37CVC Short-term Dependence Between the Arctic Oscillation (AO) and Pacific-North-American (PNA) Indices and its Connection to Predictability and Standard Flow Indices

The Arctic oscillation (AO) and the Pacific North American (PNA) oscillation are two prominent atmospheric modes of variability in the Northern Hemisphere. Here it is shown that the corresponding AO and PNA indices exhibit anomalous fluctuations that have dependence on short-term (e.g. monthly) timescales. This short-term dependence is measured through a local correlation coefficient (LCC). Recent results are presented that demonstrate that the LCC has a relationship to forecast skill, and that this relationship extends to forecast dropouts, which are acute but significant losses of forecast skill. The underlying properties of the LCC time series are further explored, showing apparent seasonal preferences and low-frequency variability. Lagged regression and other analytics suggest that extreme values of the LCC have connections to intervals of elevated or suppressed tropical cyclone accumulated cyclone energy (ACE), 500 hPa wave activity, and Eady index of baroclinic instability. Indications are also found that the extreme LCC is linked to amplitude anomalies of the Madden-Julian Oscillation (MJO) during particular phases of the MJO.