Photo Credit: Brendan Stephen

West Kaua’i

Today: Sunny and breezy. Isolated showers in the morning. Highs around 91 near the shore to around 79 above 3000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows around 74 near the shore to around 63 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Monday: Mostly sunny with isolated showers. Highs around 91 near the shore to around 79 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

South Kaua’i

Today: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 84 to 91. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

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

Monday: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 83 to 91. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Partly sunny with scattered showers. Highs 76 to 88 in the valleys to around 68 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 66 to 72 in the valleys to around 60 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers. Highs 76 to 88 in the valleys to around 68 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

North Kaua’i

Today: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 77 to 91. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 67 to 76. East winds 10 to 15 mph decreasing to up to 10 mph after midnight. Chance of rain 50 percent.

Monday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 78 to 91. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

East Kaua’i

Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 75 to 88. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 67 to 78. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers. Highs 76 to 88. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Stable conditions and gentle to breezy trade winds will prevail through much of the forecast period, with a brief weakening in wind speeds expected Monday through Tuesday. An area of increased moisture passing from east to west through the state could slightly boost windward showers today through Monday night.

Discussion

Satellite loop and radar show showery low clouds across windward and mauka sections of the state extending far upwind. However, a stable airmass keeps rain amounts light this morning. High pressure far north of the state will continue to drive gentle to breezy trade winds across the islands, with mainly scattered windward and mauka showers expected state-wide for the next couple of days.
A slight change in weather conditions will occur today through Monday night as a weak tropical wave passes from east to west to the south of the islands. Expect increased moisture across the islands, allowing for more cloud and shower coverage. The best chances for enhanced showers will be over windward and mountain areas tonight and early this morning and Monday morning. Some of the stronger showers may move across leeward locations as well at times. Expect a brief trade wind speed decrease Monday and Monday night as a front far north of Hawaii displaces the high generating our trade flow. Models show a stable, moderate to locally breezy trade wind weather pattern will prevail through much of the rest of the week.
The National Hurricane Center is forecasting a medium chance of tropical cyclone development in the East Pacific over the next seven days, with westward movement into the Central Pacific possible by the end of the week. However, models differ significantly on the existence, position, and strength of forecasted activity near Hawaii.

Aviation

Bands of clouds with embedded showers are moving into the windward and mountain slopes of most islands this morning. Surface observations are indicating BKN CIGs around 025 for north through east sections of affected islands. Moderate to locally breezy trade winds will continue.
AIRMET Sierra remains in effect for mountain obscurations over windward sections Kauai Oahu Molokai Maui and the Big Island. This AIRMET will likely continue into the early morning hours.
AIRMET Tango for moderate low level turbulence over and immediately down stream of island mountains remains in effect statewide due to the breezy trades. This AIRMET will continue into early next week.

Marine

Fresh to strong easterly trade winds will continue through Tuesday, then increase to strong levels for most waters beginning around Wednesday as high pressure builds to the north. The Small Craft Advisory in place for the typical windier waters/channels around Maui County and the Big Island will persist for much of the week, likely becoming expanded to most waters Wednesday through the second half. The National Hurricane Center in Miami, Florida is forecasting a medium chance of tropical cyclone development in the eastern Pacific over the next seven days, that could enter the Central Pacific well southeast of the Hawaiian waters late in the week. Later forecasts will highly depend on how this development evolves over the next several days.
Surf along south facing shores will begin to climb this evening as a fresh, long-period south-southwest swell arrives. Observations at the Samoa buoy came in slightly higher than predicted as this swell moved through and peaked around Thursday. This should correspond to it peaking locally Monday through Tuesday, likely just below the advisory level. For the extended (last week of August – around the 25-26th), guidance depicts a similar south-southwest swell arriving from a gale passing just south of New Zealand over the next 48 h.
Surf along north and west facing shores will trend up around Wednesday as a long-period west-northwest swell arrives from former Typhoon Ampil as it tracks northeastward over the far northwest Pacific. This should peak Wednesday through Thursday, then ease by next weekend.
Surf along east facing shores will ease slightly over the next few days as the upstream trade wind fetch diminishes. An upward trend is possible by midweek as the trades increase locally and far east of the islands.
Minor tidal flooding will remain possible into Monday due to water levels running higher than predicted during the peak monthly tide cycle. A downward trend is expected through the week.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Monday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov