Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Breezy. Mostly cloudy with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 88 near the shore to around 76 above 3000 feet. East winds up to 20 mph. Gusts up to 40 mph in the morning. Chance of rain 50 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 73 near the shore to around 63 above 3000 feet. Northeast winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 50 percent.

Wednesday: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs around 88 near the shore to around 75 above 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

South Kaua’i

Today: Breezy. Mostly cloudy with scattered showers. Highs 83 to 90. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Numerous showers in the evening, then scattered showers after midnight. Lows around 72. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Wednesday: Partly sunny with scattered showers. Highs 83 to 90. East winds 10 to 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 74 to 84 in the valleys to around 66 above 4000 feet. East winds 10 to 20 mph decreasing to up to 15 mph in the afternoon. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with numerous showers. Lows 65 to 71 in the valleys to around 60 above 4000 feet. East winds up to 10 mph increasing to up to 20 mph after midnight. Chance of rain 70 percent.

Wednesday: Breezy. Mostly cloudy with scattered showers. Highs 75 to 83 in the valleys to around 66 above 4000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

North Kaua’i

Today: Partly sunny with scattered showers. Highs 77 to 88. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 65 to 74. East winds up to 10 mph increasing to 10 to 15 mph after midnight. Chance of rain 50 percent.

Wednesday: Partly sunny with scattered showers. Highs 77 to 87. East winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 74 to 86. East winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with numerous showers. Lows 65 to 77. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Wednesday: Mostly cloudy with scattered showers. Highs 75 to 86. East winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

The remnants of an old cold front will linger over the state today, bringing increased showers. Winds will veer southeasterly over the next couple of days and ease, especially over the smaller islands. Expect a return of locally strong trades this weekend.

Discussion

Radar and satellite imagery early this morning shows an extensive shower band draped across the island chain (the remnants of an old front), bringing numerous, yet beneficial, showers into windward areas, especially the smaller islands. Winds are still strong enough to carry appreciable amounts of rainfall over to interior and leeward areas as well. Rainfall totals have been heaviest over Kauai, with several areas receiving around a quarter to half of an inch in the last 6 hours, and 1 to 3 inches in the last 24 hours (Mt. Waialeale with 4.17 inches in past 24 hours). Oahu is beginning to catch up with generally a quarter to half of an inch in the last 24 hours for many windward and interior locations. High-res models continue to show this shower band gradually dissipating through this evening.
Global models have changed little in bringing a compact shortwave southward to near 30N and the Dateline, as it deepens and briefly closes off northwest of the islands around the middle of this week. Though the GFS solution is a bit weaker, both models depict the onset of surface pressure falls immediately west of the islands beginning tonight, which will weaken the background wind field and transition the trades to a locally breezy southeasterly flow. This will place the smaller islands in the shadow of the Big Island on Wednesday and possibly Thursday, with some combination of ESE winds over windward zones and sea breezes over some leeward slopes and coasts. The dry airmass, which was displaced off to the south and east of the state by the old front, will be pulled back northwestward over the state once again as winds veer southeasterly. This increases confidence that leeward areas will remain on the drier side for Wednesday and Thursday.
Beginning Thursday afternoon, the surface trough will weaken as it is absorbed into the trade wind belt and carried off to the west. A breezy easterly trade wind pattern will quickly reestablish over the islands on Friday, as a longwave ridge builds northeast of the area. In the longer term, the global models agree on a strong surface high building in far north of the state for the latter half of the weekend, which would tighten the pressure gradient over the islands and bring another round of locally strong and gusty trade winds.

Aviation

Moderate to locally windy trade winds will persist through at least afternoon, the result of strong high pressure to the northeast of the Islands. A strong trade wind inversion, sloping from 08 kft near Hilo to around 11 kft near Lihue, will keep the air mass over the state highly stable. AIRMET Tango for low level turbulence over and downwind of terrain remains in effect for all islands, but may be canceled later today for Kauai and Oahu.
As of 2 am, a broad band of quick moving showers could be seen on satellite stretched across Kauai, Oahu, and windward portions of the remaining islands. AIRMET Sierra for occasional mountain obscuration remains in effect for Kauai and Oahu. Conditions are expected to improve this afternoon once the band of showers weakens and shifts to the southwest.
Elsewhere across the state, VFR conditions will prevail. The inversion aloft will inhibit most shower activity east of Molokai. Occasionally cloudy but mostly dry conditions are expected across the Big Island and leeward Maui through twenty-four hours and beyond.

Marine

Recent fresh to locally strong trade winds will gradually decline through the day as robust, albeit weakening, surface high pressure passes about 1,000 nautical miles north of the islands. A Small Craft Advisory (SCA) is now in effect for all waters. As the surface high moves east, winds will further weaken and the SCA will be scaled back to the eastern island waters surrounding Big Island and Maui County from tonight through early Thursday. A surface trough developing a couple hundred miles west of Kauai will veer trades more east southeast Wednesday and Thursday, especially over the western end of the island chain. SCA-level winds should hold around Big Island and Maui the next several days. As the trough dissipates going into Friday, stronger east trades will likely once again expand west that will require an western expansion of the SCA. Generally, fresh to locally strong trades will occur this weekend.
The largest surf will be along east-facing shores the next couple of days. Recent buoy observations have strong trades over and upwind of the state producing short period (around 10 second) 8 to 9 foot seas. These large east wind waves will produce rough chop along eastern shores but surf should remain under High Surf Advisory criteria today. Rough eastern shore surf will subside back to near seasonal levels late today or Wednesday. Surf along north-facing shores will be below November averages through the week as a series of primarily small 3 to 4 foot, medium period north northwest swells (340-350 degree) move in. The latest swell peaked Monday and will decline through Wednesday, followed by a couple of overlapping north northwest swells from Thursday into the weekend. Small surf continues along south-facing shores.

Fire weather

Winds will slowly weaken from northwest to southeast through tonight. Marginal fire conditions are still possible over the windier portions of leeward Big Island through this afternoon.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov