Values of the standard anomalies are retrieved from the NCEP-NCAR Global Reanalysis dataset (17 pressure levels on 2.5 by 2.5 degree grids). A nine by nine array of grid point values for the four fields listed earlier have been excerpted for more than 200 flooding events in the Northern Hemispheric mid-latitudes. The flooding events came from three sources: The National Climate Data Center's Event's database, CMORPH and the Encyclopedia Britannica's disaster articles from 1979 to 1999.
It will be shown that identifiable flood patterns differ by regions and seasons based on the moisture sources and lifting mechanisms. Patterns will be distinguished by six categories: cold season western continental, warm season western continental, cold season eastern continental, warm season eastern continental, cold season central continental, and warm season central continental.