Though a bit late I am continuing on with my posts on storms – we covered tornadoes last week. I will muddle through, though I still feel I am floundering about on the crap wagon. Once again thanks for your thoughts and prayers and for Slim filling in during my absence.
As children we may have been told that the gods were bowling in the heavens which cause all the racket in the skies during a storm. Lightning is what causes thunder. Lightning is a discharge of electricity. A single stroke of lightning can heat the air around it to 54,000°F. This extreme heating causes the air to expand explosively fast. The expansion creates a shock wave that turns into a booming sound wave.
As ice crystals high within a thunderstorm cloud flow up and down in the turbulent air, they crash into each other. Small negatively charged particles called electrons are knocked off some ice and added to other ice as they crash past each other. This separates the positive (+) and negative (-) charges of the cloud. The top of the cloud becomes positively charged while the base of the cloud becomes negatively charged.
Because opposites attract, the negative charge at the bottom of the storm cloud wants to link up with the ground’s positive charge. Once the negative charge at the bottom of the cloud gets large enough, a flow of negative charge called a stepped leader rushes toward the Earth. The positive charges at the ground are attracted to the stepped leader, so positive charge flows upward from the ground. When the stepped leader and the positive charge meet, a strong electric current carries positive charge up into the cloud. This electric current is known as the return stroke. We see it as the bright flash of a lightning bolt.
Types of cloud-to-ground lightning include staccato, forked, ribbon, and bead lightening.
–Staccato lightning is a strike which is a short-duration stroke that often, but not always, appears as a single very bright flash and often has considerable branching.
–Forked lightning is a name, not in formal usage, for cloud-to-ground lightning that exhibits branching of its path.
–Ribbon lightning occurs in thunderstorms with high cross winds and multiple strokes. The wind will blow each successive stroke slightly to one side of the previous stroke, causing a ribbon appearance.
–Bead lightning appears to break up into a string of short, bright sections. It is relatively rare.
Another lightning phrase you may have heard is heat lightning. Heat lightning is a common name for a lightning flash that appears to produce no discernible thunder because it occurs too far away for the thunder to be heard. All lightning produces thunder, if a person doesn’t hear it, it is because the sound waves dissipate before they reach the observer.
During the past two decades scientists have discovered and confirmed the existence of lightning that shoots upward into the upper atmosphere from thunderstorms. Red lightning bolts can extend upward from clouds to near the top of the atmosphere. The red bolts, however, are too quick and weak to be seen by the naked eye. Blue jets, in contrast, are limited to the stratosphere and last long enough to be seen by pilots.
Cloud-to-ground lightning comes from the sky down, but the part you see comes from the ground up. A typical cloud-to-ground flash lowers a path of negative electricity (that we cannot see) towards the ground in a series of spurts. Objects on the ground generally have a positive charge. Since opposites attract, an upward streamer is sent out from the object about to be struck. When these two paths meet, a return stroke zips back up to the sky. It is the return stroke that produces the visible flash, but it all happens so fast – in about one-millionth of a second – so the human eye doesn’t see the actual formation of the stroke.
We will continue with this discussion tomorrow….
We continue to dry out in SW Michigan – any light rain or drizzle should move out this morning with clearing skies later this afternoon. Model runs for the next system Friday and Saturday continue to trend south towards I80 which would only bring in light amounts of rain or perhaps a few snow flakes.
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