Andy S. wrote -

>As I followed the wild falcon-like gyrations of these birds with my binocs,
>they coursed, dove and wheeled against the brilliant white tops of a
>towering (the largest within my view) thunderhead high over a Lower Yakima
>Valley rangeland fire. This particular cumulonimbus, present and growing
>since early afternoon, may have formed in response to a 4,000 acre
>sagebrush and cheatgrass fire west of Mabton WA. So, once again calling on
>Jack Bowling, "Tweeters resident meteorologist": how much do fires
>contribute to the growth of thunderstorms. Am I imagining cause and effect
>here?

No you are not, Andy. It is quite common for a large wildfire to spawn
convective cumulus cells, dependent mainly on the instability and
moisture content of the overlying airmass, i.e., the more unstable and
moist the airmass above the fire, the more efficient the wildfire will
be in spawning convection. Some of these cells may become large enough
to produce lightning. Interestingly, it is well-recognized that smoke
from forest fires has a mitigating effect on the frequency of lightning
from thunderstorms. It is rare to see frequent lightning within a thick
pall of forest fire smoke. It is thought that this is due to some
electrical dissipative capacity of forest fire smoke.

- Jack
jbowling at direct.ca

writing from on the road so this may be really, really late...