Photo Credit: Tyler Rooke

West Side

Today: Isolated showers before noon. Mostly sunny, with a high near 84. East northeast wind 6 to 11 mph becoming light and variable in the morning. Chance of precipitation is 20%.

Tonight: Mostly clear, with a low around 67. East northeast wind around 10 mph.

Monday: Sunny, with a high near 84. East northeast wind around 10 mph.

South Side

Today: Partly sunny, with a high near 83. Light and variable wind becoming west northwest around 6 mph in the afternoon.

Tonight: Partly cloudy, with a low around 65. East northeast wind 11 to 13 mph.

Monday: Isolated showers after noon. Increasing clouds, with a high near 86. East northeast wind around 11 mph. Chance of precipitation is 20%.

North Shore

Today: Scattered showers, mainly before noon. Mostly sunny, with a high near 81. Breezy, with an east wind 16 to 22 mph, with gusts as high as 31 mph. Chance of precipitation is 30%.

Tonight: Isolated showers before midnight. Mostly clear, with a low around 66. Breezy, with an east wind around 17 mph, with gusts as high as 24 mph. Chance of precipitation is 20%.

Monday: Isolated showers. Mostly sunny, with a high near 81. Breezy, with an east wind around 18 mph, with gusts as high as 25 mph. Chance of precipitation is 20%.

Central Maui

Today: Scattered showers, mainly before noon. Mostly sunny, with a high near 82. Breezy, with a northeast wind 9 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: Isolated showers after midnight. Partly cloudy, with a low around 64. East wind around 14 mph, with gusts as high as 18 mph. Chance of precipitation is 20%.

Monday: Isolated showers after noon. Mostly sunny, with a high near 81. Breezy, with an east wind around 15 mph, with gusts as high as 21 mph. Chance of precipitation is 20%.

Upcountry

Today: Mostly sunny, with a high near 70. Calm wind becoming west around 6 mph in the afternoon.

Tonight: Mostly clear, with a low around 54. East wind around 14 mph, with gusts as high as 18 mph.

Monday: Mostly sunny, with a high near 70. Breezy, with an east wind 11 to 15 mph, with gusts as high as 21 mph.

East Maui

Today: Showers likely, mainly before noon. Partly sunny, with a high near 79. Breezy, with an east southeast wind 11 to 15 mph, with gusts as high as 21 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 62. Breezy, with an east wind around 16 mph, with gusts as high as 22 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 79. 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.

Lanai City

Today: Isolated showers. Mostly sunny, with a high near 76. Calm wind becoming northeast around 6 mph in the afternoon. Chance of precipitation is 20%.

Tonight: Mostly clear, with a low around 63. East northeast wind around 9 mph.

Monday: Isolated showers after noon. Mostly sunny, with a high near 75. East northeast wind around 8 mph. Chance of precipitation is 20%.

Kaunakakai

Today: Sunny, with a high near 80. Breezy, with an east wind 15 to 20 mph, with gusts as high as 28 mph.

Tonight: Mostly clear, with a low around 68. Breezy, with an east wind around 18 mph, with gusts as high as 25 mph.

Monday: Sunny, with a high near 80. Breezy, with an east wind around 21 mph, with gusts as high as 29 mph.

Detailed Forecast

Synopsis

Breezy trade winds will continue for the next couple of days, then become locally strong Wednesday and Thursday. Low clouds and showers will favor windward areas, but coverage and intensity will diminish later today as the atmosphere stabilizes. A brief increase in windward showers is possible on Tuesday, but heavy rainfall is not expected.

Discussion

In summary, trade winds remain in the forecast through next weekend. Breezy trade winds will be veered to a direction slightly S of E through Friday, becoming stronger around mid-week before returning to a more typical ENE direction next weekend while remaining breezy. Low clouds and showers will favor windward areas while most leeward areas will receive little rainfall. The island atmosphere will be somewhat unstable in the short term, but a stabilizing trend over the next day or two means that shower coverage should diminish. However, a slight increase in moisture on Tuesday may bring a brief period of increased showers. A deep-layer trough W of the islands may bring some increase in showers around mid-week. High clouds will clear today, but may return Wednesday and Thursday.
Locally breezy trade winds (supported by a 1039 mb high to the distant NE) are delivering low clouds and showers to windward areas, while a trough aloft near Kauai is producing scattered to broken high clouds over the islands from Oahu to the Big Island. Windward shower coverage increased overnight, likely due to a combination of cloud top cooling and the passage of a trough aloft. As the trough moves steadily E today, high clouds will clear and the island atmosphere will be increasing stable. However, the trough axis is expected to be over the Big Island this afternoon, and then E of all islands by tonight, so there remains a slight chance that a thunderstorm will again develop over the Big Island slopes today.
From Monday through Wednesday mid-level temperatures will warm, leading to increasingly stable conditions. The surface high to the distant NE will change little while a surface front gradually approaches from the NW, thus we expect the locally breezy trade winds to be veered to the ESE. An area of shallow moisture embedded within the trade flow arriving Tuesday may bring a brief period of increased windward showers.
On Wednesday, guidance indicates the dissipating and stalling front to the W will help seed a low-level, N-S oriented trough along 165W, supported by a trough aloft. Meanwhile, the high to the NE will strengthen to near 1047 mb. This is expected to lead to strong ESE winds, but it remains uncertain how much of a moisture and instability increase the trough will bring over the islands, with guidance indicating that it will remain just W of the islands. Closest point of approach of the convergent boundary would be to Kauai around Wednesday before it retreats to the W. The trough will dissipate by next weekend as the high to the NE remains strong, with breezy to locally strong ENE trade winds the result.
The departure of the trough aloft means high clouds will clear the chain today, but they may increase Wednesday/Thursday in association with the new trough aloft NW of the islands.

Aviation

Moderate to breezy trades will continue to push areas of clouds and showers over the islands through the forecast period. Brief MVFR conditions are to be expected, mainly along the windward slopes, with a shower or two being pushed over to leeward areas at times. Otherwise, prevailing VFR is expected through the weekend. In addition, lingering instability will allow for a slight chance of thunderstorms along the leeward slopes of the Big Island this afternoon.
AIRMET Sierra is in effect for tempo mountain obscuration due to an area of enhanced showers moving in on the trade wind flow. This activity should diminish by late morning, with improving conditions.
AIRMET Tango remains in effect for low-level mechanical turbulence over and downwind of terrain for Big Island through Molokai due to the breezy trades.
AIRMET Tango also remains in effect for mid/upper-level turbulence over the entire area between FL250 and FL450.

Marine

Strong surface high pressure located off the mainland west coast has created a tight surface pressure gradient across the eastern Pacific and is directed toward the Hawaiian Islands. This will produce and maintain fresh to strong easterly trades through the week. Healthy trades will further strengthen and increase in areal coverage from Wednesday into next weekend. Strong easterly winds will produce heightened easterly swell and wind waves that will impact the islands the next several days. Rough seas will likely reach Small Craft Advisory (SCA) thresholds for those waters exposed to this combination of easterly swell and wind driven wave action.
An SCA remains in effect for the windward waters, bays and channels surrounding Maui County and the Big Island through Monday afternoon. As large wind driven seas reach SCA thresholds early this week, the advisory will likely need to be extended and expanded westward to include all of the Hawaiian coastal waters. Advisory conditions are forecast to continue into next weekend to account for strong trades and resultant high seas.
In response to strengthened trades over and upstream of the islands, east-facing shoreline surf will be on the rise the next couple of days. Recent satellite ASCAT wind observations verify a large region of strong trades upstream of the state that will generate a long fetch region. High Surf Advisory (HSA) level surf along eastern exposures is expected to develop Monday into Tuesday. These larger wind driven seas will impact eastern-facing shores through next week.
A couple of small, overlapping longer period west northwest swells will travel around the islands in the coming days. The first of these swells is arriving today and be leveling out from tonight through Tuesday afternoon. The second set of similar low west to northwest swells will be moving through during mid to late week. Surf along north and west-facing shores will remain far below HSA levels through Friday. Energy from far Southern Hemispheric gales may clip the islands and provide a subtle bump to south-facing shoreline surf today although much of this energy will pass east of the chain.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Monday for Maui County Windward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov