The above images are Doppler radar images of Opal's precipitation bands and wind velocities as seen by the radar at Eglin AFB in the Florida panhandle.

Clicking on the top image will open a full size precipitation image taken 1612 UTC on October 4. Clicking the bottom image will open the wind velocity for the same time frame. You may also open another page to view radar images of the storm as it comes ashore.

Areas of precipitation strengths and velocities can be calculated using particle analysis techniques. For these images, 1 pixel equals 0.654 miles.

Download the velocity and precipitation folders for images to develop an animation sequence of each.

Note: The wind velocity scale associated with the velocity images indicate a "-" or "+". The + indicates the direction of the wind is towards the radar site and the - indicates the wind direction is away from the radar site.

The onset of WWII saw the invention and extensive use of RADAR (RAdio Detection And Ranging) as an instrument to detect aircraft. Not only did the early radars detect aircraft, but it was also noticed that rain clouds and in particular, thunderstorms were excellent reflectors of radar energy. It was this invention during the war that gave meteorologist their first views of the structure of weather systems. In fact, it was during a thunderstorm event in England in 1942 that the storm cells were tracked for approximately seven miles.

The radar is based upon the principle of radio waves beamed from the radar site, and striking an object. A small amount of the energy is reflected back (echo) to the site. The distance to the object is then calculated using the speed of the radio wave (speed of light) and the time required for the beam to leave the radar, strike the target, and return to the radar. Associated with radar energy is "ground clutter". Ground clutter is the reflection of strong radar echo.

After the war, great strides were made in the use of radar as an instrument in the observation, detection, and prediction of weather events. The use of this important instrument moved from just observing where weather events were occurring, to its development as a tool for precipitation totals, tracking of severe thunderstorms, observation of "hook" echoes associated with tornadoes, and the tracking of hurricanes.

The radar images seen on the Weather Channel and your local television stations are the result of the development of a new type of radar known as Doppler Radar (NEXRAD). Instead of just transmitting radio energy out and receiving the same energy, it uses the frequency shift which occurs when the reflected radio wave strikes a moving target. Doppler radar electronically compares the transmitted radio waves to the reflected radio waves and determines the direction and speed of the weather event. This feature allows meteorologist to predict very significant weather events such as tornadoes. In fact the use of Doppler radar has allowed meteorologist to predict these hazardous weather conditions ten to fifteen minutes in advance.

As a side note, Doppler radar is so sensitive that ghost images have been known to appear on the radar screen. These images are usually insects, flocks of birds, and even dust and dirt particles.

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