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The Global Ensemble Forecast System (GEFS) was upgraded on September 23rd by the National Oceanic and Atmospheric Administration (NOAA).
The model is used to produce medium range weather forecasts and in particular to identify the likelihood of different scenarios.
The GEFS is an ensemble model. That means it consists of a number of different runs each with the initiation data tweaked. The impact this has on the forecast can be used to help determine how likely a given outcome is and its sensitivity to the starting conditions.
Key changes to the model include:
1) Improved physics and resolution. The 33km grid has been replaced with a 25km one.
2) An increased number of perturbations (runs). The previous version had 20 perturbations plus the control which is a run that is initiated with untweaked starting data.
3) A longer forecast range. Previously the GEFS went as far as 16 days ahead on all four daily updates. The new version goes out to 35 days ahead on its first daily update (the 00z cycle) and then 16 days ahead on the other three which are the 06z, 12z and 18z cycles
On TWO charts from all of the individual perturbations can be viewed. In addition an increasing range of 35 day charts is available.
All charts can be selected on the GEFS viewer. The link is:
Alternatively, the latest 16 day line graph charts are available on the Ensemble forecast feature:
The latest 35 day line graphs are directly available from this link:
The range of GEFS charts and data provided will continue to be increased.
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