HMT/DTC 2010 Evaluation - Observation Description

Gauge Data

Gage precipitation totals over 24h (1200-1200 UTC) are produced from observations accessed at rain gage sites operated by several agencies: ALERT, SNOTEL, RAWS, CDEC, and WRCC Many of these sites include hourly totals which are processed and made available as the Hydrometeorological Automated Data System (HADS). Others are 24h stations, both manual and automated, that are examined at individual River Forecast Centers and subsequently provided to OHD and other users for analysis and other applications. Locations for the gage sites in these data streams can be viewed at The stations used in the verification statistics displayed here for the HMT exercises are subjected to quality control procedures at GSD before their use as verification data. Typically, about 20% of observations from automated hourly sites in the HADS data stream are rejected by these QC algorithms.

NEXRAD Stage IV data

The following information was taken from National Stage IV QPE Product page at NCEP.

What is the NCEP Stage IV analysis? It is a mosaic product produced at NCEP, from the regional hourly/6-hourly multi-sensor (radar+gauges) precipitation analyses (MPEs) produced by the 12 River Forecast Centers over CONUS. A mosaic is done at NCEP within an hour of receiving any new hourly/6-hourly data from one or more RFCs. Note that because of radar beam blockage and other observational problems, Stage IV analyses from the CNRFC do not include radar estimates.

What is available in Stage IV: Analysis on the 4km HRAP grid: ST4.yyyymmddhh.xxh.Z, where xx (=01,06 or 24) is the accumulation period and yyyymmddhh is the ending time of the accumulation period.

  • Hourly analysis: from the hourly MPEs sent by the RFCs
  • 6-hourly analysis: from the 6-hourly MPEs sent by the RFCs
  • 24-hour (12Z-12Z) analysis: summed up from the 6-hourly Stage IV