Archived Winter Forecast, 2013/01/14

Enjoy the 30 day sample forecast (experimental)! Although this source is free to use, please use proper citation if this data is being redistributed.

The 500-mb height anomaly. Blue = cold, red = warm. If you are south of the snowflake, rainfall is the most probable precipitation type. If you are inside the snowflake, good news, this is your rain/snow line. If you are just north of the snowflake, better news for snowfall.

  = Probable location of snowfall
= Likely warm anomaly

Want to be able to forecast the weather or know what it is doing far in advance? Welcome to the archive winter forecast, or better known as the "Most similar winters" forecast technique. This approach uses the most similar winters in the past to forecast what will happen with this current winter. I look for winters that had a similar pattern leading into the winter and a similar pattern in the winter before I put them together. The index was originally put together October 29th, 2012, with a modification on November 15th. Since then, what you see is unchanged since November 15th.

So what is this animation showing? It shows how high up you must fly to find an air pressure equivalent of 500 millibars. A blue spot means that height level is lower than it should be, suggesting cold air underneath. A red spot suggests the height level is higher than it should be, suggesting warm air underneath. The snowflakes highlight probable locations for snowfall while the blowtorch is an area that has temperatures way above average.

Please note that because this is historical data, not directly modeled forecast data, the sample animation is likely to be off 1-3 days in some parts. Additional error may arise from a "+" anomaly one year canceling out a "-" anomaly that appeared the next year.  This tool is recommended to be used to assist in forecasting, not to be a sole source for forecasting.

You can read the "Version 1" winter forecast here
http://lheureuxsweather.blogspot.com/2012/10/october-winter-forecast-update.html
And the "Version 2" here
http://lheureuxsweather.blogspot.com/2012/11/november-winter-forecast-update.html
To see what changes I have made (and the line of thought I had). Snow maps for the most similar archived winters can be found here.
http://lheureuxsweather.blogspot.com/2012/11/most-similar-winters.html