Tornadoes aren’t uncommon in the Houston area but strong ones are

When most people think of weather disasters in the Houston area, images of catastrophic hurricanes, such as Harvey and Ike, come to mind. However, tornadoes also have a prominent place in Houston’s severe weather history.

Tuesday’s twister that ripped across the southeastern suburbs of Space City reminded residents of that fact. The National Weather Service (NWS) office in Houston issued its first Tornado Emergency as the cyclone swept through Pasadena and Deer Park. One official described the damage as "catastrophic."

NWS survey teams said Wednesday they have found damage that falls into at least the EF-3 category on the Enhanced Fujita Scale. Officials said the winds peaked at about 140 mph during the tornado that carved an 18-mile-long path of destruction.


Weak vs. strong

The EF Scale runs from 0 to 5. Tornadoes that are rated EF-0 or EF-1 are considered weak, while tornadoes rated EF-2 or higher are considered strong. Before the EF Scale, the Fujita scale was used, which used a similar rating system of 0 to 5.

According to the National Centers for Environmental Information, there have been 246 tornadoes confirmed in Harris County, where Houston is located, since 1950. That works out to an average of about three twisters a year.

About half of all the tornadoes recorded in Harris County have been EF-0/F-0, and about 30% have been EF-1/F-1.

Strong tornadoes happen much less often. EF-2/F-2 twisters make up about 14% of the county’s tornado record, while EF-3/F-3 cyclones make up just 3%. There has only been one EF-4/F-4 tornado in Harris County. No EF-5/F-5 twisters have happened.

Tuesday’s tornado marks the first EF-3 on record in Harris County, but it should be noted there the last F-3 occurred on March 30, 2002. Tuesday's twister is also the strongest to hit the Houston area since an EF-2 touched down in 2015.

Houston’s strongest tornado

The worst tornado on record for Houston happened on Nov. 21, 1992, and has been dubbed the Channelview tornado.

According to the official storm report, the twister touched down near the confluence of Brays Bayou and the Houston Ship Channel and moved northeast. It carved a 20-mile-long path of destruction across the eastern side of the metro before lifting northeast of the town of Crosby.

Tim Marshall, a forensic engineer and meteorologist at Texas-based Haag Engineering, surveyed the damage. Images from his report showed extensive damage to homes, buildings and vehicles.

It’s worth noting that the F-4 twister was just one of seven tornadoes recorded in Harris County that day.