Photo Credit: Jason Weingardt

West Kaua’i

Today: Sunny. Isolated showers in the morning. Highs 87 to 92 near the shore to around 78 above 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 72 near the shore to around 63 above 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 88 to 93 near the shore to around 79 above 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

South Kaua’i

Today: Breezy. Mostly sunny with isolated showers. Highs 85 to 92. East winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then showers likely after midnight. Lows 72 to 77. East winds 15 to 20 mph. Chance of rain 70 percent.

Wednesday: Breezy. Mostly cloudy with showers likely in the morning, then mostly sunny with scattered showers in the afternoon. Highs 86 to 92. East winds 15 to 20 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 76 to 87 in the valleys to around 68 above 4000 feet. East winds 10 to 20 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then showers likely after midnight. Lows 66 to 71 in the valleys to around 60 above 4000 feet. East winds 10 to 25 mph. Chance of rain 70 percent.

Wednesday: Mostly cloudy. Breezy. Occasional showers in the morning, then scattered showers 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 80 percent.

North Kaua’i

Today: Mostly sunny with isolated showers. Highs 79 to 90. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows 66 to 75. East winds 10 to 15 mph. Chance of rain 70 percent.

Wednesday: Breezy. Mostly cloudy with showers likely in the morning, then mostly sunny with scattered showers in the afternoon. Highs 78 to 91. East winds 10 to 20 mph. Chance of rain 70 percent.

East Kaua’i

Today: Mostly sunny with isolated showers. Highs 76 to 89. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows 66 to 80. East winds 10 to 15 mph. Chance of rain 70 percent.

Wednesday: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 76 to 89. East winds 10 to 15 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Trade winds will begin to strengthen today, with breezy to locally strong wind speeds expected by the middle of the week. A pocket of moisture will likely increase windward showers tonight into Wednesday morning. Conditions will quickly dry out Wednesday afternoon, remaining dry through Thursday. The combination of low humidity and strong trade winds will elevate fire weather concerns Wednesday afternoon and Thursday.

Discussion

Satellite and radar imagery continue to show scattered low clouds and showers moving into windward areas on moderate to locally breezy trades, as well as scattered showers over the coastal waters in the lee plumes of the smaller islands. Expect showers to trend down slightly as some drier low-level air moves into the islands later this morning and afternoon.
Over the course of today and into Wednesday, the surface high far northeast of the state will strengthen, resulting in increasing wind speeds across the state. The global models continue to agree on a tightening of the pressure gradient over the state through the next few days.
Trade winds will further strengthen late Wednesday into Thursday. With the upper level ridge also strengthening over the area during this time, the trade wind inversion will lower. This will result in locally strong and gusty winds downwind/leeward of the terrain, with gusts of 40 to 45 mph possible Wednesday into Thursday, and could approach Wind Advisory criteria for select leeward zones of Maui County and the Big Island. A pocket of moisture moving in tonight could bring an increase of showers across windward areas through Wednesday morning. However, a much drier air mass will move in Wednesday afternoon, and when combined with the gusty winds, will elevate fire weather concerns. Therefore, a Fire Weather Watch is in effect from noon on Wednesday through Thursday afternoon. See the Fire Weather Discussion below and the Fire Weather Watch product for more information.
A more typical trade wind pattern is expected Friday into the weekend with moderate to locally breezy trade winds. Precipitable water values will be increasing back to near normal as well. Scattered showers will favor windward areas, with a few passing showers over leeward areas, primarily during the overnight and early morning hours. In the longer term, the global models are hinting at a fairly significant decrease in winds around the Sunday/Monday time frame as a surface trough moves over the state from the east.

Aviation

High pressure northeast of the state will keep moderate to locally breezy trade winds in place during the next 24 hours, strongest during the late morning and afternoon hours. Low clouds and showers may bring some brief MVFR cigs/vsbys to windward slopes and coasts, particularly during the night and early morning hours. Predominantly VFR conditions are expected at the TAF sites.
No AIRMETs are currently in effect. AIRMET Tango may be needed for low level turbulence over and downwind of the terrain of all islands later today.

Marine

Fresh to strong easterly trades will return today, then persist through Saturday (strongest Wednesday through Thursday). Small Craft Advisory conditions are expected for the typically windier channels and waters around Maui County and the Big Island today, then potentially for most exposed waters Wednesday through Thursday. For the extended, guidance shows the trades easing Sunday into early next week as the ridge weakens.
Surf along exposed north and west facing shores will remain small this morning, then return to summertime levels later today through midweek as a small north-northwest swell moves out. For the upcoming weekend, a small west-northwest (300-310 degrees) swell arriving will be possible. This will be in response to a storm- force low (former TC Damrey) racing eastward toward the Date Line from Japan over the next 24 h.
Surf along south facing shores will remain up today, then fade as a small south-southwest swell moves through. Nearshore PacIOOS and offshore NDBC buoys reflect this swell holding around 14 seconds this morning. Later this week and upcoming weekend, another small long-period southwest swell is expected.
Surf along east facing shores will gradually trend up Wednesday through the second half of the week as the trades ramp up locally and upstream of the state. Additionally, expect some groundswell mixed in with 9-10 second periods for the upcoming weekend from Tropical Storm Irwin tracking westward across the eastern Pacific.

Fire weather

Breezy to locally strong trade winds will develop Wednesday and continue through Thursday. An initially moist airmass on Wednesday morning will eventually give way to an influx of much drier air from the east Wednesday afternoon into Thursday. Red Flag conditions, characterized by sustained winds of 20 mph or greater, dry fuels, and afternoon RH values below 45 percent, will be possible on Wednesday afternoon, but more likely on Thursday when the humidities will be lower. A Fire Weather Watch is in effect from noon on Wednesday through Thursday afternoon. It is important to note that the winds for this event WILL NOT be comparable in strength to the August 8, 2023 event, where wind gusts of over 60 mph were observed. The latest forecast for Wednesday and Thursday is for winds of 15 to 30 mph with gusts of around 40 to 45 mph, with the strongest wind gusts likely downwind/leeward of terrain for Maui County and the Big Island.

HFO Watches/Warnings/Advisories

Fire Weather Watch from Wednesday afternoon through Thursday afternoon for Kauai Leeward, Oahu South Shore, Waianae Coast, Oahu North Shore, Olomana, Central Oahu, Waianae Mountains, Molokai Leeward, Lanai Makai, Lanai Mauka, Maui Leeward West, Maui Central Valley, Leeward Haleakala, Kona, South Big Island, Kohala, Big Island Interior.
Small Craft Advisory from 6 AM this morning to 6 AM HST Thursday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov