Photo Credit: Randy Alona Gallegos

West Side

Today: Frequent showers and possibly a thunderstorm. Some of the storms could produce gusty winds and heavy rain. High near 77. Breezy, with a south southwest wind 13 to 17 mph, with gusts as high as 24 mph. Chance of precipitation is 90%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Tonight: Frequent showers and possibly a thunderstorm. Some of the storms could produce gusty winds and heavy rain. Low around 64. Southwest wind 8 to 13 mph becoming north after midnight. Chance of precipitation is 90%. New precipitation amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Thursday: Scattered showers before 7am. Sunny, with a high near 75. North wind 8 to 10 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

South Side

Today: Frequent showers and possibly a thunderstorm. Some of the storms could produce gusty winds and heavy rain. High near 77. Windy, with a southwest wind 14 to 23 mph, with gusts as high as 32 mph. Chance of precipitation is 90%. New rainfall amounts between a quarter and half of an inch possible.

Tonight: Showers likely and possibly a thunderstorm before midnight, then isolated showers. Mostly cloudy, with a low around 62. Southwest wind 7 to 9 mph becoming north after midnight. Chance of precipitation is 60%. New precipitation amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Thursday: Sunny, with a high near 75. North wind around 8 mph.

North Shore

Today: Frequent showers and possibly a thunderstorm. Some of the storms could produce gusty winds and heavy rain. High near 75. Breezy, with a southwest wind 18 to 21 mph, with gusts as high as 29 mph. Chance of precipitation is 90%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Tonight: Showers likely and possibly a thunderstorm before midnight, then scattered showers. Mostly cloudy, with a low around 62. Breezy, with a west southwest wind around 17 mph becoming north northwest after midnight. Winds could gust as high as 24 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Thursday: Isolated showers. Mostly sunny, with a high near 73. North wind around 10 mph. Chance of precipitation is 20%.

Central Maui

Today: Frequent showers and possibly a thunderstorm. Some of the storms could produce gusty winds and heavy rain. High near 75. Breezy, with a south southwest wind 17 to 21 mph, with gusts as high as 29 mph. Chance of precipitation is 90%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Tonight: Frequent showers and possibly a thunderstorm before 1am, then scattered showers. Some of the storms could produce gusty winds and heavy rain. Low around 60. Breezy, with a southwest wind 13 to 21 mph becoming north after midnight. Winds could gust as high as 29 mph. Chance of precipitation is 90%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Thursday: Scattered showers, mainly before 7am. Mostly sunny, with a high near 73. Breezy, with a north wind 9 to 16 mph, with gusts as high as 22 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Upcountry

Today: Scattered showers, then frequent showers and possibly a thunderstorm after noon. Some of the storms could produce gusty winds and heavy rain. High near 61. Windy, with a southwest wind 21 to 23 mph, with gusts as high as 32 mph. Chance of precipitation is 90%. New rainfall amounts between 1 and 2 inches possible.

Tonight: Showers likely and possibly a thunderstorm before midnight, then isolated showers. Mostly cloudy, with a low around 50. Breezy, with a southwest wind 7 to 15 mph becoming north northwest after midnight. Winds could gust as high as 21 mph. Chance of precipitation is 60%. New precipitation amounts between a quarter and half of an inch possible.

Thursday: Mostly sunny, with a high near 60. North wind around 7 mph.

East Maui

Today: Frequent showers and possibly a thunderstorm. Some of the storms could produce gusty winds and heavy rain. High near 73. West southwest wind around 14 mph, with gusts as high as 18 mph. Chance of precipitation is 90%. New rainfall amounts between a quarter and half of an inch possible.

Tonight: Showers likely and possibly a thunderstorm before midnight, then scattered showers. Mostly cloudy, with a low around 59. West southwest wind 11 to 14 mph becoming northwest after midnight. Winds could gust as high as 18 mph. Chance of precipitation is 60%. New precipitation amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Thursday: Isolated showers. Mostly sunny, with a high near 71. North wind around 14 mph, with gusts as high as 18 mph. Chance of precipitation is 20%.

Lanai City

Today: Frequent showers and possibly a thunderstorm. Some of the storms could produce gusty winds and heavy rain. High near 70. Windy, with a southwest wind 23 to 28 mph, with gusts as high as 40 mph. Chance of precipitation is 90%. New rainfall amounts between 1 and 2 inches possible.

Tonight: Frequent showers, mainly before midnight. Low around 60. Breezy, with a southwest wind 11 to 16 mph becoming north after midnight. Winds could gust as high as 22 mph. Chance of precipitation is 80%. New precipitation amounts between a half and three quarters of an inch possible.

Thursday: Mostly sunny, with a high near 72. North wind 11 to 13 mph.

Kaunakakai

Today: Frequent showers and possibly a thunderstorm. Some of the storms could produce gusty winds and heavy rain. High near 75. Windy, with a southwest wind 16 to 24 mph, with gusts as high as 34 mph. Chance of precipitation is 90%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Tonight: Showers likely and possibly a thunderstorm before midnight, then scattered showers. Mostly cloudy, with a low around 62. West wind 10 to 14 mph becoming north northwest after midnight. Winds could gust as high as 18 mph. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Thursday: Sunny, with a high near 75. North wind around 10 mph.

Detailed Forecast

Synopsis

A strong cold front approaching Kauai will bring significant changes to the weather across the islands as it moves down the island chain later today and tonight. Locally windy conditions are expected today. In addition, cloud cover and showers will increase with a threat of locally heavy rainfall. There is also a chance of thunderstorms with gusty winds. Expect the northerly flow behind the front to bring drier and cooler air over the islands from tonight into the weekend.

Discussion

A strong cold front appears to a short distance northwest of Kauai early this morning. This feature, which has been moving toward the east-southeast at around 15 mph, is accompanied by overcast layered clouds with embedded showers and isolated thunderstorms. The background low-level flow ahead of this feature is from the south to southwest. The winds have increased ahead of the front, so a Wind Advisory has been issued for Kauai County and Oahu. The windy conditions with localized strong gusts will likely be most prevalent over mountain ridges and along the northeast and east sides of the islands. Note that these windy conditions may eventually spread to portions of Maui County later today.
Clouds and showers continue to increase over the western islands. As the front nears Oahu later this morning, a sharp upper-level trough digging toward the state is expected to cause increasing atmospheric instability. This scenario would likely enhance precipitation ahead of and along the front. This will likely cause locally heavy rainfall with the potential for water ponding issues on some roadways on Oahu during the morning commute. The leading edge of the front is then expected to move across Maui County during the afternoon.
As the front moves through Maui, it is expected to gradually weaken as it approaches the Big Island this evening. Thunderstorms are still possible ahead of and along the front, and the main issues will likely be related to any thunderstorm development. Temperatures will be cold enough for snow over the summits of Mauna Kea and Mauna Loa on the Big Island, and there could be several inches of snow from some time this afternoon into tonight. As a result, Winter Weather Headlines may be needed for the Big Island Summits later today or tonight.
The forecast guidance shows surface high pressure building behind the front. This will produce northerly flow across the entire state. These northerly winds will likely transport significantly cooler and drier air down across all islands. As the dew point temperatures drop into the 50s due to the cool air advection, expect minimum temperatures in the low 60s for many areas, with select location dropping into the 50s tonight and Thursday nights. Note that record minimum temperatures in some locations, such as on Kauai, are in the 50s, so it is not out of the question that a new record low temperature or two may be set somewhere in the state later this week.

Aviation

A front near Kauai has increased south winds with terrain enhancement accelerating wind speeds around and over terrain and through aligned valleys. The terminals located in Maui County and the Big Island are expected to see enhanced southerly winds Wednesday due to this terrain acceleration. Low visibility is expected as the front pushes through Kauai this early morning, Oahu mid morning, and Maui County and the Big Island later today. Expect widespread MVFR and pockets of IFR and LIFR associated with the heaviest rains. Thunderstorms will accompany the front with strong gusty winds expected. AIRMETs for mountain obscuration and strong surface winds will continue through the day. Behind the front, north winds and improving conditions are expected.

Marine

A strong cold front will slide southeastward down the island chain today and tonight, shifting east of the Big Island by daybreak Thursday. Strong south-southwest winds are expected in advance of the front, with strong northwest winds filling in following the frontal passage. Winds will shift northerly Thursday through Friday night at moderate to gentle speeds. High pressure building north of the islands will then bring a return of moderate east-northeasterly trades over the weekend, strongest on Sunday.
A Small Craft Advisory (SCA) is now in effect for most waters through 6 PM this evening, and extends through 6 AM Thursday for the waters surrounding Kauai and Oahu, as well as the windward Maui County waters the waters. The SCA will likely need to be expanded to additional waters Thursday through Saturday due to a large northwest swell moving through the islands.
The offshore NOAA buoys 51001 and 51101 show the incoming west- northwest swell continue to build this morning, although some wind wave contamination is making it difficult to determine if it’s running on time when compared to WW3 guidance. Given significant wave heights are running pretty much spot on at the moment, the swell is likely coming in on time as predicted. This swell will continue to build from northwest to southeast down the island chain today and tonight, peak on Thursday, then gradually lower Thursday night through the weekend. Surf is expected to build to warning levels along north and west facing shores of Kauai tonight, with low-end warning level surf expected to reach north and west facing shores of the Oahu, Molokai and north facing shores of Maui on Thursday. Surf will remain elevated through at least Friday night, before dropping below advisory levels on Saturday and remaining below advisory thresholds through the middle of next week.
The more west-northwest direction of this swell is expected to bring warning level surf to west facing shores of the Big Island from late Thursday afternoon through early Friday as well.
East shore surf will remain small through the middle of next week. A slight boost in short period surf is expected along south facing shores today ahead of the front, with the surf then lowering tonight and remaining small through the middle of next week.

HFO Watches/Warnings/Advisories

Wind Advisory until 6 PM HST this evening for Niihau, Kauai, Oahu.
Small Craft Advisory until 6 PM HST this evening for Maui County Leeward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters.
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.

Data Courtesy of NOAA.gov