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ABSTRACT:
A statistical learning method called random forests is applied to the prediction of transitions between weather regimes of wintertime Northern Hemisphere (NH) atmospheric low frequency variability. A dataset composed of 55 winters of NH 700-mb geopotential height anomalies is used in the present study. A mixture model finds that the three Gaussian components that were statistically significant in earlier work are robust; they are the Pacific North America (P N A) regime, its approximate reverse (the reverse P N A, or RN A), and the blocked phase of the North Atlantic Oscillation (BN AO). The most significant and robust transitions in the Markov chain generated by these regimes are P N A -> BN AO, P N A -> RN A and BN AO -> P N A. The break of a regime and subsequent onset of another one is forecast for these three transitions. Taking the relative costs of false positives and false negatives into account, the random-forests method shows useful forecasting skill. The calculations are carried out in the phase space spanned by a few leading empirical orthogonal functions of dataset variability. Plots of estimated response functions to a given predictor confirm the crucial influence of the exit angle on a preferred transition path. This result points to the dynamic origin of the transitions.

SUGGESTED CITATION:
Dmitri Kondrashov, Jie Shen, Richard Berk, F. D'Andrea, and M. Ghil, "Predicting Weather Regime Transitions in Northern Hemisphere Datasets" (October 22, 2006). Department of Statistics, UCLA. Department of Statistics Papers. Paper 2006102201.
http://repositories.cdlib.org/uclastat/papers/2006102201