A tornado that tore through the Houston area on Tuesday was the kind of early-season storm that scientists say has been occurring with increasing regularity — a sign that patterns of severe weather are shifting.

The tornado struck Pasadena, southeast of Houston, seriously damaging homes and other buildings and knocking out power to thousands in the city and its surrounding areas.

More than a dozen other tornado sightings were reported as the storm moved across the Gulf Coast, although they have yet to be confirmed by the National Weather Service.

The spate of reported tornadoes adds to changes that experts have been observing in recent years -- specifically, that where and when tornadoes occur has begun to shift.

Historically, tornadoes were most likely to strike within a column of the central U.S. that was nicknamed ‘Tornado Alley.’ The area includes parts of Texas, Oklahoma, Kansas and Nebraska. In recent years, however, researchers noticed that fewer tornadoes were touching down in the Great Plains and that more were hitting the Southeast.