Upper wind Readings

[skydude2000 3]

Hey gang,


I've gotten a few quick briefings on this before, but I seem to have trouble remembering. How do you read the upper wind measurements, mainly the speed? I understand the direction, but how do you interpret the changes in speed at different altitudes? I believe on the slip we check, it's measured at 3, 5 and 9000 feet. If anyone could also post a print-out of the slip so I could get a visual idea of the numbers I'm looking at, that would be great.

Thanks.

PULL!! or DIE!!

[AggieDave 6]

http://aviationweather.gov/products/nws/winds/

Winds aloft forecasts available at that link.

The following is a simplified beginner version of learning how to spot. It will not work for all wind conditions or give you the perfect spot every time, but it'll get you close much of the time.

For the spot the simple beginner version is to take the directions and average them then take the speed and average them.

That will give you a rough idea what direction jump run should be run. As for the speed and how far out you have to go for the spot, thats not black magic either. Freefall time vs. the speed of the wind to put you where you want to be when you open. So if the wind was 60mph and the time in freefall was 60seconds (one minute) then you would need to get out one mile away from where you wanted to open your canopy at. Thats the easy to figure example, but the concept is the same with different freefall times and wind speeds.

Play with that concept every day you're at the DZ and see how your spot works out with what the DZ is flying for a spot that day. With some practice it will start to make sense and you'll be able to glance at the forecast and determine where you should be.

You can also use vector math, but I'm an Aggie and lucky to be able to do basic addition.

--"When I die, may I be surrounded by scattered chrome and burning gasoline."

[skydude2000 3]

Thanks Dave,

That's virtually the exact thing I was talking about, although that link was for US and I'm in Canada. I understand the first 3 digits of those readings, are for direction, ie. a 270 reading would be out of the west-southwest, and so on. But what does it mean when it says '+05' or whatever number, at 6000'? And what are the different letter acronyms on the left of the screen? Airport codes?

I understand the concept of spotting, where to get out, where you want to be when you open, factor in how much FF drift, etc. I guess I just didn't understand some of the numbers on that slip.

PULL!! or DIE!!

[tombuch 0]

Check out the attached article I produced for The Ranch several years ago when I was S&TA. The web address listed is still the same, but the "help" option is now listed on the right side, near the top of the screen.

Not having looked at the numbers you reference, believe the +05 is the temperature, and I think you are correct that the letter combinations on the left are the airports. See if the attachment and the page link help.

Tom Buchanan
Instructor Emeritus
Comm Pilot MSEL,G
Author: JUMP! Skydiving Made Fun and Easy

[pchapman 279]

Here's another answer:

The acronyms are airport codes in the link given.

If in Canada you might look for Upper Winds at http://www.flightplanning.navcanada.ca.

A readout of

2517-05

means winds at 250 degrees true (not magnetic), 17 knots, -5 C temperature.

If it says 9900, that means light and variable winds (no precise measurement).

Times are in UTC.

Altitudes are above sea level.

There are a few subtleties that usually don't apply to us: At very high altitudes they don't show the + or - sign as it is assumed to always be negative. There are special rules for over 99 knots.

Full rules at
http://www.flightplanning.navcanada.ca/cgi-bin/CreePage.pl?Page=weather-products&NoSession=NS_Inconnu&TypeDoc=user-guide&Langue=anglais#fdt

[AggieDave 6]

One more thing to add to what the others have added.

9900 means the winds are light and variable at that altitude. If you have that only average the other winds, since the 0 added with the division would throw off everything.

--"When I die, may I be surrounded by scattered chrome and burning gasoline."