Photo Credit: Jason Weingardt

West Kaua’i

Today: Mostly cloudy. Breezy. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 83 near the shore to around 73 above 3000 feet. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then isolated showers after midnight. Lows 66 to 71 near the shore to around 57 above 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Wednesday: Breezy. Mostly cloudy with isolated showers. Highs around 84 near the shore to around 74 above 3000 feet. East winds up to 25 mph. Chance of rain 20 percent.

South Kaua’i

Today: Breezy. Cloudy with scattered showers. Highs around 81. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

Tonight: Cloudy and breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 64 to 70. Northeast winds 15 to 25 mph. Chance of rain 70 percent.

Wednesday: Cloudy and breezy. Numerous showers in the morning, then isolated showers in the afternoon. Highs around 82. Northeast winds 15 to 25 mph. Chance of rain 60 percent.

Kaua’i Mountains

Today: Cloudy and breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 76 in the valleys to around 65 above 4000 feet. East winds 10 to 25 mph. Chance of rain 70 percent.

Tonight: Breezy. Cloudy with numerous showers. Lows around 60 in the valleys to around 52 above 4000 feet. East winds 10 to 25 mph. Chance of rain 70 percent.

Wednesday: Cloudy and breezy. Numerous showers in the morning, then isolated showers in the afternoon. Highs around 77 in the valleys to around 66 above 4000 feet. East winds 10 to 25 mph. Chance of rain 70 percent.

North Kaua’i

Today: Breezy. Cloudy with scattered showers. Highs 75 to 82. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Tonight: Cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 60 to 69. East winds up to 15 mph. Chance of rain 70 percent.

Wednesday: Cloudy and breezy. Numerous showers in the morning, then isolated showers in the afternoon. Highs 76 to 83. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 60 percent.

East Kaua’i

Today: Cloudy and breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 74 to 80. Northeast winds 10 to 20 mph. Chance of rain 60 percent.

Tonight: Cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 58 to 71. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Wednesday: Cloudy and breezy. Numerous showers in the morning, then isolated showers in the afternoon. Highs 75 to 81. Northeast winds 10 to 20 mph. Chance of rain 60 percent.

Detailed Forecast

Synopsis

A strong high pressure system far north of the Hawaiian Islands will linger through Wednesday with breezy trade winds continuing through mid week. This high will then weaken from Thursday through Saturday producing more moderate trade winds across the island chain. A narrow upper level trough will persist above the islands with embedded upper low centers. This trough will likely enhance overnight to early morning trade wind shower activity, especially over windward and mountain areas into Saturday. Weather conditions will shift to more southeasterly winds with decreasing shower trends on Sunday and Monday.

Discussion

Water vapor satellite imagery this morning shows an interesting upper level pattern with a seasonably strong sub tropical jet stream over the islands along the southern edge of a long and narrow upper level trough. Several weak lows are embedded within this upper trough that will help to weaken the large scale subsidence (downward atmospheric motions) over the region and enhance trade wind shower activity. Trade wind inversion heights from the 2 AM HST upper air balloon soundings range from around 6,000 to 7,000 feet, which is high enough for scattered windward showers in the day becoming numerous showers at night. Leeward areas will see only isolated shower coverage. Local radar imagery this morning confirms scattered to numerous showers moving through the easterly trade wind flow.
Short and medium range guidance remains in good agreement with the breezy trade wind pattern continuing through at least Wednesday, then trade wind speeds will slowly decrease from Thursday through Saturday as the high pressure system far north of the state weakens in response to a passing cold front farther to the north. Rain shower bands will trend higher during the typical overnight to early morning hours and favor windward and mountain sections of each island into Saturday. Rainfall activity was lowered from Kauai to Maui from Thursday through Saturday in this mornings forecast package.
The long range forecast hints at some changes on the horizon. Both the American (GFS) and European (ECMWF) show the high pressure ridge north of the islands breaking down as a low pressure system near the Dateline dives south and sets up northwest of Kauai. Easterly trade winds will veer from a more southeasterly direction from Sunday into Monday and shower activity will decrease west of the Big Island due to the rain shadowing effects of southeasterly winds. Deeper tropical moisture with southerly winds in the mid levels may enhance shower activity over Kauai by late Monday. Stay tuned as models continue to hint at wet weather trends in the extended range forecast around the middle of next week.

Aviation

Strong high pressure far north of the state will bring breezy east north easterly trades through this afternoon. Sufficient moisture in the lower levels will continue to allow for scattered to numerous showers to develop along the windward coasts and slopes. Expect periods of MVFR due to lower ceilings and reduced visibility associated with this activity. Isolated showers elsewhere across the region.
AIRMET Sierra remains in effect for north through east sections of the Big Island and Oahu above 2500 feet due to low clouds and showers.
AIRMET Tango remains in effect below 8000 feet for moderate tempo turbulence over and immediately south through west of mountains.

Marine

Strong high pressure north of the state will remain nearly stationary and drive fresh to locally near gale trades through mid-week. Winds speeds are forecast to peak near gale force in the windiest eastern zones near Maui and the Big Island today into Wednesday, then weaken slightly Thursday through the coming weekend. The Small Craft Advisory (SCA) is in effect through Wednesday afternoon for all coastal waters due to winds and building seas.
A moderate north (350 deg) swell is filling in this morning above model expected guidance. This swell will result in building surf for north facing shores peaking this afternoon. East facing shores will see an increase today for select spots exposed to the north swell and short- period trade wind swell from the fresh to strong trades. Surf will be near High Surf Advisory (HSA) levels for east facing shores and may need to be updated throughout the day. A small, medium- period northwest (320 deg) swell is possible this weekend. South facing shores will continue to have minimal surf due to background long-period energy throughout the week.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Wednesday for all Hawaiian waters,

Data Courtesy of NOAA.gov