Hurricane glossary

Tropical disturbance, tropical wave
A cluster of clouds and thunderstorms in the tropics without a defined circulation.

Tropical depression:
A rotating system of thunderstorms in the tropics with winds of less than 39 mph.

Tropical storm
A rotating system of strong thunderstorms with top sustained winds of 39 to 73 mph. Storms are named when they reach this strength.

Hurricane:
An intense, rotating tropical weather system with sustained winds of 74 mph or higher.

Tropical storm watch:
Tropical storm conditions are possible in the watch area within about 36 hours.

Tropical storm warning:
Tropical storm conditions are expected in the warning area within about 24 hours.

Hurricane watch:
Hurricane conditions are possible in the watch area within about 36 hours. Your hurricane preparations should be underway.

Hurricane warning:
Hurricane conditions are expected in the warning area within 24 hours. All preparations should be complete, and if evacuating, you should be on your way to a safe place.

Storm surge:
A mound of ocean water up to 20 feet high that can come ashore with a hurricane. Evacuation zones are identified by the likelihood of being flooded by this rising water. Most hurricane-related deaths are from storm surge flooding. Storm surge flooding can occur over 100 miles of coastline and may extend inland several miles.