Study: The Norwegian cyclone storm model is flawed

One of the most basic tenets of meteorology, The Norwegian Cyclone Model is getting a makeover. From the University of Manchester:

Taking a fresh look at the weather

Given the UK’s obsession with the weather, it would seem obvious that the basic understanding of how low pressure systems evolve has been known for a long time.

The eye of the storm (credit NASA Rapid Response)

Instead, some of the biggest storms in the UK’s history, such as the Great Storm of October 1987, did not fit this basic understanding.

With groundbreaking research, Dr David Schultz, from The University of Manchester believes the way we learn about the weather is wrong and has been wrong for 90 years.

Writing in the journal Bulletin of the American Meteorological Society, Dr Schultz, along with his colleague Professor Geraint Vaughan, has worked out that the traditional model for how low pressure systems evolve is deeply flawed.

The model, used since the 1920s and devised by Norwegian meteorologists, is that when a storm occludes (evolves), it will automatically begin to weaken and pose little danger of severe weather.

However, argues Dr Schultz, this is not the case – occluded storms may well contain strong winds and regions of heavy precipitation.

Naturally, many in the public recognize that.  The Great Storm of October 1987 and the Burns’ Day storm of January 1990 were both clear reminders: occluded, but still deadly.  Dr Schultz’s new model addresses these weaknesses with the Norwegian model because the prior belief that occluded storms were weak could lead to poorly-informed predictions or forecasts.

Dr Schultz, from the University’s School of Earth, Atmospheric and Environmental Sciences, claims they now know that the deepening of a low pressure system is not dependent on when a cyclone occludes.

Specifically, the new model is called ‘wrap up’, to emphasize that the wind around the occluding cyclone wraps up the low pressure system into an anticlockwise-spiralling cloud pattern.

Dr Schultz said: “With this new interpretation of the occlusion process we can explain why not all low pressure systems occlude – the winds are not strong enough to wrap up the storm.

“The Norwegian model of low pressure systems served us well for many years, but it’s time to move on.

“This new model is better than the Norwegian model at explaining the available observations of the structure and evolution of occluded low pressure systems.”

Dr Schultz argues that how we teach about low pressure systems is wrong, and that textbooks, public information guides and models will need to be radically updated to ensure the next generation of meteorologists, as well as the public, are in possession of all the facts.

He added: “All books from postgraduate-level textbooks to basic weather books for the public need to be rewritten to convey the correct understanding.  What we teach students in school needs to be changed.  And forecasters need to be retrained to have this latest information.”

Another result of Dr Schultz’s research is a better explanation for the observed structure of storms. Previously, meteorologists believed that occluded cyclones and their associated fronts could tilt eastward with height or tilt westward with height, roughly in equal measure.  This new research demonstrates that westward-tilting occluded fronts are rare and provides an explanation for why.

Dr Schultz added: “I hope that this model will help people understand the particular weather conditions associated with these potentially hazardous storms.  Yet, this research shows how much more remains for us to learn about the weather around us.”

Notes for editors

The paper, Occluded fronts and the occlusion process: A fresh look at conventional wisdom,

by David M. Schultz and Geraint Vaughan, is available from the Press Office.

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August 2, 2011 11:08 pm

Anthony, this has got to be the most non-story “revelation” I’ve seen out of a press-release ever…I don’t know anyone in my field that had such flawed conventional wisdom to begin with.

August 2, 2011 11:09 pm

It’s also freely available at – Click the publications link and perform an article search for the title listed in this article.

David, UK
August 2, 2011 11:18 pm

So the science wasn’t settled, then?

Brian Johnson uk
August 2, 2011 11:20 pm

The Met Office has used nothing but the Norwegian model – proof is in the abject failure of its predictions. 37 Million Taxpayer Pounds and no success.
[ryanmaue: no, this isn’t remotely true. the “Norwegian model” is nothing more than a conceptual framework of understanding the extratropical cyclone evolution. it does not consist of numerical or mathematical proofs. If you note that the extratropical storm track ends in the North Atlantic near Norway, then dying or occluded systems were more likely to be observed in Norway. In 1922, their understanding of cyclone processes elsewhere was considerably hampered by their geography: they understood well the storm systems that actually went over their heads. They did not conceptualize other types of cyclone evolution that they had never observed. This isn’t a flaw per se. They accomplished a lot in terms of understanding weather with what few observations they indeed had.]

August 2, 2011 11:21 pm

Oh model…..model….model, thou art doomed to fail.

August 2, 2011 11:36 pm

I remember the 87 storm because I slept right through it and hundreds of thousands of trees the next day had been blown down. The 90 storm was more memorable as walking in 90mph winds was bad and the River Tees nearly flooded because of it.
However more interesting are flat line winds which we had in Memphis TN in 2003 called Hurricane Elvis it lasted only a few minutes but caused untold damage to the power supply in the city lasting a few weeks to repair. I watched that from a kitchen window at 6 am fortuitously enough. Three hours earlier and FEDEX would have lost 3 planes.

August 3, 2011 12:05 am

Having been through 4 hurricanes, including 2 real bastards, I will assure anyone that the model is wrong. I can well remember mini-tornadoes that were so scary that it gave all nature pause. Destroyed a reinforced house in front of my eyes in less than 10 seconds. (All four residents survived in the bath tub) These tornadoes were later to be found circling counter-clockwise to the hurricane. That was Iniki. Top wind measure by the Department of Defense was 227 miles per hour. They refused to allow publication of the result for some reason, even though it was generally known. But no, , no instrumentation , survived. Computers recorded over 230 before the exterior instrumentation went out, I was told by Navy people, but that was considered an artifact.

August 3, 2011 12:26 am

Anyone who wishes to understand meteorology and climate must read Marcel Leroux’s books, a French climatologist who died in 2008 and who has invented in the 80′ the “Mobile Polar High concept”. MPH are large discs of cold and high pressure air (1000 to 1500 m thick) originating from the polar regions on their way towards the equator. They are the cause for everything. Storms are just the vortex created by the organisation of the void left at the leading edge of MPHs. That is why depressions originate at low altitude, and not at high altitude as most meteorologist believe (jet stream has really no importance in that matter)
(in french)
Marcel Leroux explains clearly why then the Norvegian model is flawed, since storms at these latitude can not create themselves, but are the consequence of travelling MPH. These MPH are also driven by relief because of their small thickness, explaining all the regional climate. He also explains why El Nino et La Nina are also the consequence of MPHs. Marcel Leroux was also a sceptic since he very early assess irrelevancy of climatic model because they do not take into account the actual general circulation lacking MPG behaviour.
Marcel Leroux deserves a fresher look. His books are really amazing.

August 3, 2011 1:31 am

Observations don’t match forecasts.
The models are wrong (again).

Stephen Wilde
August 3, 2011 1:42 am

In many respects the Mobile Polar High concept of Leroux is very useful.
The conventional model for depressions provides that the energy for the spinning (and thus the overall wind strength) is dictated by the temperature differentials between the air masses mixing within the depression. The idea is that the air masses have different densities and so respond differentially to the Earth’s rotation to start the mixing and spinning. On that basis it is logical that once the warm sector has all been lifted aloft then those differentials decline and the depression should begin to wind down.
However that never did account for many depressions that continued to intensify after occlusion had been completed. There are many such. I have long been aware of that deficiency in the standard model.
The Leroux concept is that the movement of the MPH provides the initial ‘push’ to start the spinning and would be capable of adding even more of a push later on even after completion of the occlusion process.
That is in fact implicit in my description of a top down solar effect altering the vertical temperature profile of the atmosphere so as to change the intensity of the polar vortex and the size and position of the polar high pressure cells which then behave as Leroux suggests.

Stephen Wilde
August 3, 2011 1:57 am

Furthermore ‘hands on’ weather forecasters have been taking the phenomenon into account for decades. It is only recently that the idea seems to have lost ground with over reliance on models and a consequent loss of practical experience.
I remember many occasions in the past when Michael Fish and other well known broadcast meteorologists would explain the powerful northerly behind a passing deep depression as being exacerbated by a gowing high pressure cell giving the winds an additional impetus despite an obviously occluded front.
Dr. Schultz may be right but he has discovered nothing new. Rather, he is re stating knowledge that had becme lost.
The really important point is why those polar high pressure cells ebb, flow and shift in the first place. That is where I think I am ahead of the game.

A. C. Osborn
August 3, 2011 2:06 am

If my memory serves me correctly and the 1987 Storm is the UK one which Mr Fish got so disastrously wrong then it was made much more powerful because 2 low pressure systems came together when the 1st one stalled just off the south coast and was caught up by the 2nd system. This is very rare as nearly all systems transit over the UK in procession and are quite widely spaced.

August 3, 2011 2:46 am

I remember a recent article about someone who proposed that “everything you know about static electricity is wrong” and proceeded to impute all sorts of nonsense to the conventional wisdom under the guise of correcting the myths.
( here we go: to wit:
” it has been assumed that such contact charging derives from the spatially homogeneous material properties (along the material’s surface) and that within a given pair of materials, one charges uniformly positively and the other negatively.” which is the authors pretending that their own facile assumptions, based on something they learned in elementary school, have universal import)
This definitely has the same scent.

August 3, 2011 2:54 am

Having watched a “dying” sub-tropical cyclone rip off roofs and trundle a 250 ton container crane along its track against its brakes, then tip it off the end of the quay, I will only say that extreme weather is not something many models even come close to. In the storm I witnessed the Harbour Control’s anemometer went off the scale – then literally blew away. I can tell you it was no fun trying to cut our way into the 200 gt Pilot Launch trapped beneath the crane as the tide rose with the crew trapped below the crushed superstructure in those winds either.
The ‘forecast’ for that day predicted ‘strong winds’ – so I guess they got that bit right. This was in 1987 in South Africa and I recall that a Meteorologist said at the time that they could not really predict what these storms would do in their ‘decay’ phase.

August 3, 2011 3:02 am

after these models the weather will still be wrong

August 3, 2011 3:08 am

New research leads to update to what is thought to be how things work ,, normal science in action.
Now lets remember there are those demanding that in one area this should not be case as its ‘settled’ beyond any challenge.

Jack Jennings (aus)
August 3, 2011 3:10 am

Ah Pat, 4 people in a bathtub ?
You know, just curious.
Chrs JJ
Thanks mods, Anthony and posters … as always.

xion III
August 3, 2011 3:41 am

In whatever way the cyclones form, the shapes of the resulting logarithmic spirals appears to be consistent. Here is the Icelandic low pressure system used to illustrate the article.

August 3, 2011 5:23 am

Thank you Thierry, I am so glad you are recommending Marcel Leroux’s work, I have mentioned them on several occasions when his work is proven be someone else. I think it is essential when observing Geos satellites and one can clearly follow the origins of cyclonics and anti-cyclonics.

August 3, 2011 5:23 am

Oh it is climate change LOL. Storms are storms. 1 million trees were destroyed in unusual
storm I think they are referring to the 1987 one in UK. But what about the one in 1953.
It flooded Canvey Island, and other parts of the East Coast of England and Scotland. Holland
suffered worse. Ships were lost. Google 1953 Great Storm.
I do sympathize with people who have experienced a hurricane. While living in Bermuda in 1969
we did experience being on the edge of the hurricane belt. It was hazardous to drive as most of their roads are on the sea front, and waves were washing up over the small cars and the winds so high they threatened to push you over. However, the houses are very strong made from blocks of limestone. But the roar of the wind? And of course some of the flowers were killed from sea spray thrown up.
Anyway Norway is unique. It is a land of the midnight sun and polar nights. 22 hours of day and twilight in the summer months and darkness of polar nights in winter.

August 3, 2011 5:29 am

pat says:
August 3, 2011 at 12:05 am

Having been through 4 hurricanes, including 2 real bastards, I will assure anyone that the model is wrong. … That was Iniki. Top wind measure by the Department of Defense was 227 miles per hour. They refused to allow publication of the result for some reason, even though it was generally known.

The post is about extratropical storms which form at frontal boundaries and behave very differently than tropical storms. A storm can change between the two types, commonly a tropical storm goes extratropical as it moves over cooler water. That transition is marked by broadening of the wind field loss of the warm core and eyewall, and various other things. I haven’t looked at the paper but I doubt it has anything to add to tropical storm knowledge (and it sounds like it has little to add to extratropical storm knowledge per Ryan).
I think I’m familiar with the Iniki wind guest, but I thought it was stronger and would have supplanted the Mt Washington wind record (which has been supplanted by a typhoon). Oops, no. That was 236 mph on Guam where “As investigation of the Guam report proceeded, it became evident that the claim of a 236 mile per hour gust could not be substantiated.”
Except for record temperatures at Hawaii airports (/sarc), most remarkable records are subject to critical review. The Mt Washington record certainly was, and the Paka gust was analyzed with almost forensic detail. They found evidence that before the anemometer blew away, broken guy wires allowed the anemometer to swing back and forth, resulting in too high readings. The Iniki reading may have involved the same physics.
See for all the details.

anna v
August 3, 2011 5:29 am

This paper by Makarieva et al is relevant to the issue also, imo.

Frank K.
August 3, 2011 5:43 am

Uh oh…dissing the Norwegian model! There goes their Nobel Prize…

August 3, 2011 6:25 am

The amount of ego bugs me, particularly in light of Dr Maue’s statement about the state of the art understanding. Either the guy is seriously delusional about his own importance (ALL books need to be rewritten?), grossly uniformed or playing to the crowd for tenure’s sake.
However one cuts it – it speaks generally why I don’t trust academics…. and why we’re here wrt CAGW.

Adriana Ortiz
August 3, 2011 6:31 am

a must see

prof plimer

August 3, 2011 6:44 am

Thanks, I didnt knew Marcel Leroux, I’m going to see more of his work right now!

August 3, 2011 6:50 am

He added: “All books from postgraduate-level textbooks to basic weather books for the public need to be rewritten to convey the correct understanding. What we teach students in school needs to be changed. And forecasters need to be retrained to have this latest information.”
This sounds to me like a scientific consensus that is now wrong.

chris b
August 3, 2011 7:15 am

Kitler says:
August 2, 2011 at 11:36 pm
I think Hurricane Elvis was a derecho, an interesting weather event
From Wikipedia, the free encyclopedia
A shelf cloud along the leading edge of a derecho photographed in Minnesota
A derecho (from Spanish: “derecho” meaning “straight”) is a widespread and long-lived, violent convectively induced straight-line windstorm that is associated with a fast-moving band of severe thunderstorms in the form of a squall line usually taking the form of a bow echo. Derechos blow in the direction of movement of their associated storms, similar to a gust front, except that the wind is sustained and generally increases in strength behind the “gust” front. A warm weather phenomenon, derechos occur mostly in summer, especially June and July in the Northern Hemisphere. They can occur at any time of the year and occur as frequently at night as in the daylight hours.

Pamela Gray
August 3, 2011 7:57 am

I love posts about weather. I think they are far more educational than posts about climate. It irks the heck out of me that “climate study” has become the holy grail. But the climate cup was empty of the good stuff. Why? Some idiot decided that weather had nothing to do with climate. Think about it. If all the climate money spent so far had been spent on advanced studies of weather (pattern variations, mechanisms, affects on land and sea, oscillations, forcasting etc), in all likelihood lives and property let alone tax funded cleanups might have been spared.
As far as I am concerned, AGW climate scientists and those that fund them are thieves and are indirectly responsible for lost lives and damaged property. And now I have my dander up and my feathers ruffled. Word to the wise, do NOT get a red-headed Irish lass mad.

August 3, 2011 8:12 am

derecho = “right”
recto = “straight”
I’m not sure WUWT.

August 3, 2011 8:17 am

Thank you Anthony for that brilliant talk by Prof Plimer. I have a degree in Archaeology and Paleaoanthropology from the University of New England, (Australia) and one of my senior units to complete my degree I took a first year 100 level unit called ‘Earth in Crisis?’ Now this unit was for first year students in Geography or the humanities. We covered various subjects one the effect
of the destruction of the Amazon rain forest and the effect of the Aswan Dam on the Nile River.
Also pollution in cities like Bangkok. I also took a unit 300 level on the Archaeology of Communications. Well this was interesting. When the mini ice came from the 14th to say the
mid 18th century in UK, grapes and wine production failed. But they used the grape presses
to convert into printing presses. That’s human innovation, eh? Well – joking apart. What turned into human progression, drinking wine or reading a book.
I commend you in delivering an international site that delivers not just political but also genuine
scientific truths. Now I am Australian and haven’t seen Prof Plimer’s address.
We are an ice planet and now experiencing an interglacial. Don’t wish another glacial or mini ice age event on the human race, particularly the Northern Hemisphere. Stephen Sneider was with James Hansen one of the scientific advisers of Al Gore with the compilation of the ‘Inconvenient
Truth’ well watch U Tube and see Stephen with long hair and beard pontificating that the next ice
age will be upon us soon. Such liars, eh? Just to make a buck!

August 3, 2011 8:40 am

There was an interesting occluded front involved in huge October Rains in Southern New Hampshire, back around 1998 or so. It didn’t weaken, but instead acted something like a pipeline, stretching from a warm sector holding an unwinding hurricane, hundreds of miles out to sea to the southeast, to a stalled or very slow low to our northwest. Rather than the rain getting wrung out of the system, as soon as it occuded, a constant supply of juisy air traveled along the occlusion.
As I recall the forecast was for the rain to taper off, but it wouldn’t quit. We got over ten inches, and there were streams in the woods where I’d never seen streams before. I think there were places where it set records for the most rain from a non-hurricane, (though a lot of that moisture came from that hurricane far to the southeast.)
I had the feeling the hurricane was unrolling, the unrolled strip traveled up the occuded front pipeline, and then got rolled up again in the storm. It was fascinating to watch the maps.
Off Topic: Any chance we could get a thread on Tropical Storm Emily going?

August 3, 2011 8:55 am

Adriana Ortiz says:
August 3, 2011 at 6:31 am
a must see

Thanks; that was off-topic, but definitely worth the seven minutes it took for Professor Plimer to demolish the “CO2 drives climate” myth. Send it to your favorite schoolteacher!
/Mr Lynn

August 3, 2011 9:33 am

Thank you Thierry for being another voice in bringing the work of the late Professor Marcel Leroux to this discussion!
As many have posted before, this link is a good start.
His latest book was the second English edition of “Dynamic Analysis of Weather and Climate” completed in May 2008 and published in 2010, two years after his death.
Professor of Climatology
PhD. 1983, WMO sponsored and distributed to all member countries.
Former Director of the Centre of Research in Tropical Africa Climatology, CRCTA (Dakar, Senegal)
Former Director of the Laboratory of Climatology-Risks-Environment, LCRE (Lyon, France), Université Jean-Moulin.
1. Leroux M. (1983). PhD. Thesis : Le climat de l’Afrique tropicale. Ed. H. Champion/M. Slatkine, Paris/Genève, t.1. : 636 p., 349 fig., t. 2 : notice et atlas de 250 cartes.
2. Key peer-reviewed paper: “The Mobile Polar High: a new concept explaining present mechanisms of meridional air-mass and energy exchanges and global propagation of palaeoclimatic changes” Marcel Leroux, Global and Planetary Change, 7 (1993) 69-93 Elsevier Science Publishers B V, Amsterdam
3. Author of: “La dynamique du temps et du climat”, Editions Masson, 1996, 310pp, 1st edn; Editions Dunod, 2000, 366 pp, 2nd edn reprinted in 2004.
4. Author of “Dynamic Analysis of Weather and Climate”, J. Wiley ed. Praxis-Wiley series in Atmospheric Physics, London, NY, 365 pp, 1998.
5. Author of “The Meteorology and Climate of Tropical Africa”, Springer Verlag, Springer-Praxis books in Environmental Sciences, London, NY, 548 pp + CD: 300 pp, 250 charts, 2001, ISBN: 978-3-540-42636-3
6. Author of “Global Warming: Myth or Reality? The Erring Ways of Climatology”, Springer-Praxis books in Environmental Sciences, Berlin, Heidelberg, London, New- York, 509p., 2005, ISBN: 978-3-540-23909-3

August 3, 2011 10:35 am

ugh. This again.
Shapiro Keyser (1990) already “fixed” the “flawed” Norwegian cyclone model.
I swear, people are issuing press releases just to see their names in print.

August 3, 2011 11:39 am

mac says:
August 3, 2011 at 1:31 am
Observations don’t match forecasts.
The models are wrong (again).
Um Mac, didn’t you get the memo. If data observations data does not match the models then the data is Wrong.

August 3, 2011 1:17 pm

John X…
Though Keyner and company have added to our understanding of the Norwegian model and its’ flaws, there is in fact novel science (a better understanding of the stability parameters you need to use to fully model occlusion) in the Schultz piece. That the press is covering this as a revelation never before seen is not Schultz’s fault. Schultz is, in fact, an outstanding scientist and deserves more respect than what you’re showing here.

August 3, 2011 3:06 pm

Caleb says:
August 3, 2011 at 8:40 am

There was an interesting occluded front involved in huge October Rains in Southern New Hampshire, back around 1998 or so. It didn’t weaken, but instead acted something like a pipeline, stretching from a warm sector holding an unwinding hurricane, ….
I had the feeling the hurricane was unrolling, the unrolled strip traveled up the occuded front pipeline, and then got rolled up again in the storm. It was fascinating to watch the maps.

How about 1996? If I can unravel Google’s URL,
It’s by Barry Keim, NH state climatologist at the time. It says in part:

The surface cyclone became occluded over Pennsylvania and New York, and this occlusion drifted slowly across southern New England, with wave intensification taking place offshore along the frontal boundary on 21 October. … In addition, at the peak of New England rainfall on Monday 21 October, Hurricane Lili was a category 1 hurricane and was located at 34.20°N, 57.20°W (about 1400 km southeast of Cape Cod, Massachusetts) at 1000 EDT. It is generally believed that this tropical cyclone advected tropical moisture to New England, enhancing the amount of precipitable moisture entrained in the system over the New England states. However, the interaction between these two storm systems is not completely understood and perhaps warrants further examination.

There have been a few storms with striking satellite images showing a moisture feed from the Carribean to New England. They generally produce a lot of flooding. I think they’re a bit similar to the “Pineapple Express” that feeds moisture into northern California storms.

August 3, 2011 4:18 pm

H.R. says:
August 3, 2011 at 8:12 am (Edit)
derecho = “right”
recto = “straight”
I’m not sure WUWT.

Looks like a link with the word ‘direct’ to me.
TomRude says:
August 3, 2011 at 9:33 am (Edit)
Thank you Thierry for being another voice in bringing the work of the late Professor Marcel Leroux to this discussion!
4. Author of “Dynamic Analysis of Weather and Climate”, J. Wiley ed. Praxis-Wiley series in Atmospheric Physics, London, NY, 365 pp, 1998.
6. Author of “Global Warming: Myth or Reality? The Erring Ways of Climatology”, Springer-Praxis books in Environmental Sciences, Berlin, Heidelberg, London, New- York, 509p., 2005, ISBN: 978-3-540-23909-3

I got these two out of the library at my university today. Good stuff!

August 3, 2011 5:05 pm

Tallbloke, glad you enjoy it!
If you can get the 2010 second edition of “Dynamic Analysis…”, it’s updated with comments on droughts, floods etc…

Kevin Kilty
August 3, 2011 5:45 pm

Seems to me that T.N. Carlson had this idea twenty years ago. In his 1998 AMS monograph there is this sentence in a section devoted to the complexity of the occluded front. “High winds, accompanied by blowing and drifting snow in the wintertime, may give the correct impression in winter storms that the occluding front is powerful.” On the next page is a satellite photo of an occluded front that I remember well on the eastern Wyoming plains in April, 1988.

August 3, 2011 7:09 pm

RE: Ric Werme says:
August 3, 2011 at 3:06 pm
Yes, that sounds like the storm. Thanks for doing the reserch I’m too busy to do. I was two years off because I was using the top of my head, which is unscientific (and sometimes dangerous.)
That storm was amazing. I had never seen the flood control reservoir near my house more than 50% full, but that storm filled right up and water nearly started flowing through a wide, emergancy spillway around the side of the dam. The large pond behind the dam became an impressive lake. A huge amount of water was held back, and the people downstream should have been kissing the feet of the Army Corp of Engineers for work they did, back in the early 1960’s.
I got a little worried when I noticed small springs had appeared at the base of the dam. If that dam ever gave out, with that amount of water behind it, it would wipe out my town. I was so worried that I went back with a flashlight after dark to check on those springs, to make sure they weren’t getting bigger. The Corp had been there before me. Every spring was marked with a small flag.
I later learned that what I should have been looking for, if I wanted to worry, was any sort of cloudiness or muddiness in the springs. Clear springs are natural, and indicate no part of the dam is being washed away (as mud in the water.)
It was reassuring to know that, among so many government employees who don’t work all that hard, there was one out in a downpour, checking the dams.

August 3, 2011 11:04 pm

“The model, used since the 1920s and devised by Norwegian meteorologists, is that when a storm occludes (evolves), it will automatically begin to weaken and pose little danger of severe weather.”
Much to Dr. Schultz’s chagrin this is not what I learned when getting my Bachelors of Science in Meteorology. The occluded stage of a low pressure systems is the most intense and generally when the most severe weather is present during the life cycle of the low due to the proximity of the jet stream supporting the low and the related temperature gradient stacking down to the surface.

George Wellor
August 4, 2011 3:40 am

What is more complex – the world economy or the world weather systems? We don’t seem to be able to model the economy so why would we think we can model the weather anymore than a few days ahead

August 8, 2011 8:59 am

Long-time lurker, first-time poster. Thanks to Anthony for the posting about our article.
Before addressing some of the comments, let me say what this article is not about.
1) Climate change.
2) Tropical cyclones.
2) Numerical models for weather (or climate) prediction.
Conceptual models are frameworks for our understanding of how the weather works. If you’ve seen a graphic of sea-floor spreading at the mid-ocean ridge, a graphic of the electron orbitals of an atom, or a graphic of an idealized cross section of a warm front, that’s all a conceptual model is. A conceptual model is a simple graphic and accompanying story that describes our present understanding of a scientific concept. So, conceptual models should not be confused with computer models of the weather, which our paper doesn’t address.
Now, to address what the article is about, if you haven’t seen the article, you can read the abstract and download the article here:
Some of the comments about this post seem to be unfair characterizations of what the press release and the article are saying. It would help to at least read the abstract of our article.
1. Many others have known that aspects of the Norwegian cyclone model have been inadequate for explaining observed structures and evolutions (e.g., Carlson). We have over 170 citations in the paper, so we have placed our new results in the context of what has been known and discussed in the literature. Sometimes we are pointing out what has been published is incorrect. Other times, we are pointing out the people who have made progress in our understanding. And, also, we have some of our own new advances in the paper. We are not just restating lost knowledge.
2. There is nothing special about cyclones near Norway. The life cycle of cyclones first described by the Norwegians in the 1920s was a great step in our understanding, yet cyclones globally have been fit into their model (justly or unjustly). We have developed a much better understanding of cyclones (observationally, theoretically, etc.) now, which merits a re-examination of their conceptual model.
3. As we discuss in our article, our ideas (coupled with those elements that have been previously published) deviate substantially from what appears in all textbooks. I would have thought people would want to be presented with the latest and most scientifically accurate information. I think I have a healthy appreciation for the importance of this article on our common knowledge about extratropical cyclones, so this press release isn’t an exaggeration.
4. This article is not about Shapiro-Keyser cyclones (one alternative to the Norwegian cyclone model); it is only one small component of our paper. Our article shows that Shapiro-Keyser cyclones can be understood as having undergone occlusion in our new conceptual model. So, we are not just representing old knowledge as new.
5. As we discuss in the article, many cyclones continue to deepen after occlusion: “no fewer than 29 of the 91 northeast U.S. cyclones for which surface analyses appear in Volume 2 of Kocin and Uccellini (2004) deepen 8–24 mb during the 12–24 h after formation of the occluded front. The most extreme example from that dataset was the cyclone of 19–20 February 1972, which deepened 32 mb in 36 h after occluded front formation (Kocin and Uccellini 2004, p. 478).”
I hope that we can continue this discussion as we try to develop an improved sense of understanding among scientists and the public about how the weather works.
Dave Schultz

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