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Understanding Your Severe Storm Risk

The unusual spate of storms that has ruined the Christmas holiday for millions may not be over. Our hearts and prayers go out to those who lost loved ones and whose lives have been changed in Dallas, Mississippi and Arkansas. While not as destructive, more isolated tornadoes could strike Alabama, Georgia and the Florida panhandle on the last Monday of 2015. If you were in a storm warning, would you know, and more importantly, would you know what to do?

Ever since 2007, the National Weather Service changed the way it issues warnings for severe weather. Prior to that time, they changed from warning for entire counties to warnings based on a storm’s movements. These are called storm-based or polygon warnings, because the warnings are drawn as geometric shapes.

Here is an example of a polygon warning from the terrible tornado that struck Birmingham, Alabama on Christmas Day just before 6 pm. The red outline indicates the areas under the official NWS warning.

BHM_tornado_122515

Jefferson county is highlighted in black. Does it mean that everyone inside the red polygon will experience a tornado? That depends because the polygon is based on current storm movement and other indications seen on radar by the NWS forecaster who issued the warning. There are cases, of course, where a storm weakens and the tornado threat dissipates. There are also situations where a tornado may change direction suddenly, causing the NWS to draw a different polygon.

Keep in mind that if you are within the polygon, it is possible that you may not experience the direct impact of the tornado. However, that doesn’t mean avoiding deadly consequences. This picture, taken by the National Weather Service in Birmingham underscores the danger of being in the polygon. Common objects can become missiles; you can see what happened to that car.

birmingham_tornado_122515

So, if you are notified that you are in the polygon, get somewhere safe, like the lowest floor of your home in a room without windows like the basement, a bathroom or closet. If you’re outside, get to a sturdy building and again, stay away from windows as storm winds can hurl objects like projectiles.

How would know you are in a polygon? Well, most warning systems, like weather radios, outdoor sirens and TV broadcasts still indicate warnings based on counties. Consider subscribing to a service like WeatherCall, which will call, text or email you when your exact location falls within an NWS warning polygon.

In the warning example above, weather radios sounded in Jefferson county, panicking many. However, people in places like Gardendale, Morris and Adamsville, for example, didn’t need to shelter as it was only raining there with some occasional thunder. They were not in the polygon.

To know for sure if you are in danger get WeatherCall. Hopefully, the next storm threat won’t loom for a while, but as we’ve seen, severe weather doesn’t follow a schedule or respect holidays.

If you’d like more information on WeatherCall for home or business use, please feel free to email me: gene.norman@weathercall.net.

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