VarEPS Derived Probability Parameters

In preparation for the future link of VarEPS with the monthly forecasting system (Phase 3 of the VarEPS implementation), the event probability forecast parameters will be changed.

• New parameter names and numbers are used to describe different weather parameter thresholds.
  
• Some time range indicator values have been corrected to take into account the higher frequency in post-processing (old style definitions were based on 12-hourly steps).
  
• Additional periods have been provided for some event probability parameters.

Note that for MARS only (not dissemination):

• To retrieve probability parameters (Event Probabilities), type=EP must be specified in the MARS request instead of type=FP.
  
• To retrieve the Total Precipitation Probabilities, users must now request the time window (e.g. 24-48) as opposed to just the end accumulation step.

Details of the new event probability parameter names, numbers, the time range indicator values and additional periods, together with example MARS requests, can be found here.

A printable versionof the information provided in these pages is available.

Event Probabilities

Atmospheric parameters

• 2 metre temperature probability
• 10 metre wind gust probability
• 10 metre wind speed probability
• Total precipitation probability
• Temperature anomaly at 850 hPa

Wave parameters

• Significant wave height probability
• Mean wave period probability

Ensemble Mean and Ensemble Standard Deviation

• Ensemble mean and standard deviation

To allow for smooth transition from old to new style probability coding we will provide both types of products through dissemination for a limited overlap period until the end of March 2007.

MARS archiving of the old style products will be discontinued with the implementation of product dissemination from VarEPS.