THIS WEEK IN WEATHER NOV 25

Posted by wxrisk | GENERAL,THIS WEEK IN WEATHER | Sunday 25 November 2012 11:48 pm

2300 EST  25 NOV 2012…..   STARDATE    201211.25

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AO … Arctic Oscillation … About to turn Strongly Negative…cold DEC on the way?

Posted by wxrisk | GENERAL,WINTER 2012 -13 | Sunday 25 November 2012 5:18 am

2300  EST   24 NOV  2012 …. STAR DATE   201211.24

 

 

I am reading and seeing a lot of posts   on various FB  weather   pages and weather forms  (American wx for one) regarding o the strong signals from some of the weather models that the Arctic Oscillation ( AO) is about to turn severely negative. And in doing so this means there is a high probability that December 2012 …at some point …is likely to turn much colder which is what happened in December of 2009.
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Or so the argument goes.
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This is one of my pet peeves with regarding forecasting by Teleconnection or specific climate /weather patterns. You simply cannot look at ONE particular Teleconnection or weather pattern and develop a long range / seasonal forecast or even monthly forecast. The atmosphere does NOT work based upon ONE particular atmospheric pattern . It does not matter if the one particular atmospheric pattern or Teleconnection ..such as the AO or NAO… or PNA… or EPO.. etc etc … is powerful and dominant. There are other things that one MUST take into consideration and fit all the different aspects of the atmosphere and “mesh” them into a coherent pattern.
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But because so many do not GRASP this … when they see a model develop a very strong signal for particular atmospheric pattern or Teleconnection… they make the decision that such and such is likely to happen. The misplacement and over for emphasis on some of these atmospheric teleconnections can lead to some serious screw ups.  One of the more common misunderstandings with these atmospheric patterns are Teleconnections has to do with the Arctic Oscillation (AO). In fact all of these to various important large scale weather patterns have a certain subtleties which must be taken into consideration but with the Arctic Oscillation … there is an awful lot of misunderstanding regarding its importance.
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Don’t misunderstand me. I am NOT at all saying there the phase of AO is not important in figuring out long range weather patterns for several weeks or for next month. But you must look at the AO with other atmospheric patterns. Yet for some reason there are an awful lot of forecasters and weather hobbyists out there that get awfully excited when they see a weather Model TANK the AO into severely negative values.
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For example this is the latest CPC GFS Ensemble forecast for the AO as of November 24. As you can see there are 4 plots and all of them show the AO moving steadily and strongly into negative territory by December 1 and continuing into negative territory by the middle of December.


Or if you want to look at it another way …here is the regular or operational GFS from Saturday evening– the 18z RUN which shows a severe if not historic drop in the AO.


And if you don’t want to look at just the operational GFS this next image shows you the GFS ensemble mean plots. Not surprisingly there not as severe has the operational GFS but they do show a prolonged and persistent interval of a strongly negative AO feature.


So of course it only makes sense to forecast a colder and potentially stormy are pattern for the central and eastern U.S. as you move towards the middle of of December 2012… right ?
NO!!!!!!!!!!!!!! It does not and let me explain why.

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In my winter forecast and especially in the final winter forecast which I issued last week,,, I pointed out in the Winters of 2009-10 and in 2010-11 that it was the conjunction of both the AO and NAO operating at the same phase and both severely negative which is what help produce the stormy in cold pattern

There is gross misunderstanding that simply because the Arctic Oscillation has gone negative that it follows that

1) the NAO has also turned negative
2) or that it has to turn negative…
3)  that the overall pattern is now a much colder and stormy are one for the central and eastern US. None of this is remotely true.

There are numerous cases of the Arctic Oscillation turning negative but the cold pattern sets up over the Pacific… or say Western Canada …or Europe or Central Russia for example. Of course .. as I stated above… if you have BOTH the -AO and -NAO at the same time and with roughly same intensity… then the overall pattern over the central and eastern U.S. does favor below normal temperatures and above normal precipitation.

Let’s take a look at some of the weather models as we move into early December and we can see there a lot of other very important features to consider besides a strongly -AO.   This next image shows comparison between the operational European model at DAY 9 on the left side and the operational GFS model on the right side. We can see several very important features but the most dominating one happens to be the BERING SEA OMEGA RIDGE .    (for those of you that do not know the Bering Sea is the body of war to the separates Alaska and far eastern Siberia). It is this feature which has been persistent now for about two weeks which is the dominating or driving feature across the western hemisphere and not the AO.       The placement of the OMEGA RIDGE over the Bering sea means that you have to by definition have a trough in the jet stream over Alaska and Northwest Canada. That trough constitutes a POSITIVE PHASE of the EPO and therefore -PNA pattern ( West coast Trough in the Jet stream).


Remembering our basic high school physics for reaction as an equal and opposite reaction…. So the place another trough in the jet stream on the West Coast means the atmosphere HAS to counter it by developing a RIDGE over the eastern U.S. A pattern like this allows for the buildup of a lot of very cold air over western and Central Canada but there is simply no mechanism or path for that cold air to come into the U.S. east the Rockies.   In addition I have highlighted three other important LARGE upper Lows or vortices in the Jet stream. #1 is the Siberian  PV polar vortex)… #2 id the Northeast Canada PV AND #3 is a large and persistent upper low which develops over western and Central Europe including the United Kingdom.
The three positions of these large vortexes constitutes a three wave pattern… which is a rather stable pattern…. and not one which is likely to change anytime soon.

In this next image we can see the Day 10 European ensembles on the LEFT and the Day 10 GFS ensemble on the right. As you can see the models are in strong agreement in the first week of December as to how the overall pattern is going   to develop. There is simply no mechanism for delivering cold air into the country east the rocky mountains during the first week or two weeks of December… and possibly throughout most of the month.

This is the latest November 24 CFS Model runb….( 16 CFS runs each day going back over the last 10 days) . The map on the left hand side represents precipitation…. and we can notice of a lot of rather dry conditions over Texas the Gulf coast and up into the Middle Atlantic region and above normal precipitation over the Midwest and on the West Coast. This sort of dryness is symptomatic of a model showing a strong ridge over the southeast states.
The map on the right hand side see it shows a pretty warm December for much of the country but especially between the Rockies and the Appalachians.

Indeed the new 10 day group of CFS ensemble mean show a very mild December for most of the country. There probably is some skepticism with regard to this much warmer December CFS Model runs… Especially given the development of a strongly negative AO. But as I showed above …it is quite possible to have a-AO and still have a Mild pattern over the central and eastern US


In order to get this pattern to change the strong OMEGA Ridge in the Jet stream  over the Bering sea HAS to move to move.. HAS to. In doing so it will force the EPO to switch from +EPO to -EPO… and that in turn will allow for a strong west coast Ridge ( -PNA to  +PNA) which sets up a much colder pattern and allows the trough to form of the eastern U.S.

 

 

UPDATE ON WINTER CLIMATE MODELS FOR THE WINTER

Posted by wxrisk | GENERAL,WINTER 2012 -13 | Thursday 22 November 2012 11:41 pm

22 NOV  2230 HOURS   EST …   STARDATE  201211.22

 

There is some new information which of come out recently since I issued the final winter forecast which I believe is significant because it shows that continue trend in the CFS Model for a colder DEC and JAN east the Mississippi River.
This first image consist of three maps all focusing on December of 2012. The first two of these maps have already been posted in the FINAL WINTER FORECAST … But since then the updated version has come out . Normally I would not make a a big stink about this new run of the CFS…..
But the changes here in the December and January are pretty significant especially if you look over the last 30 days.

And remember each one of these maps covers a 10 day period. The first interval or 10 days was from middle of OCT…. the SECOND 10 day period 3-11 NOVEMBER.. and this most recent update covers 12-21 NOV.

Here are the DECEMBER CFS temperature forecasts over these last three 10 day periods. The trend it should be obvious and quite clear that since the middle of October the CFS has been turning colder and colder.

Now remember the CFS ten day mean average is NOT simply one model that is run on one particular day.  The CFS consists of 4 runs EACH day … for 10 days for a 40 member ensemble.
looking at JANUARY 2013… we continue to see the same trend with each new 10 day increments of time and each new 10 day period showing temperatures turning colder and colder east the Mississippi River. The trend here in both months are quite noticeable and I believe to be consistent and significant.

Next I have presented the mean pattern being forecasted by the Chinese climate model for the northern hemisphere  for December   January February. Posting this map may draw some cynical comments and derogatory reaction but rest assured that individuals make such comments are the actual idiots.

We all know that there are weather models out there which are generally superior to the operational GFS and the GFS ensemble.  It would follow that there are climate models out there which are superior to the GFS.   One of them happens to be besides the European model is the Chinese climate model.  The Chinese climate model did a remarkable job with the drought during the summer. I have no idea if the models correct are not with its winter forecast but it shows a pretty impressive pattern for the East Coast. In fact if the Chinese models correct this would be a historic winter for most of the East Coast as well as the Tennessee Valley and the lower Midwest.

Also here in case you missed it is the latest upper air forecast for week three and week four from NOV 22 CFS . What is significant here is that it continues to show that the first half of December is NOT going to feature Below Normal temperatures and it does NOT look very stormy for most of the country. I said this back in my initial winter forecast and I don’t see any reason to change it.

However by week 3 DEC 6-12 we see a very strong blocking feature over North Central Canada which really counts as a extremely slow large -NAO. The week 3 pattern is actually one of those rare instances where even though the NAO is large and strong … Temperatures do not show a cold pattern. The problem is that we continue to see that trough over Alaska. That feature which in the weather business is called a positive phase of the EPO (+EPO) is forcing a trough over the far eastern Pacific and along the West Coast of North America….. or a -PNA pattern. As a result the cause of the -NAO block over North Central Canada is so large… the interaction between this feature and the -PNA means that there’s no cold air flow coming into the U.S. As result temperatures dec 6-12 will be pretty mild for most of the country east the Rockies.


However by week 4… the +EPO is gone… and replacing it is a -EPO feature… which means a strong West Coast Risgw extending all way up into Northwest Canada. The expansion of this RIDGE over Northwest Canada means that the-NAO Hass to be pushed to the east a little so it moves into the more classic position over North America— between Labrador and Greenland. This setup +PNA and -NAO and a -AO is very favorable for significant East Coast or eastern U.S. winter storm to develop in mid December. The dark green areas shows the huge trough over the northeast quadrant of the country. Of course at this point in time it’s impossible to say as to whether not this is a Great Lakes or New England Low or a true East Coast storm

 

 

NOV 18 — THIS WEEK IN WEATHER –

Posted by wxrisk | GENERAL,THIS WEEK IN WEATHER | Monday 19 November 2012 3:05 am

2000 Hours  EST  18 NOV  2012…. STARDATE  201211.18

 

 

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FINAL WINTER PREVIEW 2012-13

Posted by wxrisk | GENERAL,WINTER 2012 -13 | Saturday 17 November 2012 11:18 pm

  2100  17 NOV  2012…. STAR DATE  201211.17

 

Most of the time when you are making the  final Winter forecast …the months of October and  November usually are not very active with   respect to significant weather events. But as wel all know .. that has not been the case  in 2012 with event of hurricane Sandy.  This  was followed shortly by the early November 7 nor’easter which bought significant snow to New Jersey New York City Connecticut and Long Island… and then now we have to deal with  the ocean Low which is going to pass off the East Coast NOV 19-20.

This particular updated forecast will focus on several key aspects of the last 45 days in an attempt to figure out what the winter of 2012–13  is going be like. We’ll talk about

  • snow cover over Siberia/ Eurasia during the month of October 2012
  • Key upper air atmosphere weather patterns such as the arctic oscillation the North American oscillation and the western Pacific oscillation Sea surface temperature anomalies and what they may or may not imply
  • And a few other odds and ends/ miscellaneous.

I suppose the first general question that has to be addressed is the concern that the events of late October and early November on the East Coast— specifically the historic event of hurricane sandy hitting the New Jersey Coast and the winter storm of November 7 —  and whether   those  2  events   “mean”   anything with respect to the upcoming winter. The basic answer is that the actual storms  do not  t mean anything one way or the other but the pattern which developed these particular   events    does have implications.

For example last year…on 28-29 October 2011 …there was a early season historic nor’easter which produced heavy snow over the interior portions of New Jersey southeastern New York and Connecticut into western and Central Massachusetts.  It caused serious destruction of damage to the power infrastructure in CT. Since many of the forecasts– both with NWS/ CPC and many private sector – going into that winter of 2011-12 called for a another active cold and /or snowy winter in the eastern U.S…. the general perception or belief was that ….”if this is what the pattern is producing in late October of 2011 imagine what the winter is going to be like !!…”.

Yet as we all know the winter of 2011-12 was exceptionally mild and had very few significant winter storms anywhere the country but especially east the Rockies and East of the Mississippi River.   On the other hand there have been Summer and Autumn patterns …such as the Hurricane season  of 1995 which featured several significant East Coast hurricanes and noreasters in August Sept and Oct of 1995.  Yet the pattern never shifted as we went into Winter of 1995-96 which produced several major East Coast snowstorms including the great January blizzard of 1996.

Over the past 20 years has been a lot of research done in various climate and meteorological periodicals which are shown in that autumn patterns do have a connection to the upcoming winter provided the autumn pattern is consistent and produces the same type of events.  In  other words the historic of  28  October 2011 inland snowstorm over the Northeast US was NOT  part  of a sustained Autumn pattern but a anomaly. Most of that autumn was warm and dry and the winter that followed was very much the same.

Keep in mind that the Spring and Summer of 2012 was exceptionally hot and dry over much of the country. It’s hard to remember that given what we seen in October and early NOV 2012. That dramatically shows how vastly different the overall pattern has turned.

THE UPPER AIR PATTERNS

Remember that the atmospheric  PATTERNS   are  what drives the weather.  It determines where LOWs will track… where the nice weather patterns are going to occur …where the cold air is going to move.. etc Weather models are supposed to reflect what’s going on in the atmosphere. They do not determine where weather systems actually move or develop. A Low pressure area over  . Louisiana does not  ”DECIDE”  to move to Chicago or New York City because of a weather model.  Weather features are not people and there is no decision-making process involved.

Far and away the two most important weather features or patterns which exist over the western hemisphere in determining the winter and the overall winter pattern has  to do with the Arctic oscillation (AO) and the North Atlantic  Oscillation (NAO).     If you are not a weather not or hobbyist or meteorologist you may have heard of these terms used occasionally before but not know what these terms refer to. So let me briefly explain.

There are several distinct and noticeable weather patterns which developed in the upper levels of the atmosphere over the northern and southern hemisphere which tend to move in repeating cycles. These various Jet stream patterns in certain positions or certain “phases” produce weather patterns at the surface which will support a warm pattern …or a stormy pattern …or a cold pattern …or a wet pattern.. or some combination thereof.    A good analogy might be to consider mountains or mountain ranges. We all know there are several different types of mountains and mountain ranges but no two of them or are exactly the same. But they all have the same general shape.

THE ARCTIC OSCILLATION .. or the AO

The Arctic Oscillation (AO) is one of the special and very important features which exists in the jet stream throughout the entire year. It has two distinct phases a POSITIVE phase and a NEGATIVE phase. These phases may vary in intensity ( weakly positive for example) but the important concept here to grasp is that when the AO is in one particular phase it strongly favors a certain type the weather pattern over North America and especially over Eastern North America including the U.S.. When the AO is in a different phase it has a equally strong impact on the weather patterns over Eastern North America but in a different way.

This image will show us how and why the Arctic Oscillation works and what it looks like. When there is a large area very cold air mass in the jet stream over the arctic regions — which shows up on the Jet stream map as having a big LOW over   or North of   the Arctic circle — the AO  is said to be in the positive phase. The  +AO  keeps all the cold air bottled up over the arctic region and does not allow for large scale arctic outbreaks to occur either in Europe or in North America. This was exactly the case last winter which is why we had no significant colder outbreaks.

On the other hand when the AO is in the negative phase... which on the weather maps of the Jet Stream will come across as weak or small areas of Low pressure over the Arctic circle or sometimes a blocking pattern– it is much easier for large cold air masses to move out of the arctic regions into Europe and North America. This was exactly the case in the historic winters of 2009-10 and 2010-11.

This next image shows how this typically works. The two maps correspond to the different AO phases and it’s pretty self explanatory as these maps go. When you have a  negative AO   (the map on the left hand side)    temperatures run Above Normal –relatively speaking of course — over the arctic region and especially over Eastern Canada and Greenland. And temperatures run below normal over the Midwest and the East Coast.  When  you have a  negative  AO   (the map on the RIGHT hand side)  shows exact opposite   weather pattern .  As you can clearly see the arctic regions are colder than normal and Central Russia is also much colder than normal …. while Eastern Canada central and eastern areas of the USA are much warmer than normal during the winter months.

However that being said simply having a negative or positive phase of the Arctic Oscillation doesn’t get us very far in figuring out weather patterns. It is quite possible  that    when the   AO is  Negative  that the arctic cold air coming out of the arctic region  goes into Europe but  not into Canada or the U.S.  So there of the things we have to take into consideration.

THE NAO– North Atlantic Oscillation

The North Atlantic  Oscillation (NAO) is one of the special and very important features which exists in the jet stream throughout the entire year. It has two distinct phases –a POSITIVE phase and a NEGATIVE phase. These phases may vary in intensity ( weakly positive for example)  but the important concept here to grasp is that when the NAO is in one particular phase it strongly favors a certain type the weather pattern over North America and especially over Eastern North America including the U.S.. When the NAO is in a different phase it has a equally strong impact on the weather patterns over Eastern North America but in a different way.

This image will explain our show how and why NAO is so important and the impact it has on weather patterns over North America in general and especially over the central and eastern U.S. during the  cold season  months. The diagram is pretty self explanatory but in a nutshell +NAO means a much reduced chance of saying any sort of significant colder outbreaks over the central and eastern U.S. and a much reduced chance of saying any sort of significant winter storm activity. When the NAO is in the Negative Phase… the odds significantly favor a colder than normal pattern with the potential for a significant cold air or arctic air outbreak… and the potential for some sort of significant East Coast or activity.  Of course all of that is assuming that there is some sort of Low Pressure that is coming east. (In other words…. +NAO or – NAO do not produce winter storms or mild weather patterns by themselves.

The winter of 2011-12 featured a extremely positive NAO through almost the entire winter. In fact the OCT 2011 and NOV 2011 readings for the NAO were among the strongest ever seen. On the other hand OCT 2009 and OCT 2010 featured widespread persistently negative NAO which was also among the strongest ever seen. And we know that the winter is that followed.. 2009-10 and 2010-11 were quite snowy and cold).

These two particular Jet stream patterns … the AO and the NAO…   give us several different possible combinations which forecasters MUST  take into consideration in making the seasonal forecast …or even a forecast  for the  next 2 or  3  weeks.  This image will show you the possible combinations that knowledgeable meteorologist and experience whether hobbyists are familiar with.

Let’s take a look at how the combination of the AO and the NAO often worked together and produce significant weather pattern or events for the eastern US.

This next chart shows us the NAO and the AO since August 1. I have highlighted some important features in order to ease the understanding of this significant chart.

 

The first thing that stands out is that for the most part the NAO and the AO have been synchronous or moving in this same general direction. This has not always been the case. Back during the snow-less or nearly snow-less winters of the 1980s and early 1990s… The charts back then show that the NAO and AO were not moving in the same direction and trends.
The first green box / rectangle shows the Heat  wave breaking in early and mid August. Throughout most of APRIL MAY JUNE and JULY 2012 ….the NAO and AO were both strongly positive.    However things began to change in early August which resulted  when the NAO and the AO both turned  sharply negative after AUG 4.  Not surprisingly this is exactly when the heat  wave broke and the first significant rains appeared over the Midwest.

The next green box is in early and mid September where again the NAO and AO both turned negative.  And if you go back and take a look of  surface  weather maps you will see that in early and mid September we had our first significant blast of Autumn air over the central and eastern US .

However the third and largest green box that I have highlighted shows the prolonged and sustained negative NAO and negative AO which began in early October and reached a peak in the last week of October…. which is exactly when hurricane Sandy made its left turn and crashed into as southern NJ coast. There was a secondary drop in early November which is when Noreaster of NOV 7.

But this is not just the case for this particular autumn. If we go back and take a look of the last several winters we will also see that the severe and snowy winters of 2009-10 and the active snowy winters of 2010-11 featured sustained prolonged intervals of -AO and -NAO.

This image shows the AO and the NAO from the historic eastern U.S. winter winter of 2009-10. Notice that the Arctic Oscillation turned negative and strongly negative in October of 2009 then a briefly went towards positive in November and flipped two extremely negative during the heart of the winter.  In fact the AO was the most negative EVER recorded during the heart of the winter months.  The NAO was not nearly as strong but persistently negative during the heart of the winter months.

The result was a severe and historic winter for the East Coast.

This next image shows the following winter… 2010-11. Again notice that both the AO and the NAO in October  of 2011 dropped moderately negative .. and the AO turned weekly positive during a good portion of November. But once we moved into the winter months both the AO and the NAO were consistently and strongly negative the the heart of the entire winter… up to early / Mid February of 2012.

  

Finally let us compare LAST WINTER… 2011-12 which as we all know featured very mild temperatures for all of the country east of the Rocky mountains to the East coast and very little snowfall.   Throughout the entire Autumn of 2011 the AO and the NAO were strongly positive…. never once dropping into the negative phase. This of course is totally the opposite of what we saw in the previous two examples. Then once the winter of 2011-12 began … Both the AO and the NAO were consist only an strongly positive. As I stated above the AO was at or near record a positive levels.

 

WHAT ABOUT THIS WINTER ?   WHAT WILL THE AO and NAO   ” DO ” THIS WINTER?

As I stated and showed you above… having persistently strong -AO and -NAO  in the month of October  is a strong signal that the heart of the winter months will experienced large and n persistent prolonged periods of -AO and -NAO jet stream patterns. The October 2012 reading for the Arctic Oscillation was the second strongest on record– only exceeded by the October 2009 arctic oscillation reading! In fact if you look at all the top 10 negative arctic oscillation readings in the month of October… every one of those Winters that followed winter = DEC JAN FEB) featured persistently strong negative  Arctic Oscillations.

OK… So the OCT  AO strongly favor the  AO running negative this upcoming winter.    But what about the NAO?    Over the past 10 years there has been some really great research done that shows a strong connection between SSTAs — sea surface temperature anomalies — in the North Atlantic during the month of October  and forecasting the general trend of the NAO for the upcoming winter. This image clearly shows the connection between what the idealized or textbook example of the SSTA have looked like in the month of October and Winters which featured persistently negative NAO events.

The image is pretty self explanatory but basically there is a certain or specific type / pattern which we look for in the water temperatures over the north Atlantic.

There is often a pool of very warm ocean where temperatures– relative to normal of course– off the New England or Southeast Canada Coast– then a pool of cold water over the central north Atlantic east of Newfoundland — and a pool of warmer than normal sea surface temperatures in the Davis Straits ( the area between Labrador Canada and western Greenland).

This next image shows you what the current sea surface temperature in NOV 2012   look like over the north Atlantic. As of mid November we see a pool of very warm ocean where temperatures — relative to normal– off the New England Coast and Southeast Canada which matches the textbook or schematic of the classic SSTA for the negative NAO. We also see a very warm ocean where temperatures extending up into the Davis Straits. And we also see a pool of cold water in the central north Atlantic .


In other words the current sea surface temperature anomaly maps for mid November in the north Atlantic strongly support a persistently negative NAO for this upcoming winter.

Interestingly if we compare the last three winters we see something important in different with regard to the SSTA and negative NAO. In this next image I am presented the last 3 Middle Novembers SSTA maps. — 17 NOV 2011.. 15 NOV 2010 and 16 NOV 2009 .

The first map clearly shows a very different looking SSTA configuration. Notice in the green circle that there is NO large body of warmer than Normal Sea surface temperature anomalies off the New England or Southeast Canada coasts. In fact the SSTAs temperatures there are colder than normal. This is the exact opposite of the textbook SSTAs diagram shown above that is needed for sustained negative NAO.

However the middle and right map of SSTAs from 15 NOV 2010 and 16 NOV 2009 .. show the exact opposite with classic or nearly textbook set up for sustained negative NAO patterns.

SNOW COVER

There  has   been a lot of research done over the past 10 years that shows a very strong connection between above normal snowfall over Siberia and the phase of the Arctic Oscillation.   One of the lead researchers in this is Dr. Judah Cohen  from AER. The correlation between the October snow cover over Siberia/ Eurasia and the AO  is extremely strong … near 0.90. Basically the argument is … and in MY view it has been proven… that above normal snowfall in Siberia / Eurasia in the month of October strongly correlates to the negative phase of the AO.  Likewise below normal snowfall over the same area in the month of October strongly correlates to the positive phase of the AO.   Pretty simple really. You can read about how strong here… at this link.     http://www.nsf.gov/news/special_reports/autumnwinter/model.jsp

But these images will also help show the correlation without getting too technical for some of you.

This next image shows the forecast for the temperatures across northern hemisphere in the winter of 2002-03.

For those of you that  arw weather savvy… that winter was a historically significant winter with numerous significant winter storms over the Midwest and the East Coast and large areas of below normal temperatures on a persistent bases. The map of the LEFT side shows the temperature anomalies forecasted for that winter based upon the snow cover in October of 2003 which was much above normal.   The map on the RIGHT hand side shows the actual temperature anomalies for the winter.     That was a amazing forecast.   But  that was not  a “lucky forecast”.

This next image shows the forecast made by Dr Cohen based upon the October 2009 snow cover in Eurasia of which was much above normal. This forecast cover the period from January February and March of 2010. The map of the LEFT hand side shows the forecast temperatures by Dr Cohen for JAN FEB MAR 2010. The map on the RIGHT hand side shows the actual temperature anomalies for JAN FEB MAR 2010. Again this was a exceptional forecast. As we know the Winter of 2009-10 was a historically significant winter with large areas of persistently below normal temperatures and above normal snowfall over the central and eastern US.


This method   also works quite well over in Europe. The map of the LEFT was Dr. Cohen’s forecast for the temperatures of January February March 2010… again based primarily on the snow cover over Eurasia in October 2009. The map on the RIGHT shows actual temperatures in Europe for the same time frame. That is a stunningly good forecast.


And even more impressive  was  his forecast for the winter of 2011-12. While many others were calling for another colder than normal winter with significant snowstorm potential for the central and eastern U.S. Dr Cohen looked  that the snow total for October 2011 and saw that it was substantially below normal over Eurasia.
This next image is the SNOW COVER from 22 OCT 2011 and we can see that the snowfall was in fact below normal over large portions of Canada and Eurasia 
The map on the LEFT hand side shows his forecast for last winter 2011-12… And you can see that Dr Cohen went against the consensus and forecasted an exceptionally mild winter. The map on the RIGHT hand side shows the actual temperature anomalies from last winter.   You should be impressed by this forecasting ability.

WHAT ABOUT OCT 2012 SNOW IN EURASIA?
This chart from FSU shows that during the last 45 days the snow cover has consistently run above normal over the northern hemisphere in general. But that does not tell specifically about Eurasia.

In this image here we can see this total SNOW COVER through November 14, 2012 and this snow appears to be much above normal . This matches the graph and from FSU.

The actual 31 OCTOBER 2012 snow total for Eurasia from the RUTGERS SNOW LAB …is 11.11 squared kilometers. The Rutgers snow Lab has data on snowfall coverage over the northern hemisphere… Eurasia Canada North America Greenland going back 45 years. The MEDIAN value of all these Octobers for SNOW COVER in Eurasia is 9.6 sq KM… the MEAN value is 9.88 sq KM.
Therefore the October 2012 SNOW COVER in Eurasia is much above normal by value of 1.21 square km   above normal. This is the 11th  snowiest October on record for Eurasia and closely matches the October 2009 value which was 11.28 sq KM.    This next image gives us a summary of these facts and the last three winters.


In fact if we go back and time will continue see there is very strong correlation between the SNOW COVER over Eurasia in OCT.    This next image shows a list of October Snow cover in Eurasia which preceded historically significant winters over the central and eastern U.S. As you can tell in almost every case where SNOW COVER was substantially above normal over Eurasia in October the following winter featured colder than normal temperatures and /or snowier than normal weather patterns.

Even more interesting is that if you go back and look at the early 1990s and most of the 1980s which featured very mild nearly snow less winters for much of the central and eastern U.S.. we see that on a consistent basis that in every case SNOW COVER was at or below normal in Eurasia during the month of October proceeding that winter. Now to be sure..some of these very low October SNOW COVER readings in Eurasia can be explained due to a extenuating circumstances. For example the October SNOW COVER in Eurasia of 1988 was during a very strong if not the strongest La Nina on record.

During the early 1990s… OCT 1990 OCT 1991 OCT 1992.. SNOW COVER in Eurasia during the October the proceeded those winters was substantially below normal and all three of those years also featured moderate to strong El Nino events.   Indeed the period from 1983-84 to 1992-93 or perhaps that at least snowier this record in many of the big cities and the northeast U.S. And not surprisingly during this time frame …as I just showed.. SNOW COVER was substantially below normal in Eurasia in the month of October during that 10 year period.

Another way of looking at the impact of heavy SNOW COVER in Eurasia during the month of October preceding the winter is to look at this table from the Rutgers snow laboratory. This table shows the SNOW COVER for all the Octobers going back to 1967. And the correlation is really quite striking.

SUMMARY: the explosive development of SNOW COVER in Eurasia in October of 2012 is a very strong signal that not only will this winter be vastly different from the previous super mild winter … but is a strong indication that this winter will be close to what we saw on 2009-10. Combined with the very clear signal of a strong and persistent AO and NAO in OCT of 2012…. it is becoming increasingly hard to ignore all of these are strong indications.

OTHER WEATHER PATTERNS
Besides the arctic oscillation and the  NAO  there are several other important weather patterns in the jet stream which can influence the weather patterns over North America. One of them is the PNA– for the Pacific North America  pattern.

This features is centered over the eastern Pacific and Western North America and is also strongly dependent upon large areas of Colder than normal or Warmer than Normal Sea surface temperature anomalies.  This image explains how and why the PNA pattern works.


There are several different features in the atmosphere which can alter or cause the PNA to shift from positive to negative and backed off to positive again during the course of a winter Spring  Summer or Autumn season. One of those features is the MJO… but another will feature which has to be taken into consideration are the  SSTAs  – sea surface temperature anomalies   over the far eastern Pacific from Alaska down to Baja California
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Over the past three years there has been a large and persistent pool of very cold ocean water temperature anomalies located in the eastern Pacific from Alaska down to Baja California. This large persistent pool of colder than normal ward temperatures as persistently favored ( which is called the cold Phase of negative of the PDO) has persistently favored a -PNA pattern.
We can see this persistent large pool of cold water here

During the winter months of 2009-10 and 2010-11– as I showed above —  there was widespread high latitude blocking with strong persistent negative phases of the AO and NAO. As a result the -PNA did not cause a strong ridge to form over the eastern US and a winter stay persistently cold and stormy.    However during the winter of 2011-12 the AO and NAO were persistently and strongly positive.   As a result the -PNA pattern on the West Coast of North America did in fact produce a large and strong Ridge in the jet stream during the winter … and during the Spring and Summer of 2012. In fact this was one of the primary reasons WHY the Spring and Summer was so intensely hot and dry.
However if we look at the current mid November SSTA map we see that the ocean water temperature patterns over the eastern Pacific has changed considerably. There is no longer a massive pool of very cold sea surface temperatures in the eastern Pacific along the West Coast of North America.

THIS MEANS .. That the winter of 2012-13 could see +PNA patterns develop which would allow for serious and possibly severe arctic air masses to invade the central and eastern half of North America including the US.


THE WPO…. WESTERN PACIFIC OSCILLATION.
This Jetstream configuration is often overlooked by many but it sometimes can be significant especially if it is in a particular phase for prolonged period of time.
The POSITIVE phase of the WPO features a Upper Low in the jet stream over the Bering sea / far eastern Siberia and a ridge over the central north Pacific. This is exactly what we saw last winter.  The NEGATIVE phase of the PDO produces just the opposite.. RIDGE over the Bering sea and far eastern Siberia and Low pressure over the central north Pacific. That is the current WPO phase  as you can see here.. which is  a   pretty strong negative and persistent WPO event.


Assuming that the -WPO continues into December which seems a high probability…. The pattern strongly indicates that much of central and eastern portions of the U.S. as well as the Great Lakes and the Northeast will see temperatures run persistently Below Normal during the month of December and probably into January.

THE QBO… 
In the initial forecast assessment for the upcoming Winter of 2012-13 the which has issued back in the Middle October… I emphasize the point that the current an extremely strong negative phase of the QBO was a bit of a problem with regard to forecasting a cold winter. The research clearly shows that when the QBO   is extremely negative   ( with values of -20 or lower) going into the winter months…  that the statistical correlation clearly favors a mild start to the winter which turns colder in the second half.   That is assuming that the -QBO continues to weaken and move towards NEUTRAL in January February and March.

Since then the October reading for the QBO came out on November 3 and it showed some slight weakening but still a very strong negative QBO value -25. The latest data shows that as of mid November the QB oh has begun to weekend at a pretty steady pace and I suspect that on December 3 when the November values for the QBO are released by CPC we will see the QBO make a significant rise from say -25 to something like -14 or -13.
CFS MODEL FOR THE WINTER 2012-13.


Finally we can take a look at the climate model maps from the CFS. As a general rule there’s a lot of skepticism with regard to climate models and the ability to forecast anything correctly. That certainly has been the case with some of the more primitive models but the development and the arrival of the CFS version 2.0 has ended that skepticism.   Back in the Spring season of 2012 the model anticipated El Nino conditions to develop and increase and as result … the CFS V2.0 forecasted a wet and cool Summer for the Midwest. However as we now know the El Nino conditions fell apart and the NAO and AO stayed strongly positive The CFS showed a dramatic shift in MAY of 2012 and correctly forecasted the severe outbreak of heat and dry conditions over all the Plains and the Midwest for June July and into early August of 2012.

Even more impressive is that in late July while anybody else was forecasting more extreme heat and dry conditions for August of 2012… the CFS in mid July I forecasted and significant change in the pattern with below normal temperatures and additional rainfall. Again the CFS was correct in showing this change and with the timing as well.

This first image shows us the December forecasts with respect to precipitation amounts. The map of the LEFT side is from the middle of October –specifically from OCT 14-23. As you can see it’s forecasting a fairly dry conditions over the Gulf coast and the Northeast and wet conditions over the Pacific Northwest and the entire West Coast. However the map on the RIGHT hand side shows the new forecast from earlier in November… NOV 3-12 to the specific. And it shows dramatically different weather patter which large areas of above and much above normal rainfall over the gulf coast into the Tennessee Valley and slightly above normal over the northeast and along the Pacific Northwest coast and the northern Rockies.

With respect to December 2012 temperatures the CFS model from 14-23 OCT showed a huge areas of much above normal temperatures covering all of the central lower Plains the Deep South into the Midwest and the Ohio Valley. The updated version however from early November shows a much different temperature forecast for DEC 2012. While it is true that in this second map that the Gulf coast and the East Coast are still quite warm … the warmth is not as intense and the CFS now shows a massive pool of very cold air covering all of western and Central Canada.

With respect to January precipitation... the CFS v2.0 in Middle October showed above normal rainfall or precipitation over the Gulf coast into the southeastern states while all other areas in the Conus was pretty much near normal. The November update showed a little more precipitation over the northeast… While Southern California the southwest states were much drier and the Pacific Northwest was wetter.

With respect to January temperatures the October forecast showed near normal temperatures for most of the Midwest and the northeast with slightly above normal temperatures over the gulf coast and the lower Plains… And a large area of below normal temperatures over southwestern Canada. The updated forecast from November from the CVS.. Showed a major expansion of that very cold air mass from southwest Canada into central and South Central Canada and all of Quebec. This is significant because it keeps all of the Midwest and the East Coast in near normal temperatures for January and close proximity of very cold air to the east coast could be significant with regard to snowfall and East Coast winter storms. The CFS also shows above normal temperatures over Texas and the southwest states into Nevada and Utah

 

With respect to February precipitation… The October version of the CFS showed very dry conditions over California and over the northeast with small areas of above normal rainfall over the Gulf coast and the Great Lakes. Once again however the updated version from early November of the CFS showed a major change. It has all of the deep south into the northeast and the lower Middle Atlantic states saying much above normal precipitation and the Pacific Northwest coastal areas turn drier.

With respect to February temperatures… Once again we see a huge shift in what the CFS models forecasting with regard to temperatures. The Mid OCT run showed a huge area of very warm temperatures covering all portions of the  Plains the lower Midwest the entire Deep South and into the Middle Atlantic states. In addition it should be noted that the OCT CFS run showed no area of Canada in below normal temperatures.    However the updated November run of the CFS showed a major changes with the new CFS now depicting a large pool of cold air over central and South Central Canada and over Quebec Canada. A very warm temperatures is now completely gone with only Southern Texas and the media gulf coast saying temperatures running slightly above normal   while all  of the Midwest and the East coast now seas near normal temperatures.

 CONCLUSION

The historic East Coast hurricane sandy in late October and the noreaster on NOV 6-7 that followed are indicative of a significant change the pattern from the warm dry previous winter and the extreme Heat and drought the country experienced throughout the Spring and Summer 2012. Not only has the Arctic oscillation and North American oscillation shifted into persistent negative phase … but research shows that October seems to play a key role in determining the phases of the AO and NAO.
In addition significant changes in the sea surface temperature anomalies have occurred. In the eastern Pacific along the West Coast of North America the huge pool of cold water has dissipated and the new SSTAs configuration now supports +PNA development over Western North America. While we may not see this on a consistent basis I believe there will be some intervals during the heart of the winter into the spring where we will see several bouts of very amplified West Coast Ridging ( +PNA) in the jet stream. This could lead to strong arctic air outbreaks.
The early season development of much above normal snowfall in Eurasia during October is a strong indication that this winter will be much more like the winters of 2009-10 and 2010-11.
When all of these factors are taken into consideration there is no rational reason NOT to be bullish on the upcomcing Winter of 2012-13 over the eastern half of the continent and the U.S. in particular. The only restricting factor that I can see right now… is the very strong and negative QBO cycle which is only now beginning to weaken. The data from CPC that tracks the QBO on a daily basis does show significant weakening over the past two weeks. It is quite possible then that strongly negative QBO will rise to a value -10 or higher during the second half of the winter which would be extremely favorable for above normal snowfall and below normal temperatures over the eastern half of the country.

 

THIS WEEK IN WEATHER 11 NOVEMBER 2012

Posted by wxrisk | GENERAL | Sunday 11 November 2012 10:57 pm

SUNDAY   11 NOVEMBER  2012 …. 2300 EST

 

 

LINK   FOR   THE  AUDIO      …      

 HERE  

 

ROW  1

   

 

ROW  2

              

 

 

ROW  3

               

 

ROW 4

     

ROW  5
      

ROW  6

                

ROW 7

     

 

THIS WEEK IN WEATHER NOV 4

Posted by wxrisk | GENERAL | Sunday 4 November 2012 10:04 pm

2200   EST  4 NOV  2012

  CLICK ON THIS LINK TO HEAR THE  AUDIO

http://1664596.sites.myregisteredsite.com/meteorology/NOV4.wma

 

ROW 1   …0Z NOV 4 MODEL

    

 

 

 

ROW  2   12Z  EUROPEAN  72-96-120  HRS

      

 

 

ROW 3   MIN TEMPS  MORNING OF  NOV 7  AND 8

   

 

ROW 4   12Z   MODELS…

                 

72HRS …………………………………96 HRS………………………………120 HRS

 

ROW 5……….. DAY 9  HEMISPHERIC

 

    
    

 

 

 

 

ROW  6…  WEEK 3    AND  WEEK4