new york city storm surges: climatology and an analysis of the wind and cyclone evolution dr. brian...

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: 1851-2005

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)

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*

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, 1999. Hot Nights in the City. Environmental Defense Fund, New York.

12-13 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 50-100 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?

1960s 1970s 1980s 1990s 2000s

(Gloria ‘85)Donna (’60)

Maximum daily surge at the Battery, NYC (1959 -2007)

(’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: 0.60-1.00 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) 12-50 cm over next 50-100 yrs)

Observed Moderate Flooding Events After 12.5 cm Sea-Level Rise

Impact of Sea-Level Rise on NYC Flood Events

IPCC (2007), 12-50 cm over next 50-100 yrs)

After 25 cm Sea-Level Rise After 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--10-15 cm over 50 yrs)Observed Minor Flooding Events After Sea-Level Rise Correction

Meteorological Analysis• Datasets:

-- Hourly 10-m wind observations from Bennett’s Field (1968-1971) and JFK airport (1973-2007).

-- NCAR-NCEP global (2 degree) reanalysis (1959-1978) Regional reanalysis (1979-2006)

• 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 0.8-1.0 and > 1.0 (2mb closed contour for cyclone closest to NYC).

Wind Direction Evolution at JFK/Bennetts

Minor

Time of max surge

Moderate

MinorSpeed & Direction Frequency at Time of Maximum Surge

Speed (m/s)

Wind Direction -48/+24h Surrounding Maximum Surge

Wind Speed Evolution at JFKWind Speed -48/+24h Surrounding Maximum Surge

Distribution of Wind Speeds at Maximum Surge

Time of max surge

Position at Time of Max Surge

84oW 78oW 72oW 66oW 60oW

32oN

36oN

40oN

44oN

48oN

Cyclone Tracks

Minor Surge Cyclone Tracks -48/+12h

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0.8-1.0 m events

Number of Cyclone Centers

29 5 4 3 16

0.6-1.0 m events

Moderate Surge Cyclone Tracks -48/+12h

*

1.0 m events

Number of Cyclone Centers

29 5 4 3 16

1.0 m events

Cyclone Tracks Position 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

HH

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 (1959-2007)

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 1996.

• A 10-15 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 10-50 cm over the next 50-100 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).