1. Using NOAA-Atlas 14 Return Periods to Aid in Flood Forecasting - Charles Ross and Richard Grumm SOO, NWS State College PA

2. Topics Covered NOAA Atlas 14 Overview Using the NOAA 14 data Case Studies Review

3. NOAA Atlas 14 Precipitation Frequency Information - – NOAA Atlas 14 data available for 37 states Pacific NW and Texas not available NE US states in progress but not online yet…but similar data available on NERC website – NWS Hydrometeorological Design Studies Center Precipitation Frequency Data Server (PFDS) website has converted NOAA Atlas 14 data into a point and click interface http://hdsc.nws.noaa.gov/ – Displays PDS based precipitation frequency estimates and 90% confidence interval Durations range from 5-minute to 60-days Average Recurrence Intervals (ARI) Range from 1 year to 1000 years – Data is also available in formats other then web, including GIS

5. NOAA-14 Data used by NWS State College NWS Phoenix developed a procedure to import this data into NWS AWIPS for use with FFMP NWS State College used this during the summer of 2013 with some success Unfortunately with Awips 2 this data is currently unavailable MRMS/FLASH website used in real time during heavy rain events For last two years used NOAA 14 ARI data in case studies of heavy rain and flooding events

8. Case #1 – Lebanon County, PA 7/23/13 Record rain event – 3 and 6-hour ARIs close to 1000 year return periods – Flash flooding across the county – Case study: http://cms.met.psu.edu/sref/severe/2013/23Jul2013.pdf

14. Case #2 – Flash Flood event central PA 6/27/13 Two Flash Floods on this day – Dubois, PA – Flash Flood Emergency Issued – Beech Creek, PA – 1 Fatality when a man was swept into a creek – Both Floods had ARIs close to 1000 year return periods – Case Study: http://cms.met.psu.edu/sref/severe/2013/27Jun2013.pdf

23. Case #3 – Extreme Rain Event – KPHL 7/27-28/13 Philadelphia International Airport received 8.26” of rain – ARIs close to 1000 year return periods – Case Study: http://cms.met.psu.edu/sref/severe/2013/28Jul2013.pdf

28. Case #4 – Phoenix Heavy Rain Event – KPHL 9/8/14 Monsoon moisture brought intense heavy rainfall to parts of the Phoenix area. – ARI close to 1000 year 6-hour return period – Case Study: http://cms.met.psu.edu/sref/severe/2014/10Sep2014.pdf

32. Case #5 – Long Island, NY Record Deluge – 8/13/14 Intense mesoscale precipitation band sets up over portions of Long Island, New York – 12.92” in 6-hour (13.27” for the day) – NOAA-14 data on PFDS web site unavailable for NYS. Used Northeast Regional Climate Center “Extreme Precipitation in New York and New England Website for ARI data – http://precip.eas.cornell.edu/ http://precip.eas.cornell.edu/ ARI well over the 500 year 6-hour return period – Case Study: http://cms.met.psu.edu/sref/severe/2014/13Aug2014.pdf

37. Review and Discussion Points Using ARIs should be used in flood operations similar in fashion to how we use flash flood guidance – Preferably with access in tools like FFMP Preliminary studies show to look for 1, 3 or 6- hour ARIs exceeding 50 years for moderate flooding to begin with significant flooding on the 100+ year events Currently the FLASH website is the best site to use in near real time