Tropical-cyclone related terms to know
When discussing a tropical cyclone, forecasters use a lot of different terms that everybody may not know. Here’s a list of terms used by forecasters:
- Hurricane: A tropical cyclone with minimum winds of 74 mph. The term hurricane is used for Northern Hemisphere tropical cyclones east of the International Dateline to the Greenwich Meridian. A major hurricane is a storm packings winds greater than 111 mph, or a category three storm on the Saffir-Simpson Wind Scale.
- Tropical storm: A tropical cyclone with maximum sustained winds from 39 mph to 73 mph.
- Tropical depression: A tropical cyclone with maximum sustained winds of 38 mph.
- Remnant low: Used to describe systems no longer having convection required of a tropical cyclone.
- Hurricane warning: An announcement that hurricane conditions are expected within a specified coastal area. The warning is issued 36 hours prior to the anticipated onset of tropical-storm-force winds.
- Hurricane watch: An announcement that hurricane conditions are possible within a specific coastal area. The watch is issued 48 hours in advance of the anticipated onset of tropical-storm-force winds.
- Tropical storm warning: An announcement that tropical storm conditions are expected in a specified coastal area within 36 hours.
- Tropical storm watch: An announcement that tropical storm conditions are possible within the specified coastal area within 48 hours.
- Hurricane Season: The portion of the year having a relatively high incidence of hurricanes. The hurricane season in the Atlantic, Caribbean, and Gulf of Mexico runs from June 1 to Nov. 30. The hurricane season in the Eastern Pacific basin runs from May 15 to Nov. 30. The hurricane season in the Central Pacific basin, in which Hawaii is found, runs from June 1 to Nov. 30.
- Central Pacific Basin: The region north of the equator between 140 degrees west longitude and the International Dateline. The Central Pacific Hurricane Center in Honolulu is responsible for tracking tropical cyclones in this region.
- Eastern North Pacific Basin: The portion of the North Pacific Ocean east of 140 degrees west longitude. The National Hurricane Center in Miami, Florida is responsible for tracking tropical cyclones in this region.
- El Nino/La Nina: El Nino correlates with warmer ocean temperature that cause increased storm activity and late season storms. La Nina, which features cooler waters and historically has produced below normal activity seasons. Warmer waters fuel convection and storms.
- Saffir-Simpson Hurricane Wind Scale: The scale used to estimate a storm’s potential damage. As an example, when Hurricane Iniki made landfall on Kauai in 1992 it was a category 4 storm.
|Category||Wind speed (mph)||Damage|
Winds ranging from 74 mph to 95 mph
|Very dangerous winds will produce some damage|
Winds ranging from 96 mph to 110 mph
|Extremely dangerous winds will cause extensive damage|
|Winds ranging from 111 mph to 129 mph||Devastating damage will occur|
Winds ranging from 130 mph to 156 mph
|Catastrophic damage will occur|
|Winds of 157 mph and greater||Catastophic damage will occur|
- Direct Hit: A close approach of a tropical cyclone to a particular location. For locations on the left-hand side of a tropical cyclone’s track (looking in the direction of motion), a direct hit occurs when the cyclone passes to within a distance equal to the cyclone’s radius of maximum wind. For locations on the right-hand side of the track, a direct hit occurs when the cyclone passes to within a distance equal to twice the radius of maximum wind. Compare indirect hit, strike.
- Eye: The roughly circular area of comparatively light winds that encompasses the center of a severe tropical cyclone. The eye is either completely or partially surrounded by the eyewall cloud.
- Inundation: The flooding of normally dry land, primarily caused by severe weather events along the coasts, estuaries, and adjoining rivers. These storms, which include hurricanes and nor’easters, bring strong winds and heavy rains. The winds drive large waves and storm surge on shore, and heavy rains raise rivers. (A tsunami — a giant wave caused by earthquakes or volcanic eruptions under the sea or landslides into the sea — is another kind of coastal inundation, but should not be confused with storm surge.)
- Storm Surge: An abnormal rise in sea level accompanying a hurricane or other intense storm, and whose height is the difference between the observed level of the sea surface and the level that would have occurred in the absence of the cyclone. Storm surge is usually estimated by subtracting the normal or astronomic high tide from the observed storm tide.
Source: Central Pacific Hurricane Center in Honolulu.