MIAMI, Nov 23 (Reuters) - Herbert Saffir, co-creator of the five-step Saffir-Simpson scale of hurricane intensity, has died in Miami. He was 90 years old and a structural engineer by profession.

The Miami Herald quoted Saffir's son, Richard, as saying he died of a heart attack on Wednesday night at South Miami Hospital.

Originally from New York, Saffir began developing the five-category hurricane scale in the late 1960s and worked on it with Robert Simpson, then director of the U.S. National Hurricane Center.

Their system for rating the destructive potential of hurricanes on the basis of wind speeds and storm surge moved into common usage in the mid-1970s.

Hurricanes shot into the broader U.S. public consciousness in 2005 when Hurricane Katrina swamped New Orleans and killed around 1,500 people on the U.S. Gulf Coast.

The five-step scale is now often used in short form, with Category 1 storms being the weakest and Category 5 storms the most dangerous. Storms of Category 3 and higher are called "major" hurricanes.

Hurricanes are known as typhoons in the Northwest Pacific west of the dateline and as cyclones in the Southwest Pacific and Indian Ocean. Tropical storms become hurricanes when their top sustained winds reach 74 miles per hour (119 km per hour).

(Reporting by Tom Brown; Editing by Michael Christie and Vicki Allen)

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