An Operationally Useful Relationship Between the Polar Jet Stream and Heavy Precipitation

The jet stream is recognized as an important atmospheric mechanism for vertical exchange processes. It follows that certain jet stream positions relative to moisture source regions bring about occurrences of extensive heavy rainfall. One type of such occurrence, mainly in the central United States, is identified with a “digging” polar jet stream. To better understand the meteorological relationships involved, we developed composite models from seven representative cases and studied one unusually heavy rainfall situation in more detail. For this type, there is a tendency for heavy rainfall to occur in an ellipsoidal pattern in advance of the polar jet stream.