Ensemble Prediction of Flight Rules

One of the things being explored in the Winter Weather Experiment is the use of mesoscale and high-resolution ensembles for prediction of ceiling and visibility.  The two primary ensembles being explored for this purpose are the Short Range Ensemble Forecasting (SREF) System and the Air Force Weather Agency (AFWA) mesoscale ensemble.

The SREF is composed of 21 ensemble members with post-processed output on a ~16km horizontal resolution, while the AFWA ensemble has 10 members run at a ~4km horizontal resolution.  Each individual member is obtained by the Aviation Weather Center where we perform additional analysis that is not done in the basic ensemble post-processing.

Each of the individual member solutions contains a prediction of ceiling and visibility, for which ensemble statistics are computed.  Additionally, the flight rule category is computed for each ensemble member, from which the probability of the flight category can be determined.

These probabilities for the time period between 21Z Feb 11 - 09Z Feb 12 are shown for the AFWA and the SREF below.  Note that these probabilities are not calibrated and weight each of the ensemble members equally.  Both the weighting of the members and the calibration will need to be explored in order to improve the reliability of these forecasts (see: Reliability and Resolution). 

Probability of Flight Rules as predicted by the 00Z AFWA from 11 Feb 2013.  Valid 21Z 11 Feb - 09Z Feb 12.  MVFR, IFR, and LIFR conditions are shaded in blue, red, and yellow, respectively, shaded starting at 40%.

Probability of Flight Rules as predicted by the 03Z SREF from 11 Feb 2013.  Valid 21Z 11 Feb - 09Z Feb 12.  MVFR, IFR, and LIFR conditions are shaded in blue, red, and yellow, respectively, shaded starting at 40%.