Weather Forecast

Maui Weather Forecast for May 20, 2021

May 20, 2021, 7:15 AM HST
Listen to this Article
5 minutes
Loading Audio... Article will play after ad...
Playing in :00
A
A
A

no slideshow

Photo Credit: Tyler Rooke

West Side

Today: Sunny, with a high near 88. Breezy, with an east northeast wind 10 to 15 mph becoming light and variable in the afternoon. Winds could gust as high as 21 mph.

Tonight: Mostly clear, with a low around 70. Breezy, with a light and variable wind becoming east northeast 12 to 17 mph in the evening. Winds could gust as high as 24 mph.

Friday: Sunny, with a high near 84. Breezy, with an east northeast wind 11 to 16 mph becoming light north northeast. Winds could gust as high as 22 mph.

South Side

Today: Sunny, with a high near 83. Southwest wind around 6 mph becoming calm in the afternoon.

Tonight: Mostly clear, with a low around 66. East southeast wind around 5 mph becoming northeast after midnight.

ARTICLE CONTINUES BELOW AD

Friday: Isolated showers after noon. Sunny, with a high near 85. Light and variable wind becoming east 5 to 8 mph in the morning. Chance of precipitation is 20%.

North Shore

ARTICLE CONTINUES BELOW AD

Today: Isolated showers before noon. Mostly sunny, with a high near 82. Breezy, with an east northeast wind 17 to 22 mph, with gusts as high as 31 mph. Chance of precipitation is 20%.

Tonight: Isolated showers. Partly cloudy, with a low around 67. Breezy, with an east wind 15 to 17 mph, with gusts as high as 24 mph. Chance of precipitation is 20%.

Friday: Isolated showers before noon. Mostly sunny, with a high near 81. Breezy, with an east northeast wind 15 to 21 mph, with gusts as high as 29 mph. Chance of precipitation is 20%.

Central Maui

ARTICLE CONTINUES BELOW AD

Today: Sunny, with a high near 84. Breezy, with a northeast wind 15 to 18 mph, with gusts as high as 25 mph.

Tonight: Mostly clear, with a low around 68. Breezy, with a northeast wind 13 to 16 mph, with gusts as high as 22 mph.

Friday: Sunny, with a high near 82. Breezy, with a northeast wind 13 to 18 mph, with gusts as high as 25 mph.

Upcountry

Today: Sunny, with a high near 72. West wind 5 to 11 mph.

Tonight: Mostly clear, with a low around 53. Calm wind becoming south southwest around 5 mph.

Friday: Scattered showers after noon. Mostly sunny, with a high near 70. West wind 5 to 9 mph becoming east in the afternoon. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

East Maui

Today: Scattered showers, mainly before 1pm. Mostly sunny, with a high near 78. East wind 8 to 11 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers, mainly after 7pm. Mostly cloudy, with a low around 70. East wind around 9 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Friday: Scattered showers, mainly before 1pm. Partly sunny, with a high near 78. East wind 8 to 11 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Lanai City

Today: Isolated showers after noon. Mostly sunny, with a high near 76. Breezy, with a northeast wind 9 to 15 mph, with gusts as high as 21 mph. Chance of precipitation is 20%.

Tonight: Mostly clear, with a low around 63. Northeast wind 6 to 13 mph.

Friday: Isolated showers after noon. Mostly sunny, with a high near 76. Northeast wind 10 to 13 mph. Chance of precipitation is 20%.

Kaunakakai

Today: Sunny, with a high near 83. Breezy, with an east wind 11 to 15 mph, with gusts as high as 21 mph.

Tonight: Mostly clear, with a low around 70. East wind 9 to 13 mph.

Friday: Sunny, with a high near 86. Breezy, with an east wind 10 to 15 mph increasing to 16 to 21 mph in the afternoon. Winds could gust as high as 29 mph.

Detailed Forecast

Synopsis

A surface high far northeast of the islands is maintaining locally breezy trade winds. Low clouds and passing trade showers will continue to favor windward and mauka sections through Friday. An upper-level trough moving toward the islands is expected to bring lighter winds, higher humidity, and a slight increase in showers this weekend. Expect the trade winds to strengthen again early next week.

Discussion

A nearly stationary 1030 mb surface high centered near 37N 136W, or about 1670 miles northeast of Hilo, is producing a tight pressure gradient across the Aloha State early this morning. This is maintaining locally breezy easterly trade winds in the vicinity of the island chain. Aloft, a mid-tropospheric ridge is keeping stable atmospheric conditions over the region. Loops of satellite imagery and radar reflectivity data show scattered to broken low clouds with embedded scattered showers moving in from the east toward the windward sides of the islands. The greatest coverage of low clouds and showers is currently over eastern Maui and the Big Island.
The forecast guidance shows the surface high will persist through Friday night, which will likely keep locally breezy easterly trade winds in place into early Saturday. The mid-tropospheric ridge will also maintain stable atmospheric conditions across the area, which will keep rainfall totals relatively light during the next couple of days. The low-level trade wind flow will continue to transport low clouds and brief trade showers into the windward sections of the islands. The trade showers will be most active during the nighttime and early morning hours, and may spread leeward over some of the smaller islands. The higher terrain on the Big Island and Maui will block the trade winds, and allow sea breezes to produce clouds and showers over leeward sections of those two islands each afternoon.
The global forecast models appear to be in good agreement that an upper-level trough will dig down toward the islands from the northwest this weekend. This feature will make the atmosphere slightly less stable, and may potentially allow a weak surface trough to develop in the vicinity of the islands. At the same time, a weak surface front is expected to move to a position northwest of the region. These features would likely cause the background flow to weaken across the state from late Saturday into Monday. The forecast models are showing some differences in the amount of deep moisture that may spread up from the southeast toward the eastern islands. For now, the weekend forecast shows an increase in humidity values over most of the state, with showers becoming a bit more active, especially over portions of the Big Island and windward Maui from late Saturday into Monday.
The trough aloft is forecast to move northeast away from the islands starting Monday. Therefore, the trade winds will likely strengthen again early next week. Also, expect more stable and drier atmospheric conditions to become established over the state from Monday night and Tuesday through mid-week.

Aviation

Periods of MVFR VIS/CIG in SHRA are expected over windward slopes and coasts into Friday as breezy trades deliver patches of showery low clouds. Coverage is currently sufficiently widespread to warrant AIRMET SIERRA for mountain obscuration over windward Maui and Big Island. Coverage should diminish later this morning, which should allow the AIRMET to be cancelled. AIRMET Tango will remain in effect below 8000 feet due to low-level turbulence over and S through W of all mountains.

Marine

The pressure gradient back across the islands from high pressure far northeast of the state will maintain these moderate to locally strong trade winds into the weekend. A Small Craft Advisory (SCA) is in effect for the typical windier waters around Maui County and the Big Island through Friday afternoon. The SCA may need to be extended into Saturday as advisory conditions persist over these windy marine zones into the weekend. A front northwest of chain is forecast to be north of the islands by early next week. This boundary will slacken the pressure gradient northeast of the state and subtly weaken trades. Trades are expected to restrengthen again early next week.
The current small northwest swell passing around the islands will fade through today. Another small north northwest swell is scheduled to arrive Sunday and peak surf into Monday morning along north and west facing shores with a gradual fall late Monday into Tuesday. A small northwest swell will fill in through mid week that may peak surf to near head high along many Kauai and Oahu north shores. Small, long period southerly swells will keep surf from completely going flat along southern coasts. The largest southern pulse is timed to arrive next Tuesday with a gradual decline into Thursday. Several days of sustained moderate to fresh trade winds over and upstream of the islands will maintain small period, wind wave choppy surf along most eastern exposures. A slight weakening of trades early next week may result a subtle lowering of recently elevated eastern shore surf.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Friday for Maalaea Bay, the Pailolo and Alenuihaha Channels and the waters south of the Big Island.

Data Courtesy of NOAA.gov

E-Mail Newsletters Receive daily or weekly updates via e-mail. Subscribe Now
News Alerts Breaking news alerts on your mobile device. Get the App

Comments

This comments section is a public community forum for the purpose of free expression. Although Maui Now encourages respectful communication only, some content may be considered offensive. Please view at your own discretion. View Comments