Photo Credit: Braden Jarvis

West Kaua’i

Today: Sunny and breezy. Isolated showers in the afternoon. Highs around 86 near the shore to around 73 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 70 near the shore to around 58 above 3000 feet. East winds 10 to 20 mph shifting to the northeast after midnight. Chance of rain 40 percent.

Tuesday: Mostly sunny with isolated showers. Highs around 86 near the shore to around 73 above 3000 feet. Northeast winds 10 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 around 83. Northeast winds 10 to 20 mph. Chance of rain 40 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 67 to 73. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tuesday: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs around 83. Northeast winds 15 to 20 mph. Chance of rain 40 percent.

Kaua’i Mountains

Today: Breezy. Partly sunny with scattered showers. Highs around 77 in the valleys to around 66 above 4000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 62 in the valleys to around 54 above 4000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Tuesday: Breezy. Partly sunny with scattered showers. Highs around 77 in the valleys to around 66 above 4000 feet. East winds 15 to 20 mph. Chance of rain 50 percent.

North Kaua’i

Today: Mostly sunny with scattered showers. Highs 75 to 84. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 62 to 71. East winds 10 to 15 mph shifting to the southeast after midnight. Chance of rain 50 percent.

Tuesday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 75 to 84. East winds 10 to 15 mph. Chance of rain 40 percent.

East Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 76 to 83. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 60 to 74. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 76 to 83. Northeast winds around 15 mph. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Moderate to locally breezy trade winds will focus brief showers mainly over windward and mauka areas into early Wednesday. The greatest coverage of trade showers will be during the overnight and early morning hours. Increasing moisture is expected to enhance trade showers over windward facing sections from late Wednesday through the end of the new work week. Locally strong trade winds may transport brief trade showers over to the leeward sections of some of the smaller islands starting Thursday.

Discussion

A 1036 mb surface high pressure system is located near 44N 157W, or about 1600 miles north of Honolulu. The pressure gradient south of this feature is producing moderate trade winds across the region early this morning. Loops of satellite imagery and radar reflectivity data show scattered low clouds and spotty showers moving into the windward sides of some of the islands.
The forecast guidance shows the surface high pressure system will build as it moves rapidly toward the south-southeast during the next few days. This will tighten the pressure gradient across the state from later today and tonight into mid-week. This will cause the trade winds to become locally breezy during the next day or two. In addition, expect a general drying trend with a windward and mauka shower pattern. In this regime, the greatest coverage of trade showers will likely be during the overnight and early morning hours into early Wednesday. Also, expect clouds and isolated showers to develop over some of the upslope sections of the Leeward Big Island each afternoon, followed by gradually clearing during the evening hours.
Starting late Wednesday, increasing moisture may result in greater windward and mauka shower coverage. In addition, locally strong trade winds starting Thursday may transport brief trade showers over to the leeward sections of some of the smaller islands, especially at night. The forecast models continua to show some differences in moisture availability heading into next weekend. However, based on recent trends, it appears that the surface and upper-level features that are expected to organize to the northwest of the region might allow increased moisture, and some enhancement of trade showers next weekend.

Aviation

Moderate trade winds and a typical pattern of rainfall will persist today, though some increase in winds are expected into Tuesday. Brief MVFR conditions will be confined to windward slopes of all islands, as well as over the Kona slopes of the Big Island during the afternoon and evening hours. Otherwise, VFR will prevail. No SIGMETs are in place, and none are expected through the afternoon. Conditions will be border line for AIRMET Tango due to some turbulence over and downwind of terrain today, and an AIRMET may be needed tonight or Tuesday.

Marine

Expect moderate to fresh trade winds to continue today across all Hawaiian waters. A high pressure system will build in from the north tomorrow, producing moderate to strong trade winds from Tuesday onward. Wind speeds will approach Small Craft Advisory (SCA) thresholds tonight, and we will monitor closely for the passably of a SCA issuance. Otherwise wind speeds will reach SCA thresholds for the typical windier waters around Maui and the Big Island starting on Tuesday. The coverage of SCA conditions may expand by Thursday to cover additional coastal water zones.
We will continue to see small surf along north facing shores during the next few days. Another small pulse from the north- northwest is possible later today into Tuesday followed by a slightly larger swell from the northwest late Thursday into Friday.
A series of small long-period south swells will continue to keep fun size surf along south facing shores through the week. Surf should trend down this weekend with mainly background energy by early next week. Surf heights along west facing shores will remain small through the week with a bit of south and northwest swell wrap keeping west side surf heights above flat levels.
Surf along east facing shores will remain near seasonal averages for the next several days. East facing surf heights should see an increase of size and chop along eastern exposures from Wednesday to Friday as trade wind speeds increase.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov