| Summary: | The representativeness of North Atlantic cyclone activity is assessed for the 15 January-15 March 1992 period of the second Canadian Atlantic Storms Program (CASP II). Explosive cyclogenesis is found to shift northeastward to a locus east of the Canadian seaboard along a sustained anomalous cyclone track. Active (inactive) periods are defined as comprising the quarter of the study period with the strongest (weakest) cyclone deepening: Of 24 Atlantic bombs, 14 (1) occur(s) during active (inactive) periods. During active periods, storms develop along strong baroclinic zones on the leading edge of southeasterly advancing Arctic air masses, and lead low-frequency oscillations in the position of an intensified Atlantic jet stream. Cyclone deepening shows heightened response to 500 hPa vorticity advection during active periods. Maximum deepening positions of explosive (weak) cases are preconditioned by negative (positive) 1000-500 hPa thickness anomalies 36-12 h ahead of the developing cyclones.
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