re: Doesn't quite make sense . . .
I always thought the issue was a matter of potential differences between cloud masses, between air masses, between cloud masses and air masses (above and below the cloud masses), between cloud masses and the Earth, and between air masses and the Earth. There should be no "large electric fields" to find, merely potential energy differences between these masses. Flying through clouds and taking measurements is hardly enough, without also measuring the air above and below the clouds, and for miles around, as well as the land under the cloud for miles around.
Dan