Photo Credit: Braden Jarvis

West Kaua’i

Today: Breezy. Partly sunny with scattered showers in the morning, then sunny with isolated showers in the afternoon. Highs around 85 near the shore to around 72 above 3000 feet. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly clear with isolated showers. Lows around 70 near the shore to around 60 above 3000 feet. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Wednesday: Breezy. Mostly sunny with isolated showers. Highs around 84 near the shore to around 71 above 3000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

South Kaua’i

Today: Breezy. Mostly cloudy with scattered showers early in the morning, then mostly sunny with isolated showers in the late morning and afternoon. Highs 79 to 86. Northeast winds 20 to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 70. Northeast winds 20 to 25 mph. Chance of rain 50 percent.

Wednesday: Breezy. Partly sunny with scattered showers. Highs 79 to 86. Northeast winds 20 to 25 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Breezy. Mostly cloudy with showers likely early in the morning, then mostly sunny with scattered showers in the late morning and afternoon. Highs 71 to 80 in the valleys to around 63 above 4000 feet. Northeast winds 20 to 25 mph. Chance of rain 60 percent.

Tonight: Mostly cloudy. Windy. Scattered showers in the evening, then showers likely after midnight. Lows 62 to 67 in the valleys to around 57 above 4000 feet. Northeast winds 20 to 30 mph. Chance of rain 70 percent.

Wednesday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 70 to 79 in the valleys to around 62 above 4000 feet. East winds 20 to 25 mph. Chance of rain 70 percent.

North Kaua’i

Today: Breezy. Mostly cloudy with scattered showers early in the morning, then mostly sunny with isolated showers in the late morning and afternoon. Highs 73 to 84. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Scattered showers. Lows 63 to 71. East winds 15 to 25 mph. Chance of rain 50 percent.

Wednesday: Breezy. Partly sunny with scattered showers. Highs 73 to 84. East winds 15 to 25 mph. Chance of rain 50 percent.

East Kaua’i

Today: Breezy. Mostly cloudy with showers likely early in the morning, then mostly sunny with isolated showers in the late morning and afternoon. Highs 71 to 83. Northeast winds 20 to 25 mph. Chance of rain 60 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 63 to 74. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

Wednesday: Breezy. Mostly cloudy with scattered showers. Highs 70 to 82. East winds 15 to 25 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Moisture associated with a weak cold front will move away from the islands by this afternoon, with a cool and relatively dry air mass moving over the islands. Breezy conditions Wednesday will give way to diminishing trades and warmer conditions toward the end of the week, with just a few windward showers. Winds will turn to the south ahead of a front on Saturday. The front is expected to arrive on Sunday, potentially bringing showers to leeward areas.

Discussion

Strong high pressure due N of the islands will move slowly S over the next several days, gradually weakening as it does so. This will support strong NE trade winds today as the high pushes moisture associated with a shallow frontal boundary SW of the islands later this morning. Latest satellite and radar images show numerous showers moving over the islands, but also indicate that the back edge of this moisture will soon clear most islands, except windward Big Island, which is expected to remain quite showery through the morning. A Wind Advisory remains posted for areas in Maui and Hawaii Counties where terrain most accelerates the flow.
Guidance has been trending toward a drier trade wind flow tonight and Wednesday as breezy trade winds continue. Thursday and Friday will see gradually easing moderate trade winds as the flow becomes warmer and increasingly easterly. The high will move well NE of the islands by Saturday as low pressure rapidly develops well NW of the islands, turning our winds to the S ahead of an approaching front.
This next front may bring some beneficial rainfall to leeward areas, especially as the front moves over the island chain on Sunday, bringing a wind shift to the SW, then NW. While forecast solutions have lacked run-to-run consistency, guidance now shows the front weakening over or just E of the islands early next week, with light trade winds developing.

Aviation

A dissipating front passing over the islands from the northeast will continue to bring locally strong trades to the region this morning. In addition to these enhanced winds, expect numerous showers to affect windward locations with scattered showers elsewhere. MVFR ceilings and visibility will likely accompany some of the more robust showers. By this afternoon, behind the front, drier air will filter in and allow for a decrease in overall shower activity. Trade flow, however, will remain locally strong.
AIRMET Tango is currently in effect for low-level moderate turbulence over and downwind of the mountains on all islands due to breezy trade winds. AIRMET SIERRA is currently in effect for north through east sections of Maui and the Big Island above 2000 feet due to clouds and showers.

Marine

Strong northeast winds with gales in the Pailolo and Alenuihaha Channels are expected today as a front moves through. These winds combined with a large area of strong- to gale-force northeast winds focused at the state between high pressure to the north and low pressure far northeast of the area support rough seas with heights forecast to exceed the Small Craft Advisory level over exposed waters through midweek.
Guidance shows the gradient beginning to relax Thursday through Friday as high pressure north of the area settles southward and weakens, which will result in the local winds returning to the fresh to locally strong range. Over the weekend, the progressive pattern over the northern Pacific will continue as low pressure rapidly develops northwest of the state Friday, then lifts northeastward while passing to the north around 1000 NM. A front associated with this feature will approach and potentially reach the western end of the state by the end of the weekend. If this evolves as predicted, moderate to fresh south to southwest winds will become a possibility as the front approaches.
Surf along exposed north and east facing shores will steadily rise today, then remain up into the second half of the week due to a mix of the locally wind-generated seas and a northeast groundswell arriving from the aforementioned fetch upstream. Heights are expected to exceed the High Surf Advisory criteria for east facing shores today, which should hold into Thursday. Guidance shows a medium-period reinforcing swell arriving out of the same direction (050 deg) Friday, which will be enough to support advisory-level surf returning for eastern exposures. A downward trend is anticipated over the weekend as the winds shift out of the south.
Surf along north and west facing shores will rise over the weekend as a small, long-period north-northwest swell arrives and moves through. A more significant event is possible Sunday night through early next week due to a large area of northerly gales forecast to develop nearby on the backside of the rapidly developing low passing around 1000 NM to the north this weekend. Heights with these nearby northerly sources typically come in much larger than predicted, which could lead to advisory to warning-level surf early next week.
Surf along south facing shores will trend up over the weekend as a long-period south swell arrives.

Fire weather

Despite numerous showers recently dampening most windward areas, leeward areas have remained mostly dry with just a few light showers. The combination of dry air and strong winds behind this morning's frontal passage will bring an increased risk of fire danger this afternoon, and a Red Flag Warning has been issued for leeward portions of all islands.

HFO Watches/Warnings/Advisories

Red Flag Warning from 10 AM this morning to 6 PM HST this evening for Niihau, Kauai Leeward, Oahu South Shore, Waianae Coast, Oahu North Shore, 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.
High Surf Advisory until 6 AM HST Thursday for East facing shores of Kauai Oahu Molokai Maui and the Big Island.
Wind Advisory until 6 PM HST this evening for Lanai Mauka, Kahoolawe, Maui Windward West, Maui Leeward West, Kohala, Big Island Interior, Molokai Windward, Molokai North, Lanai Windward, Lanai Leeward, Lanai South, Maui Central Valley North, Maui Central Valley South, South Haleakala, Big Island South, Big Island Southeast, Big Island North.
Small Craft Advisory until 6 AM HST Thursday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Maalaea Bay, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.
Gale Warning until 6 PM HST this evening for Pailolo Channel, Alenuihaha Channel.

Data Courtesy of NOAA.gov