– An instrument used to detect precipitation by measuring the strength of the electromagnetic signal reflected back. (RADAR= Radio Detection and Ranging)

– See ground fog.

– An instrument attached to a weather balloon that measures and transmits pressure, humidity, temperature, and winds as it ascends.

– Precipitation of liquid water particles which, in contrast to drizzle, are widely separated and larger in size.

– Optical phenomenon when light is refracted and reflected by moisture in the air into concentric arcs of color.

(RH)

– To move backwards. It relates to a ridge or trough moving from east to west. Typically in the mid-latitude, troughs and ridges move west to east. Retrograde motion is the opposite movement of normal.

– River Forecast Center. The California/Nevada River Forecast Center is located in Sacramento.