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thermals - 6/16/2002 9:35:33 PM   
scooby-RCU


 

Posts: 390
Joined: 6/11/2002
From: yessir, TX, USA
Status: offline 		can anybody tell me like alot of places to look for a thermal, and how long does it last? i live out in the country, and i have a pond will that cause a thermal on a sunny day?
       Post #: 1

Thermals - 6/17/2002 12:41:47 AM   
Ollie


 

Posts: 958
Joined: 12/8/2001
From: Punta Gorda, FL
Status: offline 		Thermals originate from surface features that heat the air near the ground. These features are hotter than their surroundings. during the day the sun heats dark dry surfaces like black top parking lots, plowed fields, flat roofs, etc. Surfaces that absorb the suns rays without being heated as much are water and green vegitation. Thermals come in all sizes and durations. When the wind is calm the air has longer to heat over the warm spot and the thermals are stronger and last longer. As the wind picks up the air has less time over the hot surface and thermals are weaker and don't last as long. Obstructions to the wind like buildings and tree lines allow the air over a hot surface to heat longer. Often the obstruction triggers a thermal of hot air that has blown across a hot spot. If you are careful to observe the air temperature over a period of time, you can feel the rise in temperature that signals the beginning of a thermal. Since the rising air of a thermal must be replaced, surface air blows into the thermal. The wind shift often points to a thermal. Circling birds such as hawks, turkey vultures, etc. are reliable markers of thermals. Dust and debris rising from the ground are indicators of strong thermals. The air cools with altitude during the day. This is called the temperature lapse rate. As the air cools around a thermal the warm air in the thermal is bouyed up more strongly by the cooler surrounding air. The greater the lapse rate on a given day, the stronger the thermals will grow. Cool clear nights followed by sunny days give rise to stronger thermals. These weather conditions usually acompany high pressure systems.

_____________________________

Regards, Ollie

(in reply to scooby-RCU)
       Post #: 2

Finding Termics - 6/23/2002 11:33:39 PM   
Landi


 

Posts: 176
Joined: 6/23/2002
From: Winter Haven, FL, USA
Status: offline 		Hi scooby

All what Ollie says is correct but to find a thermo some times is not that easy.

You have to watch to the hints mother nature gives to you for example birds (Busards, Hawks and other expert gliders) flying in circles there for sure is a thermo, also smal birds when they fly to a spezific place and circle fast this is sign for a thermo not because they are hunting a thermo to gain altitude but to hunt the insects floating in that thermo. Also you can watch the cummulus clouds the best hint is when they are forming this is a strong indication of raising air. By a big cloud watch it carefully and you will see the cloud a sot of boiling on one side there is your thermo. Closer to the ground watch for obstacles which can release a thermo from the ground, a tree, a house, a tree line from a beginnig forest, changes from collor of the terrain all this can and will work as a thermo releser.
A lack / pond is not a good place for thermiks do to the fact that it takes a long time for the water to heat up and form a thermo but the edge of a lake can be a thermo releaser. In reality it is easy to find a thermo if you are patient and start watching the hints mother nature gives to you.

regards

Landi

(in reply to scooby-RCU)
       Post #: 3

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