nav canada weather

by Greg
(Canada)

Nav Canada Organization

Nav Canada Organization

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!

Search this site for more information now.

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THANKS
by: Barry

All, thanks for you input. I intend to revisit this in the future. The article referred to is at http://www.stuffintheair.com/weatherstations.html

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just started its training
by: barty

I am undergoing its training right now. I have just started and I really do not know how to help you right now. So I will get back to you after some time. Just remember me.

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Upper wind decode
by: Anonymous

3000 ASL foot winds do not contain temperature forecast, all temperatures above 30000 ASL are negative

Coded format:
site ddss ddssttt ddssttt etc...

where site is the where the forecast is for

where dd is direction the wind is from in degrees true divided by 10 where 01 actually means 010, 35 means 350 (think runways: runway 24 is aligned along 240)

where ss is speed in knots

where ttt is temperature in celcius, the first character is + or -

exceptions: if wind speed is greater than 99 knots add 50 to dd and subtract 100 from sss (e.g. 9000 foot winds over Ottawa are forecast to be 290 at 119 knots temperature -22 is coded as 7919-22)

does that help?

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has good knowledge
by: Anonymous

was very informative and interesting

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...
by: Anonymous

those are things that meteorologists understand better. it's all science and mathematics. I'm sure that after a few weeks on learning, everyone can understand it. Nice article. 5 stars

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nav candada weather comment
by: Anonymous

At first this seemed like a promising post. There was some relatively technical information which seemed to make sense, and then you dropped the ball! You ALMOST got this thing figured out! Do a little more searching and see if you can come up with a difinitive response for this guy. Also, this is a case where a picture or diagram would be really valuable. See if you can find one of those to put on here as well.

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Nav Canada Weather
by: doglover

thought it was interesting as a first impression. it would be cool to find how the air quality and meteorology works with the plus and minus. the zulu and knots. it would be cool to learn alot more about all of it plus you can never gain too much knowledge.

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