Detecting DANGEROUS Weather Before the Storms STRIKE...

While reliable spotters remain the most important sources of information for detecting dangerous weather, radar and satellites also play a critical role in assisting the National Weather Service its primary mission of protecting lives and property.
Doppler Weather Radar

Weather radar operates by first sending out a pulse of electromagnetic energy from a large rotating antenna. When the pulse strikes rain, snow, ice or even insects, it is reflected back to the radar and the information is relayed to special computers. Usually the more intense the rain, the stronger the reflected signal or reflectivity. After processing, the information is converted  into color images on a screen with red usually indicating  very heavy rainfall or large hail. Doppler radar also has the capability to measure the wind speed and direction within a thunderstorm, allowing meteorologists to determine if the storm is producing damaging winds or stronger tornadoes. The radar can also estimate how much rain is falling at any given point.

Weather Satellites

Weather across the United States is monitored  by Geostationary Operational Satellites or the GOES system. GOES satellites are in orbit 22,238 miles above the equator and orbit the earth at the same speed as the earth is rotating. This keeps the satellites above the same spot throughout the year. The spacecraft carry sophisticated instruments which collect various types of data related to the surface, atmosphere and bodies of water across the planet. The data is processed by computers and converted to images used by meteorologists to observe and predict hazardous weather.

Visible images resemble photographic images, using sunlight reflected off  the clouds like a normal camera. Visible satellite images provide valuable information concerning the development, movement and intensification of thunderstorms but unfortunately are not available after dark. Infrared sensors measure the temperatures of the clouds and therefore provide useful information 24 hours a day. Data processors convert the temperature data into color images with certain colors representing a particular range of temperatures. Water vapor images show the amount of moisture in the middle and upper levels and are useful in assisting forecasters in locating such features as jet streams, upper disturbances and regions of deeper moisture, elements which are critical for stormy weather.

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