Min. temp for a thunderstorm to form?

[Jason Harris]

Just wondering if there's any absolute parameter for the minimum temperature needed to produce a convective storm that can generate lightning.

I suppose there must be hesitation to given an absolute since mets tend to do the same thing for tornado development:
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http://www.newton.dep.anl.gov/askasci/wea00/wea00313.htm

 

[R R Smith]

Jason,
Someone in our group with a solid meteorological background should be able to answer your question. Coincidentally, we had a brief thunderstorm (with snow and thunder) today in Shasta Valley (extreme northern California). The surface temperature at the time of the storm was 38 degrees. With very cold air aloft (-30 at 500 mb) and a short wave pushing through - it probably provided just enough instability to fire off this brief storm.

 

[Robert Edmonds]

My understanding (which may be wrong) is that you need an ice with some sort of thin liquid layer surrounding it. This thin liquid layer helps in the transfer of charge. So I guess if the temperatures are cold enough that that this liquid layer freezes out too quickly this charge transfer would not occur. What's the coldest temp this would occur, I don't know??? My initial guess was to take a look at Saturn which has lightning, and is much colder (being so far away). However, lightning on Saturn is believed (from a very brief scan of some abstracts) to occur at the 10-20 bar range. Which is deep enough down in the atmosphere that the temps would be comparable to the temps we're used to dealing with here on earth.

 

[rdale]

I suppose you could trial-and-error a lot of math to come up with a number, but I doubt anyone will It's not uncommon to see thunderstorms with temps a few degrees below freezing, but I've never seen any occur with temps < 25F or so.

 

[Chip Redmond]

I suppose you could trial-and-error a lot of math to come up with a number, but I doubt anyone will It's not uncommon to see thunderstorms with temps a few degrees below freezing, but I've never seen any occur with temps < 25F or so.

The main charging zone is typically located in the center of the storm with the lower realm near -10C and the upper near -20C. This is the location for supercooled droplets that usually carry a negative charge are present. Without liquid present below -20C ice particles cannot get large enough to hold a negative charge and are positively charged. So I would gander and say when the cloud is all ice, below -20C, it would be nearly impossible to get lightning to develop.


Chip

 

[Dan Robinson]

With elevated convection over a shallow arctic layer (heavy freezing rain/sleet configuration), you could theoretically have lightning happening over any surface temperature - of course the storms themselves would be feeding off of much warmer air aloft. Thundersnow can occur when the column is entirely below freezing. However, most thundersnow events involve some source of warm air/baroclinicity nearby (warm lake surfaces, warm sector entrainment by a bombing low, etc), even if the region with lightning may not have any above-freezing layer at that exact location.

The charging mechanism for lightning is still not understood with certainty, though strong upward vertical motion seems to be an environmental requirement. Freezing, condensation and/or collisions probably play a role, to what degree we don't know yet. Volcanic ash clouds produce lightning seemingly without freezing or condensation. To get the vertical motion usually requires some instability, which is easier to get with warmer (above freezing) low levels. The colder the air mass, the less moisture is available and the less likely there is to be instability to support upward vertical movement.

 

[Jason Harris]

Thanks to everyone for the detailed and thoughtful responses!