Photo Credit: Jason Weingardt

West Kaua’i

Today: Breezy. Mostly sunny with isolated showers. Highs 86 to 91 near the shore to around 77 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 around 72 near the shore to around 63 above 3000 feet. East winds 10 to 20 mph. Chance of rain 40 percent.

Tuesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 89 near the shore to around 77 above 3000 feet. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

South Kaua’i

Today: Breezy. Partly sunny with scattered showers. Highs 84 to 90. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 73. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tuesday: Partly sunny with scattered showers. Highs 84 to 91. Northeast winds around 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Breezy. Partly sunny with scattered showers. Highs 74 to 84 in the valleys to around 67 above 4000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 66 to 71 in the valleys to around 61 above 4000 feet. East winds 10 to 25 mph. Chance of rain 70 percent.

Tuesday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 75 to 84 in the valleys to around 68 above 4000 feet. East winds around 15 mph. Chance of rain 70 percent.

North Kaua’i

Today: Mostly sunny with scattered showers. Highs 77 to 88. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 67 to 74. East winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 78 to 89. East winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Partly sunny with scattered showers. Highs 75 to 87. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 66 to 78. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday: Partly sunny with scattered showers. Highs 75 to 87. Northeast winds around 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Locally breezy trade winds are expected to persist this week. A rather typical trade wind weather pattern is also forecast this week, with low clouds and brief trade showers favoring windward and mauka areas, especially during the nights and mornings. Clouds and a few showers will develop over the upslope sections of the leeward Big Island each afternoon, followed by gradual clearing at night.

Discussion

A 1029 mb surface high pressure system remains almost stationary near 37N 166W, or slightly less than 1200 miles north-northwest of Honolulu. The relatively tight pressure gradient south of this feature is producing locally breezy trade winds across the main Hawaiian Islands early this morning. A weak mid-tropospheric ridge is hovering above the state, which is starting to increase atmospheric stability. As a result, the low-level trade wind inversion is gradually becoming better defined, and appears to be 6 to 7 thousand feet according to the balloon soundings made at Hilo and Lihue a few hours ago. Loops of satellite imagery and radar reflectivity data show an area of broken to locally overcast low clouds with embedded scattered trade showers spreading from east to west across the islands. This is producing relatively wet conditions over most windward amd mauka areas, with a few sprinkles over some leeward sections of the smaller islands.
The latest UW-CIMSS MIMIC precipitable water data show that a slightly drier air mass appears to be moving in toward the state from the east. As a result, once the sun begins to warm the atmosphere, expect the coverage of low clouds and showers to gradually decrease from later this morning through this afternoon.
The forecast model guidance indicates the surface high will likely maintain the locally breezy trade winds this week. The guidance also shows the stable atmospheric conditions with a slightly drier trade wind weather pattern will be in place from Tuesday through Friday. Under this regime, expect low clouds and light trade showers to mainly affect windward and mauka areas, especially during the nighttime and early morning hours. In addition, this will result in a typical pattern of clouds and a few showers developing over the upslope sections of the leeward Big Island each afternoon, followed by gradual clearing each night.

Aviation

High pressure north of the islands will maintain moderate to locally breezy trade winds for the next several days. Surface observations and VAD profiles continue to show marginal winds to support low-level turbulence. However, with winds expected to increase later today will keep AIRMET Tango for mountain lee turbulence posted.
Satellite imagery continues to show a wave of moisture moving into windward Big Island and across Kauai and Oahu so AIRMET Sierra for mountain obscuration remains in effect for these areas. Expect these conditions to persist through the morning hours, with drier air expected to move across the islands this afternoon. Otherwise, expect mainly VFR conditions as clouds and showers favor windward and mauka areas. Brief periods of MVFR will be possible under passing showers.

Marine

Surface high pressure centered far north northwest of the islands is producing a tight pressure gradient down across the state. This will allow trades to slightly strengthen from recently moderate magnitudes to more fresh speeds through the week. The Small Craft Advisory (SCA) for the typical windier waters around Maui County and Big Island will be in effect through late Tuesday night. The SCA will likely be extended through the remainder of the week.
No significant swells are expected over the several days. Thus, very small surf heights are forecast this week. A small, long period south swell today should provide a minor bump in south- facing surf heights through mid week. East-facing shore surf driven by trade wind wave energy will remain small and choppy.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov