Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Breezy. Mostly sunny with isolated showers. Highs around 90 near the shore to around 79 above 3000 feet. East winds 10 to 25 mph. Chance of rain 20 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Isolated showers. Lows around 74 near the shore to around 64 above 3000 feet. East winds 10 to 25 mph. Chance of rain 20 percent.

Thursday: Mostly sunny. Breezy. Isolated showers in the morning. Highs around 90 near the shore to around 78 above 3000 feet. East winds 10 to 25 mph. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny. Breezy. Showers likely in the morning, then scattered showers in the afternoon. Highs 82 to 89. East winds 15 to 25 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 72 to 77. East winds 15 to 25 mph. Chance of rain 50 percent.

Thursday: Partly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 82 to 89. East winds 15 to 25 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Mostly cloudy. Breezy. Occasional showers in the morning, then showers likely in the afternoon. Highs 75 to 87 in the valleys to around 67 above 4000 feet. East winds 10 to 25 mph. Chance of rain 90 percent.

Tonight: Breezy. Mostly cloudy with showers likely. Lows 66 to 73 in the valleys to around 61 above 4000 feet. East winds 10 to 25 mph. Chance of rain 70 percent.

Thursday: Partly sunny. Breezy. Showers likely in the morning, then scattered showers in the afternoon. Highs 74 to 86 in the valleys to around 66 above 4000 feet. East winds 10 to 25 mph. Chance of rain 70 percent.

North Kaua’i

Today: Breezy. Mostly cloudy with showers likely. Highs 77 to 91. East winds 10 to 20 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with showers likely. Lows 67 to 75. East winds 10 to 20 mph. Chance of rain 70 percent.

Thursday: Partly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 77 to 91. East winds 10 to 20 mph. Chance of rain 50 percent.

East Kaua’i

Today: Mostly cloudy. Breezy. Showers likely in the morning, then scattered showers in the afternoon. Highs 75 to 87. East winds 10 to 20 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with showers likely. Lows 68 to 78. East winds 10 to 20 mph. Chance of rain 70 percent.

Thursday: Mostly cloudy. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 74 to 86. East winds 10 to 20 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Moderate to breezy trade winds will become stronger through Friday along with decreasing windward showers as drier air settles over the region. Trades will slowly ease into next week as relatively dry conditions continue.

Discussion

Light to moderate showers continue to impact windward areas this morning as an area of enhanced moisture lingers over the state, though coverage appears to be on the slow decrease. Rainfall amounts have varied widely overnight, but Oahu seems to have had the most widespread shower coverage with most windward areas receiving between a 0.20-0.50 inches and isolated amounts up around 1 inch. The 12Z Hilo and Lihue soundings still show higher than normal precipitable water for July, with values of 1.7 and 1.5 inches, respectively. However, these values are both around 0.15 inches less than yesterday afternoon, reflective of a drier airmass beginning to move into the local area. Meanwhile, a 1034 mb surface high pressure remains centered far north-northeast of the state, driving breezy trades over the islands.
Drier conditions and stronger trade winds will develop later today and Thursday as the high to the north builds even further. Widespread windy trades will prevail through the second half of this week, with a few of the more wind-prone spots on the Big Island and Maui potentially flirting with wind advisory criteria Wednesday and Thursday. Precipitation-wise, expect mainly light windward showers riding in on the trades and mostly dry conditions over leeward areas during the second half of the week. In addition, a weak upper level trough setting up west of us will likely bring an increase of high cirrus clouds moving in from the south Thursday through the weekend. Trade winds look to ease to breezy levels this weekend and hold, along with relatively dry conditions, through early next week.

Aviation

Moderate to locally breezy trades will gradually strengthen to become breezy to locally windy today. Showers and low clouds will still generally favor windward and mountain locations. However, showers will also build up on the Kona slopes of the Big Island during the afternoon hours. MVFR conditions will be possible within any showers. Otherwise, VFR should prevail.
AIRMET Sierra for mountain obscuration is in effect for all windward areas of the state early this morning. This AIRMET will likely be needed through the morning hours for at least portions of the island chain as a plume of moisture moves from east to west across the state.
AIRMET Tango for moderate low level turbulence is in effect for areas downwind of island terrain and will likely be needed for the next couple of days as low level wind speeds increase.

Marine

No changes to the forecast this morning, with the forecast currently on track. Overnight ASCAT passes show Small Craft Advisory (SCA) level winds in the typical windier waters near Maui County and the Big Island, and winds getting closer to SCA in other coastal waters. The SCA remains in effect for those waters near Maui County and the Big Island, and the remaining coastal waters will be under the SCA starting at 6 am. The SCA for all these waters continues through Thursday, but will likely be extended with the expectation that winds will remain elevated into the weekend.
The high to the north of the islands that is driving these strong trade winds is expected to weaken over the weekend, causing trades to decrease to fresh to locally strong speeds. This will likely result in the SCA being scaled back to the more typical windier areas at some point at the end of the week, but will be monitoring future model runs to see how things pan out.
The strong trade winds will generate higher surf along east facing shores throughout the work week. Rough and choppy surf should peak above the summer average (5 ft) Friday into Saturday, then gradually ease early next week. Local wind swell may wrap into select north and south facing shores. A background south swell will continue to decline into the middle of the week. Otherwise, no significant swells are expected this week.

Fire weather

Breezy trade winds will increase later today through Friday, as somewhat dry and stable conditions develop. This could present some fire weather concerns this afternoon, but more likely on Thursday and Friday afternoons as the inversion strengthens and humidity lowers. Trade winds will gradually ease this weekend into early next week, but dry leeward conditions will likely persist.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Thursday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Big Island Windward Waters.
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