Hilo

Tonight: Haze in the evening. Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 59 to 67 near the shore to around 54 at 4000 feet. Light winds. Chance of rain 50 percent.

Tuesday: Mostly sunny with isolated showers. Haze in the afternoon. Highs around 79 near the shore to 63 to 68 at 4000 feet. Light winds. Chance of rain 20 percent.

Tuesday Night: Partly cloudy. Scattered showers in the evening. Haze through the night. Lows 59 to 68 near the shore to around 54 at 4000 feet. Light winds. Chance of rain 40 percent.

Kona

Tonight: Partly cloudy. Isolated showers in the evening. Haze through the night. Lows around 69 near the shore to around 51 near 5000 feet. Light winds. Chance of rain 20 percent.

Tuesday: Mostly sunny. Haze through the day. Isolated showers in the afternoon. Highs around 83 near the shore to around 65 near 5000 feet. Light winds. Chance of rain 20 percent.

Tuesday Night: Partly cloudy. Haze. Lows 67 to 72 near the shore to around 52 near 5000 feet. Light winds.

Waimea

Tonight: Partly cloudy. Isolated showers in the evening. Haze in the evening. Lows 59 to 69 near the shore to 51 to 58 near 3000 feet. Light winds. Chance of rain 20 percent.

Tuesday: Mostly sunny. Haze through the day. Isolated showers in the afternoon. Highs around 77 near the shore to 67 to 75 near 3000 feet. East winds up to 10 mph shifting to the northeast in the afternoon. Chance of rain 20 percent.

Tuesday Night: Mostly cloudy with scattered showers in the evening, then partly cloudy after midnight. Haze through the night. Lows 59 to 69 near the shore to 52 to 59 near 3000 feet. Light winds. Chance of rain 40 percent.

Kohala

Tonight: Partly cloudy. Isolated showers in the evening. Haze in the evening. Lows 59 to 69 near the shore to 51 to 58 near 3000 feet. Light winds. Chance of rain 20 percent.

Tuesday: Mostly sunny. Haze through the day. Isolated showers in the afternoon. Highs around 77 near the shore to 67 to 75 near 3000 feet. East winds up to 10 mph shifting to the northeast in the afternoon. Chance of rain 20 percent.

Tuesday Night: Mostly cloudy with scattered showers in the evening, then partly cloudy after midnight. Haze through the night. Lows 59 to 69 near the shore to 52 to 59 near 3000 feet. Light winds. Chance of rain 40 percent.

South Big Island

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy after midnight. Haze through the night. Lows around 71 near the shore to around 53 near 5000 feet. Northeast winds around 10 mph. Chance of rain 40 percent.

Tuesday: Mostly sunny. Haze through the day. Isolated showers in the afternoon. Highs around 84 near the shore to around 64 near 5000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Tuesday Night: Partly cloudy. Isolated showers in the evening. Haze through the night. Lows around 72 near the shore to around 53 near 5000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

Puna

Tonight: Haze in the evening. Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 59 to 67 near the shore to around 54 at 4000 feet. Light winds. Chance of rain 50 percent.

Tuesday: Mostly sunny with isolated showers. Haze in the afternoon. Highs around 79 near the shore to 63 to 68 at 4000 feet. Light winds. Chance of rain 20 percent.

Tuesday Night: Partly cloudy. Scattered showers in the evening. Haze through the night. Lows 59 to 68 near the shore to around 54 at 4000 feet. Light winds. Chance of rain 40 percent.

Waikoloa

Tonight: Partly cloudy. Haze through the night. Lows 67 to 72 near the shore to around 53 above 4000 feet. Light winds becoming southeast around 10 mph after midnight.

Tuesday: Mostly sunny. Haze through the day. Isolated showers in the afternoon. Highs around 83 near the shore to 63 to 69 above 4000 feet. Light winds. Chance of rain 20 percent.

Tuesday Night: Partly cloudy. Haze. Lows around 70 near the shore to around 53 above 4000 feet. Light winds.

Detailed Forecast

Synopsis

Stable and dry conditions with light southeasterly background winds will continue for the first half of the week. This will result in daytime sea breezes and nighttime land breezes each day. A weakening front approaching from the northwest could increase shower chances for the western islands Wednesday through Thursday, though there remains some uncertainty. Trade winds will build back into the region and strengthen from Thursday onward, bringing back periods of passing showers to windward and mountain areas that will favor the typical overnight to early morning hours.

Discussion

This afternoon, multiple low pressure circulation centers can be seen on regional satellite imagery in the North Pacific, near and north of 40N far north of the main Hawaiian Islands. A long surface frontal boundary stretches from the southernmost of these low pressure circulations southwestward to the International Date line to near 160E. High clouds ahead of the front, which is currently located about 350nm northwest of Kauai, have begun streaming over the western end of the state today. Meanwhile, a high pressure ridge remains in place over the island chain, which has resulted in yet another day of stable conditions and light southeasterly background winds prevailing over the state. Given the light background flow, daytime sea breezes have increased interior clouds over the islands today, but these interior clouds will clear tonight as land breeze circulations resume. Rainfall has been scarce within this dry, stable regime.
This stable pattern with light southeasterly background winds will continue for most areas through at least late Tuesday into early Wednesday. Throughout this time, daytime sea breezes will increase interior clouds over the islands each day, followed by land breezes clearing skies over the islands each night. Shower chances will remain limited, and any showers that do occur would be light.
Global models continue to show that the aforementioned cold front to our northwest will gradually weaken as it approaches over the next couple of days. It is then expected to move near Kauai and stall on Wednesday. As this occurs, shower activity will likely increase over Niihau and Kauai for 12 to 24 hours, until the front breaks apart and drifts back westward away from the islands. Differences between the various global models remain, with the ECMWF notably showing wetter trends for the islands in Kauai County. The GFS, however, continues to favor a drier solution where the weakening boundary stalls and then moves back westward away from the state before reaching the Garden Isle.
A high pressure system will build in north of the state for the second half of the week, increasing easterly trade winds across the region. Expect some southeasterly winds to linger on Thursday morning, with winds becoming more easterly and stronger from Thursday night into next weekend. As the ridge over the islands lifts northward, our typical trade wind shower activity returns with brief passing showers forecast along windward and mountain areas, favoring the overnight to early morning hours each day.

Aviation

A light southeasterly wind regime will continue through Tuesday, allowing daytime sea breezes and overnight land breezes to occur. VFR conditions are expected under a relatively dry and stable air mass through Tuesday. A thin veil of high clouds will move over the state from west to east starting this evening.
No AIRMETs are in effect and none are expected.

Marine

A weak surface ridge will remain over the area through Tuesday and maintain light to moderate southeast background flow. This pattern will allow for daytime sea breezes and nighttime land breezes along waters adjacent to the coasts. A cold front is projected to approach Kauai from the northwest on Wednesday and is expected to stall and quickly weaken to a trough by late Wednesday. The trough is then expected to retrograde back westward towards the end of the week as a ridge of high pressure builds north of the state. Moderate to locally strong easterly trade winds is expected to return Friday into Saturday.
The current, large, long-period northwest (310-320 degree) swell will steadily decline through tonight. A High Surf Advisory is now in effect through tonight for exposed north and west facing shores of most islands. A series of northwest to north-northwest (310-330 degree) swells are expected during the second half of the week, with each pulse becoming slightly bigger and veering towards the north- northwest direction. The first pulse will be filling in on Wednesday and will be more of a medium period swell out of the northwest. Surf heights may approach advisory thresholds, but at this time we are expecting surf heights to stay just below advisory thresholds on Wednesday. A slightly larger and longer period pulse is expected on Thursday out of the northwest followed by a slightly larger north-northwest on Friday. Surf heights should exceed advisory thresholds around Thursday with surf heights likely holding above advisory thresholds through Saturday.
East shore surf will remain small through Thursday due to weak winds, then become choppier as trade winds increase Friday through the weekend. Expect minimal background energy for south facing shores through much of the week.

Fire weather

Critical fire weather conditions are not expected this week. Although stable and dry conditions will persist through mid-week, winds will be light and variable, preventing critical fire weather concerns. Locally breezy trades will return during the second half of the week, but increased relative humidity is expected.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Tuesday for north and west facing shores of Niihau, Kauai, Oahu, and Molokai, for north facing shores of Maui, and for west facing shores of the Big Island.

Data Courtesy of NOAA.gov