Exploring Thunderstorms

Severe storms have been rolling across the continental U.S. this week. A tornado touched down in Mississippi, killing one person and injuring others. Below is a short video from an article on CNN of the tornado.



In my area we didn't have anything as severe as a tornado, but we did have our first thunderstorms of the season. As I lay in bed listening to the thunder, I decided it was a perfect time to write a post about thunderstorms.

I had touched a bit on lightning in my post When Lightning Strikes the Vatican and now I would like to expand on the topic.

I found some great information on NOAA's National Severe Storms Laboratory website.

First, let's explore how a thunderstorm is created.

It starts with the sun heating the Earth's surface, which in turn warms the air above that part of the ground. Something then has to "bump" the air and cause it to start to rise. According to the site, this could be other colder or wetter air, mountains or hills. If this rising air remains warmer and lighter than the air around it, it will continue rising.

As the warm air rises up into the atmosphere "the water vapor it contains begins to cool, releases the heat, condenses and forms a cloud".

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The cloud grows bigger and bigger and will eventually reach air that is below freezing. Up there the water droplets freeze and start bouncing around. When they collide they pull bits of ice off of each other, along with electrical charge. This charge builds and builds then releases in a bolt of lightning either cloud to cloud or to the ground. The bolt creates a sound wave which is the thunder!

That wasn't too hard! But, how does this end? I mean, thunderstorms don't last forever, so when does it stop  and dissipate?

Thunderstorms have three stages to their lives, developing, mature, and dissipating. We have already covered the first two stages so lets take a look at the third.

During the mature part of the storm the warm air from the ground is still rising up into the cloud and pushing water vapor into the freezing air. As long as the air keeps rising the storm keeps going. Eventually, all the precipitation and wind coming down from the cloud overpowers the warm air rising up. The supply of new water stops and the precipitation raining down will slow and stop. Just be aware, even though the rain has stopped the lightning can continue for awhile.

Photo from NOAA NSSL:Severe Weather 101

Ok, so I feel like I now have a pretty good grasp on the thunderstorm itself. Let's explore lightning a little more.

Once again, NOAA's National Severe Storms Laboratory has an excellent site with all sorts of information about lightning.

You know those little jagged pictures of lightning that we drew as children?

Turns out that lightning really is jagged! "Lightning is a channel of electrical charge called a stepped leader that zigzags downward in roughly 50-yard segments in a forked pattern."

Or course, we can't actually see it, so our drawings weren't exactly accurate, but it's still pretty neat!

I thought this was cool too. "As it nears the ground, the charged step leader is attracted to a channel of opposite charge reaching up, a streamer, normally through something tall, such as a tree, house, or telephone pole."

It is when these two meet, the bolt and the streamer, that the current starts surging. I had mentioned in my previous post about lightning that the current goes through the lightning bolt multiple times. This is because when the two meet, a backlash of current actually travels back UP toward the cloud! One bolt can send up to twenty return strokes giving the bolt the appearance of flashing. Below is a short video from National Geographic on the topic.

This video doesn't mention ice particles causing the electrical charge, but it does explain the separation of the charges and the resulting release in the form of lightning.

So, what about thunder? Lightning causes thunder, so if you hear thunder you can be certain that somewhere there was lightning!

A lightning bolt heats the air around it, and heated air expands. It is so hot, and the air expands so quickly that it causes a sound wave, and that is what we hear.

Have you ever noticed that when the storm is close enough you can actually hear three distinct sounds in the thunder? First, there is a tearing sound as the lightning rips down through the sky. Then a sharp cracking sound caused by the streamer reaching up from the ground, followed by the rolling boom of thunder, which is what we hear when farther away.

This all happens very quickly so don't feel bad if you don't know what I am talking about. I have spent a lot of hours just sitting and listening to storms. It was actually a favorite activity in my family! Most people will be able to at least identify the crack and then the boom.

I think thunderstorms are amazing and are one of my favorite weather events. I love listening to them and watching them whenever possible. I will admit that I probably take too many risks when it comes to thunderstorms, but I just can't help it!

On that note, lightning safety is very important, and therefore, needs a post of its own. So, please check back soon for tips on thunderstorm safety!

When Lightning Strikes the Vatican

There has been a lot of talk this week about the Vatican and the selection of the new pope. The conclave starts Tuesday, March 12th, and even though I am not Catholic, I will be curious to see what color smoke rises from the makeshift chimney. When I saw NBC News' video of a man putting a chimney up on a Vatican roof, I was reminded of that amazing lightning strike on the day Pope Benedict XVI told the world that he was resigning.

The photo was taken by professional French photographer, Filippo Monteforte. According to a report in USA Today, it was a stormy day and Monteforte thought that maybe lightning would strike, and if it did what a wonderful picture it would make. He waited for over two hours and witnessed two bolts of lightning strike St. Peter's Basilica.

There was some speculation that, perhaps, the photo was a fake. Jesse Ferrell, a weather and social media blogger on Accuweather.com, addressed this doubt in his post, Did Lightning Really Strike Vatican After Pope's Resignation?  

According to his blog post, Ferrell believes the photo is real. Some people expressed doubts because you can't see a reflection of light in the dome or on the wet street below. He explains that when lightning strikes it sends the current through the bolt dozens of times. The first number of times are too bright to capture on film. The last few times, however, aren't as strong or as bright. so that is when the bolt can be successfully photographed. At that stage the bolt has only "minimal reflection on nearby surfaces".

There was also the video that was taken and aired on BBC, thus giving the photograph more credibility. The video can be found on Youtube, was played in numerous news reports, and Ferrell also included it in his blog post.

Lightning is not a rare occurrence. In fact, National Geographic reports that lightning strikes the Earth more than a hundred times every second! Also, the common saying that "lightning doesn't strike twice" isn't true. Lightning doesn't keep track of where it has or hasn't been, all that it cares about is reaching the ground. Tall buildings, structures, and trees are very enticing. You never want to be the tallest object during a storm! You also don't want to take cover under the tallest object. Yes, that lone tree in the middle of the field may help keep you dry, but it is also the quickest route to the ground for lightning. Monteforte, the photographer, took a risk standing outside in the storm to get his now historic photograph.

St. Peters Basilica isn't the only building to be struck by lightning. 7 Most Incredible Skyscrapers Being Struck by Lightning offers more amazing pictures. I could not find other occurrences of the Basilica being struck by lightning, but that doesn't necessarily mean it hasn't happened before. Lightning striking on a random Wednesday wouldn't be much cause for alarm or speculation. Lightning striking the day the pope resigns... well, that will get people talking.