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Tropical convection interaction with Alaskan weather

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Thursday, 27 January 2011
Tropical convection interaction with Alaskan weather
Bill Ludwig, NOAA/NWSFO, Anchorage, AK

Large areas of deep tropical convection can affect mid-latitude upper level flow by setting up Rossby wave trains. When the convection is nearly stationary or progressing slowly, these Rossby wave trains can be fairly persistent and can be a predictor for weather in the medium range (3-7 days). These wave trains often span across Alaska due to its longitudinal proximity downstream of the active convective areas of the Pacific/Indian Ocean warm pool.

This study looks at two of those patterns and their effect on Alaska weather using several case studies. Outgoing longwave radiation (OLR) is used as a proxy for tropical convection, and Hovmoller diagrams and Wheeler plots are examined as well. Maps of anomalous 150 mb winds are employed to show the Rossby wave trains. This study also explores the weather prediction potential for Alaska based on the location of the tropical convection.