Photo Credit: Jason Weingardt

West Kaua’i

Today: Breezy. Mostly sunny with isolated showers. Highs around 87 near the shore to around 77 above 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows 72 to 77 near the shore to around 63 above 3000 feet. Northeast winds up to 20 mph. Chance of rain 50 percent.

Saturday: Breezy. Mostly sunny with isolated showers. Highs around 87 near the shore to around 77 above 3000 feet. Northeast winds up to 25 mph. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 86. Northeast winds 15 to 20 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 70 to 76. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

Saturday: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs around 86. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Mostly cloudy. Breezy. Frequent showers in the morning, then scattered showers in the afternoon. Highs 73 to 81 in the valleys to around 70 above 4000 feet. East winds up to 15 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 80 percent.

Tonight: Breezy. Mostly cloudy with numerous showers. Lows 63 to 68 in the valleys to around 58 above 4000 feet. East winds up to 25 mph. Chance of rain 70 percent.

Saturday: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 73 to 81 in the valleys to around 70 above 4000 feet. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 70 percent.

North Kaua’i

Today: Partly sunny with scattered showers. Highs 76 to 86. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 66 to 76. East winds up to 15 mph. Chance of rain 50 percent.

Saturday: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 76 to 86. East winds up to 20 mph. Chance of rain 50 percent.

East Kaua’i

Today: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 75 to 86. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows 64 to 77. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Saturday: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 75 to 86. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Breezy trade winds will persist today, with showers favoring windward and mauka locations. The Central Pacific Hurricane Center is closely monitoring Tropical Storm Hone far east-southeast of the state tracking westward. On this track, Hone is expected to pass south of, or possibly near to the Big Island late Saturday through early Sunday, bringing the potential for heavy rainfall, damaging winds, and large surf. Expect the strong and gusty easterly winds to continue Sunday into Monday as Hone passes south of the smaller islands. A brief return of moderate to breezy trade winds is expected late Monday through Wednesday of next week Hone tracks away from the state and Tropical Cyclone Gilma approaches the region from the east.

Discussion

Short-term guidance remains in good agreement, showing breezy trade wind conditions continuing today due to a strong high pressure system well north of the state. Showers will predominantly affect windward and mauka areas, with some occasionally reaching leeward sections. A mid-level trough moving from east to west across the state, combined with increasing low- level moisture, has slightly enhanced our shower coverage, which should continue today.
The Central Pacific Hurricane Center forecast shows Tropical Storm Hone becoming a hurricane late in the weekend as it passes south of the smaller islands. Forecast confidence is increasing that Hone will impact our local weather conditions, regardless of its exact development and track.
On the current forecast track for Hone, winds will strengthen through the day Saturday, with widespread gusts up to 40 to 50 mph late Saturday through early Sunday. The strongest gusts are expected around South Point/Ka Lae, as well as downslope from Mauna Kea, Mauna Loa, the Kohala Mountains, and the Humuula Saddle, which could exceed 50 mph.
Drier air is expected to move across the western end of the state ahead of the tropical system on Saturday, which should result in a dry and windy period. Deep tropical moisture will move in from the east sometime later Saturday through Sunday, increasing the potential for heavy rainfall across windward and southeast areas of the Big Island. Then heavy shower coverage may expand up the island chain Sunday into early next week as Hone passes to the south. Given the potential for prolonged heavy rainfall, localized flash flooding could occur where the rain becomes concentrated.
A brief return of moderate to breezy trade winds is expected late Monday through Wednesday of next week as Hone tracks away from the state and Tropical Cyclone Gilma approaches the region from the east. Forecast confidence, with regards to impacts to our local weather, remains very low later next week due to significant differences shown between the various sources of guidance as Gilma approaches the region.
For further details on Hone's development, refer to the latest forecast issued by the Central Pacific Hurricane Center at hurricanes.gov.
Note that public and marine forecasts from WFO Honolulu will be updated on a modified schedule, in conjunction with the latest CPHC forecast issued at 5 am/pm and 11 am/pm HST.

Aviation

Breezy to locally windy trades will continue through today, increasing slightly. A mid-level trough moving through the islands will bring an increase in SHRA windward locations but spillover to leeward areas is possible. Low cigs and MVFR conds with isolated IFR conds will be possible.
Confidence in the forecast increases this weekend as Tropical Storm Hone continues to move on a westward track, passing just south of the Big Island. Aviation interests should continue to monitor the storm and view the latest forecasts issued by the Central Pacific Hurricane Center over the next few days.
AIRMET Sierra for mtn obsc is in effect for all islands.
AIRMET Tango is in effect for mod low level turb over and downwind of island terrain. This AIRMET will likely remain in effect through the weekend.

Marine

Fresh to locally strong trades will prevail today as a ridge of high pressure remains anchored to the north, then ramps up to strong to locally gale force levels this weekend. A Small Craft Advisory (SCA) in effect for the typically windy waters east of Oahu has been extended through Saturday afternoon. Winds from Saturday afternoon into early next week will be influenced by Tropical Storm Hone as it nears the islands from the southeast. A Tropical Storm Watch remains in effect for the Big Island and its surrounding coastal waters from late Saturday through Monday. However, this Watch may need to be expanded in a later package to include leeward Maui waters. Rainbands from Tropical Storm Hone will also result in occasional heavy rain, low visibility, and the possibility of thunderstorms Saturday afternoon through late Sunday night, especially for the southeastern portion of the coastal waters.
The current small northwest swell will slowly decline through early Saturday. Surf along north facing shores will then return to typical summertime flat levels over the weekend through the middle of next week, aside from some trade wind swell wrap.
Surf along south facing shores will remain small today, near or slightly below the summertime average. Meanwhile, surf along east facing shores will remain near seasonal levels today, then rise above normal this weekend as winds strengthen over and upstream of the islands. As Tropical Storm Hone approaches and passes the islands this weekend into early next week, surf along south and east facing shores will increase, possibly reaching advisory levels over some east facing shores.

HFO Watches/Warnings/Advisories

Tropical Storm Watch for Big Island,
Flood Watch from Saturday afternoon through Monday evening for Big Island,
Tropical Storm Watch for Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.
Small Craft Advisory until 6 PM HST Saturday for Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov