Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 86 to 92 near the shore to around 78 above 3000 feet. Northeast winds around 10 mph shifting to the south in the afternoon. Chance of rain 20 percent.

Tonight: Mostly clear. Isolated showers early in the evening. Lows around 72 near the shore to around 62 above 3000 feet. Northeast winds around 10 mph in the evening becoming light. Chance of rain 20 percent.

Tuesday: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 86 to 93 near the shore to around 78 above 3000 feet. Northeast winds around 10 mph shifting to the southwest in the afternoon. Chance of rain 20 percent.

South Kaua’i

Today: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 86 to 92. North winds around 10 mph shifting to the southeast in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening. Lows 70 to 75. Northeast winds around 10 mph in the evening becoming light. Chance of rain 20 percent.

Tuesday: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 86 to 92. North winds around 10 mph shifting to the east in the afternoon. Chance of rain 20 percent.

Kaua’i Mountains

Today: Partly sunny with scattered showers. Highs 76 to 86 in the valleys to around 68 above 4000 feet. Southeast winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers. Lows 64 to 70 in the valleys to around 59 above 4000 feet. East winds 10 to 15 mph in the evening becoming light. Chance of rain 20 percent.

Tuesday: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 76 to 86 in the valleys to around 68 above 4000 feet. East winds around 10 mph. Chance of rain 40 percent.

North Kaua’i

Today: Mostly sunny with scattered showers. Highs 78 to 88. South winds 10 to 15 mph shifting to the east in the afternoon. Chance of rain 40 percent.

Tonight: Partly cloudy with isolated showers. Lows 66 to 74. Southeast winds 10 to 15 mph in the evening becoming light. Chance of rain 20 percent.

Tuesday: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 78 to 88. South winds around 10 mph shifting to the east in the afternoon. Chance of rain 20 percent.

East Kaua’i

Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 77 to 89. Northwest winds around 10 mph shifting to the east in the afternoon. Chance of rain 40 percent.

Tonight: Partly cloudy with isolated showers. Lows 64 to 78. East winds around 10 mph in the evening becoming light. Chance of rain 20 percent.

Tuesday: Mostly sunny. Isolated showers in the afternoon. Highs 77 to 89. Northwest winds around 10 mph shifting to the east in the afternoon. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Light background winds are expected to prevail through Tuesday, which will allow afternoon sea breezes and nighttime land breezes to develop. Expect clouds and a few showers to form over leeward and interior areas each afternoon, followed by clearing skies at night. A few brief showers will also be transported into some windward sections, mainly during nights and mornings. Light to moderate trade wind speeds are forecast to return by mid-week, and persist into next weekend. An increase in moisture near the eastern end of the island chain may produce increased cloud and shower coverage, including a chance of afternoon thunderstorms, over portions of the Big Island Wednesday and Thursday.

Discussion

A 1030 mb surface high pressure system is located about 1700 miles northeast of Honolulu. There is a also a weak front less than 900 miles miles north-northwest of Lihue. The result is that the pressure gradient has relaxed across the area early this morning. This has caused the background trade wind flow to weaken. The light wind regime allowed local nighttime land breezes to become established across most leeward and interior sections of the island chain overnight. Loops of satellite imagery and radar reflectivity data show scattered low clouds with isolated embedded showers moving into some windward sections of Kauai and Oahu this morning. Cloud cover is minimal from Maui County to the Big Island.
The forecast guidance indicates that weak low-level troughs will pass by to the north of the state early this week, which will keep the background flow light out of the east to southeast. As a result, expect a pattern of alternating local afternoon sea breezes and nighttime land breezes over each of the individual islands. The atmosphere will remain relatively stable and dry, so little significant rainfall is expected for most areas during the next couple of days. Once the sea breezes become established, clouds and spotty showers may develop over some leeward and interior sections of the islands. This will be followed by general clearing over these same areas each night once nighttime land breezes become established. The weak east to southeast flow may also carry a few brief showers into some windward sections, mainly nights and mornings.
By mid-week, the forecast models appear to show that the low- level troughs that were passing by will exit. This will likely allow surface ridging to build north of the state, which will result in some tightening of the pressure gradient in the vicinity of the islands. This will produce light to moderate trade winds starting around Wednesday. Expect these light to moderate trade wind speeds to continue into next weekend.
The flow around a developing upper-level low far northwest of the islands will likely cause a subtropical jet stream to set up near the islands. This is expected to transport patches of high clouds across island skies from late Tuesday into Thursday. In addition, the model guidance indicates that an area of increased moisture may spread northward over the Big Island. If so, the dynamic lift associated with the upper-level jet stream may lead to increased coverage of clouds and showers, while also bringing the potential for an afternoon thunderstorm or two over the upslope sections of the leeward / interior Big Island Wednesday and Thursday. Elsewhere, expect mostly dry weather to prevail during the second half of the week as a mid-level ridge pushes in over the area from the east.

Aviation

Light trade winds will allow local scale sea breezes to develop each afternoon through Tuesday. Brief afternoon showers are possible along sea breeze wind convergence boundaries.
No AIRMETs in effect.

Marine

Trade winds will weaken through today as an approaching trough causes winds to veer to southeasterlies. Expect light southeasterlies to then persist through Tuesday before light to locally moderate easterly trades return mid-week.
A small, long period south to south southwest swell will fill in today and peak late tonight into Wednesday, resulting in moderate surf that will approach High Surf Advisory levels along south- facing shores.
Surf along north and west facing shores is decreasing as an existing northwest swell subsides. This swell will transition to a more north northwest direction by late Monday before fading out through Tuesday. Some south swell energy may wrap around to west facing shores Tuesday, bumping surf heights up there once again.
Surf along east-facing shores will continue trending lower as trades diminish.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov