Hurricanes are well defined systems with characteristics that quite literally set them apart from other storms. Large storms such as Nor’Easters are sometimes less well defined and interact more with major troughs, the jet streams, etc. We have come to understand Hurricanes as the worst case scenario, while other storms are less dangerous.
But sometimes, and I suspect more recently lately, these non-tropical storms become quite dangerous. The Great Storm of ’78 killed hundreds in New England and made us suddenly realize that coastal property was a temporary thing. But we sense the danger of recent storms less acutely because for all storms we have better warning systems, and most storms don’t kill that many people these days, like they used to. So worse storms seem less bad.
And sometimes, it turns out that these large powerful and dangerous extratropical systems and the tropical hurricanes or their remnants merge and interact, creating what sometimes emerges as a “superstorm” or at least, a “really inconvenient storm.”
Sandy is an example of the former. Perhaps Hermine is an example of the latter. Hopefully not the former as well!
The focus on hurricanes as the dangerous big brother of temperate storms (including Nor’Easters) has unintentionally shaped our storm warning system to downplay by default non-hurricane storms, including the hurricanes themselves when they become extratropical. But the “remnants” of hurricanes over land are usually very dangerous because of the flooding they cause, and late in life former hurricanes are capable of ganging up with temperate systems to become very dangerous.
In the case of Superstorm Sandy, owing to global warming driven warm waters, the storm remained as a hurricane at the time it started to interact with temperate storm systems, and the result was one of the worst storms to hit the US East Coast. Yet, it was technically not a hurricane at landfall. Rather, it was a hurricane that ate another storm on its way to Ohio, and got too big, too powerful, too messy, and too dangerous to maintain use of the term (hurricane) normally reserved for better organized, more predictable, and better behaved dangerous storms.
Maybe we are seeing a shift in where the danger lies in Atlantic storms. There will never be a storm as dangerous as a Major Hurricane moving just the right way at just the right time against just the right piece of coastline. Ivan, Andrew, Katrina, like that. But the typical Category I hurricanes and the seemingly new phenomenon of more frequent post-tropical hybrids, and more frequent certain supercharged Nor’Easters seem all in about the same category of overall badness.
We are certainly seeing some self reflection on the part of meteorologists, who are always faced with the very difficult task of properly informing and educating the public, properly modulating alarm over a given storm system, always trying to not cause problems for the next storm by overstating or understating expectations. Some of this self reflection, as well as the gory details of how these different kinds of storms (Nor’Easter or Hurricane-Extratropical hybrid) develop is demonstrated in the following passages taken from various Hurricane Center discussions or Wikipedia, pertaining to the storms as indicated. I put them here for your enjoyment and/or horror.
1991 Perfect Storm
The 1991 Perfect Storm, also known as the The No-Name Storm (especially in the years immediately after it took place) and the Halloween Gale, was a nor’easter that absorbed Hurricane Grace and ultimately evolved back into a small unnamed hurricane late in its life cycle. The initial area of low pressure developed off Atlantic Canada on October 29. Forced southward by a ridge to its north, it reached its peak intensity as a large and powerful cyclone. The storm lashed the east coast of the United States with high waves and coastal flooding before turning to the southwest and weakening. Moving over warmer waters, the system transitioned into a subtropical cyclone before becoming a tropical storm. It executed a loop off the Mid-Atlantic states and turned toward the northeast. On November 1 the system evolved into a full-fledged hurricane with peak winds of 75 miles per hour (120 km/h), although the National Hurricane Center left it unnamed to avoid confusion amid media interest in the predecessor extratropical storm. It later received the name “the Perfect Storm” (playing off the common expression) after a conversation between Boston National Weather Service forecaster Robert Case and author Sebastian Junger. The system was the fourth hurricane and final tropical cyclone in the 1991 Atlantic hurricane season.
Hurricane and Superstorm Sandy
FIRST A NOTE ON THE NWS WARNING STRATEGY FOR SANDY. IN ORDER TO
AVOID THE RISK OF A HIGHLY DISRUPTIVE CHANGE FROM TROPICAL TO
NON-TROPICAL WARNINGS WHEN SANDY BECOMES POST-TROPICAL…THE WIND
HAZARD NORTH OF THE TROPICAL STORM WARNING AREA WILL CONTINUE TO BE
CONVEYED THROUGH HIGH WIND WATCHES AND WARNINGS WARNINGS ISSUED BY
LOCAL NATIONAL WEATHER SERVICE OFFICES.
SANDY CONTINUES TO MAINTAIN AN AREA OF DEEP CONVECTION NEAR THE
CENTER…WITH AN EYE OCCASIONALLY VISIBLE ON SATELLITE IMAGERY.
ALTHOUGH THE SATELLITE PRESENTATION OF THE SYSTEM IS NOT VERY
IMPRESSIVE…SFMR MEASUREMENTS…FLIGHT-LEVEL WINDS…AND DROPSONDE
DATA FROM THE AIR FORCE HURRICANE HUNTERS INDICATE THAT THE WINDS
HAVE INCREASED TO NEAR 75 KT. SINCE THE HURRICANE WILL TRAVERSE
THE GULF STREAM THIS MORNING…AND THE SHEAR IS NOT TOO STRONG AT
THIS TIME…SOME MORE STRENGTHENING AS A TROPICAL CYCLONE IS
POSSIBLE IN THE NEXT FEW HOURS. HOWEVER…THE MAIN MECHANISM
FOR INTENSIFICATION LATER TODAY SHOULD BE BAROCLINIC FORCING. THE
OFFICIAL WIND SPEED FORECAST IS CLOSE TO THE LATEST GFS PREDICTION
AS THAT MODEL SHOULD BE ABLE TO HANDLE THE EVOLUTION OF THIS TYPE
OF SYSTEM FAIRLY WELL.
THE CONVECTIVE STRUCTURE OF SANDY HAS DETERIORATED TODAY…EVEN AS
THE CENTRAL PRESSURE HAS CONTINUED TO SLOWLY FALL…SUGGESTING THAT
THE CONVECTION IS NO LONGER DRIVING THE BUS. THE INTENSIFICATION
OBSERVED THIS MORNING WAS ASSOCIATED WITH STRONG WINDS OCCURRING TO
THE SOUTHWEST OF THE CENTER…OUTSIDE OF THE CENTRAL CORE…AND WAS
ALMOST CERTAINLY DUE TO BAROCLINIC FORCING.
SATELLITE…RADAR…SURFACE…AND RECONNAISSANCE AIRCRAFT DATA
INDICATE THAT SANDY MADE LANDFALL NEAR ATLANTIC CITY NEW JERSEY
AROUND 0000 UTC. THE INTENSITY OF THE POST-TROPICAL CYCLONE WAS
ESTIMATED TO BE NEAR 80 KT AT LANDFALL WITH A MINIMUM PRESSURE OF
946 MB. AT LANDFALL…THE STRONGEST WINDS WERE OCCURRING OVER
WATER TO THE EAST AND SOUTHEAST OF THE CENTER. HURRICANE-FORCE
WINDS GUSTS HAVE BEEN REPORTED ACROSS LONG ISLAND AND THE NEW YORK
METROPOLITAN AREA THIS EVENING. IN ADDITION…A SIGNIFICANT STORM
SURGE HAS OCCURRED ALONG A LONG STRETCH OF THE MID-ATLANTIC AND
SOUTHERN NEW ENGLAND COAST.
Satellite imagery indicates that Hermine has become a post-tropical
cyclone, with the coldest convective tops now located more than 200
n mi northeast of the exposed center. Despite this change in
structure, surface data from the Outer Banks indicate that some
strong winds persist near the center, and the initial intensity is
set to 55 kt for this advisory. During the next 48 to 72 hours,
Hermine will interact with a strong mid-latitude shortwave trough
and all of the global models show the system re-intensifying during
that time and a redevelopment of a stronger inner core, albeit one
situated underneath an upper-level low. Regardless of its final
structure, Hermine is expected to remain a dangerous cyclone through
the 5 day period.
If you are in the path…the thousand mile wide path…of Hurricane Sandy, a.k.a. Frankenstorm, then you should make sure you know what the storm could do in relationship to where you are. If you are in or near an area with mountains, look for very serious flash flooding. The winds will be strong everywhere. If you are near the coast, be aware that the highest storm surges seen in years are expected in many areas. At the same time, it is important for those of us writing or talking about this storm to be realistic and careful in making predictions. This is becasue every case of dire prediction that does not materialize is a morsel of ignorance that will be served up later by climate change denialists who profit from confusing the general public about the connection between climate change and storminess. Here, I’d like to do the following: Give a brief overview of what Sandy is all about; address the question “Can you attribute Sandy or any other large storm to Global Warming?”; and tell you about some recent research related to that question. I’ll also throw in a little bit of historical background by way of discussing a nightmare scenario that actually didn’t happen.
First the nightmare scenario. Years ago, my first long distance trip anywhere not involving aircraft was a road trip from Albany, NY to the Southeast, the Southwest, California, and back. This was in the 1970s, and it took months. On the way out, I encountered a storm in Texas that stranded me there, in Big Spring, for several days. The state was covered with a layer of ice, and there was no way to handle it. Months later, on the way back, I drove through the aftermath of that storm and a very long time after the storm had passed though, there were still wrecked semis littering Routes 30 and 40.
I did not live in Boston at the time, but that was the year Boston was hit with a very severe storm, was part of the same system that iced the Lone Star State. In Boston, so much snow fell during rush hour that the cars on the major beltways that go around the urban core were trapped in situ. People died of exposure in their own cars, or en route on foot to “safety” from more remote parts of the road. Hundreds of homes and cabins along the coast were destroyed.
That was one of several storms leading to changes in zoning and regulation along the north Atlantic coast in the US which led to no more building and in some cases the aggressive removal of structures on the open coast or barrier islands. A couple of years later I did move to the coast, and spent a fair amount of time on the shores of Cape Cod, Plumb Island and elsewhere. As an archaeologist, I fully enjoyed encountering the remains of homes or small settlements. There would be nothing standing, but the remains of houses and their contents would be poking up here and there. It was always interesting to try to figure out based on the position and location of the largest bits where the home may have originally sat, and based on the degree of deterioration of the remains, which of the recent storms had destroyed the home or cabin.
One of the great historical events one learns of while working, in historic preservation and archaeology in New York and New England is the Great Storm of 38. The big storm in the 70s happened 35 years ago, and 35 years or so before that a storm came up the Atlantic, crossed Long Island, slammed into Rhode Island and Southeast Massachusetts, and generally made a mess of the interior, destroying lots of homes and killing lots of people. We now think it was a hurricane, but the people of New England at the time, including fisherfolk who’s lives and livelihood depended on the sea and on knowledge of the weather, had not even heard of a “Hurricane” before. Surely, hurricanes had come up the coast before, but with such infrequency that they were not a named phenomenon. Just another (big) storm. Years after the Storm of ’38, when I was busy climbing all the High Peaks in the Adirondack Mountains, I was often challenged by “slides” and blowdowns caused by that storm. Anyone who knows the ADK’s of the 1960s and 1970s or earlier knows of the big slides on Giant and the other steep sloped mountains, and the blowdowns on the Dix range. Those features of hiking and climbing are mostly courtesy of the big storm of ’38.
Here’s the thing. Imagine that a storm like Sandy came along in either of two years; 70 years ago or 35 years ago. Sandy is much larger and contains much more energy than the ’38 storm, or for that matter, of any known storm of the North Atlantic (we’ll get to that below). If Sandy hit the region in the 1930s, it would have been without warning, and it would have been prior to the reconstruction of seawalls and the development of flood mitigation measures inland that have happened in recent decades. Sandy, in ’38, would kill tens of thousands and destroy thousands of structures. That would be an average Sandy, a Sandy not being as bad as the most dire predictions we are considering today as the storm begins to take a grip on the eastern seaboard.
A Sandy of 35 years ago would have been predicted. The ability to see hurricanes coming was in place, but not as well developed as it is today. We would have seen Sandy coming, but her massiveness and extent, and her exact trajectory, would probably have been unknown. But at least there would be warning. Many of the seawalls and flood mitigation systems would have been in place, but the overbuilding on barrier islands and other vulnerable coastal regions would have been at or near a peak. With evacuations, Sandy would not kill 10s of thousands… probably only hundreds. But the number of buildings destroyed would be unthinkable. Most of those buildings are now gone or shored up. A Sandy in 1975 would have left some very interesting coastal archaeology for me to have observed during my trips to the shore in the 1980s. Very interesting indeed.
Do you remember the October storm of 1991, a.k.a., the Halloween Nor’easter a.k.a. The Perfect Storm? I do. I was living in Somerville, Ma. After the storm raged for hours and finally calmed down a bit I went out for a walk. Power lines and large tree fragments littered the landscape. There would be no driving for a day or two in many neighborhoods. I was able to get out the next day, and I drove right up to Cape Anne, near Gloucester (Bass Point to be exact), where the Andrea Gail had sailed from never to return. I had not heard about the Andrea Gail yet but I went down to Glouscter to see the waves.
Is Sandy Caused By Global Warming?
I remember parking the car along side the road, and climbing over a granite riprap structure to get to the shore. I stood on that high point, and from there could see a few dozen people milling around at a much lower elevation, taking pictures of the waves that were rolling in. I did a rough calculation. How far inland would a wave wash if it was double the size of those I could see now? Double and triple size waves … rogue waves … would not be unlikely after a storm like this. When I realized that my shoes would probably get wet, and all the people down at a lower elevation would probably get washed away, if that happened, I went back to the car and drove to the clam shack in Ipswich for lunch. Later that day, I hear, the authorities cleared the beaches. The waves I was watching were 10 meters if they were a centimeter. Indeed, 30 meter waves were recorded asea in Nova Scotia, and high waves killed a couple of looky-loos on Staten Island. That storm was one of several that hit New England since the big storm of the 1970s. Everybody who lives in the region knows that the storms have become more common and more severe, and probably lager, wider, in extent.
But is there any evidence to support that?
Well, yes, actually, there is. Here’s the abstract from a recent paper:
Detection and attribution of past changes in cyclone activity are hampered by biased cyclone records due to changes in observational capabilities. Here we construct an independent record of Atlantic tropical cyclone activity on the basis of storm surge statistics from tide gauges. We demonstrate that the major events in our surge index record can be attributed to landfalling tropical cyclones; these events also correspond with the most economically damaging Atlantic cyclones. We find that warm years in general were more active in all cyclone size ranges than cold years. The largest cyclones are most affected by warmer conditions and we detect a statistically significant trend in the frequency of large surge events (roughly corresponding to tropical storm size) since 1923. In particular, we estimate that Katrina-magnitude events have been twice as frequent in warm years compared with cold years (P < 0.02).
So, over the years, it gets warmer and colder and in warmer years there is more stormosity, as it were. Warm=storm. At the same time, the amount of warm (number of warm years and how warm they are) has been going up. More storms over time, just as any honest Salt can tell you. Here’s a nice graph from the same paper:
Now, here is what you’ll hear a lot of people say. People will tell you that “you can’t attribute any given storm to global warming.” There is a certain way in which that is true, but there is also a certain way in which it is wrong, and the importance of recognizing the relationship between global warming and storminess is now so important that the former has become little more than a pedantic nuisance and we’d better start focusing on the latter.
One of the reasons why this statement is true is a little unfair to those saying it, or for that matter to the phrase itself, and is extrinsic to the logic of the statement itself, yet is still a valid reason. Here’s the thing. People often say “Well, you can’t attribute a given weather event to climate change” or, more importantly, people often hear that said, and then in their brains a disconnect between climate and weather is established or verified. In other words, people use that phrase to give themselves permission to not worry about climate change vis-a-vis storminess. One might argue that it does not matter that people use this phrase incorrectly, it is still true. But it does matter a great deal because the bigger, overwhelmingly important issue is the lack of social and political will to tackle global warming as a problem. Phrases that are a) technically true but b) miss the point and c) contribute to the end of civilization do not deserve our protection. Just. Stop. Saying. It.
The other way to look at it, the way in which we might fairly and logically say that warming weather can be said to be the cause of a particular storm, is best viewed in a thought experiment first. Suppose there were no Nor’easters, like Sandy. Suppose hurricanes were never, ever known to travel north of Georgia and were not that common. Now, imagine that we warm the world up a bit and this warming causes Nor’easters to start to form, and it causes hurricanes to start heading farther north, and then, some of those Nor’easter low pressure systems combine with some of those hurricanes and cause Frankenstorms.
Those Frankenstorms were caused by global warming.
In a world in which storms generally are more severe, more common, bigger, go farther north, or do some other nasty trick (any subset of this list may pertain, it is not necessary that all are true), one might well ask the question: “Is there any way to say that a given North Atlantic Frankenstorm emerged from the sea and the atmosphere without any of the added energy of global warming contributing to the severity, size, and northerly track of that storm?” And the answer is, “No, of course not, don’t be a bonehead.”
It is often said that storms are going to happen anyway, but global warming ramps up the probability, which is akin to saying that there is always going to be variation in temperature or some other weather related factor but global warming raises the baseline. That’s true. But the corollary to that is NOT that you can’t link climate change to a given storm. All storms are weather, all weather is the immediate manifestation of climate, climate change is about climate. Before we started talking about global warming, storms were caused by … things. Climate things. Did we ever say, back in the 1950s when a hurricane hit Florida, “Oh, ya, that was some hurricane, but the thing is, you can’t really attribute a given hurricane to the Intertropical Convergence Zone’s relationship to warm Mid Atlantic currents. The former is a weather event and the latter is a climate system.” Why did we not ever say that? Because it would have been irrelevant, even dumb.
The truth is, we experience more Atlantic severe storms because of global warming, though we are still working out the details of which features of which kinds of storms are affected most. Beyond this, it may well also be possible that something I hinted at above is true: We may be experiencing kinds of storms today that were very rare in recent centuries, because of global warming.
In any event, there’s more. From the paper:
We detect a statistically significant increasing trend in the number of moderately large surge index events since 1923. We estimate that warm years have been associated with twice as many Katrina-magnitude events compared with cold years in the global average surface temperature record.
Jeff Masters, at The Wunderblog, has an excellent post on Sandy, what’s going on now, and what might happen. It is here. Keep in mind that by the time you click through to that he may have put up a newer post, so check for that. Meantime, here’s a few salient items you may want to know about:
Sandy, the storm, is of record size, larger than any storm ever seen before. It is over 1,000 miles wide, with 12 foot seas covering that entire area. There’s been a couple of storms with this or that dimension exceeding Sandy, but in some other way they fell short. Sandy wins.
You already know about the whole “landfall” problem with storms, so I won’t go into this here. The thing is, even while Sandy’s worst rains and winds are no where near the coast, she is putting up storm surges already, and roads are being washed away as we speak with days of storminess ahead of us. (This is the thing about “Nor’easters… they go on for much longer than mere hurricanes!)
Sandy will generate modest storm surges from South Carolina to Canada, with severe storm surges from Delaware to Massachusetts.
The storm surge in New York City may be higher than ever seen before, and has about a 50-50 chance of flooding the subway system in the vicinity of the Battery. That has never happened before.
Tropical force winds will batter 1000 miles of coast on Monday and Tuesday, with hurricane force winds covering a 500 mile section of coast.
Remember all the flooding associated with Irene in 2011? Sandy will also cause major inland flooding, but not as much rain overall will fall, so overall the flooding will be less. However, what “less” means is relative. If you are in a hilly region of Pennsylvania or some other part of the northeast, you may well experience worse flooding with Sandy than you did with Irene. Or not. Overall, there will be less, but it will still be bad.
And yes, there will be snow. The usual places that get snow during Nor’easters are at risk. Any place with a high elevation or that is up north has a good chance of getting a few inches, or in some cases, a couple of feet.
I found it very interesting that the Maya recently came out to ask people to stop suggesting that somehow their cyclic calendar was going to cause the end of civilization, or the world, or whatever, at the end of the present year. This is a case of a traditional people well versed in their own indigenous technology (in this case, time tracking technology) noticing that the “civilized Western world” was making a major fool of itself, as usual, and then helpfully suggesting that certain people STFU. At the same time, we are doing it wrong for real and truly putting the future at risk, and not just with climate change, but how we address climate change. We are not making it part of the conversation in national elections, we are not making it part of our budget considerations, we are not making it part of our shovel-ready-stimulus activities. We are not even letting ourselves keep track of what we are ruining. The number of satellites that will be available to track storms like this will probably fall off in the near future to the extent that we won’t be able to do it. Talk about the end of civilization! Even if we didn’t simply screw up plans for putting up more satellites, we have this other growing problem with space junk. Our technology is warming our planet and at the same time blinding us, hampering our ability to manage the problem we are creating.
Grinsted, A., Moore, J., & Jevrejeva, S. (2012). Homogeneous record of Atlantic hurricane surge threat since 1923 Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1209542109