This map was sent to me this morning by Chief Crabtree, with permission to post here by Chief White from CalFire. It shows the spots where lightening was detected from 7 a.m. Sunday to 7 a.m. today.
For the map: the red ‘plus’ signs and black ‘minus’ signs are lightning strikes that reach the ground. The system does not detect cloud to cloud strikes. The red plus signs are positively charged strikes, the black minus signs are negatively charged strikes. Because of the physics involved (which I won’t go into here), positive strikes are MUCH MORE LIKELY to result in a fire than are negatively charged strikes. As you can see the positively charged strikes make up only about 5 – 15% of the total strikes.
I asked Chief Crabtree how the determination of positive or negative was made and was it instantaneous or not. His answer:
Instantly. There is an Automated Lightning Detection System (ALDS) that consists of magnetic detection devices that are all interconnected. They detect a change in the earth’s magnetic field that occurs when a lightning bolt hits the ground. Because they are interconnected and can detect the magnitude of the change in the magnetic field, computers are able to ‘triangulate’ and determine the precise location of the strike. This same technology can detect a positive or negative transfer of magnetic energy and hence can determine the polarity of the strike.
Although I was a Geography Major in college and took more than one meteorology class, that was a l-o-n-g time ago.
There are several websites including the National Weather Service and National Oceanic and Atmospheric Administration that have a host of information on lightning detection.
Here’s a link to the Stanislaus National Forest site regarding lightening: https://www.fs.usda.gov/detail/stanislaus/home/?cid=stelprd3845274
One final thing, CAL FIRE is sending Air Attack 440 (what you might call the ‘spotter plane’) up this morning to fly over Tuolumne and Calaveras Counties looking for ‘smokes’ from lightning strikes. They will particularly focus on the locations of know positive strikes, but will overfly the entire counties.Leave a comment