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Is the New York City Metro Area Vulnerable This Hurricane Season?

By Joe D'Aleo
Monday, August 18, 2008

Since 1995, the Atlantic has become twice as active on average as the prior 25 years, similar to the period from 1930s to 1960s.  This is due to a shift to the ‘warm” mode of the multi-decadal scale oscillation in the Atlantic Ocean  Most of the storms making landfall during the past 12 years have impacted the Mid-Atlantic region, Florida and the Gulf of Mexico.  However, though not yet realized, history tells us that the risk has also increased for more populated areas to the north New York City/(Long Island and New England).


Number of CAT3-5 hurricanes in the Atlantic versus the AMO (Atlantic mean sea surface anomaly from 0 to 70N)

It appears the Pacific plays a role too. The cold mode of the PDO (in place this summer) favors New York and New England landfalls in large part because it favors La Nina. We had a strong La Nina this past winter into the early spring but it has in recent months, warmed in the eastern tropical Pacific. It is unclear whether that will save the east coast and the northeast one more year. 

You can see La Nina years when the Atlantic is warm produced 15 landfalling east coast storms in 9 years, 11 were major hurricanes, 9 affecting the northeast directly on second or third landfall. We discussed the 1938 direct hit hurricane in a recent story here.

 

Christopher Landsea (HRD) and Roger Pielke Jr. estimated if a storm like the Hurricane of '38 were to happen today, it would be the sixth costliest of all-time.

 

FAR WORSE IF TRACKS FURTHER WEST TO NEW YORK CITY

 

Experts earlier this decade had proclaimed after Miami and New Orleans, New York City was considered the third most vulnerable major city for the next hurricane disaster.

 

AIR Worldwide’s Karen Clark at the National Catastrophe Insurance Program Summit in November, 2005 said if such a storm made landfall just to the east of New York City, it would result in approximately $50 billion of insured losses with total economic losses exceeding $100 billion…. "since the total value of exposed properties in coastal areas of New York State alone has increased to over $1.9 trillion.“

 

A major hurricane making a major hit would be the costliest storm of all time, eclipsing Katrina.

Approximately one-quarter of the $100 billion in total economic losses would be attributable to storm surge. The contour of New York's coastline and relatively shallow depth of its coastal waters make it extremely vulnerable to storm surge.

 

At the time of the 1938 storm, Long Island was a rural home for oyster fishermen, potato farmers and wealthy industrialists. More than 20 million people live in the greater metropolitan region today. Many live on coastal land, reclaimed swamp and barrier islands. Much of Lower Manhattan is built on landfill. Places like Rockaway, Coney Island and Manhattan Beach "are stretches of land that nature has created to protect the mainland from hurricanes," Mike Lee (NYCOEM) says. "In our civilization this is also the most desirable land to develop and build on. ... so we now have to deal with the threat."

 

A storm surge prediction program used by forecasters called SLOSH (Sea, Lake, and Overland Surge from Hurricanes) has predicted that in a category 4 hurricane, John F. Kennedy International Airport would be under 20 feet of water and sea water would pour through the Holland and Brooklyn-Battery tunnels and into the city's subways throughout lower Manhattan.


The highest storm surges (Category 4) would occur in the following regions:

         Amityville Harbor - 29 feet

         Atlantic Beach & Long Beach areas - 24 to 28 feet

         South Oyster Bay, Middle Bay, & East Bay areas - 24 to 28 feet

 

Army Corp Models show even worse impacts. In the event of a direct hit by a category-3+ hurricane, surge maps show that the Holland and Battery Tunnels will be completely filled with sea water, with many subway and railroad tunnels severely flooded as well. The runways of LaGuardia and JFK airports will get flooded by 18.1 and 31.2 feet of water, respectively.  If a storm like the Long Island Express makes a direct hit on the city, everything below Broome Street will be inundated, some parts under as much as 20 and 30 feet of water. Chelsea and Greenwich Village would be  completely flooded, with the Hudson spilling over all the way to 7th Avenue. Likewise, the East River and East Village become one, with ocean water surging all the way to 1st Avenue.

If you haven't evacuated before the storm, forget it. During the storm, Manhattan's east- and west-side highways vanish. Tunnels and bridges become unusable.

Today, approximately 78.5% of current New York State coastal residents have never experienced a major hurricane (Hughes). Though New Yorkers are aware what hurricanes can do (images of Katrina have been burned in their memory), there is a misguided sense that this region is not vulnerable to same kind of storm as the Gulf or Florida and would experience only minor inconveniences (downed trees, flooded basements and temporary power outages). In reality even here in the northeast, strong hurricanes threaten to bring a wall of water two stories high, winds on a large-scale the equivalent of an F2 or even F3 tornado, and a normal season's rainfall in a day.

 

Scott A. Mandia, Professor of Physical Sciences, SUNY Suffolk has put together an excellent page showing Long Island storm surge maps and animations here for various category hurricanes. From that site, the following

Hurricane storm surge causes approximately 90% of all storm deaths and injuries and much of the damage, therefore it is important for residents of Long Island, New York to be aware of the areas that will be affected by the storm surge. The southern shore of Long Island is most vulnerable to storm surge inundation because hurricane landfall will first occur there and the low elevation will allow sea water to move well inland.

The height of maximum storm surge is a function of storm strength, location of eye landfall, tidal time of landfall, elevation, and speed of storm. The images below represent the various regions of the southern shores of Long Island as well as the north and south forks as they would be affected by storm surge from various strength hurricanes. The images are derived from HURREVAC, a DOS-based software application that uses historical storm data and Long Island regional topography to estimate areas that would be inundated by water. (It should be noted that category 5 storm surges are not predicted by HURREVAC since there is little probability of such storms and no historical data exists for reference.) Each zone assumes landfall within that zone at normal tidal height. For high tide landfall, one would need to add 1/2 normal tide height to the predicted surge, while landfall at low tide would require a subtraction of 1/2 normal tide height from the predicted surge. The animated image was created using Microsoft GIF Animator and shows a loop of all maps within the zone with a five second interval between images.

The key appearing above indicates maximum storm surge height in that region for each category strength. For this example, the storm surge height for a category 4 hurricane would be 29 feet above normal sea-level.

  No Hurricane

  CAT 1 Hurricane

  CAT 2 Hurricane

  CAT 3 Hurricane

  CAT 4 Hurricane

  All Maps Animation

  No Hurricane

  CAT 1 Hurricane

  CAT 2 Hurricane

  CAT 3 Hurricane

  CAT 4 Hurricane

  All Maps Animation

  No Hurricane

  CAT 1 Hurricane

  CAT 2 Hurricane

  CAT 3 Hurricane

  CAT 4 Hurricane

  All Maps Animation

  No Hurricane

  CAT 1 Hurricane

  CAT 2 Hurricane

  CAT 3 Hurricane

  CAT 4 Hurricane

  All Maps Animation

  No Hurricane

  CAT 1 Hurricane

  CAT 2 Hurricane

  CAT 3 Hurricane

  CAT 4 Hurricane

  All Maps Animation

   No Hurricane

  CAT 1 Hurricane

  CAT 2 Hurricane

  CAT 3 Hurricane

  CAT 4 Hurricane

  All Maps Animation

  No Hurricane

  CAT 1 Hurricane

  CAT 2 Hurricane

  CAT 3 Hurricane

  CAT 4 Hurricane

  All Maps Animation

  No Hurricane

  CAT 1 Hurricane

  CAT 2 Hurricane

  CAT 3 Hurricane

  CAT 4 Hurricane

  All Maps Animation

The 1938 Hurricane was a category 3 storm that made landfall near Bellport, New York. Therefore, the three surge maps that best represent what may have occurred in 1938 are:

Some of the key observations from the above include:

  • Category 1 hurricanes inundate just about all of the immediate south shore of the Island, including the north side of Great South Bay locations and both sides of the north and south forks.
  • Montauk Highway (RT. 27A) is completely covered by flood waters during a Category 3 hurricane. Therefore, this road would be considered impassable during the storm.
  • The highest storm surges (Category 4) would occur in the following regions:
    • Amityville Harbor - 29 feet
    • Atlantic Beach & Long Beach areas - 24 to 28 feet
    • South Oyster Bay, Middle Bay, & East Bay areas - 24 to 28 feet
    • Montauk Point is completely cut off from rest of south fork during a category 1 storm.
    • Much of the north and south forks are entirely under water during a category 3 hurricane.
    • A category 4 hurricane inundates the entire towns of: Amityville, Lindenhurst, Babylon, West Islip, East Islip, Bayshore, Gilgo Beach, Cedar Beach, Great South Beach, Fair Harbor, Cherry Grove, Cupsogue, Westhampton Beach, Watermill Beach, Wainscott Beach, Plum Island, Gardiner's Island, Orient, Shelter Island (except for a few high points), Greenport, North Haven, Amagansett Beach, Napeague Beach, Montauk, Woodmere, Valley Stream, Linbrook, Long Beach, Atlantic Beach,
    • Freeport, Merrick, Wantagh, Lido Beach, Jones Beach, and Tobay Beach.

See his excellent introduction to hurricanes here.

Could this be the year? Well we had a strong La Nina and the Atlantic continues in its warm mode. Waters off the east coast are warmer than normal.

But will the warm water in the eastern most Pacific increase activity enough there to increase shear and alter Atlantic storm tracks? Official forecasts from Bill Gray and others suggest no. 

 

The upper pattern this spring and summer has featured a persistent trough in the central and eastern United States and a suppressed jet stream and storm tracks.

This may be the most telling omen of all.  However this pattern has finally weakened in August perhaps as the La Nina measures have gone neutral and the eastern Tropical Pacific has taken on an El Nino look. Hopefully this will delay the inevitable at least another year. Next week the risk for New England.

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