see the FINAL WINTER FORECAST ISSUED
For a Review of Last Summer's - JUNE - JULY AUGUST 2010- WXRISK.COM SUMMER 2010 forecast please click HERE
to see my SEASONAL FORECAST for the past 10 years click HERE
It was my intention to have this preliminary the winter forecast issued last week but my son had semi serious bicycle accident then the SAME week got sick with a mild case of the flu. Go figure.
KEY or critical ideas will be emphasized by RED BOLD text.... and KEY ASSUMPTIONS will be emphasize by GREEN BOLD text.
EUROPEAN WINTER 2010-11 forecast is HERE
SOUTH AMERICA SUMMER 2010-11 forecasts is HERE .
Comments... complaints... rude noises.... or
funny jokes ....are all welcome.
HERE WE GO..................
PRELIMINARY WINTER FORECAST 2010-11
The last of several winters have had some significant forecast uncertainties. These uncertainties made the prospect of winter forecasting even more risky than normally is and as a result we have some Winter forecasts -both government and private forecasts-- turn out to be unsatisfactory.
This particular winter forecasts however does not hold quite the same level of uncertainty because of the overpowering and dominating La Nina feature. That is not to say that as of late OCT all the variables are now known. Far from it.
But when compared to the last several winters... the WINTER 2010 - 2011 forecast does not look to be nearly as difficult in making as the last few Winter forecasts.
The winter of 2010-11 is not going to be nearly as snowy in the big cities of the Northeast as last winter. (short of glaciers developing ... how could it be snowier?). In fact for many areas over the eastern third of the us snowfall amounts will be significantly below normal.
The winter pattern across all of North America will be dominated by three factors.
1) the Upper end MODERATE La Nina event. Over the last few weeks it appears that the La Nina event has stabilized and will not reach the threshold of a strong La Nina event.
2) the Drought over the Lower Plains and Deep South
3) the enhanced Pacific Jet in the first half of the Winter.
All winter and into early Spring of 2011 the 6-10 day and 11-15 day Operational GFS is going to be giving off numerous signals or " false Alerts" that a major cold air outbreak and/ or major pattern change is coming for the central and eastern Conus. The Model will consistently misplay the powerful / enhanced Pacific Jet stream thus giving off " false alerts".
The Winter 2010-11 be characterized by Above Normal precipitation (and snowfall) across the Pacific Northwest the northern Rockies and into the Upper Plains and northern Great Lakes.
Areas in the Pacific NW will see MUCH ABOVE Normal precipitation. Seattle and Portland could see significant snowstorms and arctic cold air mass pouring over the Continental Divide.
The drought in the Lower Plains and Delta will get worse. This will have a MAJOR impact on HRWW and given the current world wide what issues a Bad HRWW crop in the CONUS is going to have a Major impact on WHEAT prices world wide.
East of the Mississippi River the only areas that will see Normal or slightly Above Normal snowfall will be central and or northern New England.
For ski and snow making operations east of the Mississippi river there will be major increase in the numerous days where overnight temperatures stay at or above 30 degrees... greatly the impacting snowmaking operations (even for northern areas such as PA NY and southern New England).
The potential exists for the end of the Winter to continue into the the early Spring. That is to say FEB and MARCH stands a good chance to be a colder and snowier relative to normal than DEC and JAN for much of the nation.
Interestingly there appears to be a seasonal pattern setting up that supports numerous and large coastal storms for the Eastern US. Some of these events may turn out to be the classic coastal storms and Noreasters or they may be Inland events. However the lack of cold air for much of the winter is going to be a problem East of the Mississippi River for many of these events.
In making a seasonal forecast there can be a significant amount of pressure to get the forecast out early. The problem in doing that is two fold: FIRST that some variables are simply not known. SECOND some known variables can often change during the the interval between the forecast in the beginning of the season.
For example when making a Winter forecast it is important to take a look at the developing snow cover across northern hemisphere (both over in Eurasia and in Northern Canada). But if you are issuing the Winter forecast in late September or early October... snow cover is a big variable and unknown. For example last winter there was a well private forecast who argued against below normal winter cold over the central and eastern Conus... because snow cover in over Eurasia and Northern Canada was below normal in the period of Sept 15- Oct 15. Not surprisingly after October 15 at the snow cover across Eurasia and Canada really developed quite rapidly and that private forecaster's Winter forecast went into the crapper.
Another potential unknown can often be the ENSO. Weak or decaying El Nino or La Nina are often poorly handled by climate models. These models can end the El Nino or La Nina much faster than forecasted or linger a weak event much longer than forecasted. This was the case in Winter of 2006-07 which featured a Moderate El Nino which helped bring on a very warm NOV and FEB 2006. Many forecasters-- both CPC and Private-- ASSUMED that the El Nino would last through the Winter. In fact the even collapsed in the 1st week of January and the pattern turned severely cold east of the Mississippi JAN 15 FEB 15 MAR 15.
THINGS WE KNOW.... the La Nina status early... the PDO .....Soil Moisture... climate Model trends... seasonal trends.... strong Pacific Jet
UKNOWNS: the La Nina late in the Winter... Snow Cover
THE LA NINA OF 2010-11
There is no doubt about it ... we have a Moderate La Nina event underway and it has been in place now since the middle of the Summer. To be sure this is been the fastest and sharpest transitioned ever seen since accurate ENSO records have been kept (1950). That is to say the amount of time for the transition from Moderate El Nino last Winter and Spring to a high end Moderate La Nina this later Summer and Autumn has been the most rapid EVER.
This image shows ENSO regions.... which are divided up into four distinct areas. While all 6 regions are important (regions 1 region 2 region 1+2 region 3 region 4 and regions 3.4) it turns out that region 3.4 is the region that is used to judge where or not there is a ENSO event (El Nino / La Nina) .
This image of SSTA-- sea surface temperatures anomalies -- from around the world shows the Major La Nina. These two images show the sub surface temps--- from SEPT 30 and OCT 15. As you can see the cold water is Deep and large which means the La Nina is NOT going anywhere.
We can track the LA
NINA by using the Aussie web site HERE...
One thing that forecasters do is look at La Nina and El Nino from the past and try and find similar types of events (the analog method). In this case we are looking at La Nina events since 1950 that were
1) MODERATE or STRONG
Got it? This Image is from CPC and it shows the all the ENSO events.. El Nino La Nina and neutral ...since 1950.
Parenthetically a leading private energy forecast service in the Middle Atlantic states has selected the 1998-99 La Nina event as the #1 closest match event to current La Nina of 2010. The Winter of 1998-99 was an amazingly warm and nearly snowless winter for much of the central and eastern US.
Ok so we know the La Nina is there and its very powerful.
What is the La Nina GOING to do? Looking at some of these climate Models we can see some clear trends.
The SEPT climate Models ...which many of the early Winter forecasts were based on... showed the La Nina lasting through winter Holding at MODERATE intensity. This Image shows the IRI graph from SEPT 2010. This show over 22 different climate Models but the KEY here is that they all show the same general trend. Come the Spring the La Nina will begin to weaken.
Here is the Sept 15 run of European ENSO forecast. This is an ensemble forecast of many members of European Models. Note the trend-- the La Nina stays Flat at around -1.8c in region 3.4.... then begins to warm steadily in February and March 2010.
THE PDO ISSUE
Without getting too technical on you the PDO "Pacific Decadal Oscillation" is one of the more important climate discoveries in the last 20 years. This link will give you a pretty good basic detailed working background if you are curious.
Basically the PDO has two phases that are determined by the to sea surface temperature anomalies and how they are configured across the Northern Pacific Basin. When the PDO is in the "COLD" or "Negative" phase there is a build up of colder than Normal SSTA in the far eastern Pacific along the West coast of North America and Warmer than Normal SSTAs in the North Pacific. When the PDO is in the "warm" or "positive" Phase (like it was last Winter ) the far Eastern Pacific Ocean along the West coast of North America is warmer than normal SSTAs and the central North Pacific has colder than the Normal SSTAs.
In some ways the PDO is sort of similar to the El Nino and La Nina affect that's actually a lot more complicated than that. These large pools of more in cold water in the Northern Pacific Basin have a dramatic impact on the overall jet stream patterns as they approach the North American continent.
There is a strong correlation between having a warm/ positive phase PDO and a Ridge in the Jet stream over the West coast of North America in some form or another. And as some of you may know having a Ridge in the Jet stream over the West coast is how we get sustained cold air outbreaks over the central and eastern portions of the Conus.
All this being said it's quite possible to have different combinations between a La Nina... El Nino.... and a PDO. There been numerous cases over the past 15 years or more where we have seen a strong La Nina with a +PDO ... strong La Nina with a -PDO.
There is a tendency with a strong persistent -PDO phase any La Nina events... IF they occur... are more often than not moderate or strong La Nina events.
CURRENTLY the PDO is in a negative or cold phase and it has been negative or cold phase for quite some time. This Link has the LATEST monthly readings on the PDO.
But as you can see from the Above Link the PDO has been Negative since July when it dropped to -1.05. The SEPT 2010 reading was -1.61c and the trend is for the PDO values to turn colder still.
This means there is Likely to be a deep persistent trough over much of the West coast and perhaps the West third of the Conus. Temps are likely to run Below Normal especially over the Pacific NW and precip is likely to run Above Normal.
Some meteorologist have noticed that this current -PDO is going to be stronger than any other -PDO Events we have seen over the pas 20 years. This interesting idea says that this current PDO is going to more like the -PDO of the 1950s.
THE ENHANCED PACIFIC JET / +EPO
This is VERY important because enhanced jet streams are much more resistant to bending and buckling. In other words there will be less Ridge building in the Jet stream over North America. That means Below Normal chances of seeing a West coast Ridge and less chance of seeing high latitude Blocking pattern in the Jet stream over central and eastern Canada. And without Ridging in the Jet stream over western North America and / or high latitude Blocking over eastern Canada sustained cold patterns for much of the Conus will be uncommon in the Winter of 2010-11.
DT THINKS THIS WEB SITE IS FABULOUS http://climate.rutgers.edu/snowcover/index.php
It is hard over state the Importance impact of snow cover on winter patterns over North America and especially over the Conus. While snow cover over North America is important the KEY fact seems to be the snow build up over SIBERIA/ Eurasian in the AUTUMN months.
That being said this is something that has to be watched daily if NOT weekly. Good skilled seasonal forecasters instead of being bored out of the skulls in the Autumn months –outside of the Occasional Hurricane threat-- should be watching weather patterns over Siberia and central/ northern Canada for snow build up.
Let me be clear. Early build up of snow cover that leads to larger and deeper than normal snowfall over Siberia and Canada does NOT necessarily increase the likelihood of colder and snowier than normal Winters over the central / eastern Conus. BUT it does mean
THIS chart shows OCT snow anomalies from 2009 to 1964.
Look at OCT 2002... again moderately Above Normal snow cover and that was a active cold stormy winter.
Take a look at the period of the 1980s … from 1980 to 1992 not a single OCT saw snow anomalies rise above to zero or ' Normal'. Every OCT featured Below Normal snow cover. Not surprisingly that was the LEAST snowiest Decade EVER in NYC PHL Chicago and many areas of the Midwest and Northeast US.
The one thing you do not want to do with snow cover is make a early judgement. Though the pressure is great to get some sort of Winter forecast out by early or Mid OCT... the snow cover issue is NOT at all decided by OCT 10 or OCT15. Indeed there have been numerous cases where snow cover by OCT 30 was well below Normal only to see major and rapid increases in NOV ( this was the case last winter and one well know private energy forecaster went for a milder Winter because he made an early call on snow cover based on SEPT Siberian snow cover Of course that forecast busted horribly as the research clearly shows that SEPT snow cover is irrelvant to cold air mass generation and intensity for the Winter months. Conversely the opposite is also true... that early build up of snow in OCT does NOT have to continue into NOV.
Thus SNOW cover is a variable that we will just have to wait and see.
That being said the snow cover over Eurasia is off to VERY GOOD start. This Link shows that as of OCT 21 snow cover is AHEAD of where it was in 2009 ...and 2009 was also Above the Norm for Middle OCT snow cover in Eurasia.
2009 Eurasia week 40= 2.04 million/ sq km BUT week 40 in 2010= 4.32 million/ sq km. This LINK shows that between week 40 and week 39 there was a HUGE increase in snow cover over Eurasia.
When compared to Mid OCT in 2009... the North America the snow cover over Northern Canada as of 21 OCT 2010 (5.88 million sq Km) is about the same as in 2009 (6.16 million sq Km).
Easterlies are generally stronger than westerlies. Major winter stratospheric warmings patterns (that's fancy weather talk for Blocking pattern in the Jet stream over the high latitudes) preferentially occur during the easterly phase of the QBO provided the easterly phase is not too strong... -10 to -20. Conversely strong Positive QBO phases (QBO of +10 or more) are negative influences on on Blocking patterns in the cold season months (NDJFM) .
SOIL MOISTURE ISSUE
Perhaps the most overlooked aspect of making a seasonal forecast is SOIL MOISTURE. While many forecasters are well aware of the short term the facts of excessively wet soil conditions or drought conditions many do not take into consideration long-term impact on seasonal weather patterns that large areas of sustained drought or large areas of excessively wet soil conditions can have.
Part of reason for this is that until fairly recently there was no real way of tracking long-term soil moisture conditions. Over the past 10 years due to the brilliant work done at CPC -- the climate prediction center-- the have become from daily was terms such as the drought monitor weekly maps.. the Palmer moisture index and LONG term and SHORT Term drought Index maps.
areas of very dry soil moisture regions and Droughts.... as well as
large areas of very wet soil moisture conditions and Flooded areas
....can and DO produce what is known as a "positive feedback
Let's take a look of the soil moisture maps from NOV 2009. If you may recall the summer of 2009 was an excessively wet and cool summer for large portions of the Midwest and the eastern US. This wet pattern continued into October and November and large areas from the Mississippi River into the Delta and the eastern US were in the dark agreeing and dark blue areas which is used to show excessively wet ground conditions.
This image is a SHORT TERM Soil moisture from NOV 2009. I have superimpose the Mean Jet stream pattern from the winter of 2009-10. You can see that the alignment is almost perfect. Of course using the soil moisture maps to get a clue about what the overall pattern is going to look like in the upcoming season has its limitations. This method ONLY works when there are LARGE areas of excessively wet or excessively dry grounds which had been in existence for several weeks or months.
For example... having a very hot and dry JULY in the state of Virginia does NOT fundamentally alter the pattern across North America. But if the dry and hot pattern over Virginia is part of a much larger pattern .....which features large areas of hot and dry conditions for months at a time ....that covers most of the Deep South into the Middle Atlantic states... THAT sort of thing DOES affect the overall pattern.
As you can see the large areas of the Midwest continue to remain excessively wet. This has been the case since last winter and actually since the summer of 2009. On the other hand the yellow areas developing over the deep south and the southwestern states are showing a trend towards significantly drier conditions.
This is telling me the that the drought which has developed from the Summer over the Deep South is going to continue and will probably have a significant impact on the overall winter pattern across the Conus and North America.
The typical lending a pattern usually produces excessively wet conditions over the west coast and especially over the Pacific Northwest. This map clearly supports that overall trend.
The very close proximity of the very dry / drought conditions over the delta into the the Ohio Valley with the WET conditions over the upper Mississippi Valley tells me that there's probably going to be a significant and persistent temperature and precipitation boundary of some type bisecting the Midwest. If this is correct then the Winter of 2010-11 over MN WI NEB and the Dakotas could be the substantially colder and snowier than conditions over St Louis Chicago Indianapolis and Columbus Ohio.
One of the things that I do different here at WXRISK is that I am a kind of a Out of the box thinker ... a Black Swan type of guy. Intended no matter how good my forecast may be a I am always anticipating problems that are being overlooked. Assumptions which one believes to be the a high probability of occurring or a fact which turn out to be specious.
Because so many private forecasters have already committed to a very warm and essentially snowless winter for the central and/or eastern half of the Conus... There may be a tendency to assume that it is also going to be a fairly quiet winter with respect to overall winter storms over the eastern third of the Conus.
It is this underlying assumption about the upcoming winter which perhaps bothers me the most about this upcoming Winter.
Given that the overall pattern it is clearly being dominated by high end Moderate La Nina event.... the first half of the Autumn 2010 has been actually quite stormy especially in the Northeast. This is somewhat unusual for a La Nina pattern.
Since October 1 we have had several significant weather systems move through the eastern Conus.
This next image shows a significant trough September 30 - October 1 over the eastern third of the Conus. On OCT 4-5-6 a Major Low developed over the Ohio valley and Moved into the Northeast. This is followed by a major long wave trough over the eastern onus October 14 - 15.
In addition the last several Model runs of the European Canadian and GFS models had been showing a the major coastal storm again developing for the East coast November 4 - 5.
Again this is a surprisingly active pattern for a 40-45 day La Nina Autumn period. Still this does not "prove" anything but it is a FACT that is sitting out there as a outlier or an aoddity.... it might MEAN something... or it might be BS.
Well that's the forecast. As you can this is detailed stuff. At WxRisk.com the forecast is a big deal but equally big is HOW you get there. This is important to me for two reason. First I love to teach this stuff.... teaching SCIENCE to folks is good and fun. Too many folks in the general public think weather forecasting is all guess work. Second by looking at how you get there you spend more time looking at your forecast and assumptions... and when something goes wrong you "see it" sooner.