Weather Forecast

Hawaii County Weather Forecast for September 13, 2021

September 13, 2021, 7:15 AM HST
Listen to this Article
5 minutes
Loading Audio...
A
A
A

no slideshow

Photo Credit: James Grenz

Hilo

Today: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 77 to 84 near the shore to 63 to 70 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with showers. Lows 63 to 71 near the shore to 54 to 59 at 4000 feet. North winds up to 10 mph in the evening becoming light. Chance of rain 90 percent.

Tuesday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 78 to 84 near the shore to 63 to 70 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 70 percent.

Kona

Today: Mostly sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 83 to 88 near the shore to around 67 near 5000 feet. Light winds. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 72 near the shore to 51 to 57 near 5000 feet. Light winds. Chance of rain 50 percent.

ARTICLE CONTINUES BELOW AD

Tuesday: Mostly sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 84 to 89 near the shore to around 67 near 5000 feet. Southwest winds up to 10 mph shifting to the west in the afternoon. Chance of rain 50 percent.

Waimea

ARTICLE CONTINUES BELOW AD

Today: Partly sunny with scattered showers. Highs 64 to 84. East winds 10 to 15 mph decreasing to up to 15 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 63 to 71 near the shore to 56 to 63 near 3000 feet. East winds around 10 mph. Chance of rain 50 percent.

Tuesday: Partly sunny with scattered showers. Highs 64 to 84. East winds up to 15 mph. Chance of rain 50 percent.

Kohala

ARTICLE CONTINUES BELOW AD

Today: Partly sunny with scattered showers. Highs 64 to 84. East winds 10 to 15 mph decreasing to up to 15 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 63 to 71 near the shore to 56 to 63 near 3000 feet. East winds around 10 mph. Chance of rain 50 percent.

Tuesday: Partly sunny with scattered showers. Highs 64 to 84. East winds up to 15 mph. Chance of rain 50 percent.

South Big Island

Today: Sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs around 83 near the shore to around 65 near 5000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Lows around 73 near the shore to around 53 near 5000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Tuesday: Sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs around 84 near the shore to around 65 near 5000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Puna

Today: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 77 to 84 near the shore to 63 to 70 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with showers. Lows 63 to 71 near the shore to 54 to 59 at 4000 feet. North winds up to 10 mph in the evening becoming light. Chance of rain 90 percent.

Tuesday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 78 to 84 near the shore to 63 to 70 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 70 percent.

Waikoloa

Today: Mostly sunny. Highs 83 to 89 near the shore to 66 to 72 above 4000 feet. North winds up to 15 mph.

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 73 near the shore to 50 to 56 above 4000 feet. Southeast winds up to 10 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny. Highs 83 to 90 near the shore to 66 to 72 above 4000 feet. North winds up to 10 mph.

Detailed Forecast

Synopsis

A high pressure ridge north of the islands will keep moderate trade winds in the forecast today. An upper level low northeast of the islands will drift slowly west through the week weakening the trade winds from Tuesday through early Thursday morning. Localized sea breezes will develop on Tuesday and Wednesday along the western slopes of each island. Instability associated with the upper low will keep periods of showers in the weather forecast for all islands through Thursday. Drying trends return from Friday onward as trade winds strengthen across the region.

Discussion

Looking at the satellite loops this morning we see bands of cumulus clouds drifting into each island on the trade winds. An unstable upper low, roughly 600 miles northeast of the state, is drifting slowly westward. Numerous thunderstorms are developing within the cold core of the low as it moves closer to the state. Local radar shows scattered showers drifting through the area with periods of numerous shower activity over the windward and mountain slopes of each island.
A weak high pressure ridge north of the islands will continue to produce moderate trade winds today. This ridge will weaken a bit with light to moderate trade winds forecast from Tuesday into Thursday as the upper level low passes just north of the island chain. Lighter large scale winds will allow a sea breeze pattern to set up along the terrain sheltered western slopes of each island from Tuesday to Wednesday. Stronger trade winds will return after the low passes by the islands from Thursday afternoon through next weekend.
Expect continued periods of enhanced showers through Thursday as a weakened ridge north of the state and the approaching upper level low will increase the trade wind inversion heights into the 7,000 to 10,000 foot range. The higher rainfall amount totals will favor windward and mountain areas with some of the stronger showers pushing into typically drier leeward areas, especially in the overnight to early morning time periods.
On Wednesday, forecast guidance continues to show the upper low passing just north of the state with increasing potential for heavy showers and isolated thunderstorms over the eastern islands from Wednesday into Thursday. Much of these weather impacts will depend on the strength and track of the approaching upper low.
By Thursday, the low will pass to the west of the islands and we will begin the transition to stronger trade winds. Drying trends are forecast from Friday into the weekend as a high pressure system builds far to the north of the Hawaiian Islands. Shower coverage was lowered a bit from Friday onward as the latest forecast guidance shows more stable conditions, with lower trade wind inversion heights, and stronger atmospheric subsidence.

Aviation

High pressure northeast of the the state will allow for moderate trades to persist across the island chain this morning and into early afternoon. Scattered shower activity will be mainly confined to the windward coasts and slopes though a few showers may pass over on leeward areas. Expect brief periods of MVFR ceilings and visibility associated with this activity.
There are currently no AIRMETs in effect.

Marine

High pressure north of the state will keep moderate to fresh trade winds in place through Tuesday, with winds flirting with Small Craft Advisory (SCA) levels across the typically windy waters around Maui and the Big Island. The trades will briefly ease on Wednesday as a surface trough slides by to the north of the islands. As this trough exits to the northwest of the state Wednesday night and Thursday, the trades will gradually ramp back up to locally strong levels, with winds reaching SCA thresholds over the typically windy Maui and Big Island waters by Thursday. The strong SCA level trades are expected to expand to most if not all waters Friday and continue into the weekend.
A series of long period south and southwest swells will keep surf near the September average through Thursday, before dropping to slightly below normal levels Friday through the weekend. Small surf will prevail on north facing shores through most of the week, with a small bump possible this weekend. East shore surf will remain well below normal through Wednesday. As trade winds ramp up Thursday through the weekend, surf along east facing shores will rise back to seasonal levels and will be quite rough Friday through the weekend.

HFO Watches/Warnings/Advisories

None.

Big Island Now Weather is brought to you by Blue Hawaiian Helicopters.

Check out their Big Island Helicopter Tours today!

Data Courtesy of NOAA.gov

Comments

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

Newsletters

Get a quick summary of what’s happening on the Big Island with our daily & weekly email of news highlights.