This dataset offers hourly estimates of radar indicated rain gage corrected precipitation at a roughly 4km spatial resolution. Mosaicked into a national product at NCEP, from the regional hourly multi-sensor (radar+gauges) precipitation analyses produced by the 12 River Forecast Centers over CONUS. Some manual QC done at the RFCs. The Stage II/IV job is run at 33min past the top of each hour. Hourly Stage IV is re-made hourly (if there is new input after valid time for the next 23 hours, then again at 1/3/5/7 days after valid time. These data have been aggregated into this service by the CIDA and are downloaded and incorporated into the archive every 30 minutes. The original Hydrologic Rainfall Analysis Projection grid cell locations redefined by unprojecting grid cell locations using spherical earth projection algorithms. The cell lat/lon locations should be interpreted as being on a modern geodetic datum. This transformation is needed because the original grid cell location's lat/lon values were on a geodetic datum but were assumed to be on a spherical datum. See: http://pubs.usgs.gov/fs/2013/3035/pdf/fs2013-3035.pdf for more information. Note that this publication references the National Precipitation Verification Unit. The data represented here are aggregated from the same source as the National Precipitation Verification Unit used prior to being shut down. National Centers for Environmental Prediction National Stage IV Quantitative Precipitation Estimate Product: http://www.emc.ncep.noaa.gov/mmb/ylin/pcpanl/stage4/ NWS Advanced Hydrologic Prediction Service About Page: http://water.weather.gov/precip/about.php CIDA Publication Documenting Grid Reprojection: http://pubs.usgs.gov/fs/2013/3035/pdf/fs2013-3035.pdf Raw Data Access here: https://cida.usgs.gov/thredds/catalog.html?dataset=cida.usgs.gov/thredds/stageiv_combined/