Hurricane Sandy Inundation Probabilities: Today and Tomorrow W. Sweet, C. Zervas, S. Gill and J. Park (2013) Joseph Park William Sweet National Oceanic and Atmospheric Admin. National Ocean Service

Sandy was a superstorm, unique by many measures. The onshore impact angle was extremely rare. Return Interval = 714 years (95% confidence range 435 to 1429) Timothy M. Hall, Adam H. Sobel Geophysical Research Letters Volume 40, Issue 10, Volume 40, Issue 10, pages 2312–2315, 28 May 2013

From: wunderground The storm’s NE quadrant funneled a massive storm surge up NY Harbor and Long Island Sound.

Storm surge: obs – pred tide Sandy hit at peak high tide.

Battery Park, NY theepochtimes.com Hoboken NJ

Sweet et al. (2013) Heights above MHHW Stars indicate highest storm tide ever observed

NCAR/UCAR Bob Henson December 31, 2012

Flood risk is increasing as the decades-old infrastructure steadily loses ground from relative sea level rise (SLR rel ).

Parris, A., P. Bromirski, V. Burkett, D. Cayan, M. Culver, J. Hall, R. Horton, K. Knuuti, R. Moss, J. Obeysekera, A. Sallenger, and J. Weiss Global Sea Level Rise Scenarios for the US National Climate Assessment. NOAA Tech Memo OAR CPO pp.

Gulfstream

Intergovernmental Panel on Climate Change (IPCC) 2007.

Sea Level Monitoring and NOAA Tide Gauges NOAA’s National Water Level Observation Network (NWLON) Relative measurements Tidal-geodetic connection Sea level trends Vertical land motion Extreme events

Product: Long-term relative Sea Level Trends

Relative SLR and Vertical Land Motion (VLM) Gauge Altimeter mm/yr SLR rates ( ) Report_NOS_COOPS_065.pdf Report_NOS_COOPS_065.pdf Zervas, Gill and Sweet (2013) VLM is an important contributor to relative SLR, especially within the mid-Atlantic and Gulf Coast regions

Product: Extreme Water Level Probabilities

Data detrended (relative mean seal level) prior to analysisData detrended (relative mean seal level) prior to analysis Sandy’s impacts levels are “fixed elevations” in timeSandy’s impacts levels are “fixed elevations” in time 1950 probabilities: model lowered by historical relative trend1950 probabilities: model lowered by historical relative trend Future (2050, 2100) probabilities using relative “Scenarios”Future (2050, 2100) probabilities using relative “Scenarios” No wave runup/setup: ~ to FEMA’s Stillwater ElevationsNo wave runup/setup: ~ to FEMA’s Stillwater Elevations Quasi-stationary approach F(x; μ, σ, ξ) = exp { - [ 1 + ξ(x-μ)/σ ] -1/ξ } μ: location (median) σ: scale (spread) ξ: shape (of upper tail) Generalized Extreme Value (GEV) of Annual Max Obs

Probability of a “Sandy-level event” is now significantly higher (return intervals lower) than in 1950 from SLR rel. A smaller storm surge is now required to innundate similar elevations. Sweet et al. (2013) Like rolling dice, but steadily losing number of sides…

Return Interval decay as a function of NCA SLR rel scenarios: Less powerful storms with smaller storm surge than Sandy will innundate similar levels… years Sweet et al. (2013) Time-dependent Sandy-impact level Return Intervals Return Interval (years)

To Conclude Hurricane Sandy was an extreme event. While rare, the probabilities (risk) of similar event impacts have and will continue to increase as sea level rises. Climate-change related sea level rise reduces the expected time between these extreme events at a given location. Models of Sea Level Rise (projections) are being used with statistical models to inform Government and Policy decision makers with estimates of future risk.