Tornadoes are a big part of life here in south Louisiana. Although we may not see the EF4/EF5 monsters of the plains, tornadoes in our tropical climate can pop up fast and be just as deadly.
Tornadoes form due to winds changing direction and speed with height. We call this wind shear. Firstly, differences in wind speed at different levels of the atmosphere cause a column of air to begin to rotate. Second, the rising air feeding the thunderstorm, known as the storm’s updraft, stretches this column vertically. With vertical stretching, comes an increase in rotation speed. The stronger the updraft and the stronger the winds aloft, the faster this column can rotate. When this column of air does not reach the surface it’s called a funnel cloud. When it does interact with the surface, it is then deemed a tornado.
Tornadoes can span from a few meters wide to miles wide. The largest tornado ever observed was over two-and-a-half miles wide, which was the El Reno, Oklahoma tornado in 2013. A mobile radar, doppler-on-wheels, measured a wind speed of 295 mph high up within the tornado! The strongest wind speed ever recorded inside a tornado was also by a doppler radar during the Bridge Creek/Moore tornado of 1999. The doppler measured estimated wind speeds of 301 mph in this EF5 tornado!
Larger tornadoes are usually more intense. We call these “wedge” tornadoes due to their large width. Stove pipe and “rope” tornadoes are usually smaller in scale, resembling the objects they’re named after, but can be just as intense.
Tornadoes are rated on a graduated scale called the Enhanced Fujita scale. Tornadoes can range from EF0-EF5 on this scale, with zero being the weakest and five being the strongest.
The majority of tornadoes in south Louisiana are EF0-EF3, as EF4/EF5 need special atmospheric ingredients more commonly seen in mid-latitude climates.
The wind speeds are determined by a National Weather Service assessment team, which comes out once the severe weather has ended. They can estimate wind speed by the severity of the damage observed. EF0-EF1 tornadoes usually create minor damage such as tree, siding, or roof damage. EF2-EF3 tornadoes create more substantial roof damage, can toss around mobile homes, and uproot large trees. Of course, EF4/EF5 damage is catastrophic, having been known to level entire neighborhoods.
If the atmosphere is conducive for the development of tornadoes, wind shear is high for example, the National Weather Service will issue a “TORNADO WATCH” for the area. This simply means anyone living within the watch area needs to be on high alert for the development of tornadoes. If a tornado is spotted on radar, or by a trained observer on the ground, a TORNADO WARNING will be issued. These are issued for smaller areas than watches and mean a tornado is imminent within the warned area.
At this point, you need to take shelter immediately. The safest thing to do is get away from windows and into an interior hallway or closet. The pressure from the extreme winds accompanying a tornado most often knocks down exterior portions of the house but leaves interior areas intact. This is why we recommend the action above. It’s also a good idea to get a blanket to cover yourself with, protecting yourself from flying debris. If you know tornadoes are possible on a certain day, try to evacuate mobile homes. With Louisiana seeing the majority of tornadoes on the lower end of the scale, being in a mobile home poses the greatest risk of bodily harm or injury, as these can get tossed around by EF2-EF3 tornadoes.
With this week being Severe Weather Awareness week, it’s always good to educate yourself about the weather, as having a plan and being ready is the best way to stay a step ahead. Download the KLFY weather app, which provides radar, but will also send you notifications directly to your mobile device if your area is under warning. Of course, on severe weather days keep it tuned to KLFY for coverage through the event.