Typical afternoon thunderstorms have the ability to cause damage

Typical afternoon thunderstorms have the ability to cause damage
(Source: KPLC)

LAKE CHARLES, LA (KPLC) - We have seen quite a few strong thunderstorms in the last week, yet none of these storms had any type of watches or warnings associated with them. Why is that?

To have a watch or warning associated with a thunderstorm, the National Weather Service has to issue one. There has to be certain atmospheric conditions in place for the need of watches and warnings. Pop-up thunderstorms do not *usually* meet the requirements to issue a severe thunderstorm warning.

The requirements for watches and warnings are:

  • Watch: conditions that are favorable for severe thunderstorms. During a watch you should monitor weather outlets for updates.
  • Warning: there is a serious threat to life and property of those in the path of the storm. Act to find a safe place to shelter. The storm also has to be producing hail greater than 1 inch in diameter (quarter size) and winds in excess of 58 mph.  

This being said, a typical afternoon thunderstorm can become strong enough to produce minor storm damage. Thunderstorms can grow strong enough to produce winds up to 50 mph with even stronger gusts without the storm being labeled as severe. These winds can cause minor storm damage such as roof damage to out buildings and downed tree limbs.

Not only can a thunderstorm become strong enough to produce 40 mph winds, but it can also produce a downburst.

A downburst is when the downdraft of a storm over powers the updraft and all the rain and hail that the storm was holding falls to the ground rapidly. This rapid release of rain can cause air below the downdraft to cool rapidly causing this air to begin to sink rapidly as well. When the air, rain and hail reach the ground it has to go somewhere and that is out and away form the storm. This can cause winds to be stronger than those of an EF0 tornado.

For meteorologists to be able identify any of these events occurring on radar they take a specific course to be able to read the data. A few quick snippits about the radar are:

  • Scans occur every couple of minutes depending on the setting of the radar. This means that not every minute of the day is accounted for.
  • The radar sends out a pulse of energy that is then reflected back to it by birds, rain drops, insects, and lots of other things (not just rain).
  • As that pulse of energy is sent from the radar it travels at an angle slightly up. The farther away from the radar site the higher into the air the beam is seeing. So, if the radar measures a gust of wind at 20 mph farther away from the radar that is likely not the speed of the wind at the surface.

To see current radar check out the 7 Storm team Weather App available for free download from the itunes or app store.

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