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The difference between tropical storm types and how they’re defined

HOUSTON, TX - SEPTEMBER 19: A school bus makes its way on the flooded Hopper Rd. on September 19, 2019 in Houston, Texas. Gov. Greg Abbott has declared much of Southeast Texas disaster areas after heavy rain and flooding from the remnants of Tropical Depression Imelda dumped more than two feet of water across some areas. (Photo by Thomas B. Shea/Getty Images)
HOUSTON, TX - SEPTEMBER 19: A school bus makes its way on the flooded Hopper Rd. on September 19, 2019 in Houston, Texas. Gov. Greg Abbott has declared much of Southeast Texas disaster areas after heavy rain and flooding from the remnants of Tropical Depression Imelda dumped more than two feet of water across some areas. (Photo by Thomas B. Shea/Getty Images) (2019 Getty Images)

With hurricane season approaching, KPRC 2 Hurricane Headquarters is here to help Houstonians power through the storms by providing our audience with everything they need to know to know, starting with terminology.

[RELATED: Tropical disturbance could get hurricane season off to an early start]

Unsure if it’s a storm or disturbance, or don’t understand the difference either way?

Here’s how it breaks down:

A tropical cyclone with sustained surface winds from 39 mph (63 km/hr) to 73 mph (118 km/hr) is categorized as a tropical storm.

In September 2019, Tropical Storm Imelda caused major flooding throughout Houston, pouring more than two feet of water over some areas.

Before being upgraded to a storm, Imelda was categorized as a tropical depression.

A tropical depression is a tier below at lower speeds. Its maximum sustained surface winds up to 38 mph (62 km/hr).

Finally, a tropical disturbance is defined as a discrete tropical weather system of apparently organized thunderstorms. These storms are generally 100 - 300 nautical miles in diameter and originate in tropic or subtropic areas.

In June 2001, Tropical Storm Allison started as a disturbance in the Gulf of Mexico before making landfall in Houston.

A tropical disturbance also is not associated with a front and maintains its identity for 24 hours or more.


More weather terms to know


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