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Greenburgh Public Library Blog

Weather: Thunderstorms

by Christa O'Sullivan on 2019-03-13T10:00:00-04:00 in Science, Adults | Comments

Weather affects us all, whether we like it or not. I’m a librarian here at Greenburgh but as many of my fellow staff members will tell you, I tend to act as the in house meteorologist. Growing up and living in the northeast, the seasons always fascinated me. Factoring in that I am a librarian, I decided to do some research about why weather happens when it does. What better place to work than a library where access to this information is plentiful. In this series of posts I’m going to shed some light on each season and our everyday weather… we know when it happens but do we know why?


You can tell it’s Springtime when we all break out the t-shirts and shorts the first time it hit sixty degrees in the northeast. Longer, sunnier and warmer days also bring unsteady atmosphere ushering in....Thunderstorms! Growing up anywhere that humidity is present, we know about the wide range of thunderstorms we can experience. The 5 minute soaker or the extended severe Thunderstorm that looks like nothing less than a tornado barreling down! Even though we know that Thunderstorms are just a part of warm weather just like snow is to cold, what exactly causes the booms and bright lights? Read on to find out!


According to the National Weather Service, a Thunderstorm has a pretty simple definition, “ a rain bearing cloud that produces lightning,” but what causes one rain cloud to produce lightning and not another? There’s a few factors that go into that. Three factors need to be present for a thunderstorm to happen: moisture (usually from the ocean), instability (when warm air rises) and a lifting mechanism (air density). How do you get all three things to happen at the same time? Thunderstorms occur when warm moist air rises into a colder air mass. This is why a thunderstorm is more likely when the air feels warm and soupy because it is thicker with more moisture. When this happens, condensation occurs. The warm air rising becomes colder from the cooler air mass which creates water vapor. When the conditions in the atmosphere are ripe, this cycle will continue with the cool air dropping into the atmosphere but then it will once again go through the same cycle of rising up, hitting the cooler air, creating water vapor, then dropping down into the atmosphere. This will causes a convection cell. When this happens in large amounts, a thunderstorm can occur.


You may wonder, if all a thunderstorm needs is the three ingredients, what makes a thunderstorm severe? There’s a few factors that go into that categorization. If a thunderstorm contains hail that has a diameter larger than one inch, wind speeds higher than 57.5 mph, or if it contains a tornado. All three don’t have to present to be labeled a severe thunderstorm, just one.  You may recall last year on May 15, 2018, when severe thunderstorms ravaged the tri state area with confirmed tornados, microbursts and macrobursts throughout the tri state area and especially in Westchester County. They may have only lasted a couple of hours but the damage was extensive.


If you ever get caught in a severe thunderstorm, here are some tips to keep you safe from the National Weather Service:

  • If there is a time, secure any loose objects outside so they do not become flying debris
  • Stay inside a shelter or building if you are already in one or near one.
  • Stay away from any windows in case of strong winds and avoid electric or plumbing
  • If you are outside try to find a sturdy enclosed building or car as fast as you can. Avoid open spaces, isolated objects, high ground and metallic objects.
  • Do not go in bodies of water such as pools, lakes, rivers, or oceans until the storm has passed. If you can hear thunder, that means lightning is close behind.

If you’d like to learn more about storms or weather in general, check out these great resources:

Surviving Natural Disasters: How to Prepare for Earthquakes, Hurricanes, Tornados, Floods, Wildfires, Thunderstorms, Blizzards, Tsunamis, Volcanic Eruptions and other Calamaties by Janice McCann

Wild Weather PBS Special

Historic Storms of New England by Sidney Perley
Thunderstorms - Brittanica



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