areas, with decaying showers spilling over into leeward communities at times as well. The main short term concern during the next few days revolves around trade wind strength and the need for any headlines.
The two highs north of the islands will merge into a single strong high today, with the high then gradually shifting southeastward through the middle of next week. Breezy to windy trades can be expected across the islands through the period, and Wind Advisories will likely be needed at times, particularly during the early to middle part of next week. Based on the latest observational trends and model guidance, winds should remain just below advisory thresholds across the islands today.
As for the remaining weather details, very little change in the overall weather pattern is expected through late next week. Precipitable water values will hold at or below normal for this time of year in the 0.8 to 1.2 inch range. Steep low level lapse rates will counteract the dry air however, allowing for efficient moisture flux into the boundary layer, while the strong trades will also assist in enhancing orographic lift. Overall, expect scattered to numerous passing showers to affect windward areas through the period, with a few showers reaching leeward communities at times due to the strength of the trades.

Aviation

High pressure to the north will maintain breezy to strong trade winds through at least Sunday with low clouds and showers favoring windward sections of the islands.
As of 2 am, Hawaii radars revealed multiple bands of low topped showers speeding quickly across the smaller islands, but stalled along the Windward Slopes of the Big Island. AIRMET Sierra for mountain obscuration is in effect for for northeast slopes of the Big Island. Conditions are expected to persist through mid- morning, then temporarily improve in the afternoon and early evening. Elsewhere, VFR conditions will prevail except for brief MVFR in passing showers.
An upper level jet will continue to stream layers of cirrus out of the southwest towards the islands. The proximity of the upper jet could also trigger moderate upper level turbulence over the state later today.
AIRMET Tango is already in effect statewide for moderate low level mechanical turbulence downwind of higher terrain. Conditions are expected to persist through twenty-four hours and beyond.

Marine

A strong high pressure system far north of the Hawaiian Islands will slowly weaken and be replaced by a new high pressure system building in far north of the state on Sunday. This replacement cycle will produce a brief and slight decrease in the strong trade winds into Sunday morning. However by Sunday afternoon, trade wind speeds will increase once again into the strong to near gale range. A Gale Warning remains a low possibility for the windier channels from Sunday into early next week. These near gale conditions do not merit a Gale Watch at this time. A Small Craft Advisory remains in effect for all coastal waters for winds and seas at least through Wednesday. An upper level low west of the islands will continue to produce isolated thunderstorms in the southwestern offshore waters through the weekend.
The strong trades over the region will maintain a large east to west upstream fetch area and continue to produce rough trade wind swell affecting exposed east facing shores into next week. The current High Surf Advisory (HSA) for east facing shores was extended in time through this afternoon. East shore surf heights will briefly drop below HSA levels from tonight through Sunday as wind speeds briefly decrease, however east facing surf heights will quickly ramp back up to advisory levels by Monday morning.
A small northwest swell (310-320 degrees) will peak today and then slowly decline through early next week. Surf heights along north and west facing shores will remain below normal through next week. Another small longer period northwest swell (310-320 degrees) will build into the islands from Thursday night into Friday morning proving a small boost to surf heights along north and west facing shores. South swell will hold at background levels through much of next week with a slight increase in surf heights above background levels from Saturday night into Monday due to the arrival of a new small long period (20-22 second) south swell.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov