Photo Credit: Jason Weingardt

West Kaua’i

Today: Mostly sunny early in the morning, then partly sunny with isolated showers in the late morning and afternoon. Highs 85 to 90 near the shore to around 76 above 3000 feet. Light winds. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers early in the evening. Lows around 70 near the shore to around 58 above 3000 feet. Light winds. Chance of rain 20 percent.

Saturday: Mostly sunny. Isolated showers in the late morning and afternoon. Highs around 87 near the shore to around 75 above 3000 feet. Light winds. Chance of rain 20 percent.

South Kaua’i

Today: Mostly sunny early in the morning, then partly sunny with isolated showers in the late morning and afternoon. Highs 83 to 89. Northeast winds around 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows around 68. Northeast winds around 10 mph. Chance of rain 20 percent.

Saturday: Mostly sunny with isolated showers. Highs 83 to 89. Northeast winds around 10 mph shifting to the southeast in the afternoon. Chance of rain 20 percent.

Kaua’i Mountains

Today: Mostly sunny early in the morning then becoming partly sunny. Isolated showers early in the morning, then scattered showers in the late morning and afternoon. Highs 75 to 82 in the valleys to around 66 above 4000 feet. East winds around 10 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy early in the evening then becoming partly cloudy. Scattered showers early in the evening, then isolated showers in the late evening and overnight. Lows 59 to 65 in the valleys to around 55 above 4000 feet. Light winds. Chance of rain 40 percent.

Saturday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 75 to 82 in the valleys to around 66 above 4000 feet. Light winds. Chance of rain 30 percent.

North Kaua’i

Today: Partly sunny with isolated showers. Highs 78 to 86. East winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 62 to 71. Light winds. Chance of rain 20 percent.

Saturday: Mostly sunny with isolated showers. Highs 78 to 86. Northeast winds around 10 mph. Chance of rain 20 percent.

East Kaua’i

Today: Partly sunny with isolated showers. Highs 77 to 86. Northeast winds around 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 60 to 73. Light winds becoming northwest around 10 mph after midnight. Chance of rain 20 percent.

Saturday: Mostly sunny with isolated showers. Highs 77 to 86. Northeast winds around 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A large low pressure system will linger far north of the Hawaiian Islands well into next week, weakening the high pressure ridge north of the islands, and keeping the trade winds light through Thursday. Sea breezes will develop each afternoon with brief afternoon to evening showers. A cold front approaching the islands from the north will stall out before reaching Kauai and fade away on Sunday and Monday. An unstable tropical moisture plume will be drawn northward over the islands producing a wet and unstable weather pattern over the state from Monday onward with enhanced showers forecast across the island chain.

Discussion

The satellite imagery this morning shows a weakening cold front stalling out just north of Kauai. This system will have little impact on island weather. Elsewhere cloud tops are building south of the Big Island, as a low level trough pulls up deeper tropical moisture as it passes south of the state over the next few days. Some of this tropical moisture will be drawn up into Hawaii and enhance shower activity through the first half of next week. High level cirrus clouds are passing over the state, these clouds are associated with the subtropical jet stream over the region.
A complex low pressure system far north of the state will drift south towards the islands and become cut off from the main polar front jet stream. The weak cold front currently stalling north of the island chain will fade away today and then be replaced by another weakening front, forecast to stall north of the state from Sunday to Monday. The larger cut off low will anchor roughly 1000 miles north of the Hawaiian Islands this weekend. This low will weaken the ridge north of the islands extending our light to moderate trade wind flow, and draw up additional tropical moisture across the islands through much of next week.
Weather conditions through Sunday will remain in a light trade wind and sea breeze pattern. Hot and humid conditions will be the rule with more variable wind direction trends. Clouds and passing showers may develop over windward areas through the overnight and early morning hours, then in the afternoon to early evening these clouds and showers will transition to leeward and island interior areas due to sea breeze wind convergence and heating. A low level trough (shown on 700 mb streamlines) currently passing south of the islands will likely enhance shower activity through this weekend over all islands in Maui and Hawaii Counties. Isolated thunderstorms are also possible over the higher elevations of the Big Island into the weekend.
Longer range weather conditions from Monday through next Thursday remain wet and unstable as the cut off low north of the state draws up tropical moisture into the island chain. Our long range guidance continues to vary a bit on the island by island impacts this far out in the forecast cycle. However, wet trends remain a likely outcome for all islands with the highest enhancement to clouds and showers expected over the northwestern islands from Kauai to Molokai. More details will be added to this extended range forecast in the next few days as the forecast time period gets closer and our confidence grows. Stay tuned for weather forecast updates as next week's weather pattern will likely evolve over time.

Aviation

A weak front located just north of the main Hawaiian Islands will continue to cause the background trade wind flow to weaken today. This will likely allow local afternoon sea breezes and nighttime land breezes to develop over each of the individual islands through Saturday. The weak low-level trade wind flow will continue to bring some low clouds and showers into the windward sides of the central islands this morning. This is likely producing periods of MVFR conditions due to broken to locally overcast low clouds and scattered showers over windward sections of Maui and Molokai. As a result, AIRMET Sierra remains in effect for mountain obscuration for the higher terrain on Maui and Molokai. This AIRMET may be cancelled later this morning if conditions improve. Elsewhere, brief periods of MVFR conditions are possible along the windward sides of the remaining islands, but VFR conditions will likely prevail over most areas through this morning.
By this afternoon, the development of afternoon sea breezes will likely cause an increase of leeward and interior clouds and showers. Increasing instability could also enhance the intensity of these showers in some locations, such as the leeward Big Island. A slight chance of thunderstorms has been added to forecast for the upslope sections of the leeward Big Island this afternoon. This may produce periods of MVFR conditions over some leeward and interior sections of the island chain later today. After sunset, expect downslope winds to clear out most of the residual cloud cover and showers over leeward areas by late this evening.

Marine

Ridges positioned both north and east of Hawaii from two different high pressure systems will result gentle to locally moderate trade winds through today. Winds will weaken becoming light and variable this weekend as an approaching low and cold front from the north forces the ridges away from the islands. Winds will veer southeast Monday and Tuesday as the front dissipates near Kauai and the low lifts away to the north allowing the ridge to nose back in from the east. Wind waves will be small around the islands until southeasterlies strengthen early next week.
The new north swell is currently filling in at the Hanalei and Waimea Bay near shore buoys. Surf will continue to build along north facing shores today to near or just below High Surf Advisory levels and hold through the weekend before dropping early next week. Surf along east facing shores will be small due to diminished wind swell, except for some select east facing shores exposed to the north swell wrap.
A small, long period south swell will fill in throughout the day today, peak over the weekend before slowly subsiding early next week and bring near to slightly below summer average surf to south facing shores. Another similar sized south swell may arrive around the middle of next week.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov