Submonthly Forecasting of Winter Surface Air Temperature in North America Based on Organized Tropical Convection

Abstract

Using outgoing longwave radiation (OLR) data as a proxy for tropical convection, the relationship between the Madden-Julian Oscillation (MJO)-related tropical convection and North American winter surface air temperature (SAT) is investigated. A lagged regression analysis between one of the leading OLR principal components (PCs) and SAT shows highly significant correlations over south-southeastern Canada, with the strongest SAT anomalies occurring at a lag of 2 to 3 pentads. The lagged temperature composite shows an extensive intensified positive SAT anomaly over southern Canada and the northern United States 10–15 days after the occurrence of enhanced convection over the Indian Ocean and the Maritime Continent and reduced convection near the tropical central Pacific. The lagged regressions of 500 hPa geopotential height with the OLR PC reveal a wave train propagating from the tropics to North America. This observation has been reproduced in a simple general circulation model (SGCM) with an idealized forcing that mimics the tropical MJO convection anomaly. A simple regression model is constructed to predict winter SAT over North America with tropical MJO convective activity as the single predictor. Under a cross-validation framework, this statistical model produces 10–15 day SAT forecasts with modest, yet statistically significant, skill in winter over North America.