Cutoff cyclones are associated with many significant forecasting problems throughout the world, but particularly so in the northeastern United States. Given the complex terrain found in the Northeast, the precipitation distribution associated with slow-moving cutoff cyclones is often a challenge to predict and can wreak havoc among local communities.

A climatology of warm season (1 May - 30 September) 500 hPa cutoff cyclones is derived from twice daily (0000 and 1200 UTC) 500 hPa gridded geopotential height fields. The data used are analyses from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis dataset: 1951-2001.

A cutoff cyclone is defined as a geopotential height minimum surrounded by at least one closed contour based on a 30 m interval. Cutoffs cyclones meeting this objective criterion are identified and catalogued. Cyclone tracks are determined to delineate favored areas for genesis/lysis and to locate “cutoff cyclone corridors.” Frequency diagrams showing total number of cutoff cyclones and number of “cutoff 12 h periods” are presented for the Northern and Southern Hemispheres and for eastern North America.

In-progress and future work includes creating objectively derived decadal subsets to see if there are trends for the orientation of the “cutoff cyclone corridors,” and correlating favorable areas of cutoff events with significant large-scale circulation teleconnection indices such as the North Atlantic Oscillation (NAO), Pacific-North American Index (PNA), and Southern Oscillation Index (SOI). Our cutoff climatology will also be used in conjunction with the Unified Precipitation Dataset (UPD) to map precipitation distributions in cutoff cyclones over the northeastern United States.