Photo Credit: Tyler Rooke

West Side

Today: Scattered showers. Mostly cloudy, with a high near 81. Windy, with an east northeast wind 24 to 29 mph decreasing to 18 to 23 mph in the afternoon. Winds could gust as high as 41 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers. Cloudy, with a low around 71. Windy, with an east wind 20 to 26 mph, with gusts as high as 38 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Tuesday: Scattered showers. Cloudy, with a high near 81. Windy, with an east wind 16 to 23 mph, with gusts as high as 32 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

South Side

Today: Isolated showers. Cloudy, with a high near 81. Northeast wind around 5 mph becoming calm in the morning. Chance of precipitation is 20%.

Tonight: Isolated showers. Cloudy, with a low around 69. Calm wind becoming north northeast 5 to 7 mph in the evening. Chance of precipitation is 20%.

Tuesday: Isolated showers. Cloudy, with a high near 81. Breezy, with a light and variable wind becoming northeast 13 to 18 mph in the afternoon. Winds could gust as high as 25 mph. Chance of precipitation is 20%.

North Shore

Today: Scattered showers. Cloudy, with a high near 79. Windy, with an east wind 18 to 25 mph, with gusts as high as 36 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers. Cloudy, with a low around 70. Windy, with an east wind 21 to 24 mph, with gusts as high as 34 mph. Chance of precipitation is 40%. New precipitation amounts between a tenth and quarter of an inch possible.

Tuesday: Scattered showers. Cloudy, with a high near 79. Windy, with an east wind 17 to 23 mph, with gusts as high as 32 mph. Chance of precipitation is 40%. New precipitation amounts between a tenth and quarter of an inch possible.

Central Maui

Today: Scattered showers. Cloudy, with a high near 81. Breezy, with a northeast wind 11 to 17 mph, with gusts as high as 24 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers. Cloudy, with a low around 68. Northeast wind 9 to 13 mph. Chance of precipitation is 40%. New precipitation amounts between a tenth and quarter of an inch possible.

Tuesday: Scattered showers. Cloudy, with a high near 80. Breezy, with a northeast wind 13 to 21 mph, with gusts as high as 29 mph. Chance of precipitation is 40%. New precipitation amounts between a tenth and quarter of an inch possible.

Upcountry

Today: Isolated showers. Cloudy, with a high near 69. Calm wind becoming southeast 5 to 7 mph in the morning. Chance of precipitation is 20%.

Tonight: Isolated showers. Cloudy, with a low around 60. Calm wind becoming east southeast 5 to 8 mph in the evening. Chance of precipitation is 20%.

Tuesday: Isolated showers. Cloudy, with a high near 69. Breezy, with a light and variable wind becoming east 12 to 17 mph in the afternoon. Winds could gust as high as 24 mph. Chance of precipitation is 20%.

East Maui

Today: Showers likely. Cloudy, with a high near 75. Breezy, with an east southeast wind 14 to 17 mph, with gusts as high as 24 mph. Chance of precipitation is 70%. New precipitation amounts between a quarter and half of an inch possible.

Tonight: Frequent showers. The rain could be heavy at times. Low around 71. Breezy, with an east southeast wind 13 to 16 mph, with gusts as high as 22 mph. Chance of precipitation is 80%. New precipitation amounts between a quarter and half of an inch possible.

Tuesday: Showers likely. Cloudy, with a high near 75. Windy, with an east southeast wind 13 to 18 mph increasing to 19 to 24 mph in the afternoon. Winds could gust as high as 34 mph. Chance of precipitation is 60%. New precipitation amounts between a quarter and half of an inch possible.

Lanai City

Today: Scattered showers. Mostly cloudy, with a high near 72. Breezy, with an east wind 11 to 16 mph becoming light and variable in the afternoon. Winds could gust as high as 22 mph. Chance of precipitation is 30%. New precipitation amounts between a quarter and half of an inch possible.

Tonight: Scattered showers. Cloudy, with a low around 66. Breezy, with a northeast wind 6 to 11 mph increasing to 13 to 18 mph. Winds could gust as high as 25 mph. Chance of precipitation is 30%. New precipitation amounts between a half and three quarters of an inch possible.

Tuesday: Scattered showers. Cloudy, with a high near 72. Light east wind becoming northeast 9 to 14 mph in the morning. Winds could gust as high as 18 mph. Chance of precipitation is 40%. New precipitation amounts between a half and three quarters of an inch possible.

Kaunakakai

Today: Scattered showers. Mostly cloudy, with a high near 79. Windy, with an east wind 17 to 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.

Tonight: Scattered showers. Cloudy, with a low around 73. Breezy, with an east wind 17 to 22 mph, with gusts as high as 31 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tuesday: Scattered showers. Cloudy, with a high near 79. Breezy, with an east wind 14 to 22 mph, with gusts as high as 31 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Detailed Forecast

Synopsis

A strong high northeast of the area and a trough to the southwest will combine to produce locally strong southeast winds over the islands through midweek. Very humid air carried by the southeast flow will keep the Big Island very wet over the next couple of days, with heavy snow over the summits. The smaller islands will be less rainy, but some of the rain may reach the smaller islands by mid-week. During the second half of the week the trough will move away to the west. Winds will shift out of the east and rainfall will diminish.

Discussion

A strong 1038 mb high far northeast of the area and a trough about 650 miles west of Kauai are combining to produce locally strong east to southeast winds over the main Hawaiian Islands. High clouds blanket the area. Radars show widespread showers moving over the Big Island from the southeast. There are numerous showers over windward east Maui, with only isolated showers elsewhere over the smaller islands.
A deep northwest to southeast trough aloft will persist west of the islands over the next couple of days. This trough is making the atmosphere over the islands unstable and helping to pull very moist air over the islands from the southeast. This will produce heavy rain over the Big Island with snow over the summits of Mauna Kea and Mauna Loa. A Flash Flood Watch and a Winter Weather Warning are in effect for the Big Island. Less rain will reach the smaller islands, at least through this evening. More of the moisture may spread over the smaller islands by tomorrow.
The global models show the trough aloft weakening starting Wednesday as a ridge aloft builds over the area from the north. The atmosphere over the islands will become more stable and the moist air will move away to the west. That should bring a decrease in rainfall for the second half of the week, with showers focused over mainly windward areas.

Aviation

Breezy east-southeast winds will continue in windward areas today and tonight. Meanwhile winds in leeward areas will remain light through mid morning, then pick up to moderate levels out of the east-southeast this afternoon, then ease again tonight. Deep tropical moisture will continue to spread northwest across the state during the next 24 hours, although the most unsettled weather is expected over east and southeast facing sections of the Big Island. In these areas, widespread MVFR conditions can be expected, with occasional IFR cigs/vsbys. Across the smaller islands, passing showers will bring temporary MVFR cigs/vsbys to windward areas, with more widespread MVFR conditions possible over Kauai tonight. Generally VFR conditions will prevail in leeward areas, although some MVFR cigs/vsbys could become more common this afternoon through tonight.
AIRMET Sierra remains in effect for mountain obscuration across northeast through southeast facing sections of Kauai, Oahu, Molokai, Maui, and the Big Island. These conditions will likely continue through the day today, and possibly through tonight.
AIRMET Tango remains in effect for low level turbulence over and downwind of the terrain of all islands. These conditions are expected to continue through tonight. AIRMET Tango is also in effect for strong surface winds over some adjacent coastal waters.
AIRMET Zulu remains in effect for moderate rime icing over the Big Island and adjacent waters to the east. These conditions will likely remain in place through today, and possibly through tonight.

Marine

Strong east-southeast winds associated with high pressure will continue over the Hawaiian waters through the week. Rough conditions with seas at and above the Small Craft Advisory level of 10 ft will be the result across exposed waters.
Surf along east facing shores will remain rough due to the aforementioned strong onshore winds locally and upstream across the eastern Pacific driving large seas through the area. The advisory in place will likely become extended into Wednesday. A slightly downward trend will be possible through the second half of the week as the upstream fetch diminishes across the eastern Pacific.
Surf along north and west facing shores will steadily lower through tonight as a northwest swell eases. Large scale pattern change across the Pacific over the past week featuring a blocking pattern setting up east of the Date Line will translate to an end to the active run of large swells that began in the second half of December and continued through the first half of January. Surf will respond and drop well below the January average Tuesday through midweek.
For the long range, guidance shows a developing hurricane-force low around 2000 nm northwest of Hawaii this morning tracking northward toward the western Aleutians through Tuesday. Wave models reflect this and show small, long-period energy arriving through the day Thursday out of the west-northwest, then trending up out of the northwest Friday into the weekend. Large errors typically associated with these sources lead to low forecast confidence.
Surf along south facing shores will trend up today through midweek, as an out-of-season Tasman source arrives. Nearshore PacIOOS buoy observations locally are reflecting this energy beginning to fill in within the 18-22 second bands. Surf should drop and return to normal levels through the second half of the week.

HFO Watches/Warnings/Advisories

Winter Weather Warning through 6 PM Tuesday for the summits of Mauna Kea and Mauna Loa on the Big Island.
High Surf Advisory until 6 PM Tuesday for east facing shores of the Big Island, Maui, Molokai, Oahu and Kauai.
Flash Flood Watch through Tuesday afternoon for the Big Island.
Small Craft Advisory until 6 PM Wednesday for all Hawaiian waters.

Data Courtesy of NOAA.gov