New York City Storm Surges: Climatology and An Analysis of the Wind and Cyclone Evolution Dr. Brian A. Colle, Katherine Rojowsky, and F. Bounaiuto School of Marine and Atmospheric Sciences Stony Brook University, SUNY

Lidar image of business district of Manhattan showing elevation and seawall locations (arrows). The imager is flying above the Hudson River looking east. (Photo Courtesy: NOAA/U.S/ Army JPSD)

The 1821 hurricane produced a storm surge of 13 feet (4 m) in only one hour at Battery Park. Manhattan Island was completely flooded to Canal Street; 3 September 1821: Only Major hurricane to hit NYC directly (category 3) NYC area tracks obtained by observations and geological survey (Scileppi and Donnelly 2007)

Tropical Storm Tracks: Figure provided by J. I. Virmani, 2007

December 1992 Nor-easter (6Z 13 Dec 1992) NARR Analysis (18Z 12 Dec 1992) ADCIRC model hindcast of water level ASL (m) using MM5 winds and pressures at 18 UTC 12 Dec (Colle et al. 2008) * * L L

FDR Drive during the December 1992 nor’easter (Bloomfield, 1999) Source: Metro New York Hurricane Transportation Study, 1995 Ref: Bloomfield, J., M. Smith and N. Thompson, Hot Nights in the City. Environmental Defense Fund, New York December 1992 Nor-easter

Motivational Questions What is the variability of minor and moderate storm surges and flooding events at NYC during the past 50 years? How will the number of moderate flooding events change as sea level rises during the next years? How does the wind speed and direction evolve around NYC for minor and moderate surge events? What are the cyclone tracks and position at maximum surge that favor storm surge events for the NYC area?

1960s1970s1980s1990s2000s (Gloria ‘85)Donna (’60) Maximum daily surge at the Battery, NYC ( ) (’92 Nor-easter) Climatological Analysis of NYC Surges A minor and moderate surge at the Battery that would result in a coastal flood advisory and warning, respectively, by the NWS during a high tide (mean high water). Minor: m above MHW Moderate: >1.00 m above MHW

Number of Minor and Moderate Surge Events Minor Surge Moderate Surge

Monthly Moderate Surge Events at the Battery, NY ‘59-‘07 Monthly Minor Surge Events at the Battery, NY ‘59-‘07

’82-‘83 ’97-’98’72-‘73 5 yr running mean Minor Surge Events at the Battery, NY ‘59-‘07

Monthly Minor Surge Events at the Battery, NY ‘59-‘07 Annual Observed Moderate Flooding Events at the Battery, NY ‘59-‘07 Annual Moderate Surge Events at the Battery, NY ‘59-‘07 *Surge + tidal = total water level (storm tide) NWS threshold Mod. Flooding = 2.44m above Mean Low-Low Water (MLLW) Moderate observed water level flooding events absent after 1996

Impact of Sea-Level Rise on NYC Flood Events IPCC (2007) cm over next yrs) Observed Moderate Flooding Events After 12.5 cm Sea-Level Rise

Impact of Sea-Level Rise on NYC Flood Events IPCC (2007), cm over next yrs) After 25 cm Sea-Level RiseAfter 50 cm Sea-Level Rise

NWS threshold = 2.04 (minor flooding – coastal flood advisory), 2.44 (moderate flooding) above Mean Low-Low Water (MLLW) Impact of Sea-Level Rise on Minor Flood Events (rise ~2.77 mm/yr at Battery cm over 50 yrs) Observed Minor Flooding EventsAfter Sea-Level Rise Correction

Meteorological Analysis Datasets: -- Hourly 10-m wind observations from Bennett’s Field ( ) and JFK airport ( ). -- NCAR-NCEP global (2 degree) reanalysis ( ) Regional reanalysis ( ) Approach: -- For 191 minor and 31 moderate events after 1968, quantified the average wind evolution at JFK and Bennett’s Field from 48-h before time of maximum surge to 24-h afterwards. -- Manually tracked cyclones within reanalysis for surge events and > 1.0 (2mb closed contour for cyclone closest to NYC).

Wind Direction Evolution at JFK/Bennetts Minor Time of max surge Moderate Minor Speed & Direction Frequency at Time of Maximum Surge Speed (m/s) Wind Direction -48/+24h Surrounding Maximum Surge

Wind Speed Evolution at JFK Wind Speed -48/+24h Surrounding Maximum Surge Distribution of Wind Speeds at Maximum Surge Time of max surge

Position at Time of Max SurgeCyclone Tracks Minor Surge Cyclone Tracks -48/+12h * m events Number of Cyclone Centers m events

Moderate Surge Cyclone Tracks -48/+12h * 1.0 m events Number of Cyclone Centers m events Cyclone TracksPosition at Time of Max Surge

NCEP Reanalysis SLP Composite of 46 > 1-m Surges at Battery, NY -36 h-24 h -12 h 0 h L L L H H H H L H -24h

NCEP Reanalysis 500Z Composite of 46 > 1-m Surges at Battery, NY -36 h-24 h -12 h 0 h

Tropical Storm Surge Tracks ( )

Conclusions Large inter-annual & inter-decadal variability. Minor surge events more prevalent during the 60’s, 70’s & mid-90’s. Only 1 moderate surface event since 2000 and no observed moderate flooding events since A cm sea-level rise over last 50 years has increased the number of minor flood events (given coastal flood advisory threshold by NWS). Flooding (even for nor-easters) will increase dramatically as sea level rises cm over the next years. Moderate event mean wind speeds 25% greater at the time of maximum surge than minor events. Wind speeds in isolation not a good predictor of minor vs. mod surge. Diverse tracks for minor & moderate, with moderate tending toward the coast (Miller Type A track).