The description of a cloud layer applies only to that single cloud layer. The description of an overcast applies only to the single cloud layer that is described as an overcast and has nothing to do with any cloud layers that are below it or above it. An "overcast" itself would cover from 90 percent of the sky to 100 percent of the sky. Any cloud layers below the "overcast" would further obscure vision.
Following is from Section 2 of Aviation Weather Services Advisory Circular AC 00-45G, Change 1, published jointly by the National Weather Service and the FAA (emphasis added to make it clear enough for you):
"When more than one layer is reported, layers are in ascending order of height. For each layer above a lower layer or layers, the sky cover designator for that layer will be the total sky cover which includes that layer and all lower layers. In other words, the summation concept of cloud layers is used.
"Transparent" sky cover is clouds or obscuring phenomena aloft through which blue sky or higher sky cover is visible. As explained in Table 2-1, a scattered, broken, or overcast layer may be reported as "thin." To be classified as thin, a layer must be half or more transparent. Remember that sky cover of a layer includes all sky cover reported below that layer."
This is from a pretty current document, but the same was true in 1971. (But, what would the weather service or FAA know about it?)
Hominid,
Reference is also made to your previous posts, and replies to them, on weather reporting.
Section 2, Aviation Weather Services Advisory Circular, AC 00-45G, Change 1, published July 29, 2010, is a three page section titled: Aviation Product Classification and Policy, and does NOT contain what you have quoted above.
The METAR format for weather reporting was NOT adopted in North America, which includes the United States of America, until June 1, 1996. Consequently, it has nothing to do with the weather reports from November 1971 or the Cooper hijacking period.
You joined the DZ Cooper thread on September 27, 2011 and on that same day I downloaded and printed out a programmed text (Teletype Sequence Reports AM-33), January 1970, from the US Army Primary Helicopter School, Fort Wolters, Texas. You and I exchanged a number of PMs in January and February, 2012 on DZ discussing this very report, which you should also have a copy of, and it says NOTHING about "cumulative" cloud cover.
And if my memory is correct, neither you nor I found any other documentation on weather reporting that was in effect on November 24, 1971.
So, how about citing chapter and verse for your claims about "cumulative" cloud reporting being valid on the date of the hijacking.
Robert99
