Understanding Your Weather Risk

Understanding Your Weather Risk

By Gene Norman, CBM

“Is it a watch or a warning?”  In all my years as a broadcaster, whether it was in Atlanta or Houston, I was constantly amazed at how many people asked me this question.  From puzzled producers in the news room to the “man on the street” and even in my own home!   Yet this very basic weather alerting terminology often trips people up and causes unnecessary confusion.  Both terms refer to a certain stage of severe weather development and it’s important that you understand the distinction before the skies grow dark.

But first, let’s define some terms.  What is meant by “severe” weather in the first place?  The National Weather Service classifies “severe” storms as those containing winds in excess of 58 mph, hail larger than 1” in diameter or producing tornadoes.  A 58 mph wind is strong enough to knock a tree branch down or topple a small, weak tree.   One-inch diameter hail is roughly the size of a quarter.  So even if you see dark clouds and lightning and hear a lot of thunder, the storm may not be considered “severe”, it just may scare you out of your wits.

When severe weather is expected, a watch is usually posted anywhere from six to eight hours before the onset of any storm activity.  This is a “heads-up” to people in the affected areas where either severe thunderstorms or tornadoes are expected.  These watches may cover several counties in one state or multiple counties across several states.  When you hear that a watch has been issued where you live, it is a good time to consider where you’ll be in the watch timeframe.  Will you be on the road or at home?  What will you do if the storms in fact do materialize? Where will family members be and how can you get a hold of them to let them know there is a threat?  Do you need to postpone a short-term trip or cancel an outdoor activity?  When a watch is issued, it is your time to plan and prepare.  Have emergency numbers handy and if power outages are possible, get needed supplies ready.

As storms develop and reach severe limits, warnings are issued.  This is the time to act.  Warnings typically can last anywhere from 15 to 30 minutes.  The National Weather Service warning takes the shape of where the storm is expected to move over that time period.  It may cover a part of a whole county, or segments of several counties, depending on their orientation.  If you hear that a warning is in effect, get indoors to a safe place as far away from windows as possible.  A good place to go is a closet or bathroom.  Remember, you may only have seconds to safeguard yourself or family members.

In case you’re wondering, yes, it is possible to have a warning without a watch.  This frequently happens in the summer-time, when air mass thunderstorms grow violently in the heat of the afternoon delivering a powerful mix of wind, hail and rain.  However, a watch usually isn’t issued because these storms are very widely scattered in nature.  There is also no warning for frequent, dangerous lightning occurring without any of the aforementioned severe criteria. 

It is also possible for a watch to be issued but no severe storms form within the defined watch area.  This occurrence is becoming far less frequent as the science of predicting severe weather improves.  However, even when all of the apparent ingredients exist, nothing happens.    

Hopefully, this clarifies the issue for you.  Knowledge is power, so share it with someone.  Who knows, it may just save a life.  Read about how forecasters determine severe weather potential.  To learn more about severe weather safety awareness, click here.