Intracloud Lightning Flashes Can Be Similar in Detail

The unpredictable shape of the channel from cloud to ground in lightning is well known. However, when we mapped repeated intra-cloud (IC) lightning flashes, we in some cases see a repeatable path over 15 minutes. A storm, on 8/18/2004 near Langmuir Lab in New Mexico, spawned six flashes between 19:52:30 and 20:06:41 UTC exhibiting remarkable similarity. When corrected for winds (i.e., when shown in a coordinate system relative to their air-parcel) all flashes originated within a roughly 1~km radius. We introduce ``lightning nursery'' to describe these fecund regions of atmosphere. The first three of these flashes were the most similar. They formed branching structures roughly 30~km in size in which the branches coincided with each other over substantial lengths to a precision of a kilometer. Several conclusions can be drawn from this. 1) When the pre-flash electric field is sufficiently strong, the distribution of charge in a thunderstorm completely determines the path of the flash, over tens of kilometers. 2) Over a period of a couple of minutes, a storm recharges itself to a very similar configuration. 3) This observation validates the use of lightning mapping techniques to deduce the charge structure of storms not just as layers, but as 3-dimensional forms.