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[bluewave]

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[skierinvermont]

http://www.ldeo.columbia.edu/~sobel/Papers/hall_sobel_grl_submitted.pdf

 

http://www.climatecentral.org/news/hurricane-sandy-unprecedented-in-historical-record-study-says-15505

 

 Abstract  Hurricane Sandy’s track crossed the New Jersey coastline at an angle closer to  perpendicular than any previous hurricane in the historic record. This steep angle  was one of many contributing factors to a surge-plus-tide peak-water level that  surpassed 4m in parts of New Jersey and New York. The lack of precedent in the  historic record makes it difficult to estimate the rate of Sandy-like events using solely historic landfalls. Here we use a stochastic model built on historical hurricane data from the entire North Atlantic to generate a large sample of synthetic hurricane 32 tracks. From this synthetic set we calculate that under long-term average climate conditions a hurricane of Sandy’s intensity or greater (category 1+) is expected to make NJ landfall at least as close to perpendicular as Sandy at an average annual 35 rate of only 0.0014 yr-1 (95% confidence range 0.0007 to 0.0023); i.e., a return period of 714 yr (95% confidence range 1429 to 435). Thus, either Sandy was an exceedingly rare storm, or our assumption of long-term average climate conditions is erroneous, and Sandy’s track was made more likely by climate change in a way that is yet to be fully determined. 

 

I'll make a bet that there is no NJ landfall of Sandy intensity and angle within the next 100 years. 

 

When you constrain the definition of an event narrowly enough, the return period always becomes exceedingly large.

 

In this case they have constrained it by location (NJ), angle of approach (a heading of ~290 degrees or less), and intensity (category 1+).

 

I could probably find a hundred storms in the United States, within the last year, with a return period of 700+ years if I defined the location within 100 miles, the heading within 20 degrees, and the intensity of equal or lower pressure.

[csnavywx]

http://www.ldeo.columbia.edu/~sobel/Papers/hall_sobel_grl_submitted.pdf

 

http://www.climatecentral.org/news/hurricane-sandy-unprecedented-in-historical-record-study-says-15505

 

 Abstract  Hurricane Sandy’s track crossed the New Jersey coastline at an angle closer to  perpendicular than any previous hurricane in the historic record. This steep angle  was one of many contributing factors to a surge-plus-tide peak-water level that  surpassed 4m in parts of New Jersey and New York. The lack of precedent in the  historic record makes it difficult to estimate the rate of Sandy-like events using solely historic landfalls. Here we use a stochastic model built on historical hurricane data from the entire North Atlantic to generate a large sample of synthetic hurricane 32 tracks. From this synthetic set we calculate that under long-term average climate conditions a hurricane of Sandy’s intensity or greater (category 1+) is expected to make NJ landfall at least as close to perpendicular as Sandy at an average annual 35 rate of only 0.0014 yr-1 (95% confidence range 0.0007 to 0.0023); i.e., a return period of 714 yr (95% confidence range 1429 to 435). Thus, either Sandy was an exceedingly rare storm, or our assumption of long-term average climate conditions is erroneous, and Sandy’s track was made more likely by climate change in a way that is yet to be fully determined. 

 

How about that massive 3+ SD block over Greenland? Amazing how little attention was paid to that, but how critically important it was for the unusual track. Interesting to note that there's been a persistent positive height anomaly centered over Greenland over the past several summers (since about 2007).

[skierinvermont]

How about that massive 3+ SD block over Greenland? Amazing how little attention was paid to that, but how critically important it was for the unusual track. Interesting to note that there's been a persistent positive height anomaly centered over Greenland over the past several summers (since about 2007).

 

The argument from some is that such blocks are made more common by AGW. I find the connection weak at best, and the connection between that and landfalling hurricanes in NJ, with 1+ intensity, and a heading of 290 degrees or less, also weak. 

 

At most, I could buy that AGW has turned a 1-700 yr event into a 1-500 or 600 year event. And that's assuming that the connection between AGW and blocking is valid. 

[csnavywx]

On the subject of the Greenland blocking phenomenon, from 2007 onwards (Jun-Aug of each year), there has been a persistent height anomaly centered over Greenland that appears nowhere else in previous periods. In fact, there are at least two pieces of research ongoing into this anomaly currently, one of which is being conducted by the ECMWF. It appears likely, based on some of the discussions I've read and digging I've done, that there appears to be a link to disappearing sea ice, ice sheet changes and rapid warming over the region.

 

As far as more generalized blocking is concerned, "weak" isn't the word I would use. It's fairly obvious that the latitudinal temperature gradient has slackened due to differential warming from the Arctic to the tropics. This naturally translates to decreased jet speeds (as several papers have noted). A weaker jet is more subject to buckling and jet patterns are generally slower moving due to the increased beta-effect on amplified ridges and troughs.

[Jonger]

How about that massive 3+ SD block over Greenland? Amazing how little attention was paid to that, but how critically important it was for the unusual track. Interesting to note that there's been a persistent positive height anomaly centered over Greenland over the past several summers (since about 2007).

 

Amazing enough, we can't buy a block this winter.

[skierinvermont]

On the subject of the Greenland blocking phenomenon, from 2007 onwards (Jun-Aug of each year), there has been a persistent height anomaly centered over Greenland that appears nowhere else in previous periods. In fact, there are at least two pieces of research ongoing into this anomaly currently, one of which is being conducted by the ECMWF. It appears likely, based on some of the discussions I've read and digging I've done, that there appears to be a link to disappearing sea ice, ice sheet changes and rapid warming over the region.

 

As far as more generalized blocking is concerned, "weak" isn't the word I would use. It's fairly obvious that the latitudinal temperature gradient has slackened due to differential warming from the Arctic to the tropics. This naturally translates to decreased jet speeds (as several papers have noted). A weaker jet is more subject to buckling and jet patterns are generally slower moving due to the increased beta-effect on amplified ridges and troughs.

 

The models and papers cited in the IPCC 2007 report predicted that the AO would increase with AGW because warmer air and water in the arctic would create storms and lower pressures. 

 

If global warming creates more blocking, why was there so little blocking 1980-2007 which was the warmest 27yr period of the last 1000 years? 4 years does not make a trend. 

[The_Global_Warmer]

Amazing enough, we can't buy a

 

The models and papers cited in the IPCC 2007 report predicted that the AO would increase with AGW because warmer air and water in the arctic would create storms and lower pressures. 

 

If global warming creates more blocking, why was there so little blocking 1980-2007 which was the warmest 27yr period of the last 1000 years? 4 years does not make a trend. 

 

block this winter.

 

Well, 19 straight months from Jun-Aug.  If August of 2006 is added has been a -NAO.

 

That is mighty impressive and no-where else seen in the modern records. 

[Amped]

North carolina is about the furthest place south  you can get a closed H5 low in October.  Thats why Sandy turned west where it did.  Not common to get a Jersey but that setup may happen more than thought.

 

 

Also I've noticed a lot of  Noreasters such as 12/26/2010 do a cut back at that Lattitude., It's just where a closed 500mb low usually gets under the storm if it's going to happen.

[skierinvermont]

Well, 19 straight months from Jun-Aug.  If August of 2006 is added has been a -NAO.

 

That is mighty impressive and no-where else seen in the modern records. 

 

That is pretty impressive given it spans 6 years with different background states (QBO, solar, ozone, ENSO, etc.). But can you think of a reason it doesn't apply for September? 

[The_Global_Warmer]

That is pretty impressive given it spans 6 years with different background states (QBO, solar, ozone, ENSO, etc.). But can you think of a reason it doesn't apply for September? 

 

The only guess I would have is maybe it has something to do with ice albedo/heating the atmosphere.

 

Since the arctic is North of the Westerlies wouldn't it be prone to having weather pattern's up there in Summer more effected by ground up mechanics? 

 

Just a guess.  We have seen fairly large changes in albedo, ice melt, drying out of land, water open, instead of ice, then heating of that land and water, new shrubbery causing more albedo changes.

 

We are talking ice/snow albedo vs a pretty steady power house sun.  Not a winter weak one.  So we have to remember how much of an effect it will have on energy changes. While that may not do much to heat the Earth, it might have big local effects.

 

 

 

 

 

[CIK62]

I am guessing that was outside the scope of their current study as others have been doing research in that area.

 

 

http://www.americanwx.com/bb/index.php/topic/36479-ecmwf-researching-declining-arctic-sea-ice-role-in-increased-summer-blocking/

 

http://www.ecmwf.int...t/ecmwfnews/301

In an interview with the BBC Science Editor David Shukman, research at ECMWF was described regarding the role of Arctic sea-ice anomalies on summer weather in north-west Europe.

We suspect that declining Arctic sea-ice cover in summer has an association with lower pressure over the UK if there are also higher than normal sea-surface temperatures in the north-west Atlantic. In these circumstances we expect there to be an increased risk of the north- having relatively poor summer weather - wet, cool and windy. This is part of a long-term and large-scale pattern called the Arctic Oscillation that means the UK’s weather can be affected by events far remote from our shores. 

The Arctic Oscillation is associated with changes to the position of the jet stream such that during this summer the UK and was in the path of a series of storms. However, there are many other factors that determine our summer weather and the year-to-year and decade-to-decade variability is large. This is why at ECMWF we use what is called ensemble prediction where the range of possibilities is explored by performing 51 parallel forecasts starting from slightly different conditions.

The interview with Professor Alan Thorpe, Director-General of ECMWF, can be watched here.

http://www.wunderground.com/blog/stuostro/comment.html?entrynum=18

Sandy's path heading northeast about halfway between North Carolina and Bermuda but then turning sharply left and making a perpendicular beeline to the New Jersey coast is unprecedented in the known historical record. That should beg the question, "What’s up with that? Did the fact that the climate is changing play a role?"

For that to be the case, a logical meteorological connection ought to be evident, and there is one. 

Recent published research by Jennifer Francis and Stephen Vavrus identified specific connections between loss of Arctic sea ice (the minimum extent of which this year broke 2007's record low during the satellite era) and changes in general circulation patterns downstream including ridges of high pressure aloft. 

And I’ve added Sandy to the >1000-slide compendium I’ve compiled of cases in recent years in which strong ridges of high pressure aloft have played a role in extreme temperatures, precipitation, and storms, in the context of an overall trend of rising pressures aloft (actually heights such as that of the 500 millibar level) not just over the Arctic but in the larger scale, in concurrence with rising temperatures. 

 

lq9.png

 

Screen shot 2013-01-25 at 7.30.25 AM.png

 

Screen shot 2013-01-25 at 9.22.01 AM.png

 

 

 

 

Has the change in avg. 500mb geopotential heights been equated to how much farther north one must go to find the same avg. height that existed in 1960.    Looks like a rise of 20m has meant a rise in surface temps. of 2deg. F.     Here in NYC the temp. @CPK has not even reached zero for 19 years, a record hiatus.  (another 3wks. to be sure about this season)   While all time record is -15F one must go back 70 years to find anything less than a -2F.   The heat island effect not withstanding, how much farther north on average must you be to get -2F or less now?

[Jonger]

I am guessing that was outside the scope of their current study as others have been doing research in that area.

 

 

http://www.americanwx.com/bb/index.php/topic/36479-ecmwf-researching-declining-arctic-sea-ice-role-in-increased-summer-blocking/

 

http://www.ecmwf.int...t/ecmwfnews/301In an interview with the BBC Science Editor David Shukman, research at ECMWF was described regarding the role of Arctic sea-ice anomalies on summer weather in north-west Europe.

We suspect that declining Arctic sea-ice cover in summer has an association with lower pressure over the UK if there are also higher than normal sea-surface temperatures in the north-west Atlantic. In these circumstances we expect there to be an increased risk of the north- having relatively poor summer weather - wet, cool and windy. This is part of a long-term and large-scale pattern called the Arctic Oscillation that means the UK’s weather can be affected by events far remote from our shores. 

The Arctic Oscillation is associated with changes to the position of the jet stream such that during this summer the UK and was in the path of a series of storms. However, there are many other factors that determine our summer weather and the year-to-year and decade-to-decade variability is large. This is why at ECMWF we use what is called ensemble prediction where the range of possibilities is explored by performing 51 parallel forecasts starting from slightly different conditions.

The interview with Professor Alan Thorpe, Director-General of ECMWF, can be watched here.http://www.wunderground.com/blog/stuostro/comment.html?entrynum=18

Sandy's path heading northeast about halfway between North Carolina and Bermuda but then turning sharply left and making a perpendicular beeline to the New Jersey coast is unprecedented in the known historical record. That should beg the question, "What’s up with that? Did the fact that the climate is changing play a role?"

For that to be the case, a logical meteorological connection ought to be evident, and there is one. Recent published research by Jennifer Francis and Stephen Vavrus identified specific connections between loss of Arctic sea ice (the minimum extent of which this year broke 2007's record low during the satellite era) and changes in general circulation patterns downstream including ridges of high pressure aloft. 

And I’ve added Sandy to the >1000-slide compendium I’ve compiled of cases in recent years in which strong ridges of high pressure aloft have played a role in extreme temperatures, precipitation, and storms, in the context of an overall trend of rising pressures aloft (actually heights such as that of the 500 millibar level) not just over the Arctic but in the larger scale, in concurrence with rising temperatures. 

 

lq9.png

 

Screen shot 2013-01-25 at 7.30.25 AM.png

 

Screen shot 2013-01-25 at 9.22.01 AM.png

 

 

 

 

Has the change in avg. 500mb geopotential heights been equated to how much farther north one must go to find the same avg. height that existed in 1960.    Looks like a rise of 20m has meant a rise in surface temps. of 2deg. F.     Here in NYC the temp. @CPK has not even reached zero for 19 years, a record hiatus.  (another 3wks. to be sure about this season)   While all time record is -15F one must go back 70 years to find anything less than a -2F.   The heat island effect not withstanding, how much farther north on average must you be to get -2F or less now?

North of the city? You would have trouble finding that answer with suburban development outside NYC.

[Derecho!]

I'll make a bet that there is no NJ landfall of Sandy intensity and angle within the next 100 years. 

 

When you constrain the definition of an event narrowly enough, the return period always becomes exceedingly large.

 

In this case they have constrained it by location (NJ), angle of approach (a heading of ~290 degrees or less), and intensity (category 1+).

 

I could probably find a hundred storms in the United States, within the last year, with a return period of 700+ years if I defined the location within 100 miles, the heading within 20 degrees, and the intensity of equal or lower pressure.

 

Yep. This really seems like an instance of statistical/probablistic illiteracy.

 

What WOULD have been interesting for them to do is run the model to come up with return periods for ALL storms that generate 4 meter storm tides in both NJ and NYC. Because you'll have some stronger storms with less favorable angles, etc. doing this, the return period will assuredly end up being a lot less than 700 years.

 

People have an astounding inablity to accept, and fear the idea, that bad things are normal.

 

At its extremes, this drives both the "God's punishment" folks, and the "Katrina/Sandy caused by AGW" folks.  The latter people are smarter, of course, but scratch below the surface and it isn't too far removed from the basic drivers of the "God's punishment" idiots.

[ORH_wxman]

I wonder what the return period is on a November 1950 storm that produces 100mph winds in NYC, 50F rain in Buffalo and 10F blizzard in Pittsburgh.

[WeatherRusty]

Yep. This really seems like an instance of statistical/probablistic illiteracy.

 

What WOULD have been interesting for them to do is run the model to come up with return periods for ALL storms that generate 4 meter storm tides in both NJ and NYC. Because you'll have some stronger storms with less favorable angles, etc. doing this, the return period will assuredly end up being a lot less than 700 years.

 

People have an astounding inablity to accept, and fear the idea, that bad things are normal.

 

At its extremes, this drives both the "God's punishment" folks, and the "Katrina/Sandy caused by AGW" folks.  The latter people are smarter, of course, but scratch below the surface and it isn't too far removed from the basic drivers of the "God's punishment" idiots.

 

When I say to people that bad things are much more likely than good things and that bad things are normal I get labled a pessimist. It takes a good deal of paddling against the tide  or smarts to make things go right consistantly. There are many more ways of breaking an egg than there are ways of keeping it whole!

 

Second Law of Thermodynamics.