14 Day Weather Forecast
Caveat Emptor

By their own admission, the organizations issuing a 14 day weather forecast do not have much confidence in them. You will find official statements to that effect on this page.

Meteorologists use computer models to simulate the behavior of the atmosphere. The forecasts and outlooks are derived from their analysis and interpretation of the numerical ouput produced by the super computers.

Here is what the major meteorological organizations around the world say about numerical weather prediction (NWP) and the long term weather forecast.

Note: To understand the power and limitations of modern meteorology, I recommend Meteorology: An Introduction to the Wonders of the Weather!



United States

Source: www.cpc.noaa.gov/products/forecasts

United Kingdom

Source: www.metoffice.gov.uk/research/nwp


Source: www.bom.gov.au/lam/climate/levelthree/analclim/analclim.htm

Why Issue An "Unreliable" Long Range Weather Forecast?

Long term weather forecast products exist primarily because there is a strong demand for them. The fact that they are produced to satisfy that demand does not mean that they can! Not by any stretch of the imagination.

You as a consumer do not necessarily know that, because the "disclaimer" is usually tucked in the fine print somewhere deep in the organization's Web site.

I conducted a survey recently to find out just how easy (or hard) it is for you to find out if you should actually plan any significant activity on these so-called forecasts.

I found the "disclaimers" (see excerpts above) after many hours of searching through the government Web sites of each country!

Terminology Issue

The UK MetOffice calls its 14 day extended forecast a "forecast" but Canada, the US and Australia use the more appropriate terms "trend" or "outlook".

The latter two terms are much closer to what these products can actually deliver: a general idea of the trend or tendency.

Even as such, they can only be relied upon to give a general idea of the tendencies such as...

  • "cooler", "warmer" or about normal, or
  • "rainier" than normal or not.

Meteorology as a science cannot produce a reliable detailed forecast much beyond 72 hours. Beyond that, "forecasting" rapidly becomes statistically less reliable than flipping a coin!

Conclusion And Recommendation

It would be wise to consider the 14 day weather forecast as an experimental product to which you are being given access. You should not use it to support critical weather-dependant decisions or activities.

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