Ryan Henning, "Field Guide to the Weather: Learn to Identify Clouds and Storms, Forecast the Weather, and Stay Safe"
English | ISBN: 159193995X, 1591938244 | 2019 | EPUB | 144 pages | 21 MB
Severe Weather Phenomena
Some weather phenomena only occur during storms or severe weather events. Lightning and tornadoes are obvious examples, but flash floods, blizzards, and heat waves can also pose dangers to both people and property. Here’s how to recognize such conditions and stay safe in them. Of course, the best preparation is staying informed; for information on weather watches, warnings, what they mean, and how to find out about severe weather in your area, see page 108.
You couldn’t have thunderstorms without lightning, which is a byproduct of the aggressive updrafts within nimbus clouds. Thunderclouds form as warm air rises very quickly (upwards of 60 miles per hour); as the air rises, warm air condenses out, and the resulting water droplets brush past each other, producing static electricity. Electricity, much like air pressure, seeks an equilibrium or balance, so all that electricity eventually needs to find an outlet, either as a lightning bolt that connects with another cloud or as a bolt that strikes the ground.
Lightning takes the path of least resistance to connect positive and negative poles, which usually means that lightning stays within clouds, but when bolts reach down to the surface, they often like to find the most exposed, highest-reaching object on the ground, either the tallest tree in a forest, the tallest point of a building, or a lonesome boat in the middle of a lake. Often, of course, doesn’t mean always. While the storms may be vast, lightning bolts are quite narrow, which means that the course a bolt takes to reach the surface might not include the absolute highest point of a region. Lightning also seeks the most conductive material, and it will bypass one tree for a more conductive type of wood or find a building with a metal antenna instead of one without. So if you hear thunder or see lightning, be sure to get someplace safe, preferably indoors. Just because lightning strikes a tree doesn’t mean it can’t finish its route to the surface by passing through someone standing near it.
On occasion, you may hear of heat lightning; this isn’t a real meteorological term. It usually refers to lightning that is seen from a distance, without thunder. In such cases, what you’re seeing is a storm that’s producing lightning; it’s just too far away for you to hear the thunder.
Thunder is the direct result of lightning; when a lightning bolt discharges, it is incredibly hot―as much as 50,000 degrees. This causes the air surrounding the lightning bolt to become superheated, and this air expands away from the bolt, creating the massive crack of a lightning bolt and the long rumbles of thunder that echo across the terrain.
Thunderstorms are an odd weather phenomenon in that they have a built-in warning system: bolts of lightning that are visible for miles and thunder, which is usually hard to miss. If Mother Nature gives you that warning, it is best to heed it and get indoors.
If you are unable to get to shelter, it is important not to be the tallest object in your area (e.g. standing in the middle of a fairway when golfing or staying on a lake when fishing). Also, don’t stand near or under other conductors because lightning bolts are capable of arcing from that object to you on their way to the ground. Trees are good conductors, and they therefore provide poor shelter from lightning.
If you are unable to get to safety and are in an open area, those that have been struck or nearly struck say that you can feel a rise in static electricity shortly before lightning strikes. If you have any reason to believe that a lightning strike is possible, the safest thing to do in an open field is to crouch and give yourself a low profile, while at the same time giving yourself less contact with the ground, which may return a charge back up to you if lightning were to strike nearby.
Tornadoes are often mistaken for clouds, but technically speaking, they aren’t a cloud type. Instead, they are a tight circulation of wind that emanates from the base of wall clouds. Often, what appears to be a cloud toward the lower portion of a tornado is actually dust and debris drawn into its path by its high winds.
Tornadoes occur in thunderstorms with very strong updrafts. Updrafts, despite their name, draw air from all around a thunderstorm, rather than just below. Updrafts at the leading edge of a storm tend to be stronger and, therefore, can cause the entire storm to rotate. This rotating column of air will start to reach down on the rear side of the storm, in a feature called the rear flank downdraft, a process that creates a wall cloud. When that rotating column reaches the ground, a tornado is born.
It’s difficult to predict the direction a tornado will move, especially in the short term, but they will generally move in the same direction of the thunderstorm. They vary in intensity through their life cycle on the ground and are measured using the Enhanced Fujita Scale, ranging from EF0 (wind speed below 85 mph) to EF5 (winds of greater than 200 mph). Unfortunately, we can only estimate the strength of a tornado after the fact, using damage surveys.
If a tornado is believed to be in the area, go to an interior, windowless room on the lowest level of the house, and put as many walls between yourself and the outdoors as you can. With strong winds and tornadoes, it is possible to get stuck out on the road or in an open area unable to reach shelter, and the best thing to do is keep a low profile. Tall vehicles, like trucks or vans, can be blown over, and remaining upright exposes you to more debris. Stay low and out of the wind if you are unable to find shelter.