Tropical Cyclone location and intensity data
The World Meteorological Organization (WMO) has assigned the task of forecasting tropical cyclones to different agencies in different regions. For instance, NOAA’s National Hurricane Center in Miami, FL, USA provides forecasts for the North Atlantic and Eastern Pacific. The Central Pacific Hurricane Center in Honolulu, Hawaii provides forecast for the Central Pacific. Several other countries have responsibility for providing forecasts in other regions (such as Japan, Australia, India, etc.). These same agencies that produce forecasts of tropical storms, also produce post season analysis of each storm’s position and intensity – which is called best track data.
In addition to the WMO agencies, numerous other entities forecast and provide best track data. For instance, countries often provide the capability in their nation’s interest, such as China forecasting storms in the Western Pacific. The U.S. Joint Typhoon Warning Center (JTWC) provides forecasts for U.S. interests around the world. These agencies also provide best track data which overlap best track data from other agencies. However, there is not always complete agreement between organization on the strength of a given tropical cyclone. This is often due to different data available to each agency, different procedures in place for forecasting systems, personnel, etc.
The data available to study, forecast and understand tropical cyclones has changed significantly through time and varies from agency to seo agency. Prior to the 1940s, the primary observations came from ships and land-based weather stations. Beginning in the 1940s, the U.S. military began testing – and later made operational – flights into Typhoons (in the West Pacific) and Hurricanes (in the North Atlantic). They found that these reconnaissance flights could be conducted safely and that they provided a wealth of information on the storm’s structure, intensity and environment. Routine aircraft reconnaissance in the Western Pacific ended in 1987 but still continues today in the North Atlantic.
The satellite era was ushered in during the 1960s, providing more information on tropical cyclones. Numerous studies began relating cloud forms to intensity, which culminated in the Dvorak Technique in 1984. However, the availability and quality of satellite data varied, with some agencies still receiving imagery by fax in the 1990s. Similarly, newer satellites provide a wealth of information beyond imagery – microwave satellites provide information on storm structure, radar satellites observe precipitation and other satellites measure wind speed at the ocean’s surface. Again, different agencies have different levels of access to this data.
The result is 1) best track data has changed in time as availability of data changes and 2) best track data varies between agency, due in part to access to different data and routine procedures. This means that differences occur in the best track record.
More information on the WMO agencies is available here.
More information on IBTrACS is available here.
Image provided by MeteoFrance