Photo Credit: Laila Reiss

West Side

Today: Sunny and breezy. Highs 76 to 82. East winds 10 to 20 mph decreasing to up to 20 mph in the afternoon.

Tonight: Breezy. Mostly clear with isolated showers. Lows 60 to 67. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tuesday: Sunny and breezy. Isolated showers in the morning. Highs 75 to 81. East winds up to 20 mph. Chance of rain 20 percent.

South Side

Today: Sunny and breezy. Highs around 82. North winds up to 20 mph.

Tonight: Mostly clear. Breezy. Lows around 61. Northeast winds 10 to 20 mph.

Tuesday: Sunny and breezy. Highs around 81. Northeast winds up to 20 mph.

North Shore

Today: Mostly sunny. Breezy. Highs 74 to 79 near the shore to around 64 near 5000 feet. East winds up to 20 mph.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 58 to 64 near the shore to around 49 near 5000 feet. East winds up to 15 mph. Chance of rain 30 percent.

Tuesday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 73 to 78 near the shore to around 63 near 5000 feet. East winds up to 20 mph. Chance of rain 30 percent.

Central Maui

Today: Sunny and breezy. Highs 78 to 83. Northeast winds 10 to 20 mph.

Tonight: Partly cloudy. Lows 59 to 64. Northeast winds 10 to 15 mph.

Tuesday: Sunny. Highs 77 to 82. Northeast winds 10 to 15 mph.

Upcountry

Today: Sunny and breezy. Highs around 60 at the visitor center to around 57 at the summit. East winds up to 25 mph.

Tonight: Mostly clear. Breezy. Isolated showers in the evening. Lows around 47 at the visitor center to around 44 at the summit. East winds up to 20 mph. Chance of rain 20 percent.

Tuesday: Sunny and breezy. Isolated showers in the afternoon. Highs around 59 at the visitor center to around 56 at the summit. East winds up to 20 mph. Chance of rain 20 percent.

East Maui

Today: Mostly sunny. Breezy. Highs 74 to 79 near the shore to around 64 near 5000 feet. East winds up to 20 mph.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 58 to 64 near the shore to around 49 near 5000 feet. East winds up to 15 mph. Chance of rain 30 percent.

Tuesday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 73 to 78 near the shore to around 63 near 5000 feet. East winds up to 20 mph. Chance of rain 30 percent.

Lanai City

Today: Sunny and breezy. Highs 71 to 78. Northeast winds 10 to 25 mph decreasing to up to 20 mph in the afternoon.

Tonight: Mostly clear. Breezy. Isolated showers in the evening. Lows around 61. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs 71 to 78. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Kaunakakai

Today: Sunny and breezy. Highs 71 to 81. Northeast winds 10 to 20 mph.

Tonight: Mostly clear. Isolated showers after midnight. Lows 54 to 66. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny. Breezy. Isolated showers in the morning. Highs 70 to 80. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A rather dry and stable airmass will prevail over the islands through much of the week, with a few showers affecting mainly windward slopes and coasts. Moderate to locally breezy trades will prevail through Wednesday, before easing Thursday and Friday allowing for daytime sea breezes and overnight land breezes across most of the state. An approaching front could bring an increase in south to southeast winds and potentially some wet weather to the islands by the end of the weekend.

Discussion

Currently at the surface, a 1007 mb low is located around 650 miles east-southeast of Hilo, while a 1023 mb high is centered around 950 miles northeast of Honolulu. The resulting gradient is producing moderate trade winds, strongest over the eastern end of the state. Infrared satellite imagery shows clear to partly cloudy skies in most areas, with a bit more cloud cover in some windward locales. Radar imagery shows a few light showers over windward Kauai, with very little rainfall elsewhere. Main short term focus revolves around rainfall and trade wind trends during the next several days.
The low east-southeast of the state will gradually weaken as it slides southwestward during the next couple days, before opening up into a trough Tuesday night and Wednesday as it slides by well to the south of the island chain. At the same time ridging will hold in place to the north of the area, keeping moderate trade winds in place, which may be locally breezy over the eastern end of the state at times. A front approaching and eventually stalling out a couple hundred miles northwest of the islands Thursday and Friday, will push the ridge southward and closer to the state. This is expected to shift boundary layer winds east- southeasterly, resulting in a light and variable wind pattern featuring daytime sea breezes and overnight land breezes across the western islands, while light to moderate trades hold over the Big Island and Maui. A new front approaching from the northwest could bring an increase in southeast to south winds over the weekend.
As for the remaining weather details, a very dry and stable airmass has overspread most of the state early this morning, with precipitable water values below 1 inch and inversion heights settling around 5 kft. There remains some lingering moisture associated with and old front over Kauai where a few showers continue to affect windward slopes and coasts, but drier air is moving in quickly and should encompass the Garden Isle by daybreak. After daybreak, very little if any shower activity is expected statewide. We should see a slight increase in trade wind showers focused mainly over windward terrain and coasts tonight through Wednesday night as PW values tick up ever so slightly and inversion heights get a very slight boost. Overall however, the pattern will remain stable and much drier than normal. The rather dry conditions should then continue Thursday through Saturday, with east-southeasterly flow favoring a few windward showers mainly during nights and mornings and perhaps a shower or two developing over the island interiors each afternoon. Deeper moisture may advect into the state from the south and west late in the weekend into early next week, potentially bringing some wet weather back to the island chain.

Aviation

Early morning surface analysis reveals high pressure northeast of the state and a surface low southeast of the Big Island. The pressure gradient between these two features will support moderate to locally breezy easterly trade winds throughout the next 24 hours, particularly across the eastern end of the island chain. Relatively stable, dry air will limit clouds and shower activity today, though any showers that do form will favor north through east facing slopes and coasts. VFR flight conditions are expected to prevail at most locations, though brief periods of MVFR cigs will be possible in developing trade wind showers.
AIRMET Tango remains in effect for moderate low-level turbulence downwind of the mountains of the Big Island, Maui, and Molokai. This AIRMET will likely remain in effect through at least tonight.

Marine

A high pressure ridge north of the region will continue to produce moderate to locally strong trade winds over the Hawaii region into Wednesday, and then winds will veer out of the southeast direction from Thursday into the weekend. Trade winds will remain strong enough with elevated seas for continued Small Craft Advisories (SCA) over most waters and channels today. A dissipating surface low southeast of the Big Island will continue to drift south and help maintain the trade wind strength between the high pressure ridge and the low center. A surface high pressure system will pass far north of the islands Tuesday and Wednesday and likely maintain border line SCA strength winds over the same waters. The high moves off to the east on Thursday and Friday, causing winds to ease and shift out of the southeast over most waters.
As one northwest swell continues to fade, an overlapping new northwest swell builds into the region maintaining High Surf Advisory (HSA) conditions along exposed north and west facing shores through this afternoon. The current HSA was extended for exposed north and west facing shores through this afternoon. Swell heights remain 1 to 2 feet above wave model guidance. Northwest swell heights will then decline from Tuesday through Thursday. Another northwest swell arriving Friday could push surf heights back near HSA levels through Saturday.
East shore surf will be at or above seasonal average today. A rare and compact subtropical gale formed far northeast of the state several days ago, and this feature has been generating a swell that will peak today, and then decline later tonight through Tuesday. By midweek, expect short period trade wind swell to produce east shore surf below seasonal averages. Surf heights along south facing shores will remain small through the week.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST this evening for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kona, Kohala, Kauai North, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala.
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, Maui County Windward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov