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Three‐dimensional evolution of ensemble forecast spread during the onset of a stratospheric sudden warming event in January 2006
Author(s) -
Nishii Kazuaki,
Nakamura Hisashi
Publication year - 2010
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.607
Subject(s) - climatology , environmental science , stratosphere , ridge , rossby wave , cyclone (programming language) , extratropical cyclone , jet stream , meteorology , sudden stratospheric warming , atmospheric sciences , polar vortex , geology , jet (fluid) , geography , physics , paleontology , field programmable gate array , computer science , computer hardware , thermodynamics
A singular value decomposition and a simple sensitivity analysis applied to an operational ensemble of monthly forecasts reveal that the prediction skill of a stratospheric sudden warming event observed in late January 2006 is particularly sensitive to uncertainty in the initial state in the vicinity of a developing synoptic‐scale cyclone that was observed over the North Pacific more than two weeks prior to the peak of the event. For the first few days in the forecast, a local maximum of the forecast spread around the cyclone is translated eastward across the Pacific in association with observed downstream development of synoptic‐scale disturbances. The spread then reaches the subpolar North Atlantic, where a blocking ridge was developing as the source of an upward‐propagating Rossby‐wave packet that gave rise to the deceleration of the stratospheric polar‐night jet (PNJ). Following the observed wave packet, the maximum forecast spread is translated upward from the ridge and finally reaches the stratosphere, causing a large forecast spread in the PNJ deceleration. Copyright © 2010 Royal Meteorological Society