nav canada weather

by Greg
(Canada)

How do I read an upper wind report from Nav Canada weather web site?

Barry's Response - Greg: That's a good one. As far as I understand these are machine generated tables which the meteorologists do not need to use on a daily basis. However I never finished the operational training.

We can see the tables are sorted by station and assigned the station id lat and long. The next two lines in the left column indicate the the forecast originates in the Canadian Meteorological Center, the computer headquarters based in Montreal.

Then it gives the date and zulu time of the last information incorporated into the model input. The column headed "for use" indicates the zulu hours for which the wind forecast is intended. The row across the top gives the various elevations (when in doubt, assume ASL).

Now comes the shakey part. Judging that the group of four digits is always begun with a pair ranging from 01 to 36, (with the exception of 99 when the next pair is 00), It looks to me like a direction (2-digit) then speed (presumably knots like all other speeds on the site). Then comes the minus (and occasional plus) sign followed by another pair of digits, but not in the column for the lowest elevation.

Could this value indicate shear in some form? perhaps a standard deviation or even gusting values. I would not expect anything except shear at the higher latitudes, but it would be best to ask an air traffic controller, flight service specialist or experienced pilot for a more complete interpretation.

Bottom line:

Ya got me!

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