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The 2011 Hurricane Season is Over: Now for the Recap

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Usually, those of us who live in the Northeast think of hurricanes as the payback Floridians have to endure to make up for their balmy winters. But this year, we were reminded that these monster storms can and do strike on our own home turf. On Aug 28, Tropical Storm Irene slammed into New Jersey — its second landfall, after hitting North Carolina the day before as a hurricane.

Flooding at the White River National Fish Hatchery in Bethel, Vt. after Hurricane Irene. Credit: flickr/USFWS Northeast Region's photostream

By the time it reached the Jersey Shore, Irene was "only" a tropical storm, with sustained winds of 65 mph, but it was still powerful enough to knock down trees and power lines. It also dropped enough rain to cause major flooding, especially in New Jersey and Vermont. All in all, Irene was blamed for 40 deaths, and caused upwards of $7 billion in damage.

But it could have been a lot worse. Wind and rain are bad enough, but the worst damage, and most deaths, from a hurricane often comes from the storm surge, the wall of water that a hurricane pushes in front of it. That's what destroyed the Mississippi coastline and helped flood New Orleans when Katrina hit in 2005. A few days before Irene made landfall, experts were worried about what was in store for New York City. Jeff Masters of Weather Underground wrote earlier today about a very plausible worst-case scenario, in which Irene would have hit New York head-on as a Category 2 hurricane:

Since Irene was an exceptionally large storm with winds that covered a huge stretch of ocean, the storm had a much larger storm surge than its peak winds would suggest, and could have easily brought a storm surge of 15 - 20 feet to New York City. The storm would arrive during the new moon, when tides were at their highest levels of the month, compounding the storm surge risk.

In the end, the surge was only about 4.3 feet at Manhattan's southern end — still formidable, wrote Masters:

enough to top the city's seawall and flood low-lying park lands and roads near the shore. Fortunately, the water was not high enough to flood New York City's subway system, which could have easily occurred had Irene's winds been just 5-10 mph stronger.

Then, just a week later, Tropical Storm Lee  came ashore in Louisiana to cut a drenching path from the Gulf Coast to Canada, adding ten or more inches of rain to the the already-soggy land and swollen rivers. 

Still, the U.S. got off relatively easy from a season that had a total of 19 named tropical storms, seven full-fledged hurricanes and three major hurricanes — the third-highest total since record-keeping began in 1851, says the National Oceanic and Atmospheric Administration (NOAA) in its end-of-season recap

NOAA animation of the 2011 hurricane season.

That may not last, however. Hurricanes seem to come in natural boom-and-bust cycles. Lately, according to NOAA, we've been in something of a boom — a "trend of active hurricane seasons that began in 1995," says the agency's website. 

But like other natural climate cycles (the El Nino-Southern Oscillation, or ENSO, is another), the hurricane trends are likely to be affected over the coming century by anthropogenic — that is, human-caused — climate change. The greenhouse gases we keep pumping into the atmosphere are warming the planet, and that in turn is likely to change weather patterns. A new report from the Intergovernmental Panel on Climate Change (IPCC), for example, has taken a look at all the available evidence and concluded that extreme weather — especially heavy rainfall, heat waves and droughts — is likely to come more often and more severely in many parts of the world over as the century unfolds.

What about hurricanes? The picture there is less clear: as best they can determine, hurricanes may actually become fewer in number in the North Atlantic over the century, but more of the ones that do happen are likely to be Category 4 and 5 storms — the most powerful and dangerous kind.

Nobody knows how many of these will make landfall in the U.S., or anywhere else, for that matter: the tracks of these hypothetical future storms are impossible for science to predict at this point. If they do strike, odds are they'll do more damage than a similar storm might today, simply because the population is growing, putting more and more people and property in harm's way. 

At least the end of this hurricane season (they run from June 1 through Nov. 30 each year) lets us breathe a sigh of relief for the moment.

Or...maybe not. Mother Nature can't read the calendar, after all, and every so often, a tropical cyclone shows up after the party was supposed to over. In 2005, for example, the cyclone named Zeta achieved tropical storm status on December 30. It was only the second named storm in recorded history to start in one calendar year and end in another.

Comments

By Paul Budline (Princeton NJ)
on December 2nd, 2011

Just for some balance that is in short supply here at Climate Central, this is from Roger Pielke Jr.‘s blog:

“On December 4, 2011 it will have been 2,232 days since Hurricane Wilma made landfall along the Gulf coast as a category 3 storm back in 2005. That number of days will break the existing record of days between major US hurricane landfalls, which previously was between 8 Sept 1900 (the great Galveston Hurricane) and 19 Oct 1906. Since there won’t be any intense hurricanes before next summer, the record will be shattered, with the days between intense hurricane landfalls likely to exceed 2,500 days.  If you are in the insurance or reinsurance business and want to stir up a little constructive mischief, you should ask your favorite catastrophe modeling firm or ratings agency to show you the mathematics behind their estimate of the probability of zero intense hurricane landfalls from 2006 to present (both made at the time and what they’d say today). (Hint: Zero. Zip. Nada.).  This remarkable streak has to end sometime, and likely won’t be repeated anytime soon.”


Also, I’m wondering why your “What We’re Reading” section doesn’t include the recent study published in Science and reported in The Economist: 

http://www.economist.com/node/21540224

To summarize, “A paper published in this week’s Science, by Andreas Schmittner of Oregon State University, suggests ...  the climate is less sensitive to carbon dioxide than was feared.”

Perhaps “what you’re reading” are only alarmist screeds that reaffirm your biases, which make Chicken Little look absolutely Panglossian.

Reply to this comment

By Andrew
on December 2nd, 2011

Hi Paul,

I don’t think Mike’s story is in any way inconsistent with Roger’s observations. Also, our “what we’re reading” section changes daily, even multiple times a day. So just because you don’t see a story on there now doesn’t mean it wasn’t on there, or won’t be on there.

In fact, I wrote a story for washingtonpost.com on that very study.
http://www.washingtonpost.com/blogs/capital-weather-gang/post/most-dire-global-warming-forecasts-unlikely-study-finds/2011/11/27/gIQAz2er4N_blog.html

Reply to this comment

By Mike Lemonick (Princeton, NJ 08542)
on December 2nd, 2011

What Andrew said. I’m not clear what sort of balance Roger Pielke, Jr.‘s quote adds. I thought I WAS pretty clear about the fact that projections about future hurricanes are still uncertain, and that whether and where a storm makes landfall is a big factor in how much damage a hurricane will do—points Pielke himself makes quite often, and very legitimately. The IPCC made a similar point in its recent report on extreme events, pointing out that climate change is only one factor, and not necessarily the most important one, in how much damage these storms are likely to do in the future.

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