Legend White lines + values = height contours at 700 hPa, each 4 gpdam. Colored zones = vertical motion 700 hPa each 2 hPa on which: positive values = downwards motion, negative values = upwards motion Useful for: negative values indicate frontal activity or instability, positive values indicate subsidence. For the negatives values: long elliptic zones indicate frontal zones, more individual cells usually indicate zones of more structured instability like troughs, region of showers. Structured negative fields near mountains are a strong indication for active orographical precipitation.