West Side

Today: Mostly sunny in the morning then becoming partly sunny. Breezy. Isolated showers. Highs 76 to 81. East winds up to 25 mph. Chance of rain 20 percent.

Tonight: Breezy. Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Lows 65 to 72. East winds up to 20 mph becoming 10 to 15 mph after midnight. Chance of rain 20 percent.

Wednesday: Sunny. Highs 76 to 81. East winds 10 to 15 mph.

South Side

Today: Mostly sunny in the morning then becoming partly sunny. Breezy. Highs around 84. North winds up to 25 mph.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Breezy. Lows 64 to 73. North winds up to 25 mph becoming 10 to 20 mph after midnight.

Wednesday: Sunny. Highs around 83. North winds 10 to 15 mph.

North Shore

Today: Breezy. Occasional showers early in the morning, then numerous showers late in the morning. Scattered showers in the afternoon. Highs around 79 near the shore to around 63 near 5000 feet. East winds up to 25 mph. Chance of rain near 100 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 68 near the shore to around 49 near 5000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Wednesday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 78 near the shore to around 62 near 5000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Central Maui

Today: Mostly sunny in the morning then becoming partly sunny. Breezy. Isolated showers. Highs 78 to 84. Northeast winds 10 to 20 mph becoming up to 25 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy. Breezy. Lows 64 to 69. Northeast winds 10 to 20 mph.

Wednesday: Mostly sunny. Highs 78 to 83. Northeast winds 10 to 15 mph.

Upcountry

Today: Partly sunny. Scattered showers until late afternoon, then isolated showers late in the afternoon. Highs around 59 at the visitor center to around 67 at the summit. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 41 to 52. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Partly sunny with isolated showers in the morning, then mostly sunny in the afternoon. Highs around 57 at the visitor center to around 66 at the summit. East winds up to 15 mph. Chance of rain 20 percent.

East Maui

Today: Breezy. Occasional showers early in the morning, then numerous showers late in the morning. Scattered showers in the afternoon. Highs around 79 near the shore to around 63 near 5000 feet. East winds up to 25 mph. Chance of rain near 100 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 68 near the shore to around 49 near 5000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Wednesday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 78 near the shore to around 62 near 5000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Lanai City

Today: Windy. Mostly sunny early in the morning, then isolated showers in the late morning and early afternoon. Partly sunny late in the afternoon. Highs 71 to 79. Northeast winds up to 20 mph increasing to up to 30 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Windy. Lows around 64. Northeast winds 10 to 30 mph.

Wednesday: Sunny. Highs 69 to 78. East winds around 10 mph.

Kaunakakai

Today: Breezy. Mostly sunny with scattered showers early in the morning, then partly sunny with isolated showers in the late morning and early afternoon. Partly sunny late in the afternoon. Highs 68 to 84. East winds 10 to 25 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Breezy. Lows 56 to 72. East winds 10 to 20 mph.

Wednesday: Sunny and breezy. Highs 67 to 83. East winds 15 to 20 mph.

Detailed Forecast

Synopsis

An old remnant frontal boundary moves swiftly through the islands today with a brief boost in showers and breezy trade winds. Easterly trade winds will quickly decrease tonight through Wednesday with a hybrid light to moderate east-southeasterly wind and sea breeze pattern setting up over the islands from Wednesday night through the Christmas holiday weekend. Shower activity will be limited from Wednesday onward after the remnant cloud band passes through the state. An approaching upper level disturbance on Sunday will spread significant high level cirrus clouds from west to east across the region. This upper disturbance will increase statewide shower trends in a light southeasterly wind pattern for the first half of next week.

Discussion

In the big picture satellite imagery, we see a high pressure ridge in place north to northeast of the Hawaiian Islands, a deep low and cold front far northwest of the state tracking northeastward,and a narrow low level cloud band drifting through the islands this morning. Breezy trade winds will push this narrow remnant cloud band through the islands today enhancing shower trends for all islands, especially over the typical windward mountain slopes.
The cold front trailing the low northwest of the islands will approach the Hawaii region from the west and stall long before reaching the western most island of Kauai. However, the main impact to island weather will be a change in wind directions as the high pressure system far north of the state drifts east, parking a low level ridge directly over the island chain. Wind speeds will weaken and veer more from a east to southeast direction from Wednesday night through the Christmas holiday weekend. Another impact of this ridge over the state will be felt in the large scale subsidence, or stabilizing downward vertical motions that will warm and dry the air over each island. Subsidence temperature inversion heights will lower, decreasing vertical cloud growth and keeping shower activity to minimum during this time period. Only brief passing showers remain in the forecast and any rainfall amounts will be light. American model (GFS) cross sections show this trend well with temperature inversion heights hovering around 5,000 to 6,000 feet elevation from Wednesday night into Sunday.
By early next week, another shallow cold front approaches Kauai from the northwest. The latest model consensus guidance suggests this weak frontal trough will stall out long before reaching the islands. However, a more interesting pattern is brewing in the upper levels as a passing and strong upper level trough will deepen into an upper low near the islands. Extended range weather model solutions project this upper low to pass from west to east across the entire state during this time period. If this long range solution works out as predicted, then all islands will see rain shower enhancement in a light wind sea breeze wind pattern. Rainfall activity will favor island mountain and interior sections with decent rainfall potential for even the normally drier leeward sections. Stay tuned as this extended range forecast period will certainly evolve over time.

Aviation

An old remnant frontal boundary moves swiftly through the islands today with a brief boost in breezy trade winds. Easterly trade winds will quickly decrease tonight with a hybrid light to moderate east-southeasterly wind and sea breeze pattern setting up over the islands with decreasing shower trends from Wednesday night onward.
AIRMET Sierra has been posted for tempo mountain obscurations for all islands as this low level cloud band passes swiftly through the islands. This AIRMET will likely be trimmed down in coverage for some islands later today as more stable air moves in from the northeast.
AIRMET Tango remains in effect for tempo moderate turbulence downwind of terrain on all islands below 8000 feet will likely continue through tonight.

Marine

Surface high pressure far north-northwest of the waters will drift east through Wednesday as low pressure far to the northwest of Kauai remains nearly stationary and weakens. Easterly trade winds will strengthen over majority of the coastal zones today into the fresh to strong range as the Small Craft Advisory (SCA) has been extended through tonight due to a combination of winds and seas. The SCA will be trimmed to the windier waters and channels around Maui County and the Big Island Wednesday. The high pressure north of the waters will weaken as it passes north of Hawaii on Wednesday, coinciding with the weakening low, thus gradually weakening the winds and veering to the southeast to south by the end of the week. Area of low pressure looks to redevelop and push a surface ridge near Kauai by the weekend.
The current small north swell will continue to gradually decline into Wednesday. A moderate, medium period north-northeast (010-030 degrees) swell will arrive late Wednesday and peak Thursday and Friday. Surf along north facing shores could approach the High Surf Advisory level during the peak, with the largest swells favoring the eastern end of the island chain, and a Marine Weather Statement will likely be needed tonight for harbor surges at Kahului and Hilo. The north swell will decline over the weekend as a small northwest swell arrives.
Surf along east facing shores have increased overnight coinciding with the short period energy from the building trade wind energy. Strong trades will produce rough and choppy conditions through Wednesday, mainly over the western islands, peaking near or briefly at High Surf Advisory levels for east facing shores before declining. Short period trade wind swell will decline by Christmas, but wrapping northerly swell will affect exposed eastern shores into Friday. Surf along south facing shores will remain very small through the week.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Wednesday for most Hawaiian Coastal Waters due to a combination of winds and seas.

Data Courtesy of NOAA.gov