Originally Posted by Manyak
condensation happens when warm air blows over cold things, not when cold air blows over hot things
Also, in sub-zero temperatures, there's no moisture in the air at all (it's all frozen solid). So even if you had something colder than the air, there would still be no condensation.
Sorry, but as a NWS qualified meteorologist, I...can't...resist...addressing...this...
Example zone roundup from 1/13/2011 9:00 am
CITY SKY/WX TMP DP RH WIND PRES REMARKS
QUINCY MOSUNNY 2 -1 88 SW7 30.56S WCI -11
GALESBURG* MOSUNNY 3 0 85 CALM 30.52S
MACOMB* MOSUNNY 9 6 89 SW3 30.56F
JACKSONVILLE* MOSUNNY 8 4 85 SW5 30.58F WCI 0
PITTSFIELD* LGT SNOW 5 1 85
The TMP column is the air temperature, the DP column is the dew point temperature, and the RH column is the relative humidity column. Dew point for simplicity sake is the temperature that ambient needs to be lowered to to achieve complete saturation, in other words, 100% RH. The higher the dew point, generally, the higher the absolute ammount of moisture is in the air.
However...when it comes to condensation on objects, the RH is the number to watch because as RH approaches 100%, the more likely, and heavier the condensation is likely to be.
How does this apply here? Notice those RH values? Pretty high at very cold temperatures, so the air is pretty close to its saturation point so it has a fair amount of moisture in it.
In most cases, you were esentially correct though. Condensation generally occurrs when relatively warm moist air passes over a cold surface, most common example is a cold beverage of choice in the summer and sweating glasses or cans. In some cases however, cold air over warm moist surfaces can cause huge amounts of condensation and even precipitation like when a very cold airmass passes over a non frozen lake, especially in early winter where the water is still relatively warm. That is basically how some places end up with feet of lake effect snow.
Now...how were you correct? Passing cold moist air over significantly warmer surfaces raises the temperature differential between ambient and cold, thus reducing the RH and making it more unlikely to get condensation
/off soapbox now