Weather radar provides a dynamic view of precipitation, helping us understand current weather conditions and anticipate what is approaching. These systems transmit signals that bounce off precipitation, like raindrops or snowflakes, and return to the radar. By analyzing these returning signals, meteorologists can determine the location, movement, and intensity of precipitation. The information is then translated into a visual display, commonly seen as a map with various colors representing different precipitation levels.
How Radar Colors Work
Weather radar operates by sending out microwave pulses into the atmosphere. When these pulses encounter precipitation, a portion of the energy scatters back to the radar antenna. The strength of this returning signal, known as reflectivity, is measured in decibels of Z (dBZ). Higher dBZ values indicate a stronger return signal, correlating with larger and more numerous precipitation particles and signifying more intense precipitation.
Radar displays translate these dBZ values into a spectrum of colors for easier interpretation. The color scale progresses from cooler colors like blue and green for lighter precipitation to warmer colors such as yellow, orange, and red for increasingly heavier precipitation. This general progression allows for a quick visual assessment of precipitation intensity.
Understanding Yellow on Radar
On a typical weather radar display, yellow signifies moderate rainfall intensity. This level of precipitation is stronger than the light rain depicted by greens but less intense than the heavy rainfall or severe weather indicated by oranges and reds. Yellow radar returns generally correspond to reflectivity values in the range of 35 to 50 dBZ.
Moderate rain associated with yellow can produce rainfall rates of up to three-tenths of an inch per hour. While not typically associated with severe weather like strong thunderstorms or hail, yellow indicates a steady amount of rain. This intensity may sometimes accompany light thunder or lightning.
Practical Implications of Yellow Radar Returns
When yellow appears on weather radar, it indicates moderate rain is occurring or approaching. This level of precipitation usually requires an umbrella or rain gear if outdoors. Drivers can expect reduced visibility and will need to operate windshield wipers continuously.
Moderate rainfall can also lead to larger puddles, and if it persists, may cause ponding in low-lying areas. While yellow on radar does not typically signal an immediate threat requiring evacuation or shelter, it warrants caution. It signifies a noticeable impact on daily activities and travel.