Oktas – Measuring Cloud Cover

posted in: Michigan Weather Forecast | 18

In meteorology, an okta is a unit of measurement used to describe the amount of cloud cover at any given location such as a weather station. Sky conditions are estimated in terms of how many eighths of the sky are covered in cloud, ranging from 0 oktas (completely clear sky) through to 8 oktas (completely overcast). In addition, in the SYNOP code there is an extra cloud cover indicator ‘9’ indicating that the sky is totally obscured (i.e. hidden from view), usually due to dense fog or heavy snow.

When used in weather charts, okta measurements are shown by means of graphic symbols (rather than numerals) contained within weather circles, to which are attached further symbols indicating other measured data such as wind speed and wind direction.

Although relatively straightforward to measure (visually, for instance, by using a mirror, oktas only estimate cloud cover in terms of the area of the sky covered by clouds. They do not account for cloud type or thickness, and this limits their use for estimating cloud albedo or surface solar radiation receipt.

Cloud oktas can also be measured using satellite imagery from geostationary satellites equipped with high-resolution image sensors such as Himawari-8. Similar to traditional approaches, satellite images do not account for cloud composition.

Oktas are often referenced in aviation weather forecasts and low level forecasts: SKC = sky clear; FEW = 1 to 2 oktas; SCT (Scattered) = 3 to 4 oktas; BKN (Broken) = 5 to 7 oktas; OVC (Overcast) = 8 oktas; NSC = nil significant cloud; CAVOK = ceiling and visibility okay.


For Grand Rapids, when the month of April was more than 3 degrees below normal (as of yesterday GRR was 10.8 below normal) in 60% of those year (1892 to 2017), most of the months for the rest of the year (May through December) averaged below normal. Only in 20% of those years had most of the months, for the rest of the year (May through December) warmer than normal.  I have seen predictions for this summer go both ways – I am thinking near normal.

Meanwhile high pressure will provide mostly sunny and mild weather, with the possibility of our first 70 degree reading of the season on Monday. Low pressure tracking south of Michigan on Tuesday will bring clouds and a chance of light rain, followed by slightly cooler weather for midweek.

 

 

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Sandy (Hudsonville)Jack EdwardsINDYMark (East Lansing)Andy W Recent comment authors
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Jack Edwards
Jack Edwards

I’m OUTTA My Head On Monday MOANIN …
Spin()()() Tommy James and The Shondells – Mony Mony – YouTube
▶ 2:48
https://www.youtube.com/watch?v=X_OoEx9WOl8

Sandy (Hudsonville)
Sandy (Hudsonville)

It was beautiful out today. We fired up the grill & cooked some burgers. They were great along with some ice tea. Monday will even be warmer. 🙂

Jack Edwards
Jack Edwards

Perfect …..Weather.

INDY
INDY

Love u guys INDYDOG14

Jack Edwards
Jack Edwards

Nothing But….Sunshine & OH MY BLUE SKY..!!!
The Allman Brothers Band – Blue Sky (Eat A Peach … – YouTube
https://www.youtube.com/watch?v=wwyXQn9g40I

Andy W
Andy W

Great song Jack, I was just listening to Midnight Rider before you posted this!

INDY
INDY

What happened to the high 60’s this week I just watched wood 8 only showing a high of 58 now on Tuesday? That blows INDYDOG14!!

Andy W
Andy W

What a gorgeous day!! Just firing up the grill on my back deck, nice WARM SUNSHINE and SPRITES from North Peak in TC, shot out to INDY!!!

INDY
INDY

Going Sprites strong all day Andy yeaaa! INDYDOG14!

Jack Edwards
Jack Edwards

Going #WeedStrong hear @ Thee YOCS …yeaaaa

Andy W
Andy W

Glad everyone is finally getting some weather to enjoy!

Slim

I would like to thank MichelV for the information over the last week. Very interest
Slim

Mark (East Lansing)
Mark (East Lansing)

Agreed. Never heard of oktas.

ROCKY (Rockford)
ROCKY (Rockford)

Enjoy your couple days of mid 60’s because the temps will be dropping like a rock after that! Highs in the low 50’s later this week into next weekend! Get ready!!

Andy W
Andy W

Enjoy your couple of days in the 50’s this week, because it will be in the 60’s the rest of the time!

https://weather.com/weather/tenday/l/USMI0344:1:US