Photo Credit: Pamela Goguen Lynch

West Side

Today: Breezy. Mostly sunny with isolated showers. Highs 81 to 88. East winds up to 15 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows around 70. East winds 10 to 20 mph. Chance of rain 20 percent.

Monday: Breezy. Mostly sunny with isolated showers. Highs 81 to 88. East winds 10 to 20 mph. Chance of rain 20 percent.

South Side

Today: Sunny. Highs 85 to 90. East winds 10 to 15 mph.

Tonight: Partly cloudy. Lows around 69. Northeast winds 10 to 15 mph.

Monday: Mostly sunny. Highs 85 to 90. Northeast winds 10 to 15 mph.

North Shore

Today: Mostly sunny. Breezy. Isolated showers in the morning, then scattered showers in the afternoon. Highs 80 to 86 near the shore to around 67 near 5000 feet. East winds 10 to 20 mph. Chance of rain 30 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 65 to 72 near the shore to around 54 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Monday: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 80 to 86 near the shore to 63 to 68 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Central Maui

Today: Mostly sunny. Breezy. Highs around 88. East winds 10 to 25 mph.

Tonight: Breezy. Partly cloudy with isolated showers. Lows 67 to 73. East winds 10 to 20 mph. Chance of rain 20 percent.

Monday: Mostly sunny. Breezy. Isolated showers in the morning. Highs around 88. East winds 10 to 20 mph. Chance of rain 20 percent.

Upcountry

Today: Mostly sunny. Breezy. Scattered showers in the afternoon. Highs around 64 at the visitor center to around 61 at the summit. East winds 10 to 20 mph. Chance of rain 30 percent.

Tonight: Breezy. Partly cloudy with scattered showers. Lows around 49 at the visitor center to around 46 at the summit. East winds 10 to 20 mph. Chance of rain 50 percent.

Monday: Breezy. Mostly sunny with scattered showers. Highs around 62 at the visitor center to around 59 at the summit. East winds 10 to 25 mph. Chance of rain 50 percent.

East Maui

Today: Mostly sunny. Breezy. Isolated showers in the morning, then scattered showers in the afternoon. Highs 80 to 86 near the shore to around 67 near 5000 feet. East winds 10 to 20 mph. Chance of rain 30 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 65 to 72 near the shore to around 54 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Monday: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 80 to 86 near the shore to 63 to 68 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Lanai City

Today: Mostly sunny. Isolated showers in the afternoon. Highs 72 to 81. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Lows around 66. Northeast winds 10 to 15 mph.

Monday: Mostly sunny. Isolated showers in the afternoon. Highs 72 to 81. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Kaunakakai

Today: Mostly sunny. Breezy. Highs 78 to 88. East winds 10 to 20 mph.

Tonight: Partly cloudy. Breezy. Isolated showers after midnight. Lows 61 to 72. East winds 10 to 20 mph. Chance of rain 20 percent.

Monday: Breezy. Mostly sunny with isolated showers. Highs 78 to 88. East winds 10 to 20 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

High pressure north of the islands will keep moderate to breezy trade winds in place through the middle of the week, with only minor fluctuations in strength from day to day. Rather dry are expected today, with light showers favoring windward and mauka areas. An upper level feature overhead, combined with occasional increases in low-level moisture will bring wetter trade wind weather to the state through the week.

Discussion

Have made some tweaks to the forecast this morning, but no significant changes to the overall forecast philosophy.
A surface high remains far northeast of the islands early this morning, with a ridge to the north. Expect this to maintain a locally breezy trade wind pattern for much of the week. The overnight soundings at Hilo and Lihue continue to show a dry and stable airmass overhead. While the Hilo trade wind inversion remains strong around 7,000 feet, the Lihue trade wind inversion is beginning to weaken. This was expected with an upper level low developing along an upper level trough to the northwest of Kauai.
The GFS and ECMWF both show the low sinking southward over the islands over the next couple of days, but vary in its intensity and exact location. The low will help to erode the trade wind inversion, and that will help to produce more showers across the state. As we head into Monday night, some remnant moisture from an old frontal boundary will approach the islands on the trade wind flow, and when combined with the upper level feature will fuel an increase trade wind showers in both coverage and intensity.
The trades may ease a bit late next week as the high to the northeast weakens slightly, though they will still maintain moderate speeds. Additional surges of increased low-level moisture coinciding with the low aloft lingering nearby have the potential to bring periods of wetter trade wind weather throughout the remainder of next week.

Aviation

Locally strong trade winds will continue, producing moderate low- level turbulence near and downwind of the terrain, requiring AIRMET Tango. VFR conditions will prevail as the the trade winds deliver randomly distributed low clouds and showers that will primarily focus over windward slopes. Brief periods of ISOL MVFR VIS/CIG will be most likely over windward areas during the night and morning, and leeward sections of the Big Island during the afternoon and evening.

Marine

A high pressure system northeast of the Hawaii region will produce moderate to locally strong easterly trades over and upstream of the island chain. A Small Craft Advisory (SCA) remains in effect for the windier waters and channels from Molokai to the Big Island. This SCA will likely be extended through at least Wednesday or Thursday.
An out of season northwest (320-330 degree) swell will gradually decline today. In the extended forecast, Typhoon Guchol will become extratropical in the northwest Pacific during the middle of next week and may send another northwest (300-310 degree) swell into the Hawaii Region by next week Friday or Saturday.
Surf along south facing shores will remain small each day as a mix of long period background south and southwest (170-220 degree) swells move through the region.
Surf along east facing shores will increase slightly through Tuesday with fresh trades winds with decreasing trends from Wednesday onward.

HFO Watches/Warnings/Advisories

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

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Data Courtesy of NOAA.gov