Comparing partial and continuously cycling Ensemble Kalman Filter data assimilation systems for convection-allowing ensemble forecast initialization

One EnKF employed continuous cycling, where the prior ensemble was always the 1-h forecast initialized from the previous cycle's analysis. In contrast, the other EnKFs used a partial cycling procedure, where limited-area states were discarded after 12 or 18 h of self-contained hourly cycles and reinitialized the next day from global model fields. "Blended" states were also constructed by combining large scales from global ensemble initial conditions (ICs) with small scales from limited-area continuously cycling EnKF analyses using a low-pass filter.

Both the blended states and EnKF analysis ensembles initialized 36-h, 10-member ensemble forecasts with 3-km horizontal grid spacing. Continuously cycling EnKF analyses initialized similar to 1-18-h precipitation forecasts that were comparable to or somewhat better than those with partial cycling EnKF ICs. Conversely, similar to 18-36-h forecasts with partial cycling EnKF ICs were comparable to or better than those with unblended continuously cycling EnKF ICs.