Analogs

1. Analogs • Done the correct way the Analog method has validity to it.  But the key thing to keep in mind is that when you are choosing a analog year you must choose one which matches the current set of conditions.  To simply assumed that all El Nino events  produce ONLY one set of conditions in the winter months  is of course folly.  Some of the most severe winters in the last 100 years have been El Nino winters and likewise.... some of the most mild winters in the last 100 years have also been El Nino winters.  

2. Analogs • On the other hand some forecasters hold  the view that analogs are not very helpful since weather records are incomplete or not sufficient enough to be considered as complete data source.  For most locations temperature and precipitation data only extends back 100 or 130 years and accurate upper air maps only go back 70 years at best . This argument is valid.  Thus ANY seasonal forecast using analogs that are based on ONE parameter is a very risky and has a high degrees of failure  built within the forecast. • One way of getting around this is to use several factors parameters and cross matching the analogs to look for common ground. (DT)

3. Analog Years • ENSO state a significant parameter in assigning analog years. • Atlantic SST anomaly also a significant parameter. • Atlantic oscillation • QBO • PNA • NAO not a good parameter for an analog • Hurricane season has never had a strong correlation when it comes to analog years.

4. Seasonal Analogs and Long Range Analogs (November/December 2006) CDC Interactive Plotting Page Analogs for Nov 2006 1. 1994 2. 1956 3. 1972 4. 1973 5. 1998 6. 1999 CDC Interactive Plotting Page (2) Composite Temperature Anomalies for November Analogs Years Relative to 2006 Composite Temperature Anomalies for December 2006 Relative to November 2006 Analog Years Composite Temperature Anomaly for December 2006

5. Using Analogs to Forecast in the Medium Range Day 11 Analogs Day 11 Analogs