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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tom T says:
“…On the other hand the failure of The National Hurricane center and the News Media to adequately warn Vermont of flooding was almost malpractice.”
Almost? In my book they are morally reprehensible and fully guilty of it. The NHC was fully aware of this thing was doing as it shows up in the staring points of the model runs of it. The one to pay attention to are the OFCI curves on the intensity projections.
http://moe.met.fsu.edu/~acevans/models/archive/2011/al092011/
Rather than going along with the excitable hype from the reporters the NHC should have EMPHATICALLY warned about the massive rainfall that was going to hit the watersheds of the North East. Every tropical storm/hurricane that I have ever seen has done one characteristic thing that they ALL do when the make landfall.
UNLOAD WATER.
And if wind speed and surge aren’t your biggest threat…. that water load is. More so in some cases.
Keith says:
September 1, 2011 at 1:43 pm
Cape Lookout is a land station, not a buoy, so it has 2-minute averages on the wind, not 8 minute …
I disagree that it is premature to say Irene was not of hurricane strength. The erroneous claim was that it was hurricane strength, and nobody has come up with a scrap of evidence to show that in fact it was of hurricane strength. I and others have looked at a host of wind records and found nothing of that strength anywhere
So until someone comes up with some actual evidence that it was a hurricane, I’m gonna continue to say it wasn’t one. The burden of proof is on them to show it was a hurricane, not on me to disprove it (which as you point out I can’t do). But they can prove it, by coming up with some evidence, somewhere, that shows winds of over 64 knots. I can’t find it.
w.
Another thing to consider:
If we now use models to estimate wind speed at 10 meters to estimate strength of hurricane, how were past hurricanes estimated?
If they used to use ground level data, then the past hurricanes would have actually been stronger than the records idicate, if modern ones use different methods. Is this another area of a bias in change of proceedure? Or do we estimate speed at altitide using the same method as they used in the past? It seems unlikely to me we use the same method, because most bias’ come from implementing new methods for increased accuracy. Hard to believe nothing has changed in 100+ years.
Is this and Willis’ post just an example of people noticing something, that has always been there, for the first time due to the new instant availiabilityof information we never had before? Or is this an example of the new available information making it harder to fool the public when they “really” wanted a storm for politics?
I dont have answers, just questions.
I thought the whole problem with Irene was she fell apart…lost her eye wall…and the upper level low got decoupled from her lower level low…..became unstacked
…if so, then that would explain why the planes found hurricane winds up high, and no one found those winds on the ground…..because there weren’t any
Anyhow, they got slammed by a really bad tropical storm……
Can they measure the wind speed with doppler radar?
Jeff
Willis Eschenbach says:
September 1, 2011 at 3:11 pm
“I disagree that it is premature to say Irene was not of hurricane strength. The erroneous claim was that it was hurricane strength, and nobody has come up with a scrap of evidence to show that in fact it was of hurricane strength. I and others have looked at a host of wind records and found nothing of that strength anywhere
So until someone comes up with some actual evidence that it was a hurricane, I’m gonna continue to say it wasn’t one. The burden of proof is on them to show it was a hurricane, not on me to disprove it (which as you point out I can’t do). But they can prove it, by coming up with some evidence, somewhere, that shows winds of over 64 knots. I can’t find it.”
[“Just the facts, Ma’am, and nothing but the facts.”]
Willis’ response shows why so many people really like him. Those who have been unable to respond to his criticism show just how deep runs the corruption that lies underneath many parts of our government, certainly including James Hansen’s operation.
We should not be making excuses for anyone, especially not for people we like. As Willis points out here, everybody blew it. This is a case of “it is itching” and we must scratch where it itches. Sorry, no excuses on this one.
ps101 says:
September 1, 2011 at 2:43 pm
Not true at all. The definition of a hurricane specifically refers to surface winds, and says nothing of the winds aloft. From the National Hurricane Center (emphasis mine):
From NOAA (emphasis mine):
(Surface winds are typically measured at an elevation of 10 metres.)
What I find interesting is that you see the possible failure of the National Hurricane Center to provide accurate information as something to do with “hype” and “conspiracy” … where is that coming from? I’m just asking for accurate information upon which to base decisions. And given your specious claim that hurricanes are measured by winds aloft, it makes me wonder about your ability to recognize hype if you saw it …
w.
The use of the 1-minute average for the “sustained” wind speed … when did that become common? NOAA glossary gives “sustained winds” as being the two-minute average, viz:
When (historically) did this become a 1-minute average for hurricane strength?
w.
tom T says:
September 1, 2011 at 2:34 pm
re: Tom in Florida: “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.”
“It isn’t the end of any story. We were constantly told that Irene had maximum sustained winds of 80mph and would hit as a “strong” cat one. I want to know on what bases was that claim made. Some people seem to think that it is ok to panic people unnecessarily as long as the intentions are good. But I disagree closing the New York City transit system for no reason cost business and people $billions and may have cost people their life. On the other hand the failure of The National Hurricane center and the News Media to adequately warn Vermont of flooding was almost malpractice.”
Tom T,
One must first understand what a Cat 1 Hurricane can due. From that same post :
“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.”
Cat 1’s are not all that damaging if one is prepared.
Here is a portion of my post on 8/28:
http://wattsupwiththat.com/2011/08/27/hurricane-irene-tv-news-reports-a-bridge-too-far/
Tom in Florida says: August 28, 2011 at 5:39 am
“What I saw with Irene this morning was that it had probably ceased to be a tropical system as soon as the forward movement exceeded the banding rotation somewhere along the New Jersey coast. You can see the eye spread out and loose its integrity. The reasons are many, dry air from the south, cooler waters, land interaction, stronger wind sheer. Tropical systems are actually fragile things that need the right conditions to sustain themselves and rarely survive for long when out of the tropics but they can bring massive amounts of moisture up from the south causing flooding and that will be the true emergency of this storm. “
Now, if I, a regular guy, can understand that why didn’t the “expert” reporters?
People have got to take responsibility to educate themselves and stop trusting the so called TV experts standing out in 50 mph winds trying to make it look worse than it really is.
The way our government is heading today, in the near future the weather stations will not give numeric data readings at all but will give either the likelihood of a particular bet or a bit of statistical theory.
To the people who keep pointing out that the power went out or trees fell over….
That is proof of nothing, except trees fell and power went out. Do you think it takes a hurricane to make the power go out? Does it take a hurricane to break off a branch? Yes hurricanes can do these things, but so do lots of smaller storms. It happens every day all over the world.
How much damage is done depends on a whole host of factors. Siding blowing off a building can be due to new types of siding as much wind speed, people often will use cheaper products if they haven’t had a good storm for decades. Tree damage can be decided more by ground moisture and time since the last goood storm, or from lots of new planting with shallow roots. Or just people planting trees that are not suited to an area that can get hurricanes. Power outages can be more common based on degrading infrastructure or increased demand not allowing for excess line capacity to replace a supply line to another source into an area.
I live in Saskatchewan and we get power outages and tree damage from thunderstorms all the time. Don’t require hurricane force winds to do it either.
What has really happened is that many people have just become too comfortable in an extended period of calm. They take it for granted and when mother nature gives you a little nudge, and a small nudge is all you got if your realistic even if it was a CAT1, it is a shock. Learn from the lessons this storm has taught and move on.
here’s the best I come up with
http://91.192.194.209/manteo.cfm
The 2035 UTC record shows 50 knots gusting to 64 knots
57.54 Mph gusting to 73.64mph – the 57.54 mph has to persist for 10 mins to make it into the METAR. 73.64mph peak speed during the hour.
57.54mph right on the border of Gale/Strong Gale http://en.wikipedia.org/wiki/Beaufort_scale
Even if we should take the peak speed (which we don’t) it would still not be a Hurricane making landfall
The data is sourced from http://weather.noaa.gov/weather/current/KMQI.html
I’m building up quite a database. Don’t worry I won’t lose the data 😉
Ah, so I see, so it won’t have a 64kt 1-minute average at Lookout unless something very odd happened.
Fair comment – those that have “officially” said it made landfall as a hurricane should demonstrate it with evidence at some point. It may be that, while it was a hurricane at landfall, the hurricane-force winds were out at sea in the eastern portion of the circulation. In which case, we’ll need to see which buoys, if any, recorded such winds. Maybe Al Gore had one of his yachts out there, electric fan pointing at his anemometer?
NHC do tend to err on the side of consistency from one bulletin to another, especially with unexpected, rapid or short-lived strengthening or weakening, rather than yo-yoing with their wind speed pronouncements (and likewise with forecast track if the global weather models are being inconsistent, or if the storm is jagging about). They may have understated wind speed during the strengthening phase and may well have overstated during the weakening phase. The latter may be particularly true for a brief landfall across a watery strip of NC ‘land’ when restrengthening was expected when Irene re-emerged over warm waters.
This bit from discussion number 31 (08/27, 11pm) is interesting:
Doesn’t sound like a typical tropical cyclone at this particular time. While there was definitely still a closed circulation and a warm core, there were no hurricane-force winds anywhere near the eyewall. An odd tropical/non-tropical hybrid?
Katia downgraded to tropical storm
http://news.blogs.cnn.com/2011/09/01/katia-downgraded-to-tropical-storm/
It seems to me that with an *observed* 1-min max wind speed of 32.6 m/s (although admittedly recorded at 19.4m instead of 10m) and a central pressure in the low to mid 950s (mb) along with the other wind analysis that Ryan linked to, that one would be hard-pressed not to think that Irene was a minimal hurricane over land in NC. I doubt the NHC will see it otherwise.
-Chip Knappenberger
IIRC, After Katrina most insurance policies were rewritten such that hurricane damage would have a deductible applied that would be approximately 5% of insured value vs the more normal $500-$1000 deduction.
Thus on a $500K property, damaged $100K by a hurricane, the deductible becomes $25K, and the cost to the insurance company is $100K – $25K = $75K.
On that same property damaged by just regular wind and rain, cost to the insurance company is $100K -$1K = $99K.
Thus, it is VERY beneficial to the insurers (Warren Buffett, etc) that Irene remain a hurricane.
Dave
Dave Day says:
September 1, 2011 at 4:29 pm
IIRC, After Katrina most insurance policies were rewritten such that hurricane damage would have a deductible applied that would be approximately 5% of insured value vs the more normal $500-$1000 deduction.
==============================================================
Dave thanks!
I’ve been looking for some reason as to why the NHC was holding on to calling it a hurricane….
Maybe before you all charge ahead with this, you first need to agree on what is a “hurricane”. Saffir-Simpson, fo example recognizes both damage and wind speed. The damage reports for Irene along much of its inland track make it a class 2-3 SS storm, but the wind speeds barely make it a cat 1. Whats in a name? Conspiratory theorists have certainly reached cat 1 in this thread… 🙂
Great article Willis, and lots of useful debate.
Although this debate is mainly over the definition of “hurricane” I find it difficult to quickly understand the intensity of hurricanes reported by the US National Weather Service, and I usually end up delving into the detailed reports to get an answer.
Maybe a better way to show the current strength and history of a hurricane is what the Australian Bureau of Meteorology (BOM) do for cyclones (hurricanes).
Here are the cyclone definitions:
http://www.bom.gov.au/cyclone/faq/index.shtml#definitions
And here is a track map for Tropical Cyclone Olga in January 2010, as it moved between a Tropical Low (L) and a Category 1/2 (1 or 2) cyclone here:
http://www.bom.gov.au/announcements/sevwx/qld/qldtc20100123.shtml
Much clearer and easier to read??
The point here is I believe that the damage that was done was by a TROPICAL STORM they need to let people know that so they can know to get out if a real hurricane shows up.
Paul Coppin says:
September 1, 2011 at 4:54 pm
Maybe before you all charge ahead with this, you first need to agree on what is a “hurricane”. Saffir-Simpson, fo example recognizes both damage and wind speed.
===================================================
I don’t think so Paul. The new revised version says:
“Thus to help reduce public confusion about the impacts associated with the various hurricane categories as well as to provide a more scientifically defensible scale, the storm surge ranges, flooding impact and central pressure statements are being removed from the scale and only peak winds are employed in this revised version.”
Says only peak winds………………….
http://www.nhc.noaa.gov/sshws.shtml
Paul Coppin says:
September 1, 2011 at 4:54 pm
Hi Paul,
While the Saffir-Simpson hurricane scale gives indicative damage, as well as expected storm surge, these are only indicative and not part of the scale per se. Damage reports may be used where precise wind speeds are not available as a kind of reverse look-up, to estimate the winds and therefore where on the scale the storm would fit.
To avoid ambiguity, the NHC have dropped all elements except wind speed from their categorisation, using what they are calling the Saffir-Simpson Hurricane Wind Scale. This then leaves them more free to give precise storm surge forecasts specific to local areas, bays and coves, with damage estimates tailored accordingly, rather than people seeing Cat 2 and assuming a 6-8ft storm surge across the board.
.PREV DISCUSSION… /ISSUED 1128 AM CDT SAT AUG 27 2011/
…MIDDLE ATLANTIC COAST…
LATEST NHC FORECASTS INDICATE IRENE WILL CONTINUE TRACKING NNEWD
ACROSS EXTREME ERN NC THIS AFTERNOON AND ALONG THE DELMARVA AND NEW
JERSEY COASTS TONIGHT. DENSE OVERCAST WITHIN THE LARGE CIRCULATION
WILL LIMIT DIABATIC HEATING DOWNSTREAM OF THE CENTER…BUT SURFACE
DEW POINTS IN THE LOW/MID 70S WILL CONTRIBUTE TO MARGINAL
INSTABILITY /MLCAPE GENERALLY AOB 500 J PER KG/ SUPPORTIVE OF
OCCASIONAL THUNDERSTORMS…ESPECIALLY OVER THE COASTAL WATERS AND
ADJACENT INLAND AREAS. CONVECTIVE BANDS NORTH OF THE CENTER OF
IRENE HAVE CONTAINED EMBEDDED SMALL SUPERCELLS THIS MORNING MOVING
ONSHORE FROM THE TIDEWATER NORTHWARD INTO ERN MD. THESE HAVE TENDED
TO WEAKEN AFTER MOVING INLAND WHERE INSTABILITY DECREASES WITH
DISTANCE FROM THE COAST. VERY STRONG LOW LEVEL VERTICAL
SHEAR/STORM-RELATIVE HELICITY IN ADVANCE OF IRENE WILL SUPPORT A FEW
SMALL SUPERCELLS WITHIN THE CONVECTIVE BANDS NORTH OF THE CENTER
WITH CONTINUED POTENTIAL FOR ISOLATED TORNADOES TO OCCUR.
http://www.spc.noaa.gov/products/outlook/archive/2011/day1otlk_20110827_2000.html
Sorry, I have to take exception to both of you on this point, and perhaps the NHC as well. I’ve seen the NHC page previous, and while they would like to insist that the scale is about wind only, they then go at great length to correlate the wind with an extensive damage discussion. To my mind, they haven’t been able, inter alia, to separate the wind scale from the damage. The problem becomes one of a single element scale that has no real reference to any utility. Its the qualitative component of the scale that gives weight to what it measures. A hurricane implies the damage, not the wind speed. There is a similar issue with the Fujita scale for tornados. Without a correlation to effect the scale itself is meaningless – its essentially a scalar quantity. Rather than trying to separate the qualitative damage component, it might more ssend to incorporate some precipitation measure to the categorization. Its the qualitative component of damage that gives EMO the focus it needs to provide the emergency response.
ummph – that should have been “make more sense to incorporate…”