AMS Forum: Climate Change Manifested by Changes in Weather


Extratropical Forecast Errors Associated with Tropical Heating Anomalies

Joshua P. Hacker, NCAR, Boulder, CO; and G. J. Hakim

Tropical convection produces Rossby waves that radiate into the extratropics and may interact with the prevailing midlatitude circulation. Significant extratropical weather forecast errors may result from these waves, particularly over the North Pacific ocean, where the Pacific jet serves as a waveguide for waves generated over the tropical Pacific warm pool.

While extensive attention has been given to the wave generation problem due to tropical convection, relatively less attention has been given to the forecast errors associated with these waves. Here we examine forecast errors associated with significant tropical heating anomalies by drawing a large sample of cases from the ensemble reforecasting project dataset available at the NOAA Climate Diagnostics Center (Hamill et al. 2006, Bull. Amer. Meteor. Soc.). Conditional sampling from the large sample is used to study the structure and importance of errors in the extratropical circulation relative to the tropics. Composite responses, and dominant patterns of tropical--extratropical covariability will be discussed for these events.

Session 3, THORPEX Special Session: Impacts of Processes over the Tropical Pacific and Indian Oceans on Mid-Latitude Weather and Predictability
Wednesday, 17 January 2007, 1:30 PM-5:15 PM, 214A

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