Anomalous Propagation Case Study

A line of showers and thunderstorms moved through North Central Texas during the morning of July 5, 2005. As the dissipating line moved though the Dallas/Fort Worth Metroplex, another area of dissipating showers was occurring to the north of the radar, west of Interstate 35, then apparently redeveloping and becoming strong, all in a span of 40 to 50 minutes.

One clue as to what is occurring is the dissipating showers. For strong superreflectivity, there needs to be a very moist layer of air near the ground with an inversion and very dry layer above it. The showers indicated both were occurring in this region as they were dissipating because of their motion into the dryer air while the rainfall from the showers helped provide the moist low layer.

However, the best way to determine if the developing storms are real or not is to look at that same region from an adjacent radar. Always look at adjacent radars to verify what is occurring in your region. Also, a look at the satellite image during this time did not indicate any clouds.

Why did the storms "disappear" suddenly? There are some tweaks to the Doppler radar's operation that provides the ability to diminish AP although it cannot always be completely eliminated. The light blue colors in the top half of the last of the looping images, while not indicating any rain, do hint the atmospheric conditions for producing AP were still present.

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