Hawaii County climate forecast is September 12, 2021

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Photo credit: James Grenz

Hilo

Today: Mostly cloudy. Numerous showers in the morning, then isolated showers in the afternoon. Heights from 77 to 83 near shore to 63 to 70 at 4000 feet. Northeast winds up to 15 miles per hour. Chance of rain 70 percent.

Tonight: cloudy. Numerous showers in the evening, then showers after midnight. Lows of 63 to 71 near shore to 54 to 59 at 4000 feet. Northwest winds up to 10 km / h. Chance of rain 90 percent.

Monday: Mostly cloudy. Numerous showers in the morning, then isolated showers in the afternoon. Highs from 77 to 84 near shore to 63 to 70 at 4000 feet. Northeast winds around 10 mph. Chance of rain 70 percent.

Kona

Today: Mostly sunny in the morning, cloudy with a few showers in the afternoon. Highs from 81 to 86 near shore to about 67 near 5000 feet. West winds up to 10 km / h. 50 percent chance of rain.

Tonight: Mostly cloudy with a few showers in the evening, then partly cloudy with a few showers after midnight. Lows of 69 to 75 near shore to 51 to 57 near 5000 feet. Breeze. 50 percent chance of rain.

THE ARTICLE CONTINUES BELOW THE ADVERT

Monday: Mostly sunny in the morning, then mostly cloudy with a few showers in the afternoon. Heights from 83 to 88 near shore to about 67 near 5000 feet. Breeze. 50 percent chance of rain.

Waimea

THE ARTICLE CONTINUES BELOW THE ADVERT

Today: airy. Partly sunny with a few showers. Highs from 63 to 83. East winds from 10 to 25 miles per hour. 50 percent chance of rain.

Tonight: Mostly cloudy with a few showers. Lows of 62 to 70 near shore to 56 to 63 near 3000 feet. East winds 10 to 15 miles per hour. 50 percent chance of rain.

Monday: Partly sunny with a few showers. Highs 64 to 84. East winds 10 to 15 miles per hour. 50 percent chance of rain.

Kohala

THE ARTICLE CONTINUES BELOW THE ADVERT

Today: airy. Partly sunny with a few showers. Highs from 63 to 83. East winds from 10 to 25 miles per hour. 50 percent chance of rain.

Tonight: Mostly cloudy with a few showers. Lows of 62 to 70 near shore to 56 to 63 near 3000 feet. East winds 10 to 15 miles per hour. 50 percent chance of rain.

Monday: Partly sunny with a few showers. Highs 64 to 84. East winds 10 to 15 miles per hour. 50 percent chance of rain.

Southern big island

Today: airy. Sunny in the morning, cloudy in the afternoon with a few showers. Altitudes around 83 near shore to 66 near 5000 feet. East wind up to 20 km / h. Chance of rain 20 percent.

Tonight: airy. In the evening mostly cloudy with a few showers, then mostly clear after midnight. Lows of 73 near shore to about 53 near 5000 feet. Northeast winds up to 20 miles per hour. Chance of rain 20 percent.

Monday: Sunny in the morning, mostly cloudy with a few showers in the afternoon. Altitudes around 83 near shore to about 65 near 5000 feet. East winds 10 to 15 miles per hour. Chance of rain 20 percent.

feedback

Today: Mostly cloudy. Numerous showers in the morning, then isolated showers in the afternoon. Heights from 77 to 83 near shore to 63 to 70 at 4000 feet. Northeast winds up to 15 miles per hour. Chance of rain 70 percent.

Tonight: cloudy. Numerous showers in the evening, then showers after midnight. Lows of 63 to 71 near shore to 54 to 59 at 4000 feet. Northwest winds up to 10 km / h. Chance of rain 90 percent.

Monday: Mostly cloudy. Numerous showers in the morning, then isolated showers in the afternoon. Highs from 77 to 84 near shore to 63 to 70 at 4000 feet. Northeast winds around 10 mph. Chance of rain 70 percent.

Waikoloa

Today: Sunny in the morning, then partly sunny. Airy. Heights from 83 to 88 near shore to 65 to 72 over 4000 feet. Northeast winds up to 20 miles per hour.

Tonight: Partly cloudy. Lows of 74 near shore to 51 to 56 over 4000 feet. Southeasterly winds up to 15 miles per hour.

Monday: Mostly sunny. Heights from 83 to 89 near shore to 66 to 72 over 4000 feet. Northeasterly winds up to 10 miles per hour in the morning will be bright.

summary

An upper level deep northeast of the islands will drift west into the region and generate increased showers through Friday. The moderate trade winds will last until the end of the week and the showers will concentrate over windward and mountain locations with less shower cover over the lee areas. That upper low will pass north of the island chain on Wednesday, increasing the likelihood of heavy showers and thunderstorm activity over the western half of the state Wednesday through Thursday. Drier conditions will return with increasing trade winds from late Friday through Saturday.

discussion

A band of unstable low cloud is slowly drifting through the Hawaiian Islands this morning, with cloud peaks ranging from 8,000 to 12,000 feet. This band of clouds will keep numerous showers in the forecast over windward and mountain slopes, with some showers moving over leeward areas in the morning hours. The upper low is approximately 850 miles northeast of the islands, as seen on satellite water vapor imagery. This low is slowly drifting west, bringing periods of heavy showers to all islands as it approaches the state.
The high pressure ridge far north of the islands will be strong enough to generate moderate trade winds throughout the region throughout the week. A slight increase in the trade winds in the moderate to locally airy range is forecast for today. Lighter trade winds are forecast from Tuesday to Thursday, as the upper low passes just north of the island chain and weakens the surface pressure gradient. Lighter, large-scale winds will enable a sea breeze to form on the protected western slopes of each island from Wednesday to Thursday. Stronger trade winds will return after the low passes on the islands from late Thursday until next weekend.
In terms of weather, the low and weakened ridge in the far north of the state will allow higher than normal trade wind inversion heights. The trade wind inversion height will be between 7,000 and 10,000 feet for most areas by the middle of next week, producing higher cloud tops. Expect prolonged periods of increased rain activity with higher amounts of rainfall concentrated in windward and mountainous areas. Some of the heavier showers push into normally drier leeward areas, especially during the night and early morning.
On Wednesday, forecasts show the upper low is north of the state, with increasing potential for heavy showers and isolated thunderstorms over the eastern islands from Wednesday through Thursday. It is too early to discuss the island-to-island weather impact as it will depend on the trace and intensity of this upper low relative to the islands. Our confidence in these rainy weather details will improve as the forecast period gets shorter. Stay tuned.

aviation

High pressure in the north of the state will keep moderate to locally breezy trade winds in place until tonight. Clouds and showers will favor windward and mauka areas, with some showers reaching leeward communities from time to time. MVFR cigs / Vsbys are common in showers along the windward slopes and coasts until mid-morning. Otherwise the VFR conditions apply.
AIRMET Sierra remains in effect for mountain darkening on windward portions of Kauai, Oahu, Molokai, Maui, and the Big Island. Conditions should improve this morning.

marine

The high pressure north of the state will maintain a sufficiently tight pressure gradient across the islands to generate moderate to fresh trade winds for the next few days. The windier areas around Maui County and south of the Big Island will experience periods of stronger winds. As a result, a Small Craft Advisory for the Pailolo Channel, Maalaea Bay, Alenuihaha Channel, and the southeastern waters of the Big Island has been released by this afternoon. The passage of a weak eastern low on Tuesday will dampen trades slightly towards midweek. As this trough moves west of the state, the northeast winds will increase again to more moderate to locally fresh strength by Friday and continue until the next weekend.
The youngest small, relatively longer south swells, which have caused almost seasonal surf on the south coast in recent days, will recede by Monday. A small, long-lasting Tasman Sea southwest swell is expected to fill in from late Monday through Tuesday with a slow decline in the second half of the week. Surfing the west coast of Kauai and Oahu should benefit from some of this southern wrap and keep waist-high sets in play through Thursday. A small, medium-term northwest-north swell could prune the islands next weekend. Choppy easterly swell will hold a small east coast surf through Tuesday with a slight dip in midweek among slightly weaker trades.

HFO watches / warnings / notices

Small Craft Advisory until 6:00 p.m. HST tonight for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Southeast Waters.

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Data courtesy of NOAA.gov

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