Analogues are a tool in producing long range forecasts. They involve a reanalysis of years combined into one based on a certain topic or a combination of topics such as El Niño Southern Oscillation (ENSO), sea surface temperature (SST) anomalies and the Quasi Biennial Oscillation (QBO). Analogues are based on historical occurrences but as every year is unique in their own right with weather, sometimes analogues can be very wrong especially if something has never happened before.
Onto the main subject of this blog post, how do I make an analogue?
Well, firstly I have to think of the topic of the analogue. What am I going to base my analogue off of? I gave some examples of such topics above like ENSO. Other examples may include the conditions / patterns of preceding months during the year, solar activity, Pacific Decadal Oscillation (PDO), Atlantic Multidecadal Oscillation (AMO) etc. After I come up with my topic for the analogue, I research years that had similar events to the current year of the topic like similar solar activity progression, similar ENSO conditions, similarly warm/cold or dry/wet conditions etc. I look up on sites like NOAA, SILSO and the UK Met Office regional series page for the years or data. You can find the links to these sites over on my useful links page here. After I complete the mentioned tasks above, I go to NOAA's composite generators. The generator I choose depends on the years in my analogue. For example, I'm gonna use the NOAA 20th Century Reanalysis v2c monthly composite generator for analogues that have years within 1851 to 2014 but I'm gonna use NOAA's monthly/seasonal composite generator for analogues that have years from 1948 to present. You can also find the links to these over on my useful links page.
To give you an example of an analogue and how to use these generators, let's just say I'll do Winters that were during or just before Solar Minimum. I have all my years as 2008-09, 1995-96, 1985-86, 1975-76, 1963-64, 1953-54, 1943-44, 1932-33, 1922-23, 1912-13, 1901-02, 1889-90, 1878-79, 1866-67 and 1855-56. It's time to put them into the composite generator over on NOAA's site. If you want to do things exactly the way I do them, please follow the pictures below which shows you around the 20th century reanalysis v2c monthly composite generator.
Hope you have found this helpful and informative. Go and show off some of your own analogues now.
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