By AIR Worldwide | July 15, 2021

We can all understand intuitively that a super typhoon is a stronger storm than a regular typhoon, but when does it become one? The National Hurricane Center labels Category 3 hurricanes and higher (with wind speeds above 111 mph) as major hurricanes. Is there a comparable benchmark for typhoons? It’s complicated.

Typhoon and hurricane are two of the regionally specific names for strong tropical cyclones—defined by NOAA as rotating, organized systems of clouds and thunderstorms that originate over tropical or subtropical waters and have closed, low-level circulation. What a tropical cyclone gets called is determined by the ocean it forms over and how severe it becomes. In the North Atlantic, central North Pacific, and eastern North Pacific, tropical cyclones are called hurricanes; in the Northwest Pacific, they are known as typhoons.

The well-known Saffir-Simpson Hurricane Wind Scale is used to categorize hurricanes in the North Atlantic (and northern Pacific Ocean east of the international date line). Their maximum sustained surface wind speed (peak 1-minute wind at the standard meteorological observation height of 10 meters (33 feet) over unobstructed exposure) determines which of the five categories storms are assigned.

The Joint Typhoon Warning Center

The U.S. Navy and U.S. Air Force together operate the Joint Typhoon Warning Center (JTWC) headquartered in Hawaii. The JTWC’s role is to provide the U.S. Department of Defense and other U.S. government agencies with tropical cyclone warnings in the North-West Pacific Ocean, South Pacific Ocean, and Indian Ocean. The JTWC is not an official member or participant in the World Meteorological Organization (WMO), a specialized agency of the United Nations dedicated to international cooperation and coordination on the state and behavior of the Earth’s atmosphere.

JTWC places typhoons into five categories using 1-minute sustained winds to determine which category a storm falls into. Its warnings are therefore comparable to those using the Saffir-Simpson Scale but its categorizations of storms, although widely reported, are unofficial. Within the western North Pacific JTWC designates tropical cyclones of 150 mph or greater super typhoons; such storms are the equivalent of a strong Category 4 or 5 hurricane on the Saffir–Simpson Scale.

The Official Agencies

In meteorology and related disciplines, the WMO is the international standardization organization. Its technical regulations provide standards and recommended practices and procedures adopted by the World Meteorological Congress for use by all members. Together the Economic and Social Commission for Asia and the Pacific (ESCAP) and the WMO support a Typhoon Committee to “promote and coordinate the planning and implementation of measures required for minimizing the loss of life and material damage caused by typhoons.” This Typhoon Committee uses estimated maximum sustained winds over a 10-minute period to sort typhoons within the Pacific basin into four separate classifications ranging from Tropical Depression to Typhoon (sustained winds of ≥73 mph); they do not have a super typhoon classification.

The official agency for cyclone warnings and watches in the Western Pacific is the Japan Meteorological Agency (JMA). Within Japan, JMA uses its own system for typhoon reporting and warnings but to meet its international obligations its Regional Specialized Meteorological Center (RSMC) Tokyo - Typhoon Center provides information on tropical cyclones in the western North Pacific and the South China Sea within the framework of the WMO’s World Weather Watch (WWW) Program. The Typhoon Center gathers information on tropical cyclones and disseminates it, particularly to members of the Typhoon Committee. The term super typhoon is not employed.

Across the Western Pacific and eastern Asia members of the Typhoon Committee issue typhoon watches and warnings for their local areas in consultation with other members. Of the 14 member states, China and the Philippines both use the term super typhoon.

The China Meteorological Agency (CMA) and the Hong Kong Observatory (HKO) each have three categories for typhoons, with the strongest (with winds above 120 mph) termed super typhoons; the CMA uses 2-minute sustained winds when assigning a category, however, while the HKO uses 10-minute sustained winds.

Since 2015 the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) has used five categories based on the strength of the storm’s winds, each associated with a different warning flag color. The most severe, a tropical cyclone with maximum wind speed exceeding 137 mph, is given storm signal #5 (purple) and designated a super typhoon. (The Manila Typhoon Center, however, considers a system to be a super typhoon once its winds reach or exceed 124 mph.)

What Does AIR Do?

To avoid confusion, when reporting or discussing typhoons (and other tropical cyclones) AIR consistently provides 1-minute sustained wind speeds and states which category on the Saffir-Simpson Scale this wind speed is equivalent to. Following JTWC practice, we employ the term super typhoon only for storms in the Northwest Pacific with 1-minute sustained winds in excess of 150 mph.

Will Typhoon Losses in Japan Keep Increasing? View the Infographic

Categories: Tropical Cyclone

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