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Archive of past heavy precipitation events

Switch to a different threshold:

Select a year: 50 year, 6-hour recurrence interval

There were 65 six-hour periods when the rainfall exceeded the threshold in 2012!

Hover mouse over a date to see the map (dates are listed as two-digit month, then two-digit date, then two-digit hour so that 050112 indicates the period ending at 12 UTC on May 1st):

012512 031218 031600 032100 041500 041612 041618 043006 050312 050406 050606 051906 052712 052800 052900 053000 060918 061000 061500 061600 061706 061900 062006 062100 062500 062600
062606 062700 070306 070512 071112 071900 072906 073106 073112 080218 080500 080712 080812 080900 081018 081618 081900 082406 082412 082506 082512 082518 082606 082612 083000 090412
090418 090500 090506 091318 091900 092800 092812 092906 092912 093000 093006 100100 103000

Data sources and notes:
Gridded recurrence interval data were provided by The Automated Geospatial Watershed Assessment Tool website.
That is based on data in Hershfield, D. M., 1961: Rainfall frequency atlas of the United States. U.S. Weather Bureau Technical Paper 40, 115 pp.
Precipitation data is the Stage IV analysis over the US, obtained in real-time from NOAA/NCEP.
Archived precipitation data come from NCAR/EOL.
The Stage IV analysis data have been coarsened slightly for this analysis, to a grid with approximately 8.25-km horizontal spacing. We have found that this helps to eliminate the identification of spurious events, although it may also remove legitimate events that occurred at very small spatial scales.
Currently, the analysis has only been conducted for states east of the Rockies, but we hope to extend it to the full US (using updated recurrence interval information where available) in the future.
Maps of events exceeding the 1-hour precipitation thresholds are not yet available, but we hope to post them soon.

Acknowledgments:
Stephanie Stevenson (undergraduate researcher at Texas A&M University) created the archived images (for the years 2002--2010) and performed most of the data analysis.
This work was published in Stevenson and Schumacher (2014, Monthly Weather Review). Please cite this paper if you make use of the data or analyses from this website in your own research.
This material is based upon work supported by the National Science Foundation under Grant Nos. AGS-0954908 and AGS-1157425. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.