Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Sunny. Isolated showers in the morning. Highs around 89 near the shore to around 76 above 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Isolated showers after midnight. Lows around 71 near the shore to around 61 above 3000 feet. East winds around 10 mph. Chance of rain 20 percent.

Thursday: Mostly sunny. Isolated showers in the afternoon. Highs around 88 near the shore to around 77 above 3000 feet. East winds around 10 mph. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 82 to 89. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows around 72. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Thursday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 82 to 88. East winds 10 to 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Partly sunny with scattered showers. Highs 74 to 84 in the valleys to around 67 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Breezy. Partly cloudy with scattered showers in the evening, then mostly cloudy with numerous showers after midnight. Lows 64 to 69 in the valleys to around 58 above 4000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Thursday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 74 to 84 in the valleys to around 68 above 4000 feet. East winds 10 to 15 mph. Chance of rain 60 percent.

North Kaua’i

Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. 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 64 to 73. East winds 10 to 15 mph. Chance of rain 50 percent.

Thursday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 76 to 89. East winds 10 to 15 mph. 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 74 to 86. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 65 to 75. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Thursday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 74 to 85. East winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

A stable trade wind pattern will persist through much of the week with breezy to locally windy trades. Periodic light showers will focus over windward and mauka areas during this time. An increase in shower activity and isolated thunderstorms will be possible over portions of the state from Friday into the weekend as an upper-level disturbance approaches and moves over the region.

Discussion

The 1027 mb surface high remains approximately 850 miles north- northwest of the islands this morning. Stable conditions continue across the region with the base of the inversion around 5000 ft. 12Z soundings from Hilo and Lihue continue to show limited low- level moisture with dry air aloft. Radar and satellite imagery continue to show mainly dry conditions across the state, with periodic light showers over the typical windward and mauka areas. Expect mainly dry conditions to continue today with passing showers under breezy to locally windy trades.
High pressure to the north is expected to weaken slightly over the next couple of days. This should relax our local pressure gradient a bit, but winds will remain breezy to locally windy through much of the week. Impulses of moisture embedded in the trade wind flow will continue to favor windward and mauka areas, though rainfall accumulation will be limited. Aside from some brief afternoon and evening showers over Kona slopes of the Big Island, leeward areas will remain mostly dry.
Conditions start to change near the end of this week and into the weekend as guidance continues to show an upper-level disturbance moving across the islands from east to west. This disturbance will help to increase instability and enhance our trade wind showers, particularly on Saturday night. Isolated thunderstorms continue to be a possibility over the slopes of the Big Island on Friday and Saturday afternoons and over the western end of the state on Saturday and Sunday as temperatures aloft cool. However, with precipitable water forecast to be below seasonal normals of 1.3 inches, the amount of moisture available will continue to be a limiting factor. Will continue to evaluate thunder chances over the next several model runs, with further refinement in timing and areal coverage expected. Otherwise, enhanced trade wind showers look to continue into Monday. Conditions return to a more typical summertime trade wind pattern by early next week.

Aviation

Breezy trade winds will persist across the island chain through Thursday. Showers and low clouds riding in on these trades will bring brief periods of MVFR conditions over windward and mauka locations. Otherwise, VFR conditions will prevail.
AIRMET Tango remains in effect for moderate low-level turbulence over and downwind of island terrain due to breezy trade winds under the tradewind inversion.
No other AIRMETs are in effect at this time. However, AIRMET Sierra for tempo mountain obscuration may be needed again if shower coverage increases.

Marine

High pressure will remain north of the state over the next couple of days. Moderate to locally strong easterly trades will persist through Thursday then weaken slightly to the gentle to fresh range as the high slowly weakens and shifts eastward Thursday night through weekend. A Small Craft Advisory (SCA) for the typically windier waters around Maui County and the Big Island remains in effect through Thursday afternoon. The SCA may be dropped as early as Thursday night into Saturday as the high weakens. An upper level low may bring isolated thunderstorms over the weekend which could imply locally higher winds and seas. SCA conditions may return to the typically windy waters Sunday into early next week as the high northeast of the state strengthens and a new high builds north of the state from the northwest.
Surf along east-facing shores will gradually ease through the week as the winds locally and upstream trend down.
A small, medium-period, south swell will slowly trend down today and become more inconsistent. Another small, medium- to long- period south swell will fill in tonight, before peaking Thursday night then gradually ease into the weekend maintaining near to below average surf along south facing shores.
Surf along north facing shores will be minimal today. A small, medium period, northwest swell could fill in later today, before peaking Thursday night which could provide a small bump along north facing shores through the rest of the week.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov