30 Year PRISM Normals Have Been Updated
The precipitation images, shapefiles and downloads have been reprocessed utilizing the updated 1981-2010 PRISM normals. Read More...
Last Update: 10/31/2014 04:04 GMT
The precipitation data are quality-controlled, multi-sensor (radar and rain gauge) precipitation estimates obtained from National Weather Service (NWS) River Forecast Centers (RFCs). The original data are in XMRG format and projected in the Hydrologic Rainfall Analysis Project (HRAP) grid coordinate system, a polar stereographic projection true at 60°N / 105°W. Our software reads each participating RFC's XMRG file and grabs the 24-hour precipitation estimate for each HRAP grid cell.
Use the form above to download these files. Alternatively you can download a program called wget that mimics ftp capability. Due to increased web security, the anonymous FTP server is no longer available.
If you wish to use wget (see above), shapefiles are stored at:
If you have any questions or problems, please contact AHPS.Precip@noaa.gov.
The following links provide more information about the observed precipitation, normal precipitation, and derived precipitation products:
The shapefile contains the following fields:
The second download option "Legend File" will help you reproduce the color scheme we are using. If using Arcview, you will need to copy it into your c:\esri\av_gis30\arcview\legend_avl\ directory and load it manually through the legend editor. This file does not change from day to day.
Worldfiles (.GFW extension) and Projection files (.PRJ extension) are available at:
Please note, grids with no precipitation (i.e. 0.00") are not in the observed data shapefiles. A shapefile with all points is available at http://water.weather.gov/precip/p_download_new/nws_precip_allpoint.tar.gz.
A precipitation data legend file can be downloaded at
A problem was discovered on August 9, 2007. The shapefile coordinates for each HRAP grid were indicative of the lower left corner of the grid rather than the center of the grid. The entire shapefile archive has been updated to correct the lat-lon issue. The shapefile http://water.weather.gov/precip/p_download_new/nws_precip_allpoint_conversion.tar.gz shows both the old and new coordinates for each point.
The two netCDF files (one for CONUS, one for Puerto Rico), may be used independently of one another. Each file contains the following fields:
NOTE -- Latitude and Longitude are not explicitly stated in the netCDF file. The second download option "HRAP-to-LatLon" contains source code for a C-program. The program contains a function that reprojects HRAP coordinates to Lat-Lon coordinates. The fully compiled program reads the netCDF files and writes ascii files with the following fields:
To compile the C-program you will need to install the netCDF library on your computer. More information about using netCDF files (including the netCDF C-library) is available from the University Corporation for Atmospheric Research (UCAR).