GEFS Ensemble Envelope Display!

Verifying date



Lead Time (hrs)


Data from the last 5 days should be available. Images update by ~0931Z (00Z) and 2131Z (12Z).

These graphics are created as follows:
1) Aggregate the 20 GEFS ensemble members and find the minimum and maximum 500 hPa height and PMSL at each grid point (1 deg data).

2) For verification, the GDAS (Global Data Assimilation System) is used (also 1 deg data).

3) Images are created be finding the difference between the verifying value and the highest (or lowest) ensemble forecast. Verification values that are greater than the highest member or less than the lowest member are plotted (mutually exclusive). This is defined as "outside the envelope." Note that a properly dispersed ensemble system will still have a percentage of area that verifies outside the envelope. For the GEFS, this is about 4-5% (1/21) on either side of the distribution (about 9-10% combined).

This is a PROTOTYPE web page that is not operationally supported. Data may not update regularly.