Research News

NASA Goes On-Line with Extra-Tropical Storm Tracks Atlas

If you're a weather fanatic, or if you've just ever wondered how stormy it was around the world on the day you were born, you can now find out. Scientists working with NASA have created a free on-line atlas that shows extra-tropical storm tracks between 1961 and 1998.

Frequency of Storms During the Winter of 1982 Image at Right: The greatest frequency of extra-tropical storms (reds) can be seen to occur along the path of warm ocean currents that follow the eastern seaboards of North America and Asia. These warm, poleward-moving currents create a large temperature contrast with the cold winter-time continents and supply energy that helps generate and strengthen storm systems. Note that a similar pattern of storms circumnavigates the cold continent of Antarctica. The scale used for the frequency plots represents the percent of time that a low pressure center (i.e. a storm) was found over a give location during the period of examination — in this case the 90 days from Dec. 1, 1981 to Feb. 28, 1982.

"Although the atlas was originally developed for use by climatologists investigating the impact of global warming on storms, the images and data have also been used by fisheries, foreign meteorological services, researchers tracking historic storms, and by teachers and students," said Mark Chandler, a Columbia University geologist at NASA's Goddard Institute for Space Studies (GISS), New York City.

Mean (Average) and Most Severe Storm Intensity of the 1982 Winter Image at Left: The intensity of storms in the atlas is defined by the central pressure level of the cyclone - lower pressures represent more intense storms. The "mean intensity" plots show the average central pressure of all storms that pass over a region during the time period, whereas the "most severe storm" plots show the lowest central pressure of any storm that crossed a region. In these maps the plots show that the strongest storms (red-purple) follow the warm ocean currents along the continental margins. In the Northern Hemisphere the storms tend to increase in severity as they traverse poleward, picking up energy as they go, until finally dissipating over the cold high latitudes. In general, the winter has more intense extra-tropical storms, because larger temperature contrasts exist between the continents and oceans during winter.

The on-line "Atlas of Extra-Tropical Cyclones 1961-1998" plots storm paths and statistics by tracking atmospheric low-pressure centers at sea level. The sea level pressures are calculated using data provided by the National Centers for Environmental Prediction and the National Center for Atmospheric Research (NCEP/NCAR) Reanalysis Project.

Fundamental information available about extra-tropical storm systems includes maps of storm frequency and intensity as well as plots of individual storms paths. In addition to the average intensity of storms over time, maps of the "most severe" storms are also calculated.

The global maps include individual monthly and seasonal averages for the years 1961 through 1998 and all frequency and intensity maps are available as either rectangular maps or polar projections (which provides a view of the tracks from both north and south poles). If a user chooses to download "Tracks," a grayscale image of the world is presented showing the tracks of all storms for the entire period selected. Together, the images presented in this atlas describe the state of the mid- and high-latitude storm tracks during much of the latter half of the 20th century.

Storm Tracks During the Winter of 1982 Image at Right: This image shows the individual paths of all storms between Dec. 1, 1982 and Feb. 28, 1982. Each dot represents the position of a low pressure cell (area) at midnight or noon (Greenwich Mean Time) and the lines connecting the dots indicate the projected path of the storm. Storms lasting less than 36 hours (three segments) are not plotted. Looking at the U.S., most of the storms develop on the lee side of the Rocky Mountains, where cool dry air from Canada mixes with warm moist air from the Gulf of Mexico.

In addition to images, the data is also available for download, along with an associated FORTRAN computer program. The program can be used to extract subsets of the database and places the information into report form. The reports identify how long a storm lasted, the latitude and longitude positions of storms at 12-hour intervals, the atmospheric pressure at the storm center (low pressure suggests a storm), as well as the day, month, year and time (Greenwich Mean Time).

Related Links

NASA GISS Atlas of Extratropical Storm Tracks

NCEP/NCAR Reanalysis Project

Media Contacts

Robert J. Gutro, NASA Goddard Space Flight Center, Greenbelt, MD. Phone: 301/286-4044

This article was derived from the NASA Goddard Space Flight Center Top Story.