Photo Credit: Braden Jarvis

West Kaua’i

Today: Mostly sunny. Scattered showers in the morning. Highs around 86 near the shore to around 74 above 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Isolated showers after midnight. Lows 68 to 73 near the shore to around 59 above 3000 feet. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Sunday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 86 near the shore to around 74 above 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

South Kaua’i

Today: Mostly cloudy in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs around 83. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 66 to 72. Northeast winds around 15 mph. Chance of rain 50 percent.

Sunday: Mostly cloudy in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs around 83. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Breezy. Occasional showers in the morning, then numerous showers in the afternoon. Highs 73 to 80 in the valleys to around 64 above 4000 feet. East winds 10 to 20 mph. Chance of rain near 100 percent.

Tonight: Mostly cloudy. Breezy. Numerous showers in the evening, then occasional showers after midnight. Lows 59 to 64 in the valleys to around 54 above 4000 feet. East winds 15 to 25 mph. Chance of rain 90 percent.

Sunday: Mostly cloudy. Breezy. Occasional showers in the morning, then scattered showers in the afternoon. Highs 73 to 80 in the valleys to around 64 above 4000 feet. East winds 15 to 20 mph. Chance of rain 90 percent.

North Kaua’i

Today: Partly sunny with occasional showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs 76 to 85. East winds 10 to 15 mph. Chance of rain 90 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 62 to 72. East winds 10 to 15 mph. Chance of rain 70 percent.

Sunday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 76 to 85. East winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 76 to 84. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 60 to 73. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Sunday: Partly sunny with scattered showers. Highs 76 to 84. East winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Breezy to locally windy trade winds will continue through the weekend due to high pressure to the far northeast, with showers favoring the typical windward and mauka areas. These showers will be enhanced some due to an upper level trough moving over the islands. Expect winds and showers to diminish some as we head into the middle of the new week.

Discussion

As anticipated have made some changes to the forecast to reflect the latest information from the National Blend of Models. PoPs have been increased over windward portions of Kauai and the Big Island through Sunday, reflecting moisture areas upstream riding in on the trades. Meanwhile PoPs have been decreased over Oahu and portions of Maui County. Monday and Tuesday see higher PoPs for windward Big Island accounting for increased precipitable water that will be skirting the southern end of the state. Meanwhile PoPs for the smaller islands will be on the decrease. By Wednesday anticipating drier conditions across the state, with clouds and showers developing over interior areas.
High pressure to the far northeast of the state will maintain breezy to locally windy trades into tomorrow. The high is expected to slowly sink southward through the weekend, with little change in the pressure gradient over the islands. Meanwhile, a mid to upper level trough developing near and to the northeast of the islands will help to enhance trade wind showers. These showers are expected to favor the typical windward and mauka areas, but a few stray showers could reach leeward areas at times.
There is good agreement in the ECMWF and GFS that the upper level trough will lift northward Monday/Tuesday and then move to the east Wednesday. During the same time, the high pressure system will weaken and be replaced by a new high. During this transition time we can expect trade winds to weaken some, and showers to diminish. The forecast now reflects this trend as mentioned above.
During the second half of the week, the new high lifts to the north, causing winds over the islands to weaken and become more southeasterly. This will likely mean more showers developing over the interior of the islands, primarily during the afternoon hours. As mentioned above, the forecast has been modified to reflect this trend.
By next weekend, moderate trades are expected to return with more typical trade wind showers favoring the windward and mauka areas.
Today marks the start of hurricane season in the central North Pacific basin. It was 67 years ago today, in 1957, when the Weather Bureau Airport Station (which later became the National Weather Service Forecast Office) began Central Pacific Hurricane Center operations. Visit hurricanes.gov throughout the season, which continues through November 30, to stay informed.

Aviation

Breezy to strong trades are expected to increase slightly this weekend, as a surface high moves closer to the state from the northeast. Low cigs and SHRA will favor windward and mauka areas. MVFR conds in SHRA are possible with VFR conds prevailing elsewhere.
AIRMET Sierra is in effect for mtn obsc for windward Big Island as well as N thru SE sections of Kauai through Maui.
AIRMET Tango is in effect for moderate low-level turb S thru W of terrain as well as for moderate turb between FL300-FL400.

Marine

A 1030 mb surface high centered 1000 nm NE of the islands will change little as it sags slowly S through early next week, resulting in fresh to strong ENE trade winds across the area. A Small Craft Advisory (SCA) continues through tonight for most zones. This product will likely need be extended through early next week, at least for the typical windy zones around the Big Island and Maui county, as fresh to strong trades remain intact. Long- range guidance indicates a trend toward diminishing and veering winds around the middle of next week as the ridge to the N is weakened by a passing front.
There will be an extended run of elevated surf along S facing shores this weekend through next week (and likely longer), with the largest of the swells generating surf near High Surf Advisory (HSA) levels of 10 feet. The first of several pulses of long- period SSW swell will gradually increase today, peaking tonight into Sunday. Latest buoy observations indicate some modest energy increases in the longer periods, resulting in inconsistent and small sets. Additional pulses of swell arriving early next week will persist through the middle of the week, with the potential for a larger swell by next weekend.
A strong, slow-moving low in the distant NW Pacific has generated a small NW swell that will arrive Monday and Tuesday, with the potential for a small follow-up NW swell generated by the extra- tropical version of former west Pacific Typhoon Ewiniar. Trade winds will continue to generate short-period wind waves that will support choppy surf along exposed E facing shores.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Sunday for Kauai Northwest Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov