Photo Credit: Tyler Rooke

West Side

Today: Isolated showers, with thunderstorms also possible after 1pm. Some of the storms could produce heavy rainfall. Mostly sunny, with a high near 80. East northeast wind 11 to 14 mph, with gusts as high as 18 mph. Chance of precipitation is 20%.

Tonight: A slight chance of showers and thunderstorms, then scattered showers after 7pm. Some of the storms could produce heavy rainfall. Mostly cloudy, with a low around 68. East northeast wind 11 to 14 mph, with gusts as high as 18 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Monday: Scattered showers. Partly sunny, with a high near 82. East northeast wind 8 to 13 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

South Side

Today: Scattered showers and thunderstorms after 1pm. Mostly sunny, with a high near 81. East northeast wind 9 to 14 mph, with gusts as high as 18 mph. Chance of precipitation is 30%.

Tonight: Scattered showers and thunderstorms before 7pm, then isolated showers. Partly cloudy, with a low around 66. East northeast wind 9 to 14 mph, with gusts as high as 18 mph. Chance of precipitation is 30%.

Monday: Scattered showers, mainly after 1pm. Partly sunny, with a high near 81. East northeast wind 9 to 13 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

North Shore

Today: Scattered showers, with thunderstorms also possible after noon. Some of the storms could produce heavy rainfall. Partly sunny, with a high near 78. Breezy, with an east wind 16 to 18 mph, with gusts as high as 25 mph. Chance of precipitation is 30%.

Tonight: Scattered showers. Mostly cloudy, with a low around 67. Breezy, with an east wind around 18 mph, with gusts as high as 25 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Monday: Scattered showers. The rain could be heavy at times. Partly sunny, with a high near 80. Windy, with an east wind 16 to 25 mph, with gusts as high as 36 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Central Maui

Today: Isolated showers, with thunderstorms also possible after noon. Some of the storms could produce heavy rainfall. Mostly sunny, with a high near 79. Breezy, with an east wind 14 to 16 mph, with gusts as high as 22 mph. Chance of precipitation is 20%.

Tonight: Scattered showers. Mostly cloudy, with a low around 65. Breezy, with an east wind around 15 mph, with gusts as high as 21 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Monday: Scattered showers. Partly sunny, with a high near 81. Breezy, with an east wind 11 to 16 mph increasing to 17 to 22 mph in the afternoon. Winds could gust as high as 31 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Upcountry

Today: Isolated showers, then scattered showers and thunderstorms after noon. Some of the storms could produce heavy rainfall. Partly sunny, with a high near 66. Breezy, with an east wind 16 to 20 mph, with gusts as high as 28 mph. Chance of precipitation is 40%.

Tonight: Isolated showers before midnight. Partly cloudy, with a low around 54. Breezy, with an east wind around 21 mph, with gusts as high as 29 mph. Chance of precipitation is 20%.

Monday: Isolated showers after noon. Mostly sunny, with a high near 67. Breezy, with an east wind 14 to 16 mph, with gusts as high as 22 mph. Chance of precipitation is 20%.

East Maui

Today: Isolated showers, then scattered showers and thunderstorms after 1pm. Some of the storms could produce heavy rainfall. Partly sunny, with a high near 76. East wind 9 to 14 mph, with gusts as high as 18 mph. Chance of precipitation is 50%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Tonight: Scattered showers and thunderstorms, then showers likely after 7pm. Mostly cloudy, with a low around 63. Breezy, with an east wind 9 to 15 mph, with gusts as high as 21 mph. Chance of precipitation is 70%. New precipitation amounts between a quarter and half of an inch possible.

Monday: Showers likely before 7am, then frequent showers and possibly a thunderstorm between 7am and 1pm, then showers likely after 1pm. Some of the storms could produce heavy rainfall. High near 78. Breezy, with an east wind 13 to 15 mph, with gusts as high as 21 mph. Chance of precipitation is 80%. New rainfall amounts between a quarter and half of an inch possible.

Lanai City

Today: Isolated showers. Mostly sunny, with a high near 74. Breezy, with an east northeast wind 16 to 18 mph, with gusts as high as 25 mph. Chance of precipitation is 20%.

Tonight: Isolated showers. Partly cloudy, with a low around 62. Breezy, with an east northeast wind 17 to 20 mph, with gusts as high as 28 mph. Chance of precipitation is 20%.

Monday: Isolated showers. Mostly sunny, with a high near 73. East northeast wind 11 to 13 mph. Chance of precipitation is 20%.

Kaunakakai

Today: Isolated showers before noon. Sunny, with a high near 77. Windy, with an east wind 24 to 26 mph, with gusts as high as 38 mph. Chance of precipitation is 20%.

Tonight: Scattered showers. Mostly cloudy, with a low around 69. Windy, with an east wind around 26 mph, with gusts as high as 38 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Monday: Scattered showers. Partly sunny, with a high near 79. Windy, with an east wind around 24 mph, with gusts as high as 34 mph. Chance of precipitation is 30%.

Detailed Forecast

Synopsis

Unsettled weather is likely for the upcoming week as an upper level disturbance interacts with tropical moisture. Breezy trade winds will give way to light and variable winds by mid week as a surface trough forms over the state. Strong northeast winds will then follow Friday over Kauai, and to the remaining islands over next weekend.

Discussion

Although the evening has been rather tame, there are a couple of spots that we are watching closely. The two areas are windward Kauai and windward Haleakala above Hana, where heavy showers are occurring.
There has been a significant shift in the wind forecast during the second half of the week. Instead of strong and gusty trade winds through the week, models are suggesting a surface trough forming over the islands Tuesday and remaining in the vicinity of the state through Friday. Strong and gusty northeast winds are expected to build back in to the area next weekend as high pressure passes north of the islands.
Another addition to the forecast is a slight chance of thunderstorms has been introduced for the Big Island and windward Maui starting this afternoon and remaining in forecast through at least Monday. The rest of the forecast package is pretty much the same, that is it will be showery for most of the week. This prolonged period of unsettled weather will likely warrant a Flash Flood Watch for most if not all of the islands and a Winter Weather Advisory for the Big Island Summits.
An east to west oriented upper level trough with cold temperatures of around minus 13 degrees C is located just north of the islands this morning. An upper low is forecast to form later today west of Kauai as enhanced low level moisture moves toward the Big Island from the southeast. This moisture will then spread up the island chain through Monday night. The upper low then drifts over the islands by Wednesday night and stalls through Friday. The combination of the cold temperatures aloft and the moist air mass near the surface will likely result in an extended period of heavy rains and possible thunderstorms.

Aviation

FR conditions prevail at all TAF sites with some brief periods of MVFR conditions at PHLI and PHTO in low clouds and shra. Expect these conditions to continue into the morning hours. AIRMET Sierra is currently in effect for Kauai, Maui and the Big Island due to mountain obscuration. They will be brief periods of MVFR conditions elsewhere along windward slopes through into the morning hours as low clouds interact with island terrain.
AIRMET Tango is currently in effect over and immediately south thru west of mountain ranges due to low level mechanical turbulence.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Monday for all Hawaiian waters.

Data Courtesy of NOAA.gov