Looking Back at Sandy's Surge

Hurricane Sandy devastated much of the Mid-Atlantic Coast this week with ferocious winds, record-setting storm surge and destructive waves. While the economic toll from this disaster could total up to $50 billion (Huffington Post, November 2, 2012), the staggering human loss has made this storm a catastrophe. The latest death toll has risen to 80 fatalities in the U.S., including 38 victims in New York City (New York Times, November 2, 2012.)

The record-breaking storm surge, which smashed ashore most viciously in New Jersey and New York, caused many of these fatalities and much of the damage. On Staten Island, for example, a two-year-old boy drowned when the surge swept him from his mother’s arms (New York Times, November 1, 2012). Photos of the surge damage depict homes which were either smashed to pieces or floated off their foundations, as well as debris-covered streets, which were also buried under feet of sand.

Preliminary surge observations have provided a maximum surge level of 14.6 feet at Bergen Point, NJ (www.abcnews.go.com.) However, surge levels were devastatingly high all along the New Jersey Coast, in the metropolitan New York City area, on Long Island, and even in coastal New England.

Battery Park, NY, located at the southern tip of Manhattan Island, set a new record high water level of 17.33 feet above the station datum, a vertical reference line for measuring water heights. This water level was reached through a combination of high astronomical tides and a 9.23-foot storm surge, which is the storm-driven water height above normal tide levels. Such high water levels enabled salt water to pour over sea walls in Lower Manhattan and inundate the subway system under many feet of water.

Sandy’s water level at Battery Park broke Hurricane Donna’s (1960) previous high-water record by more than four feet. It is also interesting to note that Hurricane Sandy’s massive surge comes just 14 months after Hurricane Irene inundated much of the coastline, producing the fourth highest water level of all time at Battery Park.

These surge observations will be incorporated into SURGEDAT, the world’s most comprehensive storm surge archive. This dataset has been developed through funding made possible by NOAA-funded SCIPP, the Southern Climate Impact Planning Program. SURGEDAT has identified the peak storm surge level in more than 450 global surge events since 1880, including more than 300 events in the United States. Recently this dataset was expanded to include the entire inundation footprint for more than 240 U.S. surge events. These footprints contain more than 6,100 historic storm surge observations in the United States.

These data are useful for coastal decision makers, emergency management professionals, insurance professionals, as well as coastal scientists and storm surge modelers. For example, such data are very useful for risk-assessment studies, which identify critical inundation thresholds, such as the 100-year storm surge level for a given location. These data are also useful to validate storm surge models, which often need actual observed data to validate model runs.

Prior to Sandy’s landfall, SCIPP mapped out hurricane paths and inundation envelopes for five previous hurricanes that generated storm surges in the New York City area. These maps provided historical context as Sandy approached. One of the key messages of these historical maps is that Sandy’s storm track was unprecedented along the Mid-Atlantic Coast. These maps also provided evidence that the area of coastline near New York City is very effective at funneling in storm surge, presumably because water gets trapped in this area. Storm surge levels during the 1944 Hurricane and Hurricane Donna (1960) were higher in this region than other areas along the coast- a realization that hopefully encouraged many people in the metro New York area to evacuate Sandy’s devastating storm surge.

A Few Storm Surge Photos from Hurricane Sandy

Surge inundating Battery Park, NY on Monday, October 29. Source: http://www.slate.com/articles/news_and_politics/gallery/2012/10/hurricane_sandy_floods_the_eastern_seaboard.html

Surge pours down an elevator shaft in New York City on Monday, October 29. Source: http://www.ticotimes.net/Current-Edition/News-Briefs/Apocalyptic-scenes-as-New-York-bears-brunt-of-Sandy_Monday-October-29-2012

Storm surge pours into New York City on Monday, October 29, 2012. Source: http://www.cnbc.com/id/49603293

Catastrophic Storm Surge Pounds Northeast

Storm surge levels in The Battery, or southern region of Lower Manhattan, have exceeded nine feet this evening. Storm tide (surge + tide) levels are approaching 14 feet, which means water has almost certainly flooded Lower Manhattan. Source: NOAA Tides and Currents

Surge levels at King's Point exceeded 12 feet earlier this evening. Fortunately the peak surge arrived near low tide. Although surge levels are slowly falling, high tide is approaching, which is keeping the total water level over 13 feet. These levels mean flooding is likely occurring over portions of northern and northeastern NYC. Source: NOAA Tides and Currents

Sandy's catastrophic storm surge has arrived along the Mid-Atlantic and Northeast Coast. A brief update on water levels:

1. Water levels in The Battery are 13.81 feet above Mean Lower Low Water (a datum over which we measure surge levels.) This is more than nine feet above normal tide levels for this evening, and may move Sandy's surge into first place all time for this location. However, these data must be adjusted for tides and datums, then compared on equal footing with other storms.

2. Storm surge levels exceeded 12 feet at King's Point, on the southwest portion of Long Island Sound. This is a tremendous surge level for this area, as Sandy pushed water from E to W through the Sound. This likely flooded portions of New York City, including the eastern Bronx.

3. Winds in the New York metro area have shifted more towards the south, which has increased surge levels near The Battery but enabled surge levels to drop a bit at King's Point.

Water levels overnight will remain extremely localized, but will likely be highest in areas such as Northern NJ, The Battery and portions of NYC exposed by water to the south and southeast, as well as the south coast of Long Island. Strong southerly winds will also make it difficult for excess water to drain out of Long Island Sound.

Listen to Isaac

Image: http://www.awesomestories.com/assets/isaac-cline1

We would be prudent to listen to the words of Isaac Cline, the Chief Meteorologist at Galveston, Texas, when the great Galveston Hurricane of 1900 hit. Prior to landfall, the winds were blowing strong offshore, yet water levels were rising. Then, as the storm made landfall, the winds quickly changed direction and the water levels rose incredibly fast!

Read his words below....especially the quote that, "the sudden rise of 4 feet brought it [the water] above my waist before I could change my position."

Quote from Isaac Cline:

The water rose at a steady rate from 3 p.m. until about 7:30 p.m., when there was a sudden rise of about four feet in as many seconds. I was standing at my front door, which was partly open, watching the water, which was flowing with great rapidity from east to west. The water at this time was about eight inches deep in my residence, and the sudden rise of 4 feet brought it above my waist before I could change my position.

Story source: http://www.history.noaa.gov/stories_tales/cline2.html

Bringing this back to Hurricane Sandy:

Winds right now are generally blowing from the northeast across much of coastal NJ and NY. This is driving water down Long Island Sound from east to west, causing the highest surge levels (according to NOAA Tides and Currents) of more than eight feet at King's Point (on extreme SW Long Island Sound.) Surge levels at Battery Park are between 6.5 and 7 feet. 

Beware of sudden water level rise in The Battery, NYC area, and south-facing shores of Long Island, this evening. After Sandy makes landfall in NJ, winds will quickly change direction, blowing in from the SE, then S, which may cause rapid water-level rises near NYC. You may not have time to escape the sudden water-level rise.

Sandy Pounding Coast with Surge and Waves

Source: http://www.newsday.com/news/weather/hurricane-sandy-speeds-up-as-officials-give-last-warning-to-evacuate-1.4162130?qr=1

Sandy is pounding the East Coast with surge and waves. Surge is overwashing roads and flooding buildings in some places. This pic above shows wave action slamming the coast on Long Island.

Speaking of Long Island, the highest surge level available right now on the NOAA Tides and Currents is actually from Kings Point, on the extreme southwest portion of Long Island Sound, where surge levels are 7.62 feet, as of approximately 5:00PM EDT. This means winds are blowing hard from the E or NE, pushing water down Long Island Sound from E to W.

Surge levels at Sandy Hook, NJ were 7.37 feet, and in other portions of coastal NJ and NY, surge levels ranged from 5 to 7 feet. Large, destructive waves are riding on top of this surge.

Sandy is forecast to make landfall in the next few hours. Peak surge levels often occur near the time of landfall, to the "right" of the storm path.

Take note- after Sandy makes landfall, the wind direction in Northern NJ, NYC, and Long Island, should be from the southeast. This will likely produce even higher surge levels in these areas, even though the eye of the hurricane already hit the coast. Winds will eventually come from the south on Tuesday, which will push surge into the southern portion of Long Island, Long Island Sound, CT, RI, and MA. Southerly winds may keep surge levels near NYC high through Tuesday.

Some areas of southern Long Island may be experiencing offshore winds, if winds are howling from the northeast right now. This may serve to temporarily reduce surge levels, however, when winds come from the southeast or south later, surge levels may rapidly rise.

High water is washing over the roadway in Ocean City, MD

http://www.usnews.com/pubdbimages/image/39015/FE_DA_121028sandy_ocmd425x283.jpg

Lessons from Previous Storms

One last entry this morning. Just wanted to quickly summarize two main points that we can learn from storm surge history of the Mid-Atlantic/ Northeast Coast.

1. No storm in modern history has taken this track

The Southern Climate Impacts Planning Program (SCIPP) recently plotted maps which depict the storm tracks and storm surge/ storm tide levels of previous hurricanes to impact the Mid-Atlantic/ Northeast Coast. An interesting observation is that no previous hurricane in modern history has taken a track similar to Hurricane Sandy, which will approach the coast from the southeast.

That said, it is important to realize we're entering unprecedented territory with this storm. This means we should have lower confidence in surge forecasts because we've simply never been here before and have not been able to validate surge models. It's always prudent to approach uncertainty with caution, and all interests along the Mid-Atlantic and Northeast Coast, particularly in New Jersey, the New York City area, and Long Island, should be prepared for a catastrophic storm surge potentially exceeding 12 feet.

2. The 1944 Hurricane and Hurricane Donna (1960) demonstrated the ability of surge to pile up in "the corner" near New York City

Although the 1944 Hurricane and Hurricane Donna (1960) passed to the east of New York City, the highest surge levels in the area were near the city/ Northern New Jersey, even though these areas were on the "weak" side of the storm (see maps on previous blog post.) This should prove as a testament of the ability of that section of coast to trap storm surge and quickly enhance surge levels.

What will happen this time, as this portion of coast (Northern Jersey/ NYC) is in the area of highest surge risk for the first time? We don't know, as this is new territory, but an abundance of caution should be taken and people in this area should follow evacuation areas as communicated by authorities.

Comparing Sandy to a "typical" Mid-Atlantic hurricane

Hurricane Sandy's track, or storm path, will likely help generate a catastrophic storm surge along the Mid-Atlantic and Northeast Coast Monday and Tuesday, including the New York City area. This storm is taking an unprecedented track, as it turns to the northwest and will make landfall at a more perpendicular angle to the coast, unlike most storms, which travel along the coast. The graphics above show the difference between Sandy and "typical" Mid-Atlantic hurricanes.

The Southern Climate Impacts Planning Program (SCIPP) identified surge and storm tide levels in other destructive hurricanes that impacted New York City (see earlier blog post). All of these previous storms took a track "along the coast," which means Sandy's path, and storm surge, may be unprecedented.

All interests from the Delmarva Pensinsula to Cape Cod should monitor this storm closely. The largest and most destructive surge will likely occur to the north of landfall, in Northern New Jersey, the New York City area, Long Island and Long Island Sound. Keep in mind that Sandy is a very large storm, so surge levels will rise rapidly long before the storm makes landfall, likely inundating evacuation routes by early Monday.