Colder Temperatures / Thermals

[Trek2120]

Late September brings much cooler temperatures here in Cincinnati, and I'm curious if there's a point where the existence of thermals tapers off. I'm certainly not opposed to spending some chilly afternoons "in search of". I'm guessing that regardless of the temperature, thermals are simply a differential of their temperature from the air around them.

Any input anyone?

Thanks!

[Paul Naton]

Spring and fall can be just as good as summer for thermal finding. Its the temperature differential with altitude that makes for good lift. Fall brings cooler unstable air aloft which makes any thermal energy rising able to go higher. Sure, there is less sun heating units available but that is only part of the thermal creation equation. My video Secrets of Thermal Soaring explains all. Shamless plug: http://radiocarbonart.com/Pages/asecthermalmain.html

Good luck!

[John Gallagher]

Without a doubt, there are fewer winter thermals. It might be that during the fall, the ground is still warm from the summer so the lift is strong (difference in temperature from the ground and the cool air). This deep ground temp lag doesn't last thru the winter, so the air is more stable during the winter.
How dry the winter is also determines how much lift you'll find. Last winter was wet so the lift was tough to find. The year before was dry and I had two handlaunch flights around 20 minutes in February - I've had only two 20 minute hand launch flights this year since last September! - had about 15 the previous year).
We had draught conditions during 2001- 2002, and this year we've had ample rain.

Does anyone know what is the average length of the wet/dry weather cycle. Three years? five years? Seven years?

John

[rloose]

Hi John-

I have gotten some of my best thermals in Dec. But in southern NM that can still be shirt-sleve weather. I'm attaching a figure that shows wet/dry cycles in the Southwest for the last thousand years (more than you wanted to know?). The swings are about 25% above and below average. Looks like about 3 major wet/dry cycles per century. Your mileage may vary :D

Rich

[Ollie]

A large, dry, black top parking lot surrounded by snow in freezing weather can produce very strong lift, for example. It's the temperature difference between surface areas and the temperature lapse rate with altitude that are more important than the average air temperature.

The direct sun is not the only source of temperature diffierences. A town surrounded by snow covered fields can procuce rising air currents on overcast days and even at night.

[John Gallagher]

Great Rich. Could I get the same info for the NorthEast area?
The bottom of that page looks like Arizona U. Kind of doubt that they would care about the east coast.

John

[rloose]

Hi John-

Good eye. The Univ. of Ariz. in Tucson has been using tree rings to date archeological sites for years. Turns out it was a good climate (rainfall anyway) indicator also. They use pine trees like Pinon and Ponderosa, and the local Junipers. I don't know of any work like it back east.

Rich

[FLL]

Our thermals are the product of Mother Natures HVAC system for keeping the outer part of the planet cool. As long as there's something on the surface warmer than the air above it, lift (thermals) will be created regardless of season.

Frank

[viti]

if you can fly the bluffs on the coast of the great lakes ,water spouts can be found ,they are basic thermals coming off the warm water that can be very strong,we soar on the south shore of georgian bay until late november and have had un real flights,

many sailers in the great lakes will tell you stories of water spouts that can suck water up to 100 ft in the air

the idea time is the day after a cold front,, many weather services will warn you of there presents viti

[fprintf]

Cold weather seems to be fine for finding thermals. It's getting the plane up to the appropriate height that seems to be the problem for me.

The highstart rubber really doesn't work well at colder temperatures. At 40 degrees my Hobby Lobby Red barely has a spring in it, below that it just oozes out and back in!

So handlaunch, electrics (even those are limited as NiMH don't work as well in the cold), or winch launches with masonary twine instead of monofilament seems to be the rule (snow does a pretty good number on monofilament, but doesn't seem to abrade the twine as much).

Stuart

[emersunn]

SHAMELESS PLUG II

If you get thermal withdraw, head to AZ for the SW classic in Feb! Plenty of air year round, and night thermals in the summer ;) More info available soon at www.casl.net

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