West Kaua’i

Today: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 86 to 92 near the shore to around 78 above 3000 feet. Northeast winds up to 10 mph. Chance of rain 40 percent.

Tonight: Mostly clear. Isolated showers in the evening. Lows 71 to 76 near the shore to around 62 above 3000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

Friday: Sunny with isolated showers. Highs 86 to 92 near the shore to around 77 above 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

South Kaua’i

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 83 to 91. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Tonight: Partly cloudy with isolated showers. Lows around 74. Northeast winds around 10 mph. Chance of rain 20 percent.

Friday: Sunny. Isolated showers in the morning. Highs 82 to 91. East winds around 10 mph. Chance of rain 20 percent.

Kaua’i Mountains

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 77 to 85 in the valleys to around 68 above 4000 feet. East winds up to 10 mph. Chance of rain 40 percent.

Tonight: Partly cloudy with isolated showers. Lows 65 to 71 in the valleys to around 60 above 4000 feet. East winds around 10 mph. Chance of rain 20 percent.

Friday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 76 to 85 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 isolated showers. Highs 79 to 88. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 66 to 75. East winds up to 10 mph. Chance of rain 20 percent.

Friday: Mostly sunny with isolated showers. Highs 79 to 88. East winds up to 10 mph. Chance of rain 20 percent.

East Kaua’i

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 76 to 88. East winds around 10 mph. Chance of rain 40 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 65 to 78. East winds around 10 mph. Chance of rain 40 percent.

Friday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 74 to 88. East winds around 10 mph. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Low pressure north of the islands will remain embedded in a broad, quasi-stationary area of high pressure for the next several days, resulting in a hybrid sea breeze and moderate trade wind pattern. Hot and dry conditions will prevail with little to no rainfall expected.

Discussion

A surface low and its associated trough remain embedded within a broad, quasi-stationary high pressure ridge northeast of the islands. Trades will persist into the light to locally moderate speed range through early next week, as a result. Additionally, the atmosphere will remain very stable heading into next week, courtesy of the aforementioned broad high pressure ridge. This is evident in the 12Z soundings from Hilo and Lihue this morning, with strong temperature inversions around 6,000 to 7.000 feet. Moreover, expect hot and dry conditions to continue through the weekend and into early next week as rainfall producing shower activity will be extremely limited across the state.
Trade speeds reduce even more this weekend into early next week, resulting in a more widespread hybrid sea breeze and trade wind pattern, likely enhancing leeward and interior region cloud buildups in the afternoons. However, little to no precipitation is expected from any showers that do develop as a drier airmass consumes much of the region. Furthermore, afternoon temperatures are progged to be quite high throughout the forecast period; upwards of 90 degrees in some areas, which could pose some elevated fire weather concerns (see latest fire weather section).
The latest deterministic model guidance from the GFS and ECMWF remains in good agreement that the aforementioned surface low and associated trough will eventually lift northward next week. This will open the door for high pressure to rebuild and may result in trades strengthening a bit around the middle of next week.

Aviation

A hybrid sea breeze and light to locally moderate trade wind pattern will prevail today and persist through the next several days. Periods of MVFR conditions will briefly affect windward slopes, and aside from isolated pockets of afternoon MVFR ceilings on leeward terrain, VFR will dominate over most leeward sections.
No AIRMETs are in effect and none are expected.

Marine

A weak trough embedded in the broader ridge north of the islands will keep gentle to locally fresh trades blowing through the weekend. Trade wind speeds might increase back to more typical levels by the middle of next week.
A small, long period south swell continues to slowly fill in with yet another reinforcing pulse building into the region later today. South swell energy will peak on Friday with surf heights along south facing shores near the summer averages before declining over the weekend. A smaller portion of this long period south swell energy will wrap around into west facing shores. Surf heights will return to background levels early next week along south facing shores.
A storm force low developing near Kamchatka over the next few days will generate some longer period energy out of the northwest around September 2nd. This swell could generate surf near the September average during its peak. For the month of September the average surf heights along north facing shores is 4 to 6 feet (Goddard-Caldwell Database).
Small short-period surf along east facing shores will decrease on Thursday as winds locally and upstream ease through the weekend into early next week.

Fire weather

Low relative humidity values and hot conditions will continue through the first half of next week due to the arrival of a drier airmass. However, low wind speeds will keep us from reaching critical fire weather thresholds. By midweek next week, the broad high pressure ridge will rebuild, and may result in winds strengthening a bit, though still does not appear to reach critical thresholds at this time. Temperature inversion heights near Maui and the Big Island will range from around 6,000 to 7,000 feet today.

HFO Watches/Warnings/Advisories

None.