Photo Credit: Travis Guthrie

West Side

Today: Sunny, with a high near 83. Calm wind becoming east 5 to 8 mph in the afternoon.

Tonight: Isolated showers after 1am. Mostly clear, with a low around 65. East wind 5 to 8 mph becoming calm in the evening. Chance of precipitation is 20%.

Monday: Isolated showers before 1pm. Mostly sunny, with a high near 82. Light and variable wind. Chance of precipitation is 20%.

South Side

Today: Isolated showers after noon. Mostly sunny, with a high near 83. Calm wind becoming west 5 to 7 mph. Chance of precipitation is 20%.

Tonight: Partly cloudy, with a low around 63. Light and variable wind becoming east northeast 5 to 7 mph after midnight.

Monday: Isolated showers after noon. Mostly sunny, with a high near 82. Light and variable wind becoming east 5 to 9 mph in the afternoon. Chance of precipitation is 20%.

North Shore

Today: Isolated showers. Mostly sunny, with a high near 81. Breezy, with an east wind 11 to 20 mph, with gusts as high as 28 mph. Chance of precipitation is 20%.

Tonight: Isolated showers. Partly cloudy, with a low around 64. Breezy, with an east wind 11 to 16 mph, with gusts as high as 22 mph. Chance of precipitation is 20%.

Monday: Isolated showers. Mostly sunny, with a high near 80. Breezy, with an east wind 15 to 20 mph decreasing to 9 to 14 mph in the afternoon. Winds could gust as high as 28 mph. Chance of precipitation is 20%.

Central Maui

Today: Isolated showers before noon. Mostly sunny, with a high near 81. Breezy, with a light and variable wind becoming east northeast 12 to 17 mph in the morning. Winds could gust as high as 24 mph. Chance of precipitation is 20%.

Tonight: Partly cloudy, with a low around 62. East northeast wind 6 to 11 mph becoming light north northeast in the evening.

Monday: Mostly sunny, with a high near 80. Light and variable wind becoming east northeast 8 to 13 mph in the morning.

Upcountry

Today: Mostly sunny, with a high near 69. Calm wind becoming west around 6 mph.

Tonight: Partly cloudy, with a low around 53. Calm wind becoming east around 5 mph after midnight.

Monday: Mostly sunny, with a high near 69. Calm wind becoming west northwest 5 to 7 mph in the afternoon.

East Maui

Today: Scattered showers. Partly sunny, with a high near 79. East southeast wind 5 to 10 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 60. East southeast wind 7 to 9 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Monday: Scattered showers. Partly sunny, with a high near 78. Breezy, with an east southeast wind 11 to 15 mph, with gusts as high as 21 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Lanai City

Today: Scattered showers, mainly after noon. Mostly sunny, with a high near 75. North northeast wind 5 to 8 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Isolated showers before midnight. Partly cloudy, with a low around 62. Northeast wind 3 to 8 mph. Chance of precipitation is 20%.

Monday: Scattered showers after noon. Mostly sunny, with a high near 75. Calm wind becoming north northeast around 5 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Kaunakakai

Today: Mostly sunny, with a high near 80. Calm wind becoming east 5 to 9 mph in the morning.

Tonight: Mostly clear, with a low around 66. East northeast wind 5 to 9 mph becoming light east.

Monday: Mostly sunny, with a high near 80. East wind 5 to 9 mph.

Detailed Forecast

Synopsis

Light to moderate trade winds will return today through Monday as high pressure builds north of the islands. Passing showers will favor windward and mauka areas, with a stray shower reaching leeward areas from time to time. A sea breeze and land breeze pattern should take hold on Tuesday as the trades become disrupted due to an approaching cold front. This cold front is forecast to bring an increase in showers Wednesday through Thursday as it moves into and gradually dissipated across the islands. A couple new cold fronts may approach or move into the islands late in the week and next weekend, potentially bringing some periods of unsettled weather.

Discussion

Currently at the surface, a weakening surface trough is located between Oahu and Kauai, and is moving westward at around 10 mph. Meanwhile, a west-east oriented ridge of high pressure is located around 400 miles north of the Garden Isle. Aloft a vigorous upper level low responsible for the thunderstorms last night is seen dropping steadily south-southwestward just to the west of the Big Island. Infrared satellite imagery shows clear to partly cloudy skies across most of the state, with a few pockets of more extensive cloud cover moving into some windward areas. Radar imagery shows isolated to scattered showers moving into windward areas, with mainly rain free weather in leeward locales. Main short term focus revolves around the returning trades and rain chances during the next couple days.
The trough of low pressure will continue to shift westward today, while high pressure builds to the north of the islands. This will bring a return of light to moderate trade winds which will persist through Monday. The trades won’t stick around long however, as an approaching cold front will bring light and variable winds back to the island chain Monday night and Tuesday, with land breezes and sea breezes common. As the front draws closer Tuesday night, light south to southwest winds will develop, with moderate westerly winds expected on Wednesday. Winds should shift around to the north and northeast at moderate levels Wednesday night, then become more easterly on Thursday as the front stalls out and dissipates around the central or eastern end of the state. A pair of cold fronts are then forecast to approach from the west Friday through next weekend, and this should bring another period of light and variable winds to the state with sea breezes and land breezes developing in many areas.
As for the remaining weather details, quite the progressive pattern is in store for the islands through the next week, with a series of front approaching and/or moving into the state. In the near term, high pressure building north of the islands and an upper level low shifting south of the state, should bring a stable and relatively dry trade wind pattern during the next couple days, featuring brief passing showers over windward and mauka areas, along with the occasional leeward spillover. A sea breeze/land breeze pattern should set up on Tuesday in advance of the next cold front, with a few showers possible near the coast in the morning and mainly over the island interiors in the afternoon. Rain chances should increase from west to east as a cold front slides into the western islands Wednesday, then stalls out and slowly dissipates over the central or eastern islands Wednesday night and Thursday. Forecast confidence diminishes considerably Friday through next weekend, as model solutions begin to diverge. A couple cold front may approach or move into the state during this time, potentially bringing periods of unsettled weather to portions of the island chain.

Aviation

An upper level low pressure system, currently located southwest of the Big Island, will continue to drift further south and away from the state over the next several hours. Expect light to moderate easterly trades to develop in its wake.
For the remainder of this morning and into the afternoon, isolated showers will mainly occur along the windward coasts and slopes. Brief periods of MVFR ceilings and visibility may accompany this activity. Otherwise, partly cloudy skies and VFR conditions should prevail on the leeward sides.
AIRMET TANGO remains in effect for all the Hawaiian islands between 25000 and 40000 feet due to tempo moderate turbulence.

Marine

A large north-northwest swell associated with a recent hurricane- force low north of the state peaked at the offshore buoy (51000: N of Maui) around midnight (17 feet at 17 seconds), which is well above predicted. Altimeter passes reflected this and showed around 15 ft seas within 100 nautical miles north of Oahu. These observations prompted the upgrade to a High Surf Warning for north and west facing shores today. Nearshore PacIOOS buoys should reflect this peak through the early morning hours or between daybreak and noon today, then gradually ease this afternoon through Monday as the swell lowers. The Small Craft Advisory for seas exceeding 10 ft has been expanded to include most waters today.
In addition to the seas, fresh to locally strong easterly trades will fill back in across the islands from east to west through Monday. Wind speeds should reach Small Craft Advisory levels over the typical channel waters around Maui County, south of the Big Island, and Maalaea Bay today. The progressive winter-time pattern is progged to continue through the week across the northern Pacific with the next cold front approaching and moving into the area Tuesday through midweek. Guidance shows the winds collapsing across the state beginning late Monday night ahead of this front, which will lead to a land and sea breeze regime setting up around the coasts. West winds will precede the front Tuesday night into Wednesday with a shift out of the north over the western end of the islands following the front Wednesday into Wednesday night. Long-term guidance shows the trades briefly returning Thursday, then diminishing again as another front approaches Friday into the weekend.
Surf along north facing shores will peak at low-end warning levels this morning, then lower later this afternoon through Monday as the aforementioned north-northwest swell moves through. Expect the active winter mode to continue for exposed north and west facing shores through the week with advisory-level surf continuing through much of the week. The next long-period swell in the series will arrive out of the north-northwest (330 deg) through the day Monday, peak Monday night, then slowly ease Tuesday and Tuesday night. Surf could briefly dip below advisory levels by Wednesday before the next large north-northwest (330-340 deg) arrives Wednesday night behind the front. Guidance shows this source peaking late Thursday and Thursday night around warning levels. This swell will gradually ease into the weekend.
A combination of large surf this week coinciding with peak monthly water levels will only worsen beach erosion issues for shores exposed to north and northwest swells. Additionally, low- lying vulnerable coastal locations not exposed to the large swells may experience nuisance flooding at and around the peak daily tide cycles this week (between midnight and daybreak).
Surf along east facing shores will remain small each day due to the previously discussed pattern with trades being disrupted frequently and the lack of fetch upstream across the eastern Pacific.
Surf along south facing shores will remain small into Monday, but could trend up slightly by midweek from recent activity down south in the Tasman Sea.

HFO Watches/Warnings/Advisories

High Surf Warning until 6 PM HST this evening for Niihau, Kauai Windward, Kauai Leeward, Waianae Coast, Oahu North Shore, Oahu Koolau, Molokai, Maui Windward West, Maui Central Valley, Windward Haleakala.
High Surf Advisory until 6 AM HST Monday for Big Island North and East.
High Surf Advisory until 6 PM HST this evening for Maui Leeward West.
Small Craft Advisory until 6 PM HST this evening for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Kaiwi Channel, Maalaea Bay, Pailolo Channel, Big Island Leeward Waters, Big Island Southeast Waters.
Small Craft Advisory until 6 AM HST Monday for Maui County Windward Waters, Alenuihaha Channel, Big Island Windward Waters.

Data Courtesy of NOAA.gov