About this page

This website provides precipitation forecasts 6 hours in advance using hourly-updated global precipitation data based on satellite observation.

The RIKEN Data Assimilation Research Team (DA team) performs cutting-edge research on weather forecasting by integrating computer simulations and observation data. Based on an advanced data assimilation technique, we developed a precipitation nowcasting system* that provides precipitation forecasts. Operation of the nowcast system involves hourly updates and accuracy verification, and results are used for research purposes.

Data Utilization

JAXA distributes GSMaP RNC binary data generated by RIKEN. If you would like to get them, please register from here. If you already register for [JAXA Global Rainfall Watch (GSMaP RNT)] or [JAXA Realtime Rainfall Watch (GSMaP_NOW)], it is not needed to re-register. The information about ftp site is same as them. Please refer data format description.

Release note

Please note that the weather forecasts on this website can differ from weather forecasts provided by the JMA. Please give precedence to the latest warnings and advisories from the JMA.

Use of information or data from this website is undertaken at the user's own risk. JAXA and RIKEN takes no responsibility for any direct or indirect damage that may arise through the use of this information or data. Any part or all of this website may be changed, deleted, or removed without notice.


We acquired the weather forecasting license from the Japan Meteorological Agency (JMA) for the area surrounding Japan defined by 0-60ºN and 100-180ºE, and provide the precipitation forecasts from 10 am to 5 pm on weekdays. Areas on the map shaded in gray indicate out-of-service locations.

More detail explanation and notes are available in RIKEN DA Team "GSMaP RIKEN nowcast (GSMaP_RNC)".


  1. Otsuka, S., S. Kotsuki, and T. Miyoshi, 2016: Nowcasting with data assimilation: a case of Global Satellite Mapping of Precipitation. Wea. Forecasting, 31, 1409-1416.