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Meteorological Development Laboratory

Description of Global Ensemble MOS Message

Ensemble MOS forecasts are based on the 0000 UTC run of the GFS Global model ensemble system. These runs include the operational GFS, a control version of the GFS (run at lower resolution), and 20 bred perturbation runs. Older operational GFS MOS prediction equations** are applied to the output from each of the ensemble runs to produce 21 separate sets of alphanumeric bulletins in the same format as the operational MEX message.

** The current operational GFS MOS equations were developed with GFS model predictors that are not available in the current Global ensemble output. Therefore we are using operational MOS equations from 2002 to create the ensemble guidance. Ensemble MOS is not available for all stations and elements in the current operational GFS MOS guidance.

At this time, the experimental MOS ensemble summary message (described below) is not available.

For each element and projection, the ensemble MOS summary message contains the operational forecast (OPRN), a mean forecast computed by averaging the separate ensemble MOS forecasts together (MEAN), the standard deviation of the forecasts (STDV), and the most extreme MOS forecasts included in the set (HI,LO). Forecasts of mn/mx, 12-hr PoP and 24-hr PoP valid 12 - 192 hours after 0000 UTC are provided for the same sites as the operational MOS guidance. The ensemble MOS message is updated daily at approximately 1000 UTC.

This product is NOT OPERATIONAL. It is experimental in nature, and has yet to be objectively verified.

For more information about NCEP's Global Ensemble Prediction System see

National Weather Service
Office Of Science and Technology
Meteorological Development Laboratory
Statistical Modeling Branch
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Silver Spring, MD 20910
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Page last Modified: Monday, 25 February 2008 17:33 UTC