Cyclone
In case anyone else was curious why they are calling the storm in the Gulf a Cyclone.
What's the difference between a tropical cyclone and a hurricane?
What's a cyclone and why is the National Hurricane Center using that term to describe storms in the Caribbean and Gulf of Mexico? What happened to the normal words - tropical depression, tropical storm and hurricane?
The questions popped up from various NOLA.com | The Times-Picayune readers in response to updates over the weekend about a low pressure system in the Gulf of Mexico that's likely to become at least a tropical depression this week.
Cyclone is a catch-all phrase, according to Phil Grigsby, a meteorologist with the National Weather Service's New Orleans/Baton Rouge office, based in Slidell.
"It covers all the bases," he said Monday morning (June 19).
A cyclone is an umbrella term and includes a tropical depression, a tropical storm and a hurricane. Forecasters will continue to use those terms, he said, but when it is early, a "cyclone" update is the preferred term because it includes all possibilities.
But don't confuse a cyclone with a typhoon. A typhoon is the the name for hurricanes in the Pacific west of the International Dateline.
Here are the official definitions from the National Hurricane Center of frequently used terms (read more):
Cyclone:
An atmospheric closed circulation rotating counter-clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.
A tropical cyclone in which the maximum sustained surface wind (using the U.S. 1-minute average) is 64 kt (74 mph or 119 km/hr) or more. The term hurricane is used for Northern Hemisphere tropical cyclones east of the International Dateline to the Greenwich Meridian. The term typhoon is used for Pacific tropical cyclones north of the Equator west of the International Dateline.
Subtropical Cyclone:
A non-frontal low-pressure system that has characteristics of both tropical and extratropical cyclones. Like tropical cyclones, they are non-frontal, synoptic-scale cyclones that originate over tropical or subtropical waters, and have a closed surface wind circulation about a well-defined center. In addition, they have organized moderate to deep convection, but lack a central dense overcast. Unlike tropical cyclones, subtropical cyclones derive a significant proportion of their energy from baroclinic sources, and are generally cold-core in the upper troposphere, often being associated with an upper-level low or trough. In comparison to tropical cyclones, these systems generally have a radius of maximum winds occurring relatively far from the center (usually greater than 60 n mi), and generally have a less symmetric wind field and distribution of convection.
Subtropical Depression:
A subtropical cyclone in which the maximum sustained surface wind speed (using the U.S. 1-minute average) is 33 kt (38 mph or 62 km/hr) or less.
Subtropical Storm:
A subtropical cyclone in which the maximum sustained surface wind speed (using the U.S. 1-minute average) is 34 kt (39 mph or 63 km/hr) or more.
Tropical Cyclone:
A warm-core non-frontal synoptic-scale cyclone, originating over tropical or subtropical waters, with organized deep convection and a closed surface wind circulation about a well-defined center. Once formed, a tropical cyclone is maintained by the extraction of heat energy from the ocean at high temperature and heat export at the low temperatures of the upper troposphere. In this they differ from extratropical cyclones, which derive their energy from horizontal temperature contrasts in the atmosphere (baroclinic effects).
Tropical Depression:
A tropical cyclone in which the maximum sustained surface wind speed (using the U.S. 1-minute average) is 33 kt (38 mph or 62 km/hr) or less.
Tropical Storm:
A tropical cyclone in which the maximum sustained surface wind speed (using the U.S. 1-minute average) ranges from 34 kt (39 mph or 63 km/hr) to 63 kt (73 mph or 118 km/hr).
Tropical Wave:
A trough or cyclonic curvature maximum in the trade-wind easterlies. The wave may reach maximum amplitude in the lower middle troposphere.
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Originally Posted by Timsmith
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