Enhanced Fujita scale

The Enhanced Fujita scale (abbreviated EF-Scale) is a way to measure how strong a tornado intensity is by looking at the damage it causes. It is mainly used in the United States, Brazil, and France, but other countries like China also use it sometimes. To decide a tornado's rating, experts go out and look at the damage after the storm.

The EF scale has six levels, from zero to five, with five being the most powerful. It was created to give a better idea of how fast the winds were by looking more closely at the damage. This helps make the ratings more accurate because it looks at different kinds of buildings and nature, like trees, and thinks about how strong they were built.

Even though the EF scale helps us understand tornado strength, it is still just an estimate of the wind speeds. The numbers for wind speeds were figured out by asking experts and using studies from engineers, instead of direct measurements, because that can be very expensive. The ratings are based on how much damage was done by short bursts of wind lasting three seconds.

History

The Enhanced Fujita scale replaced the older Fujita scale, which was created in 1971 by Ted Fujita. The new scale started being used in the United States on February 1, 2007. Other countries like Canada, France, and Brazil also began using it in the following years, sometimes with changes to fit their own building styles and measurements.

The Enhanced Fujita scale was first shown to the public in 2004 at a weather conference in Hyannis, Massachusetts. It was created between 2000 and 2004 by a team of weather and engineering experts at Texas Tech University. The scale was first used in the United States in 2007 after tornadoes hit central Florida.

In November 2022, researchers announced plans for an even newer version of the scale. This update would use better ways to measure tornado winds, including mobile doppler radar. In 2024, researchers suggested that over 20% of certain types of tornadoes might be strong enough to cause very serious damage.

Parameters

The Enhanced Fujita scale, or EF-Scale, helps us understand how strong a tornado is by looking at the damage it causes. There are seven levels, from the weakest to the strongest. Experts mostly use how different buildings and trees look after a tornado to decide its strength.

The EF scale uses 28 different types of structures and plants to judge damage. Each type can show many levels of damage, with total destruction being the highest level.

Scale	Wind speed estimate			Frequency	Potential Damage	Example of damage
	mph	km/h	knots
EFU	N/A	N/A	N/A	3.11%	No surveyable damage.Intensity cannot be determined due to a lack of information. This rating applies to tornadoes that traverse areas with no damage indicators, cause damage in an area that cannot be accessed by a survey, or cause damage that cannot be differentiated from that of another tornado.	N/A
EF0	65–85	105–137	57-74	52.82%	Minor damage.Well-built structures are typically unscathed, though sometimes sustaining broken windows, with minor damage to roofs and chimneys. Billboards and large signs can be knocked down. Trees may have large branches broken off and may be uprooted if they have shallow roots.
EF1	86–110	138–177	75-95	32.98%	Moderate damage.Damage to mobile homes and other temporary structures becomes significant, and cars and other vehicles may be pushed off the road or flipped. Permanent structures can suffer major damage to their roofs, with corners or edges of roofs being torn off completely. Larger trees can be uprooted.
EF2	111–135	178–217	96-117	8.41%	Significant damage.Well-built structures can suffer severe damage (including roof loss), and the collapse of some exterior walls may occur in poorly built structures. On the other hand, mobile homes are often heavily damaged or even destroyed. Vehicles can be lifted off the ground, and lighter objects can become small missiles, causing damage outside of the tornado's main path. Wooded areas have a large percentage of their trees snapped or uprooted.
EF3	136–165	218–266	118-143	2.18%	Severe damage.A few parts of affected buildings are left standing. Well-built structures lose all outer and some inner walls. Unanchored homes are swept away, and homes with poor anchoring may collapse entirely. Trains and train cars are all overturned. Small vehicles and similarly sized objects are lifted off the ground and tossed as projectiles. Wooded areas suffer an almost total loss of vegetation and some tree debarking may occur.
EF4	166–200	267–322	144-174	0.45%	Extreme damage.Well-built homes are reduced to a short pile of medium-sized debris on the foundation. Homes with poor or no anchoring are swept completely away. Large, heavy vehicles, including airplanes, trains, and large trucks, can be pushed over, flipped repeatedly, or picked up and thrown. Large, healthy trees are entirely debarked and snapped off close to the ground or uprooted altogether and turned into flying projectiles. Passenger cars and similarly sized objects can be picked up and flung for considerable distances.
EF5	201+	323+	175+	0.05%	Catastrophic damage.Well-built and well-anchored homes are swept cleanly off their foundations and obliterated. Large, steel-reinforced structures such as schools are completely leveled. Low-lying grass and vegetation are shredded from the ground. Trees are completely debarked and snapped. Very little recognizable structural debris is generated with most materials reduced to a coarse, dispersed mix of small, granular particles. Large, multiple-ton steel frame vehicles and farm equipment are often mangled beyond recognition and tossed miles away or reduced entirely to unrecognizable parts. Tall buildings collapse or suffer severe structural deformation. The official description of this damage highlights the extreme nature of the destruction, noting that "incredible phenomena can and will occur".

Differences from the Fujita scale

The Enhanced Fujita Scale looks at how well buildings are made and considers different types of structures. Experts found that the original scale estimated winds too high to cause certain damage. For example, the old scale said an F5 tornado had winds of 261–318 mph, but the new scale shows that winds above 200 mph are enough for that level of damage.

The EF Scale keeps the same 0–5 rating system but uses new methods to decide the ratings. It includes 28 ways to look at damage and 8 levels of how badly something can be damaged. It also looks at how strong the building is. This means some tornadoes that used to be rated F5 are now rated EF4, unless the building was very strong. Studies show this change means fewer tornadoes are rated at the top level, but including very strong EF4 tornadoes gives a similar number to the old F5 ratings. The EF Scale still uses damage to guess wind speeds, and there is no highest wind speed for an EF5 rating.

Rating classifications

The Enhanced Fujita scale helps us understand how strong a tornado is by looking at the damage it causes. Scientists group these ratings into classes: EF0 and EF1 are considered weak, EF2 and EF3 are strong, and EF4 and EF5 are very violent. Tornadoes rated EF2 and higher are also called significant. Some weather offices, like the one in Quad Cities, Iowa/Illinois, use special words for each rating, ranging from weak to catastrophic.