Hawaii County Weather Forecast for August 31, 2023
Hilo
Today: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 85 near the shore to 70 to 75 at 4000 feet. Northeast winds up to 15 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.
Tonight: Mostly cloudy with scattered showers. Lows around 70 near the shore to around 56 at 4000 feet. North winds up to 15 mph shifting to the west after midnight. Chance of rain 50 percent.
Friday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs around 85 near the shore to 70 to 75 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.
Kona
Today: Mostly sunny in the morning then becoming mostly cloudy. Isolated showers. Highs 83 to 88 near the shore to around 70 near 5000 feet. Southwest winds up to 10 mph shifting to the west in the afternoon. Chance of rain 20 percent.
Tonight: Mostly cloudy in the evening then becoming mostly clear. Isolated showers. Lows around 73 near the shore to around 57 near 5000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.
Friday: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 83 to 88 near the shore to around 70 near 5000 feet. West winds up to 10 mph. Chance of rain 40 percent.
Waimea
Today: Windy. Mostly sunny with isolated showers. Highs around 83 near the shore to 70 to 80 near 3000 feet. East winds 10 to 30 mph with gusts to 50 mph. Chance of rain 20 percent.
Tonight: Breezy. Partly cloudy with scattered showers. Lows around 70 near the shore to 58 to 64 near 3000 feet. East winds up to 25 mph with gusts to 45 mph. Chance of rain 50 percent.
Friday: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs around 83 near the shore to 70 to 80 near 3000 feet. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 50 percent.
Kohala
Today: Windy. Mostly sunny with isolated showers. Highs around 83 near the shore to 70 to 80 near 3000 feet. East winds 10 to 30 mph with gusts to 50 mph. Chance of rain 20 percent.
Tonight: Breezy. Partly cloudy with scattered showers. Lows around 70 near the shore to 58 to 64 near 3000 feet. East winds up to 25 mph with gusts to 45 mph. Chance of rain 50 percent.
Friday: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs around 83 near the shore to 70 to 80 near 3000 feet. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 50 percent.
South Big Island
Today: Sunny in the morning then becoming partly sunny. Windy. Highs around 87 near the shore to around 74 near 5000 feet. East winds up to 30 mph increasing to 10 to 30 mph in the afternoon. Gusts up to 50 mph.
Tonight: Breezy. Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Lows around 72 near the shore to around 55 near 5000 feet. Northeast winds 10 to 25 mph. Chance of rain 20 percent.
Friday: Breezy. Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 87 near the shore to around 74 near 5000 feet. East winds up to 25 mph. Chance of rain 20 percent.
Puna
Today: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 85 near the shore to 70 to 75 at 4000 feet. Northeast winds up to 15 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.
Tonight: Mostly cloudy with scattered showers. Lows around 70 near the shore to around 56 at 4000 feet. North winds up to 15 mph shifting to the west after midnight. Chance of rain 50 percent.
Friday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs around 85 near the shore to 70 to 75 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.
Waikoloa
Today: Sunny and windy. Highs around 87 near the shore to 71 to 77 above 4000 feet. Northeast winds up to 30 mph with gusts to 50 mph.
Tonight: Partly cloudy. Breezy. Isolated showers in the evening. Lows around 74 near the shore to 53 to 60 above 4000 feet. East winds up to 25 mph with gusts to 45 mph. Chance of rain 20 percent.
Friday: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs around 87 near the shore to 71 to 77 above 4000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.
Detailed Forecast
Synopsis
Breezy to locally windy trades will persist today with mostly dry conditions. The trades will ease slightly tonight with a few more trade showers expected as some moisture works in from the east. Moderate to locally breezy trade winds are then expected Friday through Saturday, with fairly typical trade wind weather expected, with showers favoring windward slopes and coasts. Drier trade wind weather is expected to move into the state Saturday afternoon and continue through Sunday, with the trades gradually easing to moderate levels. Light and variable winds are expected early next week, with land and sea breezes common statewide. A disturbance aloft could bring an increase in showers and potentially a few downpours to the smaller islands early next week as well, while the Big Island should remain mostly dry.
Discussion
Currently at the surface, a 1030 mb high is centered around 1200 miles north-northeast of Honolulu, and is driving breezy to locally windy trades across the island chain early this morning. Meanwhile, the remnant low of former tropical cyclone Irwin is located around 1150 miles east of Hilo, and another broad area of low pressure is embedded in the ITCZ around 800 miles south of the Big Island. Infrared satellite imagery shows mostly clear to partly cloudy conditions across much of the state, with a bit more cloud cover in some windward areas as well as portions of leeward Big Island. Radar imagery shows isolated to scattered showers moving into windward areas, with a decaying shower or sprinkles reaching leeward communities from time to time. Main short term focus revolves around Wind and Fire Weather headlines.
High pressure north-northeast of the state will continue to drive breezy to locally windy trades today, with the trades easing tonight as the high shifts further north. A Wind Advisory remains in effect for much of Maui County and the Big Island through 6 PM this evening. Moderate to locally breezy conditions will then hold in place Friday and Saturday, with the trades easing to moderate levels Sunday as broad troughing develops north of the islands. The trough will hold in place north of the islands early next week, with light and variable winds expected to result in a land/sea breeze pattern statewide. The trades could begin to return around the middle of next week as the troughing north of the islands begins to break down.
As for the remaining weather details, drier and more stable conditions with precipitable water values at or below 1 inch and inversion heights of 5 to 6 kft have moved into the Big Island and Maui County, and will spread westward into Oahu and Kauai later this morning. This will result in dry trade wind weather today, with nothing more than isolated showers affecting windward areas. Moisture appears to increase a bit from east to west across the state tonight, so a return to more typical trade wind weather is expected, which should hold in place through Friday night. Drier trade wind weather is then expected to build back over the islands Saturday and Sunday, with limited showers affecting mainly windward/mauka locales.
A mid/upper level trough pivoting southward just to the north of the western islands Sunday night through Tuesday, may bring a better shot for rainfall to both windward and leeward sections of the smaller islands, particularly Kauai and Oahu. The added instability along with sea breezes could result in a few downpours each afternoon as well. Meanwhile drier conditions should prevail over the Big Island as the deeper moisture doesn't appear to make it this far south. The deeper moisture and forcing from the upper low appears to lift north of the island chain Wednesday, with rather dry conditions expected to return. However, some deeper moisture with a connection to the tropics may pivot far enough northward to increase rain chances over the Big Island around the middle of next week.
Aviation
A robust area of surface high pressure positioned north of the state will help generate breezy to locally windy tradewinds today, especially late this morning into the afternoon. Drier air is expected to filter in from the east and allow for isolated showers along windward locations. Mostly sunny with dry conditions elsewhere across the islands.
AIRMET Tango remains in effect for low level turbulence over and downwind of the terrain across all islands.
Marine
Surface high pressure northeast of the state drifts slowly west resulting in fresh to strong easterly trades for all Hawaiian waters through tonight. Winds are expected to ease slightly Friday through Saturday as the ridge begins to weaken and a broad trough approaches from the east. Guidance continues to advertise light to gentle east-southeast winds Sunday night through early next week as the trough moves closer to the area. Small Craft Advisory conditions include all waters through tonight. Seas will respond and become rough, with some of the windier channels and waters exceeding the 10 ft advisory level.
Rough choppy surf along east facing shores will continue through the week as the trades remain strong. Additionally, expect some groundswell mixed in with 9-10 second periods for the upcoming weekend from former Tropical Cyclone (TC) Irwin tracking westward across the eastern Pacific. Surf heights should stay below the 10 ft (faces) High Surf Advisory (HSA) criteria through the peak of this event today through Saturday. A downward trend is expected Sunday into early next week as the trades weaken.
Surf along south facing shores will remain small through the weekend as overlapping background level long-period southerly pulses move through. For the extended, guidance is advertising a south swell arriving next week (Monday night through midweek) originating from an area of gales east of New Zealand. Expect a late season event with heights potentially nearing the HSA level during the peak late Tuesday through Wednesday.
Surf along exposed north and west facing shores will trend up again this weekend as a small west-northwest (300-310 degree) swell arrives. This will be in response to a storm-force low (former TC Damrey) racing eastward toward the Date Line from Japan over the past couple of days.
Fire weather
The combination of dry fuels, strong and gusty winds and low humidity levels will result in very high fire danger and the risk for extreme fire behavior today. The lowest humidity levels and strongest winds are expected from mid morning through late this afternoon. During this time, any fires that start will likely spread rapidly and be very difficult to control. Outdoor burning should be avoided until these critical conditions end.
It is important to note that the winds for this event WILL NOT be comparable in strength to the August 8, 2023 event, where wind gusts of well over 60 mph were observed. The latest forecast for Thursday is for trade winds of 20 to 30 mph with gusts of 40 to 50 mph, with the strongest wind gusts expected downwind / leeward of the higher terrain on the islands of Maui County and the Big Island.
HFO Watches/Warnings/Advisories
Red Flag Warning until 6 PM HST this evening for Kauai Windward, Kauai Leeward, Oahu South Shore, Waianae Coast, Oahu North Shore, Olomana, Central Oahu, Waianae Mountains, Molokai Leeward, Lanai Makai, Lanai Mauka, Maui Leeward West, Maui Central Valley, Leeward Haleakala, Kona, South Big Island, Kohala, Big Island Interior.
Wind Advisory until 6 PM HST this evening for Lanai Mauka, Kahoolawe, Maui Windward West, Maui Leeward West, Kohala, Molokai, Lanai Windward, Lanai Leeward, Maui Central Valley North, Maui Central Valley South, Windward Haleakala, South Haleakala, Big Island South, Big Island Southeast, Big Island North.
Small Craft Advisory until 6 AM HST Friday for all Hawaiian waters,
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Data Courtesy of NOAA.gov