Predictability of anomalous storm tracks

Gil Compo
NOAA-CIRES Climate Diagnostics Center

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Abstract

The present study details a global comparison of changes of variance on synoptic (2-7 days), intraseasonal (8-45 days), monthly, and seasonal timescales associated with ENSO. The results suggest that the patterns of variance changes associated with ENSO differ in the extratropics depending on timescale, while they are nearly the same in the Tropics across timescales. We estimate the predictability of synoptic variance anomalies associated with anomalous storm tracks and compare this to the predictability of seasonal mean precipitation and 500 mb height. We make quantitative estimates of the predictability based on a previously-derived analytical expression that is valid for any distribution. NCEP/NCAR Reanalysed data (1948-2000) and general circulation model (GCM) simulations of northern hemisphere winter (January through March) are used. The NCEP atmospheric GCM is integrated with prescribed seasonally-evolving sea surface temperatures for warm, cold, and neutral ENSO conditions. 180 seasonal integrations, differing only in initial condition, are made for observed climatological mean SSTs, 180 with SSTs for an observed warm event (1987), and 180 with SSTs for an observed cold event (1989). With this 540-member ensemble, we show the potential predictability of seasonal means and storm track anomalies even in regions not usually associated with an ENSO effect.

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18 Oct, 2000
3:30 PM/ DSRC 1D 403
(Coffee at 3:20 PM)
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