Hilo

Today: Mostly cloudy. Occasional showers in the morning, then numerous showers in the afternoon. Highs around 83 near the shore to 68 to 73 at 4000 feet. North winds up to 15 mph shifting to the east in the afternoon. Chance of rain 80 percent.

Tonight: Mostly cloudy with numerous showers. Lows around 69 near the shore to around 55 at 4000 feet. East winds up to 10 mph. Chance of rain 70 percent.

Monday: Mostly cloudy. Numerous showers in the morning, then occasional showers and isolated thunderstorms in the afternoon. Highs around 83 near the shore to 68 to 73 at 4000 feet. East winds up to 10 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 80 percent.

Kona

Today: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 81 to 86 near the shore to around 68 near 5000 feet. West winds up to 10 mph. Chance of rain 40 percent.

Tonight: Partly cloudy. Lows 70 to 75 near the shore to around 56 near 5000 feet. Light winds.

Monday: Mostly sunny. Isolated showers and thunderstorms in the afternoon. Highs 81 to 86 near the shore to around 68 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Today: Mostly cloudy. Breezy. Occasional showers in the morning, then numerous showers in the afternoon. Highs around 81 near the shore to 68 to 78 near 3000 feet. East winds 10 to 20 mph. Gusts up to 40 mph in the morning. Chance of rain 80 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Breezy. Isolated showers. Lows around 69 near the shore to 57 to 63 near 3000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Monday: Breezy. Mostly sunny with isolated showers in the morning, then mostly cloudy with scattered showers and isolated thunderstorms in the afternoon. Highs around 81 near the shore to 68 to 78 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Kohala

Today: Mostly cloudy. Breezy. Occasional showers in the morning, then numerous showers in the afternoon. Highs around 81 near the shore to 68 to 78 near 3000 feet. East winds 10 to 20 mph. Gusts up to 40 mph in the morning. Chance of rain 80 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Breezy. Isolated showers. Lows around 69 near the shore to 57 to 63 near 3000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Monday: Breezy. Mostly sunny with isolated showers in the morning, then mostly cloudy with scattered showers and isolated thunderstorms in the afternoon. Highs around 81 near the shore to 68 to 78 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

South Big Island

Today: Mostly sunny. Breezy. Scattered showers in the afternoon. Highs around 85 near the shore to around 72 near 5000 feet. East winds up to 25 mph. Chance of rain 40 percent.

Tonight: Mostly clear. Breezy. Lows around 71 near the shore to around 54 near 5000 feet. East winds 10 to 20 mph.

Monday: Mostly sunny. Breezy. Scattered showers and isolated thunderstorms in the afternoon. Highs around 85 near the shore to around 72 near 5000 feet. East winds 10 to 20 mph. Chance of rain 30 percent.

Puna

Today: Mostly cloudy. Occasional showers in the morning, then numerous showers in the afternoon. Highs around 83 near the shore to 68 to 73 at 4000 feet. North winds up to 15 mph shifting to the east in the afternoon. Chance of rain 80 percent.

Tonight: Mostly cloudy with numerous showers. Lows around 69 near the shore to around 55 at 4000 feet. East winds up to 10 mph. Chance of rain 70 percent.

Monday: Mostly cloudy. Numerous showers in the morning, then occasional showers and isolated thunderstorms in the afternoon. Highs around 83 near the shore to 68 to 73 at 4000 feet. East winds up to 10 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 80 percent.

Waikoloa

Today: Mostly sunny. Breezy. Scattered showers in the afternoon. Highs around 85 near the shore to 69 to 75 above 4000 feet. North winds up to 20 mph. Chance of rain 50 percent.

Tonight: Mostly clear. Lows around 73 near the shore to 52 to 59 above 4000 feet. East winds up to 10 mph.

Monday: Mostly sunny. Scattered showers and isolated thunderstorms in the afternoon. Highs around 85 near the shore to 69 to 75 above 4000 feet. East winds up to 10 mph shifting to the north around 10 mph in the afternoon. Gusts up to 30 mph. Chance of rain 30 percent.

Detailed Forecast

Synopsis

Breezy trades will continue into the middle of the week, before weakening and giving way to land and sea breezes during the second half of the week. An upper level trough over the islands through Tuesday may bring some heavier showers at times, especially over interior Big Island where there will be also be a chance for afternoon thunderstorms.

Discussion

No major changes to the forecast this morning, however the winds for the Big Island summits over the next couple days was nudged upwards. Used a blend of the ECMWF and the GFS to account for the upper level trough moving over the islands which will bring some stronger, but still below advisory level, winds into mid week.
The overall forecast philosophy remains the same. A breezy trade wind pattern to remain in place through Tuesday. A mid to upper level trough has moved closer to the islands from the east overnight. The overnight soundings from Lihue and Hilo haven’t shown many changes, but expect colder temperatures at the 500 mb to move in tonight.
High pressure remains far to the northeast of the islands, with a ridge north of 30N, which will maintain the breezy trade wind pattern into the middle of the week. Satellite derived precipitable water shows a drier airmass has moved over the smaller islands, and that is reflected in the Lihue sounding overnight which reported 1.12 inches. More moisture is found near the Big Island where the sounding had 1.28 inches. Several gages on the eastern side of the Big Island have reported more than an inch of rain since last evening. Anticipate additional showers over the east side of the Big Island, and to a lesser extent over Maui. The remaining islands will have some clouds overhead, but the chance for showers will be significantly lower.
A mid to upper level trough moving over the islands from the east will lead to an increasing unstable airmass over the islands through Tuesday. The trough is expected to sharpen and pivot over the islands during this time, before lifting north and then east away from the region. The global models are in good agreement that this trough will bring colder temperatures to 500 mb. The ECMWF keeps temperatures around -10/-11C, while the GFS brings in even colder temperatures of -12/-13C. These temperatures are significantly colder than normal for June. At 700 mb there isn’t much different in the temperatures between these models with temperature getting to around 4/6C which is colder than normal but not as climatologically colder. Additional the coldest temperatures at 700 mb look to be focused near Kauai, while the colder 500 mb temperatures reach most of the islands. Thunderstorms were added with the afternoon package to the Big Island forecast for Monday and Tuesday afternoon, with the best chance being Tuesday afternoon. Leeward island plumes over the nearshore waters will also be candidates for nocturnal thunderstorm activity during this time, however confidence is lower so that is not currently reflected in the forecast.
The second half of the week will see the a new mid-level ridge setting up far northwest of the islands, as a front north of the islands weakens to a trough. This will cause our winds to weaken and turn to the southeast. This could lead to some land and sea breezes over the islands. With a decrease in precipitable water and a more stable airmass overhead, expect a decrease in shower activity, with clouds and showers more likely during the afternoon and evening hours over interior and southeast facing portions of the islands.

Aviation

Breezy to strong trades will continue, as a surface high moves closer to the state from the northeast. Low cigs and SHRA will favor windward and mauka areas with periods of MVFR conds possible in any SHRA. VFR conds should prevail elsewhere.
AIRMET Sierra is in effect for mtn obsc for windward Big Island and N thru SE sections of the smaller islands.
AIRMET Tango remains in effect for moderate low- level turb S thru W of terrain, as well as for moderate turb between FL300-FL400.
AMD NOT SKED for PMDY as equipment remains unavailable with no time table for return to service.

Marine

A 1028 mb surface high centered about 900 nm NE of the islands will remain nearly stationary through the remainder today. A Small Craft Advisory (SCA) has been scaled back to only include zones in the typically windy areas around Maui county and the Big Island. The high is expected to weaken slightly on Monday, but will still help to support fresh to locally strong ENE trade winds through Tuesday. On Wednesday, a frontal system approaching from the northwest will allow the high to weaken significantly, and lead to light and variable winds through the end of the week.
An extended period of elevated surf along S facing shores is now underway, with numerous swell pulses expected, mainly from the SSW. A High Surf Advisory (HSA) is likely to be needed for the largest of the swells, which may not arrive until next weekend. Nearshore buoys S of the islands continue to indicate increased energy in the longer 15-17 second period bands this morning, equating to elevated surf, but below HSA levels. This swell likely peak today into Monday, then gradually ease Tuesday before additional long-period swells arrive.
A strong, slow-moving low in the distant NW Pacific generated what will be a small NW swell when it arrives in the islands Monday and Tuesday (3 to 4 foot medium period swell from 320 direction), with the potential for a small follow- up NW swell later in the week. Trade winds will continue to generate short- period wind waves that will support choppy surf along exposed E facing shores the next couple of days.

HFO Watches/Warnings/Advisories

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

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Data Courtesy of NOAA.gov