Types of thunderstorms and thunder

The first half of June was warmer than normal in Coeur d’Alene and the rest of the Inland Northwest. The average temperature was around 80 degrees, compared to the average of 73 degrees during the first 15 days of the month. Over the last week, weather patterns changed as highs were much cooler along with occasional showers. On June 20, the high at Cliff’s station was only 57 degrees. This was also a record-low maximum temperature for the day.

As far as precipitation, conditions have turned drier than normal. So far, June’s moisture total is only 0.92 inches, compared to the monthly total of 1.93 inches. The long-range forecast models are indicating that the western ridge of high pressure will be locked in over the western U.S. from now until at least the middle of July. There’s always the possibility of some isolated showers or thunderstorms sneaking into our region from the south, but it now appears we’re in our drier-than-average summer pattern across the northwestern U.S.

However, we still don’t believe that the July and August period will not be as dry as last year. In 2022, the total precipitation for July and August was only 0.76 inches. July’s normal rainfall in Coeur d’Alene is 0.92 inches with 1.23 inches normally expected in August. We also believe the best chances of rainfall in the region would be during the middle of July and the middle of August.

I received an interesting question from a reader about thunder last week. Jim asked about the types of thunder that we hear. Well, thunder is the byproduct of lightning. During a thunderstorm that produces lightning, thunder is the sound of the shockwave that lightning produces. The bolt literally heats up the air to over 50,000 degrees Fahrenheit in less than one second. With the rapid heating, the air surrounding the lightning suddenly expands, quickly followed by rapid cooling and contraction, which creates a shockwave. This process produces the sound waves of thunder that we hear.

According to an article by the Canadian government, there are a number of factors that determine how we hear the thunder. The temperature of the surrounding air, the amount of clouds and water in the air, and where the lightning strike is located relative to where one is on the ground.

The sound most commonly heard with thunder is the “clap.” Many will hear this type of thunder when the lightning and the channel it creates are perpendicular to the person on the ground. During some thunderstorms when lightning flashes from cloud to cloud, you would often hear a “rumbling” sound of thunder. This happens when the lightning channel is parallel to the person’s line of sight on the ground.

During strong thunderstorms, there are often instances of multiple strikes simultaneously. In this instance, there are multiple sound waves that are formed and each one will reach you at different times. Therefore, we would hear a combination of claps and rumbles, or perhaps a rolling type of thunder.

To determine how far a thunderstorm is away from you, there is a formula. When sound waves are created by lightning, they travel an average of about 1 mile for every five seconds. Therefore, when you see lightning, start counting and then divide by five. For example, if the count was 20 seconds, the distance the thunderstorm is away from you is about 4 miles. If the thunderstorm is relatively far, such as more than 20 miles, then you may be able to see the lightning, but not the thunder due to temperature, humidity and other atmospheric conditions that prohibit the sound waves from traveling that distance.

In addition to the different types of thunder, there are also four main types of thunderstorms that produce lightning and thunder.

The first is a single-cell thunderstorm, which is typically small and brief that will usually form during a hot afternoon. They are short but can produce brief periods of heavy rain and lightning.

Some of the most common types of thunderstorms are multi-cell storms. They usually form along the leading edge of rain-cooled air, weather or gust front. Most of these thunderstorms will last from 30 to 60 minutes, but there have been instances when they will last for hours. We’ll often see hail, strong winds, flooding, and isolated tornadoes from multi-cell storms.

When a group of storms looks like a line on a radar map, they are referred to as a “squall line.” These squalls will typically bring periods of high winds and heavy rainfall. They also move more quickly, so the chances of tornadoes forming within these cells are much lower.

The big thunderstorms that will produce tornadoes are called “supercells.” These cells will last much longer, usually greater than an hour. There are strong updrafts that can be tilted and rotated. The rotation in the cloud can lead to the formation of tornadoes. The most intense tornadoes, including the strongest (EF5), are associated with a supercell.

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Contact Randy Mann at randy@longrangeweather.com.