Tropical Storm Irene

Guest Post by Willis Eschenbach

When is a hurricane not a hurricane? Well, when it doesn’t blow 64 knots (33 m/sec, 74 mph), because then it’s only a tropical storm. Inspired by a post over at the Cliff Mass Weather Blog, I’ve been trying to find a single report of sustained hurricane force winds anywhere along Irene’s path at or near landfall … no joy. I knew exaggeration was the order of the day for some folks in the climate debate, but I hadn’t realized that the illness had infected the Weather Service itself.

Figure 1. The path of Tropical Storm Irene over the mainland of the US. Symbols with a yellow center to the black storm symbol indicate a (claimed) hurricane. SOURCE ibiseye

We were fortunate in that we have very good records of the wind speed when Irene made landfall. It went almost directly over the wind recording station at Cape Lookout, at the bottom of Figure 2.

Figure 2. A closeup of Irene’s landfall. There are four wind recording stations in the area, at Beaufort (below the “70” marker at lower left), at Cape Lookout (bottom left) and at Cape Hatteras (upper right). The Onslow Buoy is located offshore, southwest of Cape Lookout.

The wind record at Cape Lookout is quite interesting, as the eye of the hurricane passed right over the anemometer there. Figure 3 shows the wind dropping as the eye went over, coincident with the deep plunge of the barometric pressure to 950 hPa.

Figure 3. TS Irene wind (light blue) and barometric pressure (violet) at Cape Lookout before, during, and after landfall. Green line at the top shows the minimum wind speed for a storm to be classified as a hurricane (64 knots).

Figure 3 shows the classic pattern of a hurricane passing directly overhead. The “eye” of the hurricane has almost no wind, and is at the center of the low pressure area. You can also see the “calm before the storm. But what you can’t see is any trace of hurricane force winds.

Not finding hurricane force winds at the eye, I looked at the other nearby stations as well. The weather station at Cape Hatteras is in the “dangerous semicircle”, the right hand side of the storm track (Fig. 2) where the speed of the storm is added to the speed of the winds circulating around the eye. Beaufort, on the other hand, is in the safer half of the storm, where the speed of the storm is subtracted from the circulating speed of the winds. The Onslow Buoy is also in the safer semicircle, on the left of the storm track in Figure 2. Figure 4 shows those records.

Figure 4. Winds at TS Irene landfall for Cape Lookout, Beaufort, Onslow Offshore Buoy, and Cape Hatteras.

As you can see, although Irene definitely qualifies as a solid tropical storm (winds greater than 35 knots), it does not reach or even really approach the 64-knot threshold for hurricanes. Other than at the eye itself, the winds did not exceed 50 knots, much less reach 64 knots.

After crossing over the land near Cape Hatteras, Irene headed back out to sea again. I thought perhaps it might have picked up steam when it went out over the ocean again. It made a second landfall in Atlantic City and went along the coast to New York.

Figure 5. Second landfall for Irene.The nearest stations to Irene’s track are Costeau (near Mystic Island above Atlantic City), NY Harbor Buoy (outside the mouth of the harbor, in the dangerous semicircle), Sandy Hook (hook shaped peninsula just above Long Branch and central hurricane symbol) and Kings Point (near New Rochelle above New York City). Note that the storm is claimed to be a hurricane until it gets well into New York State.

It appears from an examination of the station data shown below in Figure 6 that it did not pick up strength over the water. By the time Irene reached land a second time, it barely qualified as a tropical storm, much less a hurricane.

Figure 6. Wind speed from Tropical Storm Irene as it made the second landfall.

So, despite looking at Irene before, during, and after both landfalls, there is no hint of a hurricane anywhere. By the time it got to New York the eye of the storm had dissipated, what was left were huge bands of rain clouds.

Is there a moral in this story? Well, I can understand people taking extra precautions, better safe than sorry is a good rule. And I certainly imagine that when the Weather Service re-examines the records, the error will be corrected.

But that doesn’t help in making the decisions. As soon as Irene hit land, it should have been downgraded immediately to a tropical storm. That’s what it was, not a hurricane making landfall but a tropical storm. As far as I can tell, we still haven’t had a hurricane make landfall during Obama’s presidency, a historical oddity.

Individuals and city mayors and the people in charge of the emergency response can call for any level of reaction to storm threats. They may decide an exaggerated response is appropriate.

But they need accurate information to do that, not exaggerated claims. They need the actual facts, the best estimates with no exaggeration on either the high or low side.

In this case, it appears that people got so wrapped up in the question of the winds, and the fear of the winds, that they overlooked what actually made Irene unusual. This was not the wind speed, but the size of the storm. Combined with Irene’s generally slow movement over the ground, Irene’s huge dimensions meant that any given area would get rained on for a really, really long time.

And in turn that meant that the cities and towns along the coast, the ones receiving all of the attention from the fear of high winds and attendant storm surges, weren’t the towns in danger. Unlike the coastal cities, the vast expanses inland were not able to have the rainwater just flow back into the ocean. Inland, the water piled up and overflowed the banks.

And so, because of the overestimation of the wind speeds, our attention was diverted from the real threat. Because of the claimed hurricane-force winds, a storm surge up to eight feet was predicted in New York Harbor. But in the event, the storm surge was barely three feet, a non-event … and meanwhile, New England was getting badly flooded.

So the moral to me is, honesty is the best policy for a National Weather Service. Don’t exaggerate the possible effects to be on the “safe side”, don’t minimize the possible effects. Just give us the best information you have, and let us make up our own minds. As Sergeant Friday used to say … “Just the facts, ma’am” …

w.

NOTE: All wind data is from the NOAA National Buoy Data Center http://www.ndbc.noaa.gov/.

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C. Shannon

Just to play devil’s advocate, aren’t there a myriad of factors that go into determining if a storm is a “Hurricane of Category [x]” or just simply a “Tropical Storm”?
-If so could you elaborate on how many of those criteria a storm has to meet or exceed?
-Is it possible it met enough criteria elsewhere?
And finally, there was talk that meteorologist were pushing for certain metrics based on barometric pressure to be added to the list of factors, was this “creative labeling” maybe a bit of inside politics on their part to push for a change in the assessment of these storms?
Any constructive replies appreciated.

Theo Goodwin

“Just the facts, Ma’am. Nothing but the facts.”
Excellent post, Willis. Our federal weather guys have a lot of explaining to do,

Jim G

Fellow I know who rode out the “hurricane” on the Jersey shore in his condo 100 yds from the water says he has been fishing in more windy conditions.

Thank you! As I posted before Irene hit landfall, it would move east and be insignificant. However, it did quite a bit of damage and produced flooding from heavy rain.
Maybe if a forecast is understated, they risk losing their job. Better for job security to over state a certain degree of possibility than to sleep under a bridge after the blame game ends.. 🙂

Bloke down the pub

In the US, aren’t former presidents formally addressed as Mr President? Maybe it’s just a case of once an hurricane always an hurricane .

Curiousgeorge

The thing is, the media was all set up along the coast for a big surge, etc. You could practically see Anderson Cooper drooling over a Katrina repeat. In order for them to cover the rain/ flooding they had to move inland and follow the track. Whole lotta hassle, and money to do that, and far less dramatic watching the creek rise. The NWS was just catering to the newsies.

Dell from Michigan

If Al Gore and Bill Nye the Anti-Science guy are claiming that global warming causes more quantity and severity of Hurricanes, then doesn’t that same logic prove that global warming must have ended the past 3 years?

John Cooper

I was discussing this on another forum, and have some suspicions about what happened. First, the semantics. To be classified as a hurricane, a tropical cyclone must have maximum sustained winds of at least 74 mph. A couple of things about that. Note that it doesn’t specify surface winds. Secondly, the only way to find the maximum wind is to traverse the hurricane at altitude with an aircraft, which is what NOAA does to find the maximum, which may not fall over a surface weather station or weather buoy.
It’s my suspicion that NOAA takes these winds aloft readings and converts them to “surface winds” by some algorithm. If that’s the case, there algorithm may be busted, or the maximum winds never passed over a weather station.
Since hundreds of millions of dollars (at least) were spent preparing for Hurricane Meh, I think NOAA owes the world an explanation.

Tom M.

Did you account for wind speed average times which may be different for different locations? Also, did you account for meter height at each location. I’m not disagreeing with the general idea of the story only wanting to make sure the data is being correctly reported before comparing different station locations.

geo

In 1972, I was living in Western Pennsylvania. Look up Hurricane Agnes on Wiki some time; that did the vast majority of its damage as a TS. My two vivid memories are pictures of the governor’s mansion in Harrisburg flooded to the second story, and my mother (the MN tornado veteran) herding us into the basement.
Which is not to suggest that scientists and the media shouldn’t be getting it right in their reporting on the details, because of course they should.

Joe Bastardi

Gasp, I cant believe I would ever disagree with Willis. But just here me out.
The damage done indicates this was a hurricane. You dont blow down that many trees on Long Island and have wind gusts to 91 mph at Sayville at 10 feet without hurricane conditions.
By this logic, Houston did not have a hurricane with Ike as there were no sustained hurricane force winds anywhere within the city. Intercontinental gusted to 81 with a sustained of 56.
Here look for yourself, the obs all through the city of Houston. All the glass, all the damage, etc should have been downgraded, right?
http://www.srh.noaa.gov/hgx/?n=projects_ike08_pshhgx
I have been through 4 eastern hurricanes. They are not as they are in the tropics. The winds come in fits and spurts and often the damaging winds come and go quickly not in a building crescendo, but in on and off fashion, multiple times and even while the storm is pulling away. This is because the turbulent transfer needed to bring the strong winds down to the surface is only left in bands as the storm weakens and the air cools around it. Still the flow on the eastern side of the storm aligned will do this, and behind the storm ( the sinking in the drier air often brings roaring west wind). On the northwestern side, the cooling from the trough picking up the storm is like a giant seeding experiment, spreading the rain out and forcing the condensation process to be rapid away from the center, spreading the energy out.. So you have to understand, its very different from the classroom donut of perfect wind everyone wishes to see. . I agree this is not the kind of hurricane you see in the tropics, but that kind of damage to the NC outer banks and the kind of major tree damage and storm surge to southern New England and Long Island is not caused by a tropical storm. There was more tree damage in Rhode Island than in Bob which hit as a cat two and blew away the anemometer at block island at gusts over 120 mph
It is a reason for why the power scale I have gives a more accurate description of what the storm will do.
think of it this way. Suppose you had an Anthony Watts tested anemometer every 25 feet on the beach from Montauk to JFK, 10 meters high , or across all of Long Island. Do you really believe, given the damage, which in some cases was worse than GLoria , you would not have found hurricane winds.
heres what we can agree on.. if it was a tropical storm, it had the lowest pressure and did the most damage from wind that we have ever seen from a tropical storm on the east coast, since it did more tree damage than other hurricanes that we are NOT arguing about. 7 million people without power, 20-30% of trees damaged.. a 951 mb tropical storm, unloading a foot of rain,blowing down trees killing dozens and causing 7-15 billion dollars of damage.
Sadly, this whole argument is probably finding its root with the maliciousness of the AGW crowd that wants to pump weather events up to emphasize global warming. And I understand our need to fight back. But against the backdrop of history, and previous storms and damage patterns, I think Irene belongs as a hurricane. And let not your heart be troubled, for history and facts are on our side in that fight, whether we wish to argue about this. I only ask that you ask yourself, well how did that house get pushed over and why were so many trees knocked down with this, but not with others. It cant all be because of the rain.
Keep up the good fight. and please dont take this as anything else than what it is, bringing up other ideas to go along with the observations presented here.
cheers

Are the graphs of hourly wind speed? There look to be about 24 data points per day.

Jeremy

Being from the west coast, I have heard people say the east coast blows, it’s good to know it doesn’t blow as hard there as some people say.

An Inquirer

Pointing out that Irene was actually a Tropical Storm — not a Hurricane — at landfall is like pointing out that the Recession ended in July of 2009. Could be technically correct, but the impact doesn’t feel like the it.

Doug in Seattle

The over exaggeration of all things weather or climate related has long been the standard for the media and has now become the same for government “science” organizations.
I am sure there is way back from this precipice we have created, but I am sure we will get there soon. It seems every one who brings up the subject is shouted down with the precautionary principle argument.

Steve from Rockwood

I think the push-back (against the great Hurricane Irene) is warranted and nice work Willis. Joe Bastardi makes an important point (wind speed alone doesn’t define a hurricane) but when the American President is on standby for a tropical storm (and nowhere to be seen on the economy) it makes me wonder if someone is waiting for a weather miracle (i.e. here we are to save the day, and oh by the way we told you so). If Irene turned into a Cat 3 they would be looking pretty good. Oh well, on to the next disaster in waiting..

eyesonu

Thank you sir.
I tried to follow this storm very closely as I have family in the Wilmington, NC area approx 5 miles from the beach. The NHC maps were so large scale that it was impossible to get any decent idea where the eye was. I had to use local weather forecasts (Accuweather, Wunderground, Intellicast, etc.) to try to follow what was happening. Using the local radar images, possibly originating from the Nat Weather Service, I would locate the center of circulation as best as possible and then check the local forcast but there were no major wind issues. I was baffled. The NHC was reporting hurricane force wind extending out +- 60 miles but I could not find anything close to it. I followed it up through Virginia and the same results. Took a break and Sunday morning (4:00 a.m.) began following it again. NWS radar was not available so I used the same technique using local weather reports and using the animate features I was able to determine that Irene was making landfall in NY about daylight. Local report at about that time at the big airport just to the east of NYC was reporting about 35+- mph and gusts to upper 40’s if I remember correctly. At that point I was confirming to those within my circles that I was certain someone was playing political games on a big scale.
Through my observations of estimated rain storm totals derived from radar, I could see that 30-50 miles east of the center of the so-called hurricane, they were in the 10-12″ rain estimates. TV was still concentrating on wind, but that was not the real issue with this storm.
There is a lot of lost credibility with regards to this storm. Does the public now need to take a boat offshore to determine what the reported status of a storm is? Do we trust the NHC? If the next one is the ‘real thing’, will anyone listen? Time will tell, but this one will be hard to sweep under the carpet. If this is defended as actions of the ‘Nanny State’ for our own good, then I want a new Nanny.

Tony Raccuglia

Irene was not a hurricane on landfall-the facts undeniably speak for themselves-in terms of damage done, we have to remember that the East coast has not seen a tropical system of this strength in quite some time-its been since Gloria that Long Island has seen winds even near 60mph-thats a span of over 25 years-so there were likely many trees that had not even seen those kinds of winds-that combined with the wet ground would account for the seemingly worse damage. Before Gloria-which did contain much higher winds-there was Belle in 1976, and Doria in 1971 along with Donna in 1960. I am referring to this winds with the trees fully in leaf-there have been many noreasters with winds as strong-but with no leaves on the trees its a whole different ballgame.

Tom M.

In reply to Joe B;
It seems that the destruction your are describing can be attributed to the long duration of the high winds associated with the size of Irene as much as potentially higher localized winds. Would it not be better for future warnings to say “hey, look what a large tropical storm could do – you better leave for the next “true” hurricane”.

Anyone who says Irene was not a hurricane has not lived through both tropical storms and hurricanes. I can tell you from experience that this was a hurricane. Barely a hurricane, but one nonetheless. The wind speed near the surface can be different than the wind speed higher up.

Doug in Seattle

Bloke down the pub says:
September 1, 2011 at 10:37 am
In the US, aren’t former presidents formally addressed as Mr President? Maybe it’s just a case of once an hurricane always an hurricane .

This business of calling former presidents as “Mr. President” is relatively new. They used to be “Mr. Hoover” or “former president Eisenhower” to signify they were once again ordinary citizens.
I could be wrong, but in my memory it is only in the post-Kennedy era, that the job descriptor senator became the title “Senator” and ex- presidents became “President” for life.
I personally think it is sign of the trend in America to create a permanent elite class like the European nobility. Some perhaps see this as a way to keep the common rabble down. After all they know what is best.

Wil

I was screaming exactly that at my television all day from here in Alberta, Canada – and turned to CNN and Holy Mother of Jesus Armageddon had struck the fatal blow to the US east coast. The CNN anchors and reporters were hysterical – running around looking for hurricane wind, and other assorted hurricane events. Was New York washed away or was it just CNN or is New York now missing under the flood?

Keith

From satellite presentation, and from the location of wind reports, might Irene have been a subtropical storm of hurricane strength at landfall? Having been picked up by the trough, the cloud pattern resembled part tropical system, part extratropical frontal system. The winds presented here aren’t of hurricane strength, but a subtropical system doesn’t necessarily have its strongest winds in the centre/’eye’, and would be far from symmetrical, as was the case with Irene according to NHC.*
NHC’s discussion comments regarding Irene having a much lower-than-normal ratio of surface winds to flight-level winds is also perhaps more indicative of a non-tropical or subtropical system, where 950mb would be expected to produce some hurricane-force winds somewhere but not necessarily across a broad area and not high up the Saffir-Simpson scale.
Wind damage to structures will be good evidence of wind strength, but I’d be more cautious when looking at fallen trees in New England. Irene hit after previous rains had already made the ground softer and trees were in full leaf, so trees that may have stood up to a nor’easter in November would’ve been uprooted by Irene.
Depending on where it goes (and it could be Louisiana, Mexico or Sydney Harbour at this rate), I suspect Lee will render the No Hurricanes Under Obama tag obsolete anyway.
*On a cautionary note, look at the NHC report on Katrina and you won’t find any reported sustained winds that get close to Cat 3. Wind sampling can be very hit-and-miss, even by the Hurricane Hunters.

Chris D.

As weak as this one was, it still managed to take out a section of Hatteras Island. Also, if memory serves, it appears to have tracked almost right over the sample site for the recently discussed paleo study that looked at sediments.
Thanks for this post, by the way.

Kitefreak

Doug in Seattle says:
September 1, 2011 at 11:11 am
The over exaggeration of all things weather or climate related has long been the standard for the media and has now become the same for government “science” organizations.
I am sure there is way back from this precipice we have created, but I am sure we will get there soon. It seems every one who brings up the subject is shouted down with the precautionary principle argument
—————————————————————————–
Agree totally. This Irene business – whatever the precise facts may be – is another example of media-overhype. Lies, basically. The media lie to us all the time and not just about this.
Put it this way: if you knew somebody had definitely lied to you about one thing, would you trust them on another?
Don’t be so sure about being allowed to back away from the precipice anytime soon though… And we didn’t create it, they did

Keith

Chris D: might that have churned the layers a bit, rendering any further reconstructions or verification somewhat tricky?
Good thing that no other paleo reconstructions have ever suffered from any issues or events that may have resulted in loss of resolution or blending of figures across time…

Roger Knights

My opinion is that if the NHC had downgraded Irene just before landfall to Cat. 1 (as it should have) and then downgraded it to a TS after landfall (instead of absurdly claiming then that sustained hurricane-force winds extended for hundreds of miles from the center), it would have embarrassed Mayor Bloomberg and other politicians who’d been whooping it up (like Obama). And they’d have been mad at it–in a period when the NWS is fighting against a 20% cut in its funding and it needs all the friends it can get. So it quailed and failed.

Willis Eschenbach

Joe Bastardi says:
September 1, 2011 at 11:02 am

Gasp, I can’t believe I would ever disagree with Willis. But just hear me out.
The damage done indicates this was a hurricane. You dont blow down that many trees on Long Island and have wind gusts to 91 mph at Sayville at 10 feet without hurricane conditions.

Thanks, Joe. Certainly, if you have any evidence of sustained winds over 64 knots anywhere on the mainland or offshore, please let us know where they were recorded. I find nothing. There’s a buoy in Long Island Sound north of Sayville. The maximum wind there was just under 35 knots, with maximum gusts of 45 knots. In general, average gust speed is 5-10 knots faster than wind speed. The maximum gusts at landfall were about 15 knots more than the maximum wind speed. The maximum gusts at the NY Harbor Entrance Buoy were 12 knots faster than the wind speed.
So I find nothing even remotely resembling 90 mph in any record of Irene’s landfall, including the gust records, but if you have it, I’d like to see it. The nearest land station record I can find to Sayville is Islip, with maximum sustained wind speeds of a whopping 27 knots, and gusts to 57 knots … so even the gusts in Islip didn’t reach hurricane speed, much less 90 mph.
Is it possible there were gusts at ninety mph? Sure, anything’s possible, but we need evidence.
Until then, I’m going to say that a 91 mph gust is an anecdote. In any case, as you know the speed of the wind gusts is immaterial to whether it is a hurricane or not.
w.

Willis Eschenbach

Peter H says:
September 1, 2011 at 11:06 am

Are the graphs of hourly wind speed? There look to be about 24 data points per day.

The graphs show the maximum of 8-minute wind speed averages for each hour.

Robert Smith

I’m depressed. Here in Orkney, North Scotland, we had sustained wind of 50kts with gusts over 70 last sunday and nobody cared. 🙁

Bill Parsons

Tony Raccuglia says:
September 1, 2011 at 11:19 am
Irene was not a hurricane on landfall-the facts undeniably speak for themselves-in terms of damage done, we have to remember that the East coast has not seen a tropical system of this strength in quite some time-its been since Gloria that Long Island has seen winds even near 60mph-thats a span of over 25 years-so there were likely many trees that had not even seen those kinds of winds-that combined with the wet ground would account for the seemingly worse damage.

I was in Amherst, Mass, Saturday through Wednesday, arriving there just as the storm did, and leaving after it peaked. The town has an elevation of about 300 feet, and is a couple hours’ drive inland from Boston.
Power failed Saturday night for an hour or so. On Sunday the skies were overcast with the storm clouds, which moved across the horizon from right to left at a good clip. Over time it was possible to imagine their circular direction, though we must have been on the outer edge of the vortex. The temps were hot and humidity rose into the 80 to 90 % range. The rain fell intermittently throughout the day.
I’m not a regular in the area, but I thought this was a fairly serious storm, whatever name you give to it. As Mr. Raccuglia points out above, hurricanes usually spend their energy as they drive northwards, and as soon as they hit land. This one hit the Carolinas and kept on going, delivering enough wind and rain to the New England area to cause severe flooding more than a hundred miles inland along the Connecticut River, and as far north as Vermont. By now everyone has seen the video of cars being swept away in the river flooding with their drivers still inside. As we drove around on Sunday, I was pretty impressed with the downed limbs and whole trees, the flooding of several feet above flood stage, and (yes, even the MSM coverage of) the flooding and winds along the coasts.
The point, I suppose, is that, “classifying” anything for political purposes is risky. I’m sure that emergency managers in various administrations have more to gain by hyping the state of emergency in order to prevent people from getting into trouble, and to bring in more emergency funds. From the perspective of some, it’s possible to consider this was “just another storm”. For others – especially people near the coast or living in river valleyes – it may have turned horrific. In either case, one can only be grateful for good, honest up-to-date reporting without any slant.

Willis Eschenbach

alexwade says:
September 1, 2011 at 11:21 am

Anyone who says Irene was not a hurricane has not lived through both tropical storms and hurricanes. I can tell you from experience that this was a hurricane. Barely a hurricane, but one nonetheless. The wind speed near the surface can be different than the wind speed higher up.

You may be able to tell us from experience. Unfortunately, your experience (and my experience as well) is meaningless in determining whether Irene was a hurricane. A hurricane requires sustained winds, not gusts but sustained winds of over 64 knots. If you can show me where such winds were recorded, then we’ll have something to discuss.
w.

Willis Eschenbach

Keith says:
September 1, 2011 at 11:44 am

From satellite presentation, and from the location of wind reports, might Irene have been a subtropical storm of hurricane strength at landfall?

No, because the data to date clearly shows that Irene did not have “hurricane strength at landfall”.
w.

John Cooper says:
September 1, 2011 at 10:52 am
“Note that it doesn’t specify surface winds. Secondly, the only way to find the maximum wind is to traverse the hurricane at altitude with an aircraft, which is what NOAA does to find the maximum, which may not fall over a surface weather station or weather buoy.”
Do you mean to suggest that NOAA is so confused about their basic mission that they are not telling the viewing audience the speed of the surface winds? Your defense of them makes them look downright moronic.

Willis Eschenbach

Chris D. says:
September 1, 2011 at 12:00 pm

As weak as this one was, it still managed to take out a section of Hatteras Island. Also, if memory serves, it appears to have tracked almost right over the sample site for the recently discussed paleo study that looked at sediments.

As the author of that post (actually two posts, here and here), I had to laugh remembering their claims.

Thanks for this post, by the way.

More than welcome.
w.

Gary

After four and a half days and still without power here in RI, I have to say you’re nit-picking, Willis. The damage was worse than Hurricane Bob in 1991 which passed right over rather than 100 miles to the west. Irene was a hurricane at one point and parsing wind speeds between category 1 and tropical storm hardly matters except for statistical analysis ex post facto. The surge was not a non-event along the southern New England coast. Coming with high tides it eroded beaches and damaged property even if only half as large as forecast. Although I think there was media over-hype at times, please don’t not get carried away with contrarianism.

Larry Miller

Others have made several cogent observations re: tree damage on the east coast – as a professional forester allow me to add my 2 cents worth.
* the ground was saturated in many areas due to heavy rains within the preceding 10 days. Soggy wet ground makes trees inherently less windfirm.
* trees with leaves make excellent sails, catching much more air than leafless trees
*much of the area covered has been heavily developed over the years – streets, roads, houses, and shopping centers can wreak considerable havoc on the root systems of trees
*the species of trees in the east, once you move out of the southern pine region, are heavy to hardwoods (oaks, hickories, maples, e.g.). Unlike southern pines, such species grow in a region that hurricanes and tropical storms rarely visit. Thus, these species are less adapted to such storm conditions when they do occur.
*many of the communities hit very hard are older, with older trees. Trees do not live forever, and older trees become creaky and decadent just as do we – such trees will be much more easily damaged than younger trees

Willis, your analysis is fine, but premature. Wait until all of the data is in before throwing the NWS/NHC under the bus.
http://www.aoml.noaa.gov/hrd/Storm_pages/irene2011/wind.html
Look at the H*WIND site and see the maximum 1-min wind swaths for NC and NY. Then cross-reference the individual maps to get the correct snapshots. Only 12-hours before landfall in NYC, 62-knot winds were analyzed off of the DelMarVa peninsula — which could easily to 64-knots due to sampling issues.

So if you wish to give the NHC/NWS the benefit of the doubt, then you are quibbling over 2-knots of wind between the definition of TS and HURR, which is well within the 5-knot reporting thresholds in the best-track dataset.

Tom in Florida

Willis Eschenbach says:
September 1, 2011 at 12:25 pm
“The graphs show the maximum of 8-minute wind speed averages for each hour.”
http://en.wikipedia.org/wiki/Maximum_sustained_wind#Definition
“The United States National Weather Service defines sustained winds within tropical cyclones by averaging winds over a period of one minute, measured at the same 10 metres (33 ft) height. This is an important distinction, as the value of a one-minute sustained wind is 14% greater than a ten-minute sustained wind.”

MikeU

I suspect John Cooper is correct… according to what I’ve read they’re supposed to measure winds at a height of 10 meters for 10 minutes to get an average wind speed when classifying hurricanes, but that’s rather impractical. Surface stations aren’t suspended 10m up in the air, and aircraft cannot measure that low to the ground (nor for 10 minutes). They must use some sort of algorithm to translate from aircraft and/or ground readings to get *estimated* wind speeds at 10 meters.
As long as the methods they’ve used to measure hurricane strength have been consistent over recent history (the past few decades)… we have a common point of reference, and this can properly be considered a class 1 hurricane when it made landfall. If those methods have changed, bumping the classifications up artificially – that might warrant closer scrutiny.

JR

The graphs show the maximum of 8-minute wind speed averages for each hour.
In the U.S., 1-minute sustained winds are used to classify tropical cyclones.

Houston Russ

Joe Bastardi says:
September 1, 2011 at 11:02 am
Living in the southwest corner of Houston, I can assure you that Ike was a tropical storm when it got to us. Leaves were blown out of trees, some branches were broken, some property damage and the electric lines were down for two weeks. Ho hum. Bolivar peninsula, at ground level, didn’t have hurricane force winds either. It was under 20 foot of water.

The 5AM discussion by the NHC on Irene for 08/28 was good, showing landfall as a 60-knot tropical storm. But since a hurricane is 64 knots, of course H warnings were held.
IRENE IS EXPECTED TO REMAIN NEAR HURRICANE STRENGTH UNTIL IT MOVES INTO SOUTHERN NEW ENGLAND LATER TODAY…
AND IT WILL ONLY TAKE MODEST CONVECTION TO BRING DOWN STRONGER WINDS ALOFT TO THE SURFACE AS SUSTAINED HURRICANE-FORCE WINDS OR GUSTS.
SLOW WEAKENING IS EXPECTED AFTER LANDFALL AS IRENE BECOMES A POST-TROPICAL CYCLONE IN ABOUT 24 HOURS.
INIT 28/0900Z 39.2N 74.5W 65 KT 75 MPH
12H 28/1800Z 41.8N 73.2W 60 KT 70 MPH…INLAND
24H 29/0600Z 46.0N 70.4W 55 KT 65 MPH…POST-TROP/EXTRATROP

SixnaHalfFeet

Splitting hairs.
Sure you may want to say Irene was not a hurricane, but the definition of a hurricane is a little arbitrary. Irene was definitely a tropical cyclone, it looked like one, it acted like one. Tropical cyclones vary in intensity from what we call tropical storms to what we call category 4 hurricanes, but they are all still tropical cyclones that look and act similar. Irene was still what it was, just a little weaker than was expected.

Willis Eschenbach

Robert Smith says:
September 1, 2011 at 12:27 pm

I’m depressed. Here in Orkney, North Scotland, we had sustained wind of 50kts with gusts over 70 last sunday and nobody cared. 🙁

My point exactly … the issue with Irene was the rain.
w.

JohnInSoCal

It doesn’t require 75mph winds to knock a tree down if the ground is soaked. Irene was just the latest rough weather the NE has undergone this year. Before Irene, their rivers were at Springtime runoff rates – not late summer. Trees that can withstand 90mph can fail at 35mph when they are rooted in mud.

Willis Eschenbach

Ryan Maue says:
September 1, 2011 at 12:49 pm

The 5AM discussion by the NHC on Irene for 08/28 was good, showing landfall as a 60-knot tropical storm. But since a hurricane is 64 knots, of course H warnings were held.
IRENE IS EXPECTED TO REMAIN NEAR HURRICANE STRENGTH UNTIL IT MOVES INTO SOUTHERN NEW ENGLAND LATER TODAY…
AND IT WILL ONLY TAKE MODEST CONVECTION TO BRING DOWN STRONGER WINDS ALOFT TO THE SURFACE AS SUSTAINED HURRICANE-FORCE WINDS OR GUSTS.
SLOW WEAKENING IS EXPECTED AFTER LANDFALL AS IRENE BECOMES A POST-TROPICAL CYCLONE IN ABOUT 24 HOURS.
INIT 28/0900Z 39.2N 74.5W 65 KT 75 MPH
12H 28/1800Z 41.8N 73.2W 60 KT 70 MPH…INLAND
24H 29/0600Z 46.0N 70.4W 55 KT 65 MPH…POST-TROP/EXTRATROP

Thanks, Ryan. For those who don’t recognize the name, Ryan is an authentic hurricane scientist.
Unfortunately, at the time that the above warning was issued, the position was almost to Atlantic City (39.2N, 74.5W), and they claim it was still a hurricane at that time, well after passing over Cape Hatteras … so why can I find nothing even remotely resembling their claimed 65 knot winds anywhere in the area?
Can you shed any light on why, when Irene was just barely a tropical storm about to hit Atlantic City, the NHC still had it as a hurricane?
w.

Willis Eschenbach

SixnaHalfFeet says:
September 1, 2011 at 12:56 pm (Edit)

Splitting hairs.
Sure you may want to say Irene was not a hurricane, but the definition of a hurricane is a little arbitrary. Irene was definitely a tropical cyclone, it looked like one, it acted like one. Tropical cyclones vary in intensity from what we call tropical storms to what we call category 4 hurricanes, but they are all still tropical cyclones that look and act similar. Irene was still what it was, just a little weaker than was expected.

You miss the point. Sure, it’s a big revolving tropical weather system. The question is, how strong is it? The National Hurricane Center was claiming it was blowing more than 64 knots at a time the anemometers in the area were barely registering over 35 knot winds …
And that makes it very hard to do any planning. The name is not the issue. The misrepresentation of the wind strength is the problem.
w.

Tom in Florida

Wind speed is the measuring stick to estimate potential damage of a land falling hurricane.
http://pcbdaily.com/hurricane-category-rating-system says this:
“The Saffir-Simpson Hurricane Scale
The Saffir-Simpson Hurricane Scale is a 1-5 rating based on the hurricane’s present intensity. This is used to give an estimate of the potential property damage and flooding expected along the coast from a hurricane landfall.
Category One Hurricane:
Winds 74-95 mph (64-82 kt or 119-153 km/hr). Storm surge generally 4-5 ft above normal. No real damage to building structures. Damage primarily to unanchored mobile homes, shrubbery, and trees. Some damage to poorly constructed signs. Also, some coastal road flooding and minor pier damage.”
In the case of Irene, potential damage was estimated to be that of a Cat 1 hurricane and it certainly was without regard to the recorded wind.
End of story.

Jeremy

Interesting analysis. The NOAA data seems to indicate significantly higher wind speeds though:
http://www.nhc.noaa.gov/archive/2011/al09/al092011.public_b.027.shtml
http://www.nhc.noaa.gov/archive/2011/al09/al092011.update.08280937.shtml
Do you disagree with their methods of obtaining this data?
Either way, it’s all semantics. They had it pegged as a Category 1 storm by the time it got to the coast. Anyone expecting Category 5 winds from this storm was insane, but that’s hardly the fault of the NWS.