NASA Satellite Catches a Hurricane Transforming Itself
Hurricanes can completely re-structure themselves inside. Recently, a NASA satellite was able to see Hurricane Ophelia in 2005 rebuild the clouds and rains around its open “eye” of the storm.
Image to right: This is an image of Hurricane Ophelia (2005) from the Geostationary Operational Environmental Satellite (GOES)-12 during the storm's warm-core tropical stages. Credit: Naval Research Laboratory, Marine Meteorology Division.
Because hurricanes can re-structure themselves, it makes it difficult for forecasters to predict the strength of their rains and wind and to predict the kind of damage a hurricane can do when it strikes land.
Recently, scientists used data from NASA’s Tropical Rainfall Measuring Mission (TRMM) satellite to study the changes that take place inside a hurricane. Stephen Guimond, a graduate research assistant at Florida State University, Tallahassee, Fla., lead a study that used TRMM data to see temperature changes and melting ice near the eye of several tropical cyclones (the generic name for hurricanes or tropical storms), including Hurricane Ophelia in 2005.
Image to left: This image, also from the GOES-12 satellite, shows Hurricane Ophelia (2005) interacting with a mid-latitude front draped across the northeastern U.S. as it loses some of its tropical characteristics. Credit: Naval Research Laboratory, Marine Meteorology Division.
"The temperature structure of a tropical cyclone is directly related to a storm’s wind speed and rainfall, which indirectly affects the storm surge,” Guimond said. Storm surge is water that is piled up ahead of a hurricane, and when the storm makes landfall the water can flood coastal areas like beaches and low lying areas further inland. It is important to watch a storm’s inside temperatures because it helps meteorologists estimate how a hurricane will affect places where it makes landfall. By knowing this information, forecasters will have a better idea about high winds, flash flooding and large storm surge.
Many tropical cyclones transform into what are called “extra-tropical storms” as they move northward out of the tropics and into the mid-latitudes. During this stage, the storm’s clouds and high winds spread out over a wide area. As a result, the chance for heavy rainfall and large storm surge increases far from the eye of the storm, which would affect life and property of more areas in the path of the hurricane.
Image to right:The Tropical Rainfall Measuring Mission (TRMM) satellite's Precipitation Radar instrument captured this view of Hurricane Ophelia on September 14, 2005. This TRMM image was overlaid with visible imagery from the GOES-12 satellite to show more detail. The light yellow lines represent the path of the TRMM satellite's track and the light green below the storm's eye indicates the heaviest rainfall. Credit: Naval Research Laboratory, Marine Meteorology Division
When Guimond and his colleagues at the Naval Research Laboratory in Monterey, Calif. looked at the data from TRMM’s Precipitation Radar instrument, they could see the temperature changes inside a tropical cyclone. One piece of information that gave researchers a clue that a storm was becoming extra-tropical was that ice particles, which are found high up in the cold regions of thick clouds surrounding the eye of the storm, melted at lower levels. Usually, when a tropical cyclone is still in the “tropical stages,” ice particles melt higher in the clouds.
By analyzing when and where ice particles are melting in tropical cyclones, researchers can better understand the various stages of an extra-tropical storm. This knowledge will help scientists re-create storms on computer forecast models, which can assist in the forecasting of future tropical cyclone transformations.
Image to left: This animation (click on image to view animation - no audio - 4.5 Mb) shows the coverage of the TRMM satellite during the life cycle of Typhoon Meari (2004) in the western Pacific Ocean when the storm changed from tropical to extratropical. In the beginning of the animation during Meari's tropical (warm-core) stages, the cloud tops are very high and clustered close to the storm center. However, as Meari enters the mid-latitudes and begins change into an extratropical storm (cold-core), the cloud tops are not quite as high and are moved away from the storm center. As a result, the large amounts of rainfall, high winds and storm surge expand and get shifted away from the storm center potentially affecting larger amounts of people. Credit: FSU
There is another benefit to using the data from NASA’s TRMM radar. Guimond said that the heat data from the satellite reveals information on storm strength and also gives clues about how a storm formed. This will help hurricane forecasters and researchers gain a better sense of how the tropical cyclone will develop in the future.
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