Stratospheric Memory and Skill of Extended-Range Weather Forecasts
Mark P. Baldwin,1
David B. Stephenson,2
David W. J. Thompson,,3
Timothy J. Dunkerton,1
Andrew J. Charlton,2
Alan O'Neill2
We use an empirical statistical model to demonstrate significant skill in making extended-range forecasts of the monthly-mean Arctic Oscillation (AO). Forecast skill derives from persistent circulation anomalies in the lowermost stratosphere and is greatest during boreal winter. A comparison to the Southern Hemisphere provides evidence that both the time scale and predictability of the AO depend on the presence of persistent circulation anomalies just above the tropopause. These circulation anomalies most likely affect the troposphere through changes to waves in the upper troposphere, which induce surface pressure changes that correspond to the AO.
1 Northwest Research Associates, 14508 NE 20th Street, Bellevue, WA, 98007, USA.
2 Department of Meteorology, University of Reading, Reading RG6 6BB, UK.
3 Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523, USA.
