Operational mesoscale NWP at the Japan Meteorological Agency (JMA) was started in March 2001. Accuracy of the quantitative precipitation forecast of JMA has been remarkably improved in recent years, but precise prediction of heavy rainfalls in unstable atmospheric conditions is still a tough subject for the current operational NWP.

Several studies have been conducted at the Meteorological Research Institute (MRI), which include development of a cloud-resolving data assimilation system, assimilation of mesoscale remote-sensing observation data, and development of a mesoscale ensemble prediction system (MEPS) in the WWRP Beijing Olympics 2008 Research and Development Project (B08RDP).

Toward the dynamical and probabilistic forecasts of local heavy rainfalls, a plan of high performance NWP with the cloud resolving ensemble data assimilation has been endorsed to use the Next Generation Super Computer of Japan. A field campaign in the Tokyo metropolitan area with a dense observation network is also planned by the National Research Institute for Earth Science and Disaster Prevention (NIED) and MRI in 2011-2013 as an international test-bed for deep convection.