Subseasonal Convection-Permitting Global Weather Prediction

Global weather prediction tends to fade rapidly after roughly 10 days, even when  surface conditions (like warm sea surface temperatures) should be providing some predictability.   A potential problem for extended forecasts (and shorter-period forecasts as well) is the inability of the convective parameterizations of current numerical prediction models to properly simulate convection.  The obvious solution is to run globally at sufficiently high horizontal resolution (convection-permitted grid spacing, 4 km or less), although this takes an immense amount of computer resources.
kk

In this project, sponsored by NOAA/NWS, we have run the NCAR WRF model globally at 3-km grid spacing for four one-month periods.  We have also tried other configurations (e.g., high resolution in the tropics along, no convective parameterization at 12-km grid spacing).  The results have been very promising, showing that convective-permitting resolution results in much better precipitation statistics as well as improved general predictability in the thirds week.  We plan on repeating this work, for more cases, using the new NOAA/NWS FV-3 system.
kk