Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Mostly sunny. Isolated showers in the afternoon. Highs around 88 near the shore to around 76 above 3000 feet. Northwest winds up to 10 mph shifting to the west in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers early in the evening. Lows 65 to 70 near the shore to around 56 above 3000 feet. Light winds. Chance of rain 20 percent.

Columbus Day: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 87 near the shore to around 75 above 3000 feet. Southeast winds up to 10 mph. Chance of rain 50 percent.

South Kaua’i

Today: Mostly sunny. Isolated showers in the afternoon. Highs around 85. Light winds becoming southwest around 10 mph in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers early in the evening. Lows 63 to 69. Light winds. Chance of rain 20 percent.

Columbus Day: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 84. South winds up to 10 mph. Chance of rain 40 percent.

Kaua’i Mountains

Today: Mostly sunny. Isolated showers in the afternoon. Highs 75 to 82 in the valleys to around 66 above 4000 feet. Light winds. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers early in the evening. Lows 56 to 61 in the valleys to around 51 above 4000 feet. Light winds becoming southwest up to 10 mph after midnight. Chance of rain 20 percent.

Columbus Day: Mostly sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 74 to 81 in the valleys to around 65 above 4000 feet. Southwest winds up to 10 mph. Chance of rain 50 percent.

North Kaua’i

Today: Mostly sunny. Isolated showers in the afternoon. Highs 78 to 87. Northwest winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers early in the evening. Lows 59 to 69. Light winds. Chance of rain 20 percent.

Columbus Day: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 77 to 86. Light winds becoming northwest up to 10 mph in the afternoon. Chance of rain 50 percent.

East Kaua’i

Today: Mostly sunny. Isolated showers in the afternoon. Highs 78 to 86. Light winds. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers early in the evening. Lows 57 to 71. Light winds. Chance of rain 20 percent.

Columbus Day: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 77 to 85. South winds up to 10 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Humid conditions and light winds will continue through much of the week, as low pressure remains positioned far to the north of the islands. During the next couple days, clouds and showers will favor island interior and leeward locations during the afternoon and early evening hours and areas near the coast at night. A thunderstorm or two and some localized downpours will also be possible on the Big Island each afternoon. More widespread rainfall, particularly over the western islands, is expected Tuesday through Thursday as a front develops near or over the western end of the state. A cold front could move into the islands Friday and Saturday, bringing a return of trade winds and potentially delaying a return of drier weather.

Discussion

Currently at the surface, a deep 988 mb low is located around 1050 miles north of Honolulu, with a cold front extending from the low to a position around 125 miles north of Kauai. The proximity of the front has placed the islands in a light wind regime, with land breezes dominant across the entire state early this morning. Infrared satellite imagery shows high clouds streaming through the region, resulting in partly to mostly cloudy conditions. Meanwhile, radar imagery shows isolated showers out over the coastal waters, with very little shower activity over land. Main short term focus revolves around rain chances during the next couple days, with longer term focus on a potential for some more widespread rainfall during the middle part of the upcoming work week.
The cold front north of the state will move slowly southward today, stall out just north of Kauai tonight, then dissipate on Columbus Day. A new front is expected to develop near or over the western islands Monday night and Tuesday, then remain nearly stationary through Wednesday, before slowly edging eastward and weakening Wednesday night and Thursday. This front will be followed by yet another cold front potentially moving southward into the state Friday and Saturday. Overall this pattern is expected to produce an extended period of light winds, with land and sea breezes common in most areas through Thursday. Trade winds could begin to fill in Thursday night, then strengthen to moderate levels Friday into the weekend.
As for the remaining weather details, not much change to the weather pattern is expected through Monday. A land and sea breeze driven pattern should keep showers confined primarily to interior and leeward sections of the islands during the afternoon and evening hours, and locations near the immediate coast at night. Additionally, with mid-level moisture and instability in place over the Big Island during the next couple days, a few downpours along with a thunderstorm or two will be possible each afternoon.
Beginning Monday night, a deep closed low north of the islands appears to draw some deep tropical moisture northward into the state. This closed low will open up and lift northward on Tuesday, but will quickly be replaced by a potent shortwave trough closing off into another nearly stationary closed low north of the islands on Wednesday, before opening up and shifting eastward Thursday and Friday. Overall, this set up has the potential to bring a steady influx of deep tropical moisture into the islands with precipitable water values in excess of 2 inches for multiple days. There remains some differences in the model guidance regarding how widespread the shower activity will be, but they are in fairly good agreement showing the higher rainfall totals remaining over the western islands. The deeper moisture should begin to exit the region to the northeast on Thursday, with a new front potentially bringing some more wet weather particularly to windward areas Friday into next weekend.

Aviation

Localized land and sea breezes will continue to drive local weather patterns over the next twenty-four hours and likely beyond. Light land breezes will linger through mid-morning. Gentle sea breezes will return in the afternoon. Clouds and showers will become focused over island interiors by late afternoon with isolated heavy showers possible over island interiors. For the Big Island, there will also be a slight chance of thunderstorms in the late afternoon and early evening.
Additionally, upper level southwest winds will continue to stream bands of layered high clouds across the islands. High clouds are expected to persist throughout the day and into the night.

Marine

Low pressure system far north of the islands will continue to suppress trade winds across the area, with light and often variable, winds prevailing through the forecast period.
A reinforcing north swell is expected to rise through the day today reaching low end advisory levels this afternoon for north facing shores before slowly fading through Wednesday. Therefore, a High Surf Advisory (HSA) has been issued for north facing shores of Niihau, Kauai, Oahu, Molokai, Maui, and the Big Island, which will go into effect today at 12 PM HST. Another north swell may build surf heights along north facing shores near the HSA level late in the upcoming week.
A long period south swell will peak this weekend a pinch above the summer average before slowly subsiding early next week. Another similar sized south swell may arrive around the middle of next week. Surf along east facing shores will remain small due to lack of trade winds, except for some select east facing shores exposed to the north swell wrap.

HFO Watches/Warnings/Advisories

High Surf Advisory from noon today to 6 AM HST Monday for Oahu North Shore, Olomana, Maui Windward West, Kauai North, Kauai East, Koolau Windward, Molokai Windward, Molokai North, Maui Central Valley North, Windward Haleakala, Big Island East, Big Island North.

Data Courtesy of NOAA.gov