Why is the downdraft from a thunderstorm cool?

Question

If it is high altitude air, meaning lower pressure, how does it manage to descend in the first place? And as it descends, should it not warm up?

Answer 1

Generally speaking, t-storm downdrafts occur where moisture is falling (and evaporating) in the form of precipitation. The evaporating moisture particles cool the air. The resultant cooling makes the air heavier, so it may descend quite rapidly, as in a microburst. If all the moisture evaporates before the downdraft reaches the ground (as with virga), the downdraft will be cool/cold and dry.

It's just the opposite process as what occurs in the updraft. If the air feeding the updraft has a lot of moisture (high dewpoint), a lot of latent heat is released as the water vapor condenses, and that's much of the explanation for how you get high instability. You've surely heard how warm, moist Gulf of Mexico air contributes to Tornado Alley being what it is.... that's why.

Yes, it does indeed warm as it descends and contracts, but it's relative. At 10,000 feet it may be 40 degrees F, whereas the ambient air is 55 degrees, and may warm to 65 degrees upon reaching the surface, where an ambient temperature of 77 degrees may exist.

Answer 2

The downdraft originates from a cumulonimbus cloud.The life cycle of the cumulonimbus cloud is divided into three stages.They are (1)developing stage(2) mature stage and (3)dissipating stage.In the developing stage,the core of the cloud is warmer than the sorroundings and the rising air becomes a strong updraft throughout the cloud and this updraft increases with elevation.Hydrometeors (snow,rain,and ice etc) are formed but are prevented from coming down due to strong updrafts.
The mature stage is taken to begin when rain first begins to fall from the base of the cloud.The frictional drag exerted by hydrometeors within the cloud retards the updraft and the downdraft starts.Melting of snow and ice below the freezing level will cool the air.The downdraft of strong cold air along with the hydrometeors increases.As more and more hydrometeors melt, the temperature of the cloud consquently becomes colder than the sorroundings.This downdraft thus becomes cooler as it descends because it is inside the cloud and is insulated from the warm sorroundings by the cloud.When the downdraft ends, the temperature becomes equalised with the sorroundings.When the updraft completely ceases and the downdraft spreads horizontally occpying a major portion of the cloud, the dissipating stage starts.
The low pressure at higher altitudes has nothing to do with the formation and dissipation of this thunder cloud.

Answer 3

Why can't people give resorces to there answers

any how
http://www.srh.noaa.gov/srh/jetstream/mesoscale/wind.htm
the reason that a downdraft is cooler is because in the down draft comes from the higher altitudes where it is cooler. but there are also warm downdrafts in the case of an inversion
(Inversion: Generally, a departure from the usual increase or decrease in an atmospheric property with altitude. Specifically it almost always refers to a temperature inversion, i.e., an increase in temperature with height, or to the layer within which such an increase occurs. This occurs when warm air sits over cold air, possibly trapping moisture and pollutants in the surface air layer. An inversion is present in the lower part of a cap.)

Answer 4

Because the Cooler air up in the Thunderstorm is much
heaver. Cold air sinks. Warm air is lighter. In the upper
parts of the atmosphere is much colder than it is a ground level. As the colder air descends it puts pressure down on the ground. That's why the pressure starts to rise.

Answer 5

The pressure has little to do with it. Cold air sinks and there is cold air in a thunderstorm, hail forms there, right? Early in a T storms development most of the air is rising but in the decaying stage there is huge rush of descending air. Yes, it warms but not at the same rate that it cooled while ascending.

Answer 6

hot air rises and cool air sinks...would that be the culprit. the fact that it's sitting in a low pressure zone shouldn't matter should it?