JARGON

Hurricane vocabulary: The difference between a typhoon, a cyclone, and a tropical storm

The end of August into September is peak hurricane season, which means ever-expanding news coverage full of weather-related storm terms that you might find relatively unfamiliar.

Here is a list of some of the more common hurricane-related terms you should know as three major storms rage in the warm waters around the United States:

American GFS model is the Global Forecast System storm model run by the National Weather Service that predicts a storm’s projected path. It uses a supercomputer to run data through a complex algorithm pulled from satellites, observation stations, and weather balloons.

The best track is a smoothed representation of a storm’s location and intensity over its lifetime. The best track contains the storm system’s latitude, longitude, maximum sustained surface winds, and minimum sea-level pressure at six-hour intervals, based on a post-storm assessment of all available data.

The European model is considered by meteorologists to be the most accurate model for predicting hurricanes in the mid-latitudes. The European Centre for Medium-Range Weather Forecasts (ECMWF), which runs the model, developed a its method for integrating real-time meteorological data into their algorithm (so it starts with more accurate initial conditions), and invested in very advanced computer hardware. Both the European and the American models are predictive mathematical models, so they don’t necessarily reflect the hurricane path issued by the National Hurricane Center.

The eyewall is the band or ring of cumulonimbus clouds that surround the eye of the storm. The most severe weather of the hurricane occurs in the eyewall: Towering thunderstorms, heavy rainfall, and high winds.

The Fujiwhara effect occurs when two tropical cyclones orbit around one another.

A hurricane is a tropical cyclone with maximum sustained winds of 74 mph.

The hurricane categories are a naming convention system. Hurricanes are classified into five categories based on the intensities of their sustained winds, which is known as the Saffir-Simpson hurricane wind scale.

  • Category 1: Winds speeds of 74-95 mph; very dangerous winds will produce some damage
  • Category 2: Wind speeds of 96-110 mph; extremely dangerous winds will cause extensive damage
  • Category 3: Wind speeds of 111-129 mph; devastating damage will occur
  • Category 4: Wind speeds of 130-156 mph; catastrophic damage will occur
  • Category 5: Wind speeds greater than 156 mph; catastrophic damage will occur and most areas will be uninhabitable

A hurricane warning is an announcement that hurricane conditions (sustained winds of 74 mph or higher) are expected somewhere within the specified area in association with a tropical storm.

A hurricane watch is an announcement that hurricane conditions (sustained winds of 74 mph or higher) are possible within the specified area in association with a tropical storm.

Latent heat is the heat required to convert a solid into a liquid or vapor without a change in temperature. When water vapor condenses to form clouds, latent heat (energy) is released, which helps storms intensify by warming the surrounding air and causing instability.

A major hurricane has winds greater than 110 mph.

Maximum sustained winds is the standard measure of a tropical cyclone’s intensity. It refers to the highest one-minute average wind speed (at an elevation of 10 meters with an unobstructed exposure) associated with that weather system at a particular point in time.

A monsoon is not a storm, but a large-scale, seasonal wind shift over a region accompanied by large amplitude seasonal changes in precipitation (whether heavy rains or draught).

The radius of maximum winds is the distance from the center of a tropical cyclone to the location of the cyclone’s maximum winds. In well-developed hurricanes, the radius of maximum winds is typically at the inner edge of the eyewall.

A storm surge is the rise in sea levels following a hurricane or major storm, where the height is the difference between the observed sea level and the level the water would be without a cyclone. Storm surge is usually estimated by subtracting the normal high tide from the observed storm tide.

A storm tide is the actual level of sea water resulting from the normal tide combined with the storm surge.

A tropical cyclone is a general term for warm weather storm systems that occur over tropical waters, such as tropical storms, hurricanes, and typhoons. A cyclone has a well-defined center, and rotates counter-clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.

A tropical depression is a tropical cyclone with a maximum sustained wind speed of less than 39 mph.

A tropical storm is a tropical cyclone with maximum sustained wind speeds between 39 mph and 73 mph.

A typhoon is a tropical cyclone that forms in the Pacific Ocean between 180° and 100°E, with winds of 74 mph or greater. Typhoons are the same weather phenomena as hurricanes; the only difference between them is the location where the storm occurs.

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