Tennessee tornadoes: What classifies as one? What is an EF-3? EF-2? Different windspeeds, more

Keep up to date with the latest coverage of the Middle Tennessee tornado outbreak here.

Tornadoes slammed into communities across Middle Tennessee this weekend leaving a path of death and destruction in the wake.

An estimated 13 tornadoes hit communities around the greater Nashville region late Saturday, according to the National Weather Service. On Sunday, emergency workers and storm-survey teams spread out across Middle Tennessee to take stock of the damage and determine where on the EF scale these tornadoes ranked.

The National Weather Service has ranked two tornadoes so far and more could be on the way as surveying continues into Monday.

Here's a look at what makes a tornado a tornado, what the EF ranking system is, how many tornadoes hit Middle Tennessee and more.

What part of Tennessee was hit with tornadoes? What were the wind speeds?

The National Weather Service confirmed storm survey findings Sunday evening for two tornadoes that hit communities in Middle Tennessee.

The Clarksville tornado was marked as an EF-3, with winds of 150 mph. The Madison/Hendersonville/Gallatin tornado received a preliminary rating of EF-2, with winds of 125 mph.

What causes a tornado?

The National Weather Service defines a tornado as " a violently rotating column of air touching the ground, usually attached to the base of a thunderstorm".

The main reason we can see a tornado is because of the funnel made up of water droplets, dust and debris.

While the wording of definitions may vary, there is one constant: For a weather phenomenon to be classified as a tornado, it must be in contact with the ground and a thunderstorm cloud at the same time, the Storm Prediction Center of the National Oceanic and Atmospheric Administration states.

No ground contact means it's just a funnel cloud.

Tornado watch vs warning: What to know when severe weather strikes

What does EF mean when rating tornadoes?

The Enhanced Fujita scale is what the EF stands for in the ranking of tornadoes.

The scale measures the strength of a tornado based on the damage it caused. Tornadoes are only rated after they've made their way through a region.

What are the different categories of a tornado?

Tornadoes rate from EF-0, which brings light damage, to EF-5 tornado which brings incredible damage. Where a tornado ranks is based on a list of damage indicators and degrees of damage, which help estimate the range of wind speeds the tornado likely produced, according to the National Weather Service.

What are the wind speeds for an EF-3 tornado? EF-4?

The EF scale still is a set of wind estimates (not measurements) based on damage that is seen after a possible tornado has come through an area, according to the NWS. Here's how the EF rating and windspeeds correlate with one another.

This article originally appeared on Nashville Tennessean: Two TN tornadoes ranked EF-3, EF-2. What it means and windspeeds