Spying on Storms

The cloud cover that often accompanies tropical storms, obscuring potentially dangerous developments from the eyes of forecasters, just got a whole lot clearer. With the help of two orbiting NASA satellites, scientists can now see through the clouds into the storms below and search for telltale signs of hurricane formation.

Unlike most weather satellites, which can watch only the storm surface, these storm spies sport cloud-penetrating microwave sensors. One of the satellites, dubbed QuickSCAT, conducts daily surveys of 90 percent of the ice-free oceans, using a so-called radar scatterometer to measure surface wind speed and direction. In the QuickSCAT image at the right, for example, purple and blue regions indicate slower winds, and pink and yellow areas represent high winds. Data on rainfall and sea surface temperature are collected by the Tropical Rainfall Measurement Mission (TRMM) satellite.

According to a new study conducted by NASA and NOAA scientists, 1999 QuickSCAT data could be used to identify potential hurricanes one to three days in advance of warnings issued by the National Hurricane Center. And a study published earlier this year demonstrated the QuickSCAT and TRMM data combined could help portend a hurricane's particulars. "Hurricanes are especially devastating when they are accompanied by strong winds and heavy rain," observes W. Timothy Liu of NASA's Jet Propulsion Laboratory. "QuickSCAT and TRMM provide the only opportunity for us to view the interplay between wind and rain before landfall, and help us to understand and predict hurricanes."