Anomaly and Mean Weather Patterns Associated with Extreme High and Low Temperatures during summer and winter in Southeast Alaska

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Sunday, 17 January 2010
Exhibit Hall B2 (GWCC)
Richard, C. Lam, NOAA/NWSFO, Juneau, AK

The Juneau Forecast Office, responsible for producing weather forecast products for Southeast Alaska, have to forecast extreme events such as heavy snow, heavy rain, high wind, flooding, low relative humidity, fog, and extreme temperatures. By learning more about the synoptic patterns associated with these anomalous events, forecast confidence can be enhanced. This study focuses on extreme low and high temperatures events in both summer and winter for zones 17 to 28. The top 20 events for each category are used to generate composite averages and anomalies. Weather patterns, associated with these extreme temperature events, such as surface pressure and temperature; 850-mb height and temperature; 700-mb height and relative humidity; 500-mb height and temperature; 300-mb height and wind are plotted and analyzed. Several conclusions can be made according to the evaluation of several cases. For example, to have extreme high summer temperatures in the Alaska Panhandle, there needs to be an anomalously strong surface high in the Yukon Territory in order to advect warmer and drier air from the Interior into the coastal region. On the other hand, the same high pressure may bring in anomalously cold air from the Arctic region to Southeast Alaska during winter months. However, there are still many unresolved questions from this project that needs to be answered. In summary, forecasting for Southeast Alaska is much more challenging then forecasting in the Lower 48.