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Sandy Continues to Batter the Outer Banks and Southeast Virginia, Targets the mid-Atlantic and Northeast on Monday
Accuweather

Oct 29, 2012 12:42 AM

Hurricane Sandy is a Category 1 Hurricane located at 35.9° N, 70.5° W with maximum sustained winds of 85 mph, gusting to 105 mph

Sandy is around 270 miles east-southeast of Cape Hatteras, N.C. as of Sunday evening, and she will continue to track off to the northeast this evening before making a north and then northwestward turn late tonight and tomorrow towards the mid-Atlantic coast. A landfall is likely late on Monday evening in southern New Jersey, near Atlantic City. Heavy rain bands and wind gusts as high as 50 mph will continue to batter southeastern Virginia and the Outer Banks of North Carolina tonight as the storm moves northeastward east of the Carolinas. The rain and wind along the vulnerable Outer Banks, will cause coastal flooding, some power outages and possible wash outs of some coastal roadways as well.

Sandy will then take a turn back to the northwest and west and make landfall on Monday evening in southern or central New Jersey, likely not far from the Atlantic City area. This will be a large storm that has hybrid characteristics of a tropical system and a non-tropical low such as a nor'easter. Thus, the heavy rain and damaging winds will occur far out ahead of the center of this storm and will spread out in a several hundred mile radius away from the center of Sandy. Thus, we expect the storm to impact millions and cost billions as it produces damage across a large, heavily populated section of the country and travel disruptions and power outages can last for days if not over a week after the storm passes.

Damaging wind gusts on Monday through Tuesday in the 60- to 80-mph range will affect areas from Virginia to southern New England, causing widespread power outages and downed trees. In addition, there will be coastal flooding due to a 5- to 10-foot storm surge along the coast along and to the north and northeast of the center of circulation of Sandy and waves offshore can be as high as 30-40 feet. A widespread area of 4-8 inches of heavy rain will also batter much of the mid-Atlantic leading to flooding of creeks, streams and small rivers that will rise quickly due to all the rainfall. Wind gusts of 80 to as high as 100 mph could occur late tomorrow and tomorrow evening across some areas of the Jersey Shore or southern Long Island. Even hurricane-force wind gusts could impact New York City tomorrow afternoon and evening.

Wind and rain will gradually subside on Tuesday and then diminish more so by Wednesday and Thursday as the center of Sandy drifts northward into New York state and weakens.

In addition, Sandy will throw moisture into unseasonably cold air coming south through the Midwest, cold enough to cause snow in the mountains of West Virginia. Blizzard warnings are in effect for mountainous regions of West Virginia and Garrett County in Maryland where over a foot may fall.

Elsewhere across the Atlantic Basin, we are not anticipating any tropical development in the next 24 to 48 hours.

Worst of Sandy Yet to Come: Northeast Impacts

An extremely rare and dangerous storm will turn in from the Atlantic, affecting 60 million people in its path and could lead to billions of dollars in damage.

Hurricane Sandy is forecast by AccuWeather.com to slam into New Jersey Monday evening.

Coastal inundation and damaging wind will occur in the Garden State and the New York metropolitan area. However, damaging and life-threatening impact from the giant, powerful storm will reach as far inland as the central Appalachians and will span the coast from North Carolina to southern New England. Conditions will deteriorate through Sunday night with the worst of the storm raging Monday into Tuesday.

Sandy will weaken over land at midweek, but conditions will remain adverse throughout the Northeast, eastern Great Lakes and upper Ohio Valley.

Ripple-effect flight delays and cancellations are possible over a large part of the nation, as the storm will target major airports from Boston to Washington, D.C., with New York and Philadelphia in the middle. Many aircraft originate from or travel to these hubs on a daily basis.

Impacts from heavy rain and wind will be felt hundreds of miles inland and the power in some neighborhoods could be out for days.

Storm surge flooding will occur over a much larger area, when compared to a hurricane and more severe than a typical nor'easter. It is likely to be more than just a few waves over washing the seawall in the hardest-hit areas.

Sandy has the potential to bring historic storm surge flooding near and north of the center.

There is the potential from central New Jersey to New York City and western Long Island have some of their worst coastal flooding on record with Sandy tracking into New Jersey.

Communities, neighborhoods, roads, rail yards, subway stations and other low-lying areas near the coast, generally north of the track can take on feet of salt water.

AccuWeather.com meteorologists are expecting a storm surge of 5 to 10 feet, but locally higher levels are possible near and just north of the storm track.

The full moon during the afternoon of Monday, Oct. 29, will add to high tide levels spanning the 28th through the 30th.

Near-coast waves will average 10 to 15 feet, while seas well offshore will range from 30 to 40 feet.

Damaging wind gusts will reach from Boston to Washington, D.C., and inland to the central Appalachians. Sandy will not be your typical hurricane when it moves in from the southeast. Hurricanes are small and compact.

Sandy will be more like a large nor'easter on steroids. It could have the impact of a Category 2 hurricane. Tropical storm wind gusts will extend out hundreds of miles from the center, so focusing on the center alone in terms of the severity for wind and rain is not recommended.

A extended period of wind gusts between 40 and 60 mph is forecast for two days, which will take its toll on structures, trees and power lines.

There is the potential for tens of thousands of trees to be downed and millions of utility customers could be without power at some point. Flying debris, including airborne panes of glass in the larger cities will pose a danger. Some secondary roads could be blocked by trees. Depending on the landscape, such as heavily wooded areas, the power could be out for a week or more.

Flash, urban and small steam flooding from rainfall will also be a significant impact. Sandy has the potential to bring over a half of a foot of rain to some areas on its west, northwest and north flanks.

Places in Delaware, southern New Jersey and southeastern Pennsylvania--including Philadelphia--could top Sandy's rainfall totals with more than 8 inches expected.

Fallen leaves will block storm drains in some towns and cities. Small streams will immediately rise in response to the rainfall.

Enough cold air will wrap into Sandy's far western side to bring heavy, wet snow to the mountains from northern North Carolina to southwestern Pennsylvania Monday into Wednesday. It is possible that snow zone extends northward to extreme western New York.

Snowfall should top a foot in the higher terrain of West Virginia.

Central and northern New England will be spared the worst of the storm due to the forecast track well to the south. However, there will be problems with strong wind gusts, heavy rain, coastal flooding and beach erosion. These conditions will trend more serious heading west along the South coast.

Eastern North Carolina will be spared the worst as well with the storm making landfall over New Jersey. However, north to northeast winds will bring above-normal tides and coastal flooding concerns to the Outer Banks. Strong, gusty winds can also cause power outages during and in the wake of the storm for a time.

Click for our complete daily Tropical Weather Information

Sandy Cuts Power to Millions, Causes Historic Flooding

Latest:
Sandy: Worst of Storm is Over, Impact Continues

Millions of people are without power in 16 states, after Sandy slammed into New Jersey on Monday evening. The storm shut down the New York City subways and the Battery has registered record-high flooding.

Photos: Hurricane Sandy Floods New York City, New Jersey

The Stats Are In: Superstorm Sandy Totals

The National Hurricane Center said that post-tropical cyclone Sandy officially made landfall near Atlantic City around 8 p.m. EDT Monday, Oct. 29, 2012.

LATEST UPDATES:
1:55 p.m. EDT Tuesday: National Guard's aerial footage of the New Jersey coast shows the extent of damage.

1:35 p.m. EDT Tuesday: More than 15,000 flights have been canceled due to Sandy's impact since Sunday, according to FlightStats.com. La Guardia Airport remains shut down.

1:20 p.m. EDT Tuesday: Sandy didn't have the impact of a hurricane everywhere. In portions of the Appalachians and Midwest, it was and continues to bring cold rain, biting winds and even blizzard conditions. Details

1:15 p.m. EDT Tuesday: New Jersey received the biggest blow from Sandy. For details on Sandy's impacts in New Jersery, a link to photos and when the weather will improve, click here.

12:10 p.m. EDT Tuesday: The worst of Sandy is over, but some impacts will still be felt in the coming days. Details

12:00 p.m. EDT Tuesday: We have compiled all of the stats from Sandy in one place.

11:30 a.m. EDT Tuesday: Nearly one million customers are still without power on Long Island alone. Latest power outage map.

10:30 a.m. EDT Tuesday: "There are currently 2.4 million households without power, twice the number from Irene. #Sandy," Governor Christie tweeted.

9:38 a.m. EDT Tuesday: The Chicago Sun-Times reports that 7.4 million lost power from Sandy and 17 people were killed in the U.S. The power outages from Sandy fall just short of those caused by Hurricane Ike.

9:20 a.m. EDT Tuesday: WABC-TV Channel 7 Eyewitness News: "Governor Cuomo announced this morning the reopening of the Tappan Zee Bridge, effective at 9 a.m. Motorists are reminded to drive carefully. Local roads in Westchester and Rockland may be closed due to flooding or blockage from storm debris. With extensive recovery efforts underway, the Governor advises against any unnecessary travel, which will enable repair crews to move quickly to the areas requiring immediate attention."

9:15 a.m. EDT Tuesday: Major travel problems are continuing in the big Northeast cities as a result of Sandy. Hundreds of flights have been canceled today at Philadelphia International Airport, Newark Liberty International, La Guardia Airport, John F. Kennedy International and Logan International Airport in Boston. According to FlightStats.com, a total of 5,815 flights have been canceled in the U.S. so far today.

8:30 a.m. EDT Tuesday: There will be a risk of damaging thunderstorms across portions of New England today, including across Rhode Island, Massachusetts, Connecticut, New Hampshire, Vermont and southeastern Maine. Gusty winds will be the primary concern. AccuWeather Expert Senior Meteorologist Mark Mancuso emphasized that this is a bad scenario with many people without power and means of communication.

7:00 a.m. EDT Tuesday: Flooding occurred along the Hudson River due to Sandy's storm surge. The Hudson River rose to 9.54 feet at Poughkeepsie, N.Y., located 59 miles north of Central Park, setting a new record high. The old record was 8.00 feet set on Aug. 28, 2011. The Hudson River reached 11.30 feet at Albany, N.Y., located 135 miles north of Central Park. Flood stage at Albany is 11.00 feet.

6:35 a.m. EDT Tuesday: Moderate flooding is occurring in the Chesapeake Bay with high tide. Minor flooding is being reported in Baltimore, Md. Meanwhile, major flooding is occurring in Cleveland, Ohio, along the Cuyahoga River. The water level is at 20.92 feet there, which is not too far short of the record flood stage 23.3 feet.

6:10 a.m. EDT Tuesday: Reuters reports that a levee has broken in northern New Jersey, in Bergen County, flooding three towns with as much as 4-5 feet of water. The towns impacted include Moonachie, Little Ferrie and Carlstadt. Click here for details.

6:05 a.m. EDT Tuesday: NYC Fire Update: 200 firefighters involved with massive 6-alarm fire in Breezy Point section of the Rockaway peninsula in Queens.

4:15 a.m. EDT Tuesday: Approximately 1/4 of the population of New Jersey is now without electricity.

4:00 a.m. EDT Tuesday: NYC Fire Update: Breezy Point section of the Rockaway peninsula in Queens engulfed in 6-alarm fire. 60 structures are involved.

3:15 a.m. EDT Tuesday: Massive 5-alarm fire burning scores of homes in Breezy Point section of the Rockaway peninsula in Queens.

2:15 a.m. EDT Tuesday: A total of nearly 7 million people are now without electricity due to Sandy.

1:00 a.m. EDT Tuesday: 17 inches of snow has fallen so far in Davis, WV. Much more to come.

For reports from Sandy before landfall on Monday, click here.

For reports from Sandy over the weekend, click here.

Thumbnail image from New York City was tweeted by Elias Lopez on Monday, Oct. 29, 2012. To see an entire collection of photos from Sandy, click here.

Sandy: Worst of Storm is Over, Impact Continues

The worst of the wind and storm surge flooding from Sandy has passed, but ongoing problems with travel disruptions, power outages and the mess to clean up continues.

Residents of coastal New Jersey and Long Island are dealing with the shock, and officials continue to assess the damage. Houses have been knocked off the foundation in Seaside Heights, N.J. Piers and boardwalks have been torn up along the mid-Atlantic coast. The sea wall in Narragansett, R.I., was damaged. Some areas were still under water Tuesday midday in the coastal Northeast.

NYC subway lines remained closed as well as the Path Train from New Jersey to NYC Tuesday. Storm surge entered tunnels during the height of Sandy Monday evening. Some below ground transit services could be out for days.

Normal flight operation is still "up in the air." More than 5,800 flights were canceled Tuesday. LaGuardia, JFK, Newark and Teterboro airports remained closed to start the day. With many aircraft originating from or going to these airports, flight impacts will continue to be felt not only in the U.S., but overseas for days.

This combination of photos shows above, lower Manhattan dark after the hybrid storm Sandy on Monday, Oct. 29, 2012, and below a fully lit skyline on Jan. 6, 2012, both seen from the Brooklyn borough of New York. (AP Photo).

Downed trees and blown transformers in New York state and New Jersey contributed to over 4 million homes and businesses being without power during the storm. Hundreds of thousands of people were without power in New England with outages reaching into Vermont, New Hampshire and Maine.

Images from around the Northeast are available in this AccuWeather.com photos story.

AccuWeather.com Forecast
Fortunately, as large and powerful as Sandy was, it continues to move inland and unwind. Showers will continue to rotate through the Northeast through the middle of the week.

For those without power, the weather will continue to trend chilly. Colder air will filter eastward through the end of the week, erasing the wedge of warmth in portions of New England.

Folks in northern New England should be thankful Sandy pushed westward as projected, rather than northward, like Irene did. Folks over the interior of the mid-Atlantic should be thankful cold air held on near the surface, forcing most of Sandy's damaging winds far over the heads of where most people live. Otherwise, the situation, as bad as it was on the coast, could have been much worse for inland areas.

Despite the cold air to the west, damaging wind gusts have been felt as far west as Great Lakes.

Runoff from torrential rainfall over portions of Maryland and southern Pennsylvania will lead to moderate flooding along the Potomac River late Wednesday.

Meanwhile, the storm is far from over in the Midwest and southern Appalachians, where, cold wind and even snow continue.

Sandy Statistics
A record high water level of 13.88 feet occurred at Battery Park, N.Y., Monday evening.

The Stats Are In: Superstorm Sandy Totals

Peak wind gusts: 96 mph at Eatons Neck, N.Y.; 85 mph at Madison, Conn.; 78 mph at Newark, N.J.; 69 mph at Westerly State, R.I.; 74 mph at East Milton, Mass.; 70 mph at Allentown, Pa.; 68 mph at Wallops Island, Va.; 64 mph at St. Inigoes, Md.; 63 mph at Portland, Maine; 58 mph at Wilmington, Del.; 55 mph at Morrisville, Vt.; 55 mph at Concord, N.H.; and 54 mph at Washington-Dulles, D.C.

Rainfall: 9.57 inches at Virginia Beach, Va.; 8.27 inches at Patuxent River, Md.; 6.22 inches at Glencoe, Pa.; 5.76 inches at Millville, N.J.; 3.03 inches at East Milton, Mass.; 4.69 inches at Wilmington, Del.; 2.96 inches at Niagara Falls, N.Y.; and 1.32 inches at Willimantic, Conn.

A near-record low barometric pressure occurred with Sandy offshore Monday afternoon. The pressure bottomed at 27.76 inches. For a storm north of Cape Hatteras, N.C., Hurricane Gladys of 1977 holds the record at 27.73 inches. Gladys was a Category 4 hurricane which remained off the coast of the U.S.

SOURCE

Why did Hurricane Sandy take such an unusual track into New Jersey?
Jeff Masters

4:33 PM GMT on October 31, 2012

We're used to seeing hurricane-battered beaches and flooded cities in Florida, North Carolina, and the Gulf Coast. But to see these images from the Jersey Shore and New York City in the wake of Hurricane Sandy is a shocking experience. New Jersey only rarely gets hit by hurricanes because it lies in a portion of the coast that doesn't stick out much, and is too far north. How did this happen? How was a hurricane able to move from southeast to northwest at landfall, so far north, and so late in hurricane season? We expect hurricanes to move from east to west in the tropics, where the prevailing trade winds blow that direction. But the prevailing wind direction reverses at mid-latitudes, flowing predominately west-to-east, due to the spin of the Earth. Hurricanes that penetrate to about Florida's latitude usually get caught up in these westerly winds, and are whisked northeastwards, out to sea. However, the jet stream, that powerful band of upper-atmosphere west-to-east flowing air, has many dips and bulges. These troughs of low pressure and ridges of high pressure allow winds at mid-latitudes to flow more to the north or to the south. Every so often, a trough in the jet stream bends back on itself when encountering a ridge of high pressure stuck in place ahead of it. These "negatively tilted" troughs have winds that flow from southeast to northwest. It is this sort of negatively tilted trough that sucked in Sandy and allowed the hurricane to take such an unusual path into New Jersey.


Figure 1. Inlet section of Atlantic City, N.J., after Hurricane Sandy. Image credit: 6 ABC Action News.

The 1903 Vagabond Hurricane
The only other hurricane to hit New Jersey since 1851 besides Sandy was the 1903 Category 1 Vagabond Hurricane. According to Wikipedia, the Vagabond Hurricane caused heavy damage along the New Jersey coast ($180 million in 2006 dollars.) The hurricane killed 57 people, and endangered the life of President Theodore Roosevelt, who was sailing on a yacht near Long Island, NY, when the hurricane hit. However, the Vagabond Hurricane hit in September, when the jet stream is typically weaker and farther to the north. It is quite extraordinary that Sandy was able to hit New Jersey in late October, when the jet stream is typically stronger and farther south, making recurvature to the northeast much more likely than in September.


Figure 2. The path of the 1903 Vagabond Hurricane, the only other hurricane to hit New Jersey since 1851.

The blocking ridge that steered Sandy into New Jersey
A strong ridge of high pressure parked itself over Greenland beginning on October 20, creating a "blocking ridge" that prevented the normal west-to-east flow of winds over Eastern North America. Think of the blocking ridge like a big truck parked over Greenland. Storms approaching from the west (like the fall low pressure system that moved across the U.S. from California to Pennsylvania last week) or from the south (Hurricane Sandy) were blocked from heading to the northeast. Caught in the equivalent of an atmospheric traffic jam, the two storms collided over the Northeast U.S., combined into one, and are now waiting for the truck parked over Greenland to move. The strength of the blocking ridge, as measured by the strength of the North Atlantic Oscillation (NAO), was quite high--about two standard deviations from average, something that occurs approximately 5% of the time. When the NAO is in a strong negative phase, we tend to have blocking ridges over Greenland.


Figure 3. Jet stream winds at a pressure of 300 mb on October 29, 2012, as Hurricane Sandy approached the coast of New Jersey. Note that the wind direction over New Jersey (black arrows) was from the southeast, due to a negatively tilted trough of low pressure over the Eastern U.S. caused by a strong blocking ridge of high pressure over Greenland. Image credit: NOAA/ESRL.

Arctic sea ice loss can cause blocking ridges
Blocking ridges occur naturally, but are uncommon over Greenland this time of year. According to NOAA's Climate Prediction Center, blocking near the longitude of Greenland (50°W) only occurs about 2% of the time in the fall. These odds rise to about 6% in winter and spring. As I discussed in an April post, Arctic sea ice loss tied to unusual jet stream patterns, three studies published in the past year have found that the jet stream has been getting stuck in unusually strong blocking patterns in recent years. These studies found that the recent record decline in Arctic sea ice could be responsible, since this heats up the pole, altering the Equator-to-pole temperature difference, forcing the jet stream to slow down, meander, and get stuck in large loops. The 2012 Arctic sea ice melt season was extreme, with sea ice extent hitting a record lows. Could sea ice loss have contributed to the blocking ridge that steered Sandy into New Jersey? It is possible, but we will need to much more research on the subject before we make such a link, as the studies of sea ice loss on jet stream patterns are so new. The author of one of the new studies, Dr. Jennifer Francis of Rutgers, had this say in a recent post by Andy Revkin in his Dot Earth blog: "While it's impossible to say how this scenario might have unfolded if sea-ice had been as extensive as it was in the 1980s, the situation at hand is completely consistent with what I'd expect to see happen more often as a result of unabated warming and especially the amplification of that warming in the Arctic."

Sandy by the numbers: trying to comprehend a stunning disaster
Jeff Masters

7:19 PM GMT on November 01, 2012

The immensity of the impact of Superstorm Sandy on the Eastern U.S. is difficult to comprehend, and the scenes of devastation coming from the impact zone are stunning and heart-wrenching. To help understand the extraordinary scale of this historic storm, I've put together a list of notable statistics from Sandy:

Death toll: 160 (88 in the U.S., 54 in Haiti, 11 in Cuba)

Damage estimates: $10 - $55 billion

Power outages: 8.5 million U.S. customers, 2nd most for a natural disaster behind the 1993 blizzard (10 million)

Maximum U.S. sustained winds: 69 mph at Westerly, RI

Peak U.S. wind gusts: 90 mph at Islip, NY and Tompkinsville, NJ

Maximum U.S. storm surge: 9.45', Bergen Point, NJ 9:24 pm EDT October 29, 2012

Maximum U.S. Storm Tide: 14.60', Bergen Point, NJ, 9:24 pm EDT October 29, 2012

Maximum wave height: 33.1' at the buoy east of Cape Hatteras, NC (2nd highest: 32.5' at the Entrance to New York Harbor)

Maximum U.S. rainfall: 12.55", Easton, MD

Maximum snowfall: 36", Richwood, WV

Minimum pressure: 945.5 mb, Atlantic City, NJ at 7:24 pm EST, October 29, 2012. This is the lowest pressure measured in the U.S., at any location north of Cape Hatteras, NC (previous record: 946 mb in the 1938 hurricane on Long Island, NY)

Destructive potential of storm surge: 5.8 on a scale of 0 to 6, highest of any hurricane observed since 1969. Previous record: 5.6 on a scale of 0 to 6, set during Hurricane Isabel of 2003.

Diameter of tropical storm-force winds at landfall: 945 miles

Diameter of ocean with 12' seas at landfall: 1500 miles


Figure 1. The Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite acquired this image of Superstorm Sandy around 3:35 a.m. Eastern Daylight Time (7:35 Universal Time) on October 30. This image is from the "day-night band" on VIIRS, which detects light wavelengths from green to near-infrared. The full Moon lit up the tops of the clouds. Image credit: NASA.



Figure 2. Preliminary death and damage statistics for Sandy as compiled by Wikipedia on November 1, 2012.



Figure 3. Precipitation from Superstorm Sandy for the 7-day period ending at 8 am EDT Thursday, November 1, 2012. Image credit: NOAA/NWS/AHPS.



Figure 4. Top five weather-related power outages in the U.S.



Figure 5. Strong winds from Sandy blow snow in West Virginia on October 30, 2012. Image credit: Facebook/Cheryl Clay


Sandy's snows
Several cities set records for snowiest October day on record during Sandy: Elkin, WV (7", previous record, 4.6" in 1917) and Bluefield (4.7", previous record 3.2" in 1993.) Heavy snows caused roof collapses in West Virginia, and snows of two feet or more fell in four states--West Virginia, Tennessee, Maryland, and Virginia. However, Sandy fell short of setting the all-time record for snowfall from a hurricane. The Vermont Journal estimated that the Snow Hurricane of 1804 dumped up to 4 feet of snow in Vermont.

36" Richwood, WV
34" Mount Leconte, TN
34" Sevier, TN
33" Clayton, WV
32" Snowshoe, WV
29" Quinwood, WV
28" Frostburg, WV
28" Davis, WV
28" Huttonsville, WV
28" Flat Top, WV
26" Redhouse, MD
26" Garret, MD
26" Craigsville, WV
24" Oakland, MD
24" Alpine Lake, WV
24" Nettie, WV
24" Norton, VA
24" Quinwood, WV
24" Alexander, WV

Links
Impressive loop of 1-minute visible satellite imagery spanning 6 days of Sandy's life.

A one-day time lapse video from a New York City webcam showing Sandy's impact on the city. It's eerie to see the city suddenly plunged into darkness.

First round of damage assessment aerial imagery collected by NOAA's National Geodetic Survey on Oct. 31 along the New Jersey coast.


Figure 6. Flooding in Haiti from Hurricane Sandy. Image credit: The Lambi Fund of Haiti.

Charities mobilize for Sandy
The outpouring of charitable donations in the wake of the devastation wrought by Hurricane Sandy has been one of the bright spots in the gloomy aftermath of the storm. The main owners of The Weather Channel have agreed to match donations of up to $1 million to the American Red Cross, if you text SANDY to 90999 ($10). I also recommend my favorite disaster relief charity, Portlight.org. They are focusing their response efforts exclusively on the post-Sandy neeeds of people with disabilities.Check out the Portlight blog to see what they're up to; donations are always needed.

Sandy's greatest devastation occurred in Haiti, where rains of up to 20 inches in 24 hours unleashed rampaging flood waters that killed at least 54, left 200,000 homeless, wiped out thousand of acres of crops, and killed massive numbers of livestock. For impoverished families in Haiti still struggling to recover from the earthquake in 2010 and Hurricane Isaac in August, Sandy was devastating.  These crops are the very essence of rural Haitian's livelihoods, and there are fears widespread starvation will result. A disaster relief charity in Haiti that I've contributed to for many years, The Lambi Fund of Haiti, is seeking donations to help farmers purchase local seeds so that they can replant their crops in the wake of this latest terrible Haitian catastrophe.

Hurricane Sandy's huge size: freak of nature or climate change?

Hurricane Sandy was truly astounding in its size and power. At its peak size, twenty hours before landfall, Sandy had tropical storm-force winds that covered an area nearly one-fifth the area of the contiguous United States. Since detailed records of hurricane size began in 1988, only one tropical storm (Olga of 2001) has had a larger area of tropical storm-force winds, and no hurricanes has. Sandy's area of ocean with twelve-foot seas peaked at 1.4 million square miles--nearly one-half the area of the contiguous United States, or 1% of Earth's total ocean area. Most incredibly, ten hours before landfall (9:30 am EDT October 30), the total energy of Sandy's winds of tropical storm-force and higher peaked at 329 Terra Joules--the highest value for any Atlantic hurricane since at least 1969. This is 2.7 times higher than Katrina's peak energy, and is equivalent to five Hiroshima-sized atomic bombs. At landfall, Sandy's tropical storm-force winds spanned 950 miles of the the U.S. coast, and high wind warnings were posted from Chicago to Eastern Maine, and from Michigan's Upper Peninsula to Florida's Lake Okeechobee--an area home to 120 million people. Sandy's winds simultaneously caused damage to buildings on the shores of Lake Michigan at Indiana Dunes National Lakeshore, and toppled power lines in Nova Scotia, Canada--locations 1200 miles apart!

Largest Atlantic tropical cyclones for area covered by tropical storm-force winds:

Olga, 2001: 780,000 square miles
Sandy, 2012: 560,000 square miles
Lili, 1996: 550,000 square miles
Igor, 2010: 550,000 square miles
Karl, 2004: 430,000 square miles



Figure 1. Hurricane Sandy's winds (top), on October 28, 2012, when Sandy was a Category 1 hurricane with top winds of 75 mph (this ocean surface wind data is from a radar scatterometer on the Indian Space Research Organization's (ISRO) Oceansat-2.) Hurricane Katrina's winds (bottom) on August 28, 2005, when Katrina was a Category 5 hurricane with top winds of 175 mph (data taken by a radar scatterometer on NASA's defunct QuickSCAT satellite.) In both maps, wind speeds above 65 kilometers (40 miles) per hour are yellow; above 80 kph (50 mph) are orange; and above 95 kph (60 mph) are dark red. The most noticeable difference is the extent of the strong wind fields. For Katrina, winds over 65 kilometers per hour stretched about 500 kilometers (300 miles) from edge to edge. For Sandy, winds of that intensity spanned an region of ocean three times as great--1,500 kilometers (900 miles). Katrina was able to generate a record-height storm surge over a small area of the Mississippi coast. Sandy generated a lower but highly destructive storm surge over a much larger area, due to the storm's weaker winds but much larger size. Image credit: NASA.

How did Sandy get so big?
We understand fairly well what controls the peak strength of a hurricane's winds, but have a poor understanding of why some hurricanes get large and others stay small. A number of factors probably worked together to create a "prefect storm" situation that allowed Sandy to grow so large, and we also must acknowledge that climate change could have played a role. Here are some possible reasons why Sandy grew so large:

1) Initial size of the disturbance that became Sandy was large
Sandy formed from an African tropical wave that interacted with a large area of low pressure that covered most of the Central Caribbean. Rotunno and Emanuel (1987) found that hurricanes that form from large initial tropical disturbances like Sandy did tend to end up large in size.


Figure 2. The initial disturbance that spawned Sandy, seen here on October 20, 2012, was quite large.

2) High relative humidity in Sandy's genesis region
The amount of moisture in the atmosphere may play an important role in how large a hurricane gets (Hill and Lackmann, 2009.) Sandy was spawned in the Caribbean in a region where the relative humidity was near 70%. This is the highest humidity we saw during 2012 during the formation of any Atlantic hurricane.

3) Passage over Cuba
Sandy struck Cuba as an intensifying Category 2 hurricane with 110 mph winds. While the core of the storm was over Cuba, it was cut off from the warm ocean waters surrounding Cuba. Most of Sandy's large circulation was still over the ocean, though, and the energy the storm was able to extract from the ocean went into intensifying the spiral bands over water. When Sandy's core re-emerged over water, the hurricane now had spiral bands with heavier thunderstorm activity as a result of the extra energy pumped into the outer portion of the storm during the eye's passage over land. This extra energy in the outer portions of Sandy may have enabled it to expand in size later.

4) Interaction with a trough of low pressure over the Bahamas
As Sandy passed through the Bahamas on October 25, the storm encountered strong upper-level winds associated with a trough of low pressure to the west. These winds created high wind shear that helped weaken Sandy and destroy the eyewall. However, Sandy compensated by spreading out its tropical storm-force winds over a much wider area. Between 15 and 21 UTC on October 25, Sandy's area of tropical storm-force winds increased by more than a factor of two.

5) Leveraging of the Earth's spin
As storms move towards Earth's poles, they acquire more spin, since Earth's rotation works to put more vertical spin into the atmosphere the closer one gets to the pole. This extra spin helps storms grow larger, and we commonly see hurricanes grow in size as they move northwards.

6) Interaction with a trough of low pressure at landfall
As Sandy approached landfall in New Jersey, it encountered an extratropical low pressure system to its west. This extratropical storm began pumping cold air aloft into the hurricane, which converted Sandy into an extratropical low pressure system, or "Nor'easter". The nature of extratropical storms is to have a much larger area with strong winds than a hurricane does, since extratropical storms derive their energy from the atmosphere along a frontal boundary that is typically many hundreds of miles long. Thus, as Sandy made landfall, the hurricane's strongest winds spread out over a larger area, causing damage from Indiana to Nova Scotia.

Are we likely to see more such storms in the future?
Global warming theory (Emanuel, 2005) predicts that a 2°C (3.6°F) increase in ocean temperatures should cause an increase in the peak winds of the strongest hurricanes of about about 10%. Furthermore, warmer ocean temperatures are expected to cause hurricanes to dump 20% more rain in their cores by the year 2100, according to computer modeling studies (Knutson et al., 2010). However, there has been no published work describing how hurricane size may change with warmer oceans in a future climate. We've seen an unusual number of Atlantic hurricanes with large size in recent years, but we currently have no theoretical or computer modeling simulations that can explain why this is so, or if we might see more storms like this in the future. However, we've seen significant and unprecedented changes to our atmosphere in recent decades, due to our emissions of heat-trapping gases like carbon dioxide. The laws of physics demand that the atmosphere must respond. Atmospheric circulation patterns that control extreme weather events must change, and we should expect extreme storms to change in character, frequency, and intensity as a result--and not always in the ways our computer models may predict. We have pushed our climate system to a fundamentally new, higher-energy state where more heat and moisture is available to power stronger storms, and we should be concerned about the possibility that Hurricane Sandy's freak size and power were partially due to human-caused climate change.

References
Emanuel, K. (2005). Increasing destructiveness of tropical cyclones over the past 30 years. Nature, 436(7051), 686-688.

Hill, Kevin A., and Gary M. Lackmann (2009), "Influence of environmental humidity on tropical cyclone size," Monthly Weather Review 137.10 (2009): 3294-3315.

Knutson, T. R., McBride, J. L., Chan, J., Emanuel, K., Holland, G., Landsea, C., ... & Sugi, M. (2010). Tropical cyclones and climate change. Nature Geoscience, 3(3), 157-163.

Rotunno, R., & Emanuel, K. A. (1987). An air-sea interaction theory for tropical cyclones. Part II: Evolutionary study using a nonhydrostatic axisymmetric numerical model. J. Atmos. Sci, 44(3), 542-561.

Jeff Masters