Skydiving temp question

[vegasskydiver 0]

I am going skydiving on Sunday . I haven't gone since last summer. Temp is supposed to 72. How much colder is it at altitude? Thanks!

[JohnRich 4]

Subtract 3.5 degrees per thousand feet of altitude.

[Spills 0]

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Temp is supposed to 72.

Must be nice! 46 here on sunday (with a 182) and I'm sure I don't have it bad.

Have fun.

[vegasskydiver 0]

Ooohhhh...that makes it somewhere in the 20's....burrr...I better undle up. No wonder it felt so good when it was 120 on the ground at altitude.

[vegasskydiver 0]

Thanks...I plan on having a lot of fun....I'm having withdrawls!!!
Blue skies!

[PiLFy 0]

Here:

http://www.ncdc.noaa.gov/oa/climate/conversion/windchill.html

http://en.wikipedia.org/wiki/Lapse_rate

I live well north of you. It's usually approximately 50 colder @altitude around here. Summer days vary more (Lapse Rate) between a 35-45 degree difference. Then, just add the windchill ... 72 is balmy. Wear an extra layer or two, & you'll be fine. Be careful not to wear too much ( = show an instructor).

I used to freeze very easily when I was a student. I now like winter jumping. It's different, & a lot of fun. I think I've jumped down to around -100° F. As far as I'm concerned. Seventy two degrees is still summer.

Have Fun.

[JohnRich 4]

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Ooohhhh...that makes it somewhere in the 20's....burrr...I better undle up. No wonder it felt so good when it was 120 on the ground at altitude.

If the plane has a jump door on it that closes while you're climbing to altitude, you'll be comfortable inside. And once the door opens, your mind will be so focused on other things that you won't notice the cold. So if you bundle up, you'll likely just be too hot 95% of the time, in order to be comfortable 5% of the time. I think the trade-off makes it easier to just be cold for a little while, in order to be comfortable all the rest of the time.

[5.samadhi 0]

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Subtract 3.5 degrees per thousand feet of altitude.

unless there's an inversion :)

[SlackBeef 0]

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Subtract 3.5 degrees per thousand feet of altitude.

unless there's an inversion :)

You got to love those inversions!

GO BIG OR GO HOME!

[SansSuit 1]

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I used to freeze very easily when I was a student. I now like winter jumping. It's different, & a lot of fun. I think I've jumped down to around -100° F.

Exqueeze me? Minus 100 degrees Fahrenheit ???

Peace,
-Dawson.
http://www.SansSuit.com
The Society for the Advancement of Naked Skydiving

[vegasskydiver 0]

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Subtract 3.5 degrees per thousand feet of altitude.

unless there's an inversion :)

What is that?

[PiLFy 0]

Sorry, Jeff. Ain't gonna squeeze ya, brother...

http://www.ncdc.noaa.gov/oa/climate/conversion/windchill.html

I've jumped when it was about 20° F on the ground. That's about -30° F @altitude. Then, factor in the windchill from the chart. Or, you can scroll down further, & use the calculator. Depending on how you figure it (chart & calculator differ. Plus, the calculator only goes to 109 MPH.). It's between -86° & -100° F. In other words, PFC.

[SansSuit 1]

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I've jumped when it was about 20° F on the ground. That's about -30° F @altitude. Then, factor in the windchill from the chart. Or, you can scroll down further, & use the calculator. Depending on how you figure it (chart & calculator differ. Plus, the calculator only goes to 109 MPH.). It's between -86° & -100° F. In other words, PFC.

My bad. I totally missed the reference to the wind chill chart. I thought maybe you were jumping at the North Pole or something.

Now, what is the coldest you've ever jumped nekked?

Peace,
-Dawson.
http://www.SansSuit.com
The Society for the Advancement of Naked Skydiving

[PiLFy 0]

"I thought maybe you were jumping at the North Pole or something."

I'm not that sick.

"Now, what is the coldest you've ever jumped nekked?"

Probably around 0° F. I once had to jump out of my sleeping bag in the middle of the night to pee. It was a winter camping trip in the Boy Scouts. It taught me never to drink too much before bed. As I recall. I jumped back into the bag pretty quick, too.

[JohnRich 4]

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I once had to jump out of my sleeping bag in the middle of the night to pee. It was a winter camping trip in the Boy Scouts. It taught me never to drink too much before bed. As I recall. I jumped back into the bag pretty quick, too.

Take an empty wide-mouth bottle, with a lid, into the tent with you, to minimize the trauma.

[vegasskydiver 0]

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"I thought maybe you were jumping at the North Pole or something."

I'm not that sick.

"Now, what is the coldest you've ever jumped nekked?"

Probably around 0° F. I once had to jump out of my sleeping bag in the middle of the night to pee. It was a winter camping trip in the Boy Scouts. It taught me never to drink too much before bed. As I recall. I jumped back into the bag pretty quick, too.

Thanks for that, I really needed a laugh this morning!!!!

[PiLFy 0]

Phew... You guys are letting me off easy. I thought you'd ask what I was doing in a Boy Scout sleeping bag, naked (?!). I was actually wearing long johns, etc. It sure felt naked, though.

Yep, live N learn.

[PiLFy 0]

[theplummeter 14]

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Subtract 3.5 degrees per thousand feet of altitude.

unless there's an inversion :)

What is that?

An inversion is when the temp climbs with altitude rather than dropping. It's usually caused by the passage of a cold front. The cool dense air of the cold front slides under the warm air mass and displaces (lifts) it. With any moisture present in either air mass, but especially in the warmer air, most severe summer weather is caused by this lifting action.

When NWS or other agencies prepare thunderstorm forecasts they use the adiabatic temp lapse rate to determine the stability of the air and predict storms. The more the rate differs from the standard, the more likely it is to be turbulent and produce thunderstorms when adequate moisture is present.

Almost forgot, the wind speed and direction as well as temperatures aloft can be found in 3000ft-6000ft increments here:

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

Click on your area, find the airport identifier and read the columns across. The first two digits are wind direction (27 means 270, from the west), the next two or three digits are wind velocity in nautical miles per hour, and the last digits are temp in Celsius.

[base283 0]

Forget factoring in windchill factor. That is for exposed skin. Unless you are jumping nekkid.
It is a useless factor unless you are the media and get paid to oversensationalize irrelevant data.
Google the term and you will have an understanding of what it really means.
Take care,
space

[PiLFy 0]

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Forget factoring in windchill factor. That is for exposed skin. Unless you are jumping nekkid.
It is a useless factor unless you are the media and get paid to oversensationalize irrelevant data.
Google the term and you will have an understanding of what it really means.
Take care,
space

I jump w/an open-face helmet. Vee don't need no shtinkin Balaclava. Plus, temps that low, & a 120MPH wind, go through a lot of clothing. You think windchills that cold are a joke? Pop out wearing your summer suit & a balaclava. Hey, your skin won't be exposed. When you land in tears from the pain in your hands, shaking uncontrollably. Don't over-sensationalize it. It'll be irrelevant.

[base283 0]

I do think windchills that cold are a joke unless one is naked.

Wind goes thru your clothing? Mine doesnt let that happen.

Why would I jump summer clothes in the winter?

So do you actually think your skin will freeze if the ambient temp is above freezing but the windchill is below whether the skin is exposed or not?
It doesnt work that way. Dress for the lowest ambient temp and keep exposed skin to a minimum and you'll be ok.

[PiLFy 0]

20° on the ground = ~-30° @alt. Windchill adds to the fun. Most rational people would agree that -30° is pretty freakin cold. -100° on your face & neck is colder. Wear enough clothes, & it won't make it through. It wants to, though.

Cold is cold. You wanna argue yellow is green? Go for it...

[billvon 2,400]

>Wind goes thru your clothing? Mine doesnt let that happen.

It will indeed get through your clothing. You're just not going to be as warm in freefall when it's cold out as when you are sitting still at the same temperature - no matter how high tech your clothing is. You may well be warm _enough_ but you're not going to be as warm.

[pchapman 261]

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Forget factoring in windchill factor. That is for exposed skin. Unless you are jumping nekkid.
It is a useless factor unless you are the media and get paid to oversensationalize irrelevant data.

I'll jump into this "glass half full or half empty" argument.

Wind chill does have an effect. I've had frost nip (a mild frostbite) on my nose after winter freefall jumps from full altitude, when I've never had that sort of damage from other outdoor winter activity.

Of course it is for exposed skin -- that's what we are worrying about! You might as well say that there in no vacuum in space because you'll be in a spacesuit -- but you're in a spacesuit in the first place because there's a vacuum in space.

Yes, windchill can be over hyped or over interpreted.

And the older North American scales, until redesigned by Canadian scientists in about 2001, were poorer, missed some important effects, and predicted colder equivalent temperatures in cold windy conditions than we now calculate.

And yes it isn't about the final temperature something will reach. A below freezing wind chill won't cause a bottle of water to freeze if the actual temperature is above freezing. But it will extract heat from exposed skin at about the rate one would get at that low temperature (given certain reasonable assumptions), without the wind.

The current tables do show that once there is a lot of wind, adding more wind doesn't change the apparent temperature much.

I will agree that getting to -100 is a bit tough, even using "just" Fahrenheit. With the current US / Canadian scale, to get -100F equivalent you need to be at belly fly speeds (say, 120mph) at about -40F (=-40 C). Bumping the speed up to 175 mph only moderately affects things, requiring a -34 F day to give -100 equivalent. Pilfy did admit that his initial calculation was a little on the high side, since he was working off only a simple source for calculation.

We'd probably agree that for skydiving it is probably better usually to just quote the actual temperatures at altitude and on the ground, to give an impression of what kind of day it was skydiving.