Large scale cyclone events in the North Pacific are instances of persistent cyclonic flow regimes that occur primarily during the cold season. These events are characterized by the formation of anomalously intense large-scale surface cyclones and extended and more equatorially displaced polar and subtropical jets. At maturity, during the winter season,these cyclones share characteristics of the positive phase of the Pacific-North American teleconnection pattern. As a consequence of their impact on North American weather, understanding the the development of these events as well as the characteristics of the larger-scale flow the arise following their development, will contribute to an understanding of the flow-dependent predictability associated with these events.

In this study, we present the results of a 25 year climatology of these events. In particular, we describe the distribution of these events over the N. Pacific (sorted by duration), the variation of events with respect to phases of ENSO, and the differences in composite evolution for cold and warm season events.

Additionally, using the adjoints of both research and operational NWP models, we study the sensitivity of growth of these cyclones to upstream initial conditions. Further, once these cyclones are established, we focus on the predictability of downstream flow over North America by identifying differences in the singular vector amplification factors for event and non-event periods.