https://doi.org/10.5061/dryad.7m0cfxq4j

Description of the data and file structure

This dataset consists of gridded probabilistic forecasts of precipitation exceeding a large number of precipitation thresholds derived from the operational NCEP High Resolution Ensemble Forecast (HREF) v3 during 2021-2024. The forecasts are on the HREF grid, and are derived using the operational methodology for HREF QPF exceedance probabilities, using a neighborhood radius of 40 km, and weighting time-lagged ensemble members less than non-time-lagged members. The thresholds include fixed precipitation thresholds, average recurrence interval thresholds, and ratios of flash flood guidance.  

Files and variables

HREF forecasts are zipped up by month and initialization time (0000 UTC or 1200 UTC). For example, the file named 202106_00.tar.gz contains daily HREF forecasts initialized at 0000 UTC every day during June 2021.

Individual HREF forecasts are in netCDF files.  The naming convention is as follows:

href_f12-36${yyyymmdd00}.nc (probabilities of exceeding QPF thresholds during 24-h period contained within the 12-36 h forecast initialized at 0000 UTC)
href${yyyymmdd12}.nc (probabilities of exceeding QPF thresholds during 24-h period contained within the 0-24 h forecast initialized at 1200 UTC)
href12h_f12-36${yyyymmdd00}.nc (probabilities of exceeding 12-h QPF thresholds during 1200-0000, 1500-0300, 1800-0600, 2100-0900, or 0000-1200 UTC, based on forecast initialized at 0000 UTC)
href12h${yyyymmdd12}.nc (probabilities of exceeding 12-h QPF thresholds during 1200-0000, 1500-0300, 1800-0600, 2100-0900, or 000-1200 UTC, based on forecast initialized at 1200 UTC)
href6h_f12-36${yyyymmdd00}.nc (probabilities of exceeding 6-h QPF thresholds during 1200-1800, 1500-2100, 1800-0000, 2100-0300, 0000-0600, 0300-0900, or 0600-1200 UTC, based on forecast initialized at 0000 UTC)
href6h${yyyymmdd12}.nc (probabilities of exceeding 6-h QPF thresholds during 1200-1800, 1500-2100, 1800-0000, 2100-0300, or 0000-0600, 0300-0900, or 0600-1200 UTC, based on forecast initialized at 1200 UTC)
href3h_f12-36${yyyymmdd00}.nc (probabilities of exceeding 3-h QPF thresholds during 1200-1500, 1500-1800, 1800-2100, 2100-0000, 0000-0300, 0300-0600, 0600-0900, or 0900-1200 UTC, based on forecast initialized at 0000 UTC)
href3h${yyyymmdd12}.nc (probabilities of exceeding 3-h QPF thresholds during 1200-1500, 1500-1800, 1800-2100, 2100-0000, or 0000-0300, 0300-0600, 0600-0900, or 0900-1200 UTC, based on forecast initialized at 1200 UTC)

In each file, the probability of exceeding each threshold is encoded as a different variable. The naming convention is as follows:

24-h thresholds:
prob{fixed} where ${fixed} is a number in inches
prob{recurrence}yARI where ${recurrence} is a recurrence interval in years

Other thresholds:
prob${duration}h${fixed} where ${duration} is the duration of the QPF threshold and ${fixed} is a number in inches
prob${duration}h${recurrence}yARI where ${duration} is the duration of the QPF threshold and ${recurrence} is a recurrence interval in years
prob${duration}h${ratio}FFG where ${duration} is the duration of the QPF threshold and ${ratio} is the ratio of flash flood guidance

The verification dataset is shared in the following files:

grid_stat.zip contains all the UFVS events as well as the 0900 UTC day one WPC excessive rainfall outlook
st4gffg.zip contains all Stage IV exceedances of flash flood guidance
st4gari.zip contains all Stage IV exceedances of the 5-year average recurrence interval
lsrreg.zip contains all local storm reports of regular flooding
lsrflash.zip contains all local storm reports of flash flooding
usgs.zip contains all USGS stream gauge indications of flooding

The naming convention of the individual files uses ${yyyymmdd}12, where ${yyyymmdd} is the ending day of the 24-h verification period (1200 UTC to 1200 UTC)

Code/software

The data can be analyzed using python or other open source packages.

Access information

Data was derived from the following sources:

• Raw forecasts (in GRIB2 format) from the HREF members were downloaded from NOMADS in real time, or obtained from the NOAA High Performance Storage System (HPSS).
• Average recurrence interval (ARI) grids were derived from NOAA Atlas 14 and as described in the manuscript.
• Flash flood guidance (FFG) grids were obtained from the NOAA High Performance Storage System (HPSS).
• Observed occurrences of excessive rainfall were obtained from the NOAA Weather Prediction Center.