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NCEP/EMC U.S. Gridded Gage Only Hourly Precipitation (4 km)


This dataset contains the National Centers for Environmental Prediction (NCEP) Environmental Modeling Center (EMC) 4 KM GRIB gage-only analysis ("GAG") data. A prototype, real-time, hourly, multi-sensor National Preciptation Analysis (NPA) has been developed at NCEP in cooperation with the Office of Hydrology (OH). This analysis merges two data sources that are currently being collected in real-time by OH and NCEP. Hourly digital precipitation (HDP) radar estimates are created by the WSR-88D Radar Product Generator on a 131 X 131 4-km grid centered over each radar site. Data analysis routines, including a bias correction of the radar estimates using rain gage data, have been adapted by NCEP on a national 4-km grid from algorithms developed by OH and executed regionally at NWS River Forecast Centers (RFC). This dataset only contains the NCEP 4 KM GRIB Data gage-only hourly, 6-hourly, and daily analysis. 6-hourly data are generally available at 00Z, 06Z, 12Z, and 18Z. Daily data are generally available at 12Z. Depending on the time period selected, all three datasets may or may not be available. Other NCEP 4 KM GRIB Data including multi-sensor analysis (gage and unbiased radar), radar estimate, radar estimate after bias removal, and gage-only analysis using 24h accumulated ("RFC") data are available as independent datasets. Depending on the time period selected, all five types may or may not be available. Please see GCIP/EOP: Surface NCEP Ancillary Catalogue of Available GCIP Precipitation Data (NCEP/EMC). The format of the files is GRIB. The files are compressed using the UNIX "compress" command and "uncompress" must be used before decoding. This dataset is provided as is and was not quality controlled by UCAR/JOSS. Beginning 1 Jan 2002, the analysis grid has been changed to conform with the official NWS HRAP grid. File names have also been changed. See the readme provided with this dataset for details. As of April 2017 this data includes Alaska and Puerto Rico stations.

Archive note

15 January 2020 - Data for 26 September 2019 was added when it was determined that this date had been omitted.

31 August 2020: Start and end dates/times on the files were updated.

7 October 2020: Stage 2 files will not be available after 28 July 2020.

3 February 2021: Files missing from January 2002 and January 2012 were added.

Missing Data:
April 4, 2019 - all data missing
September 26, 2019 - all data missing
November 20, 2019 - some stage 2 and some stage 4 missing
November 21, 2019 - some stage 2 missing

Data access

  • ORDER data for delivery by FTP

Additional information

Data Quality final
  • 1.0 (2011-08-11)
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Related projects
Spatial Type point
Frequency hourly
Language English
GCMD Science Keywords Expand keywords
Related links

Temporal coverage

Begin datetime 2001-12-31 12:00:01
End datetime 2020-07-28 11:00:00

Spatial coverage

Map data from IBCSO, IBCAO, and Global Topography.

Maximum (North) Latitude: 71.413, Minimum (South) Latitude: 17.853
Minimum (West) Longitude: -176.836, Maximum (East) Longitude: -65.544

Primary point of contact information

Jun Du <>

Additional contact information


Du, J. 2011. NCEP/EMC U.S. Gridded Gage Only Hourly Precipitation. Version 1.0. UCAR/NCAR - Earth Observing Laboratory. Accessed 23 Jul 2024.

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Ancillary information

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