11/13/12

Weak El Nino This Winter? Much Ado About Nothing; Winter 2012-13 Outlook - Parts 1 - 3



Winter 2012-13 Outlook For Southeast Lower Michigan
Part - 1

After last winter's outlook fiasco; I must say I and nearly all who put together an outlook last season (at least that I saw), scampered away with their tails between their legs. Yes indeed, the Winter of 2011-12 left many a meteorologist and winter weather enthusiast crushed with repeated dashed hopes of basically, winter weather! Early in the game (in fact at climatologically, winters open) I theorized that we were in for a troublesome forecastable winter.  Later in the winter; in my mid winter update 1/22/12, I discussed the relevance between the winter weather that had occurred up to that point and those exact same issues.  

On the doorstep of the new winter at hand, already there are conflicting signals about El Nino that was "supposed" to develop this fall into early winter. Granted, it was likely to be weak anyway but to me; it's really was much ado about nothing. Therefore; I will go forward with the assumption that La Nada, or a Neutral ENSO phase (with Pacific SST 3-month average temperatures in area 3.4  between -0.5 and 0.5) is in the can for this winter. With that premise in mind; generally other winter producing elements will definitely overrule the ENSO phase and thus it's importance is negligible. I've always felt the ENSO phase, unless moderate to strong, is of lesser importance than many make it out to be, especially over the eastern half of the nation. More often than not; ENSO should be down on the list of important winter influencing factors for Southeast Lower Michigan and the Great Lakes, as a whole. We'll only use it as a "square one" or beginning of this discussion. (Note; interestingly upon just checking the CPC's ENSO page; they have just "discontinued" El Nino watch, so I guess we are on the same page, anyway). 


Studying the latest actual data from the Pacific SST's show the following;



Note; the determining area 3.4 showed a slight decrease in the above normal anomalies since September, while area 4 showed a bit warmer results. In addition; in areas 1 and 2, the SST anomalies just are hovering around normal. This is suggesting if there is any El Nino, it is/would be a west based El Nino  meaning any above normal SST's will continue to reside mainly over the western and possibly central areas of the Pacific (in areas 3 and 4  and  we'll get back to its importance later in the actual winter forecast section of my Outlook).

                                                                   Areas of SST's


As stated, the beginnings of the earlier predicted El Nino have certainly sputtered in the latest analysis and  most recent model projections; which are now converging on basically aa Neutral Winter. The CFSv2 model's most recent projection (as of 11/12) reveals the following:



This obviously shows one of the main reasons why CPC discontinued the "El Nino Watch"; simply because latest model projections say there isn't going to be one or at least not during this winter. Humorously; if anything besides a Neutral pattern, the CFSv2 model even intimates it may cool enough for possibly another weak La Nina by Spring 2013. Ah the models; got-a- love em! At this time, however, the general consensus of all the models shows a downsloping toward the Neutral phase as well but with less sloping downward for the winter than the CFSv2 above.





Longer term, the ENSO cycle is evident on the graph below. The sine-wave cyclical nature of the ENSO index is apparent from the sketched-in cycle I drew. Note; La Nina years dominated from the late 1940s into the mid 1970s; then mainly El Nino years took over from the late 1970s into the mid 2000s. Recently; the cycle has been shifting to the La Nina dominant phase again.




Typical upper air patterns seen during Enso-Neutral years since 1961 are displayed below and while this pattern may very well dominate this winter; these Neutral years do not take timing (meaning; the sequence of events leading up to the Neutral conditions) into consideration. Therefore; not all of these Neutral years are analogue years to this winter simply because they were Neutral.



Part -2

Influencing Factors for the Winter 2012-13

NAO/AO
In addition; probably THE most important element in this winter's forecast and its subsequent success (especially its temperature forecast) is the dominant phase of the North Atlantic Oscillation /NAO/ along with the Arctic Oscillation /AO/ phase. As seen in the climate history chart below; whether the prevailing and projected NAO/AO is positive, neutral or negative can certainly help determine the winter's temperature and lesser extent; snowfall outcome. As an example; just with the projected Neutral (or La Nada) pattern alone, reveals the array of possibilities (highlighted) is somewhat variable. As I stated several times in the past "with a Neutral ENSO, we are totally at the mercy of the NAO/AO along with other meteorological winter influencing variables." Keeping this in mind brings the likelihood of more volatile temperatures and weather under these conditions!



Predicting the NAO/AO still remains one most elusive "nuts to crack" in the meteorological world. Even out for a week or two can be a challenge. The web site I generally go to for the prediction of the NAO/AO is at the Climate Prediction Center /CPC/ found here. An interesting experimental web site I found in projecting the NAO, AO, PNA and SST's for three months while researching for the Winter Outlook is a web site run out of University at Albany/SUNY, Albany, NY. It is done by an industrious young graduate student there named Kyle MacRitchie.  I'm still relatively new to the site but the predictions are based on current ensemble forecast data that is projected out for three months. Remember; the projection takes information from daily ensemble data so; like the ensemble data, the projections further out are subject to change, sometimes daily. Kyle also includes an "esemble variance line" projection. This shows where the esemble data is too variable for somewhat; reliable projections. He also includes his definition of the NAO/AO/PNA/SST's projections. As an example; the latest run of the NAO/AO and PNA out for three months on November 17th, 2012 shows the following:




As one can see; while the NAO projection is variable in the general sine-wave pattern, the AO has been projected (and again, as of the Nov 17th data) to be generally negative. We'll keep watch on the data through the winter for long range projections occasionally along with updates, in upcoming blogs. One thing is interesting to note, at least at this time; is the pronounced negative AO projection throughout the winter (I'm sure that will change however, at least somewhat in the succeeding days and weeks).

Snow Cover
Other theories and ideas that influence the winter somewhat over the central and eastern US is the snow cover over the northern hemisphere mid-late fall. Extensive snow cover forming October into November would tend to help "refrigerate" the cold air masses originating over Siberia and the Polar region that moved south across Canada into the states. Maps of the snow cover have been available for several years now and a "norm" has been established since 1995. The snow cover this autumn "up north" has been quite extensive to the north and northwest (see map below as of Nov 5th; note the comparison to average, in green).


From Rutgers University Snow Lab:
Across North America, snow cover extent for October 2012 was above average. Canada had much above average snow cover during the month, while the contiguous U.S. experienced below-average snow cover. The North American snow cover extent was 696,000 square km (269,000 square miles) above the long-term average of 8.1 million square km (3.1 million square miles). For the continent, above-average snow cover was observed across the Canadian Rockies and Prairies, while the U.S. Rockies and much of Alaska experienced below-average snow cover.

The Pacific Decadal Oscillation
The Pacific Decadal Oscillation (PDO) is the long-term ocean fluctuation of the Pacific Ocean. The PDO waxes and wanes approximately every 20 to 30 years. The graph below shows the cyclical nature of the PDO (like the ENSO) with its warm and cool phases. Most scientists think we have just entered the cool phase (see below: PDO Cycle -red arrow- during mid 2000s). The cool phase is characterized by a cool wedge of lower than normal sea-surface heights/ocean temperatures in the eastern Pacific and a warm horseshoe pattern of higher than normal sea-surface heights connecting the north. The last time the PDO trended into the negative phase was also in the early 1950s, lasting into the mid 1970s. There is good evidence by the ENSO chart (above) that during the cooler phase, La Nina’s tend to be more commonplace and last longer.

                                                                            
                                                                           PDO Cycle
The cool water anomaly below shows the lingering effect of the year old La NiƱa back in April 2008. The much broader area of cooler than normal water temperatures off the coast of North America from Alaska (top center) to the equator is the classic feature of the cool phase of the Pacific Decadal Oscillation /PDO/ talked about, above. The cooler waters wrap in a horseshoe shape around a core of warmer than normal water temperatures. (In the warm phase, the pattern is reversed - Image is courtesy of NASA)


                                                                             April 2008


While we are assuming mainly Neutral phase for ENSO this winter; I would be remiss if I didn't discuss where El Nino conditions do prevail (highest above normal SST's) out in the Pacific and what influence that has on the States. Referring back to part-1 of my Winter outlook, I discussed where the warmest of waters where located; out over the western Pacific. The departure map below give an idea of how west based El Nino's affect the US.



Part - 3

The Analogues

My earliest of Winter Outlooks were predicated on the analogue years I decided upon by researching basically, hemispheric conditions were of a similar nature to the upcoming winter. Interestingly; local conditions also mimicked some of the years but not always with more precedence given to the similar "preseasons". In this particular Winter 2012-13 set of analogues; the winters followed a similar sequence of events (though timing may vary a bit) that were recently observed over the Eastern Pacific during the past few seasons. La Nina prevailed during the previous winter, spring and into the summer. The second half of the year saw a gradual return to Neutral conditions such as seen this fall. While data this fall did show a trend toward a weak El Nino, a prevailing weak El Nino for the upcoming winter was discounted for reasons discussed above.


       WINTER 2012-13 ANALOGUES




Local Comparisons/Results:

TEMPERATURES:

Clearly, the trend seen in this year’s analogue winters is the dominance of below normal temperatures. Taking recent past seasons into account; it is thought the coldest of winters are too cold for our recent trend and longer term winter trend. Another trend seen during the winters may prove helpful is that there tended to be a notable period of below normal temperatures with many of the seasons showing this more likely to occur during the first half of the winter (or first half of the cold season of mid Nov-mid Mar). Many (but not all) of they analogues did reflect a harsher first half of the winter as a trend. After taking into account all the data contained in this research and displayed here, a somerwhat colder winter seems likely. Also, considering the Neutral conditions expected; this leaves the door open for variances in temperatures with wide swings.


SNOWFALLS:

Season snowfall ranges of the winters tended to be closer to normal (or a bit above  when averaged across the region). The most notable trend in the snow and precipitation this go around also happens during the first half of the winter; when snowier conditions (total snowfall thru mid winter) are projected. Though I did not post Flint and Saginaw analogues at this time; central and northern areas of Southeast Lower Michigan seemed to have the better chance of at least normal snow; while areas further south over extreme Southeast Lower Michigan (basically south of a Detroit – Ann Arbor line) showed normal to below snowfall.  Of course, this is highly dependent on storm tracks and speaking of...

UPPER WIND PATTERNS/ STORM TRACKS






The upper wind pattern averaged for all analogues is a cold one for the Northeast quarter of the country.  This not surprising since there were only two "mild" winters in the study. I used a composite of the jet streams for the analogue Winters of 1951-52 and on for the storm tracks (see map above); being they were the most pronounced however; all winters indicated a similar trend.  

The dominant upper wind jet streams this winter are projected by the analogues and also have been seen in recent fall patterns; a predominant split flow with the Arctic/Polar jet  from Canada and the sub-tropical jet in the south, both are displayed in the warm colors on the above map storm track map. These two distinctive jet streams will dominant this winter and phase. Most winter see these tracks more or less during the winter but it is their dominance that makes or breaks a snowy winter.  The most dominant of the storm tracks expected this winter are (numbered in order of precedence):


 1- Alberta Clippers bore by the northern Pacific jet and/or the Polar/Arctic jet which will usher in polar or arctic air originating from western Canada or the Arctic.

2- Two other storm tracks will be induced by later phasing of jets over the Ohio valley or up the East Coast. This pattern has already been active this fall. The storm track up the East Coast was noted more in the Neutral winters than La Nina’s especially with a negative NAO when troughing more prevalent in the eastern half of the country.  It is these two tracks which bear watching to see if strong arctic pushes of air keep more snow to the south of the region.

3- The Southern Plains/ Texas Low which we be bore over that region by phasing of the Arctic/Polar jet  from Canada and the sub-tropical jet in the south.

Composites for the Winter Analogues




The composites of the analogue winters show a broad area of below normal readings over the north-central part of the country; east across the Lakes/Ohio Valley into the Northeast. With the upper wind pattern from those winters, this isn't at all surprising. Note in the precipitation composite, the distinct "below normal-normal precipitation" region north/south over the Ohio Valley. This intimates a storm track up through the Ohio Valley just west of the Appalachians. It's also interesting to note that the East Coast averaged a bit drier, I say "averaged" that dry region could be misleading as some years may too have been wetter. What it does say is that more often than not; a storm track was in the vicinity of the Ohio Valley to the Northeast. If this bears out again; where she places will have a definite affect on our precipitation and snowfall; at least from the southern tracks.

Solar Cycles in Analogue Years

Ever since writing my Outlooks back in the mid 1990's; I've been a supporter of more research on solar cycles influence on the earths climate and even shorter term patterns. Many article have been written on researching this same topic. Scientists studying climate change are interested in understanding the effects of variations in the total and spectral solar irradiance on Earth and its climate. More and more evidence has been published on the solar cycle and its direct affect on earth's climate. One such fascinating study was done by NCAR  back on 2009 on the effects of the 11 year solar cycle and ENSO.

From the article:

"The research may pave the way toward predictions of temperature and precipitation patterns at certain times during the approximately 11-year solar cycle. These results are striking in that they point to a scientifically feasible series of events that link the 11-year solar cycle with ENSO"
                                                           
In my analogue study; one of many items I look at is the past winter analogue seasons and attending solar cycle and correlate with our upcoming Neutral 2012-13 season and current placing in the solar cycle.






































All years highlighted in light blue are "close" to our current time (red x); disregarding the lowest and highest years gives us 1904-05, 1976-77 as the closest analogue winters, solar cycle speaking. The winter's of 1956-57 and 1985-86 are a close second. Taking this one step further; all those winters were on the up cycle like our present winter.

Both winters of 1904-05 and 1976-77 were cold, brutal winters. The Winter temperature average of 1904-05 was 20.5; while the Winter of 1976-77 was even worse at 19.8. Many of us lived through the Winter of '76-77 and do remember it vividly. The Winter's of 1956-57 was one of two "mild" winters with an average temperature of 28.9; while the winter of 1985-86 was again colder with an average of 23.6! So; out of the four closest analogue winter's; three out of four were cold and below normal. Before we get too carried away, solar cycles are most likely to have the least affect on our winter weather! With climate change so much in the news and importance; I would surmise studies will continue to go on as to their short term affects on weather. Therefore; this section is added for interest sake only and to me anyway, it is interesting. 






































       Summarizing:

























Temperatures
Look for temperatures during the winter to average below normal /-3.0 to -0.5/ compared to the 30 year /1981-2010/ normals. While the trend of our winter analogues show mainly significantly below normal; it is felt the coldest of analogues are too cold and thus skewing the average down. However, at the same time, some of the cold outbreaks seen this winter may rival some of the outbreaks seen in recent winters and thus; a colder than average winter is likely. Considering the Neutral conditions expected; this leaves the door open for variances in temperatures with wide swings.

The biggest caveat will be of course, the phase of the NAO/AO and where that ridge and trough dominants during the winter! If the ridge moves inland too much and continues to cross the country like it has for so many months; I'm in trouble. I'm banking on the mother-lode of cold (upper low in Canada) to help squelch the ridge.
I must say; it is hard to go below normal after what happened last year but the evidence for at least normal to below temperatures is compelling. More often than not; my analogues have held me in "good stead" as the British say (to be of great use and benefit to someone) so on with the show!


      Snowfall and Rainfall:

Snowfall and rainfall ranges in the Winter analogues for 2012-13 are a little closer to normal over extreme Southeast Lower Michigan (when compared to many other years I've done). Therefore, while snowfalls last season were predominantly below to well below normal; this winter indications suggest the best snows will be closer to normal (within 5 inches of). Indications are the best snows will fall  across the northern areas of the regionor from Detroit’s northern suburbs across Flint and Port Huron and on into the Saginaw Valley and Thumb Region. Near normal to below snow is expected south of a line from Ann Arbor to Detroit. The analogue winters are strongly hinting toward a two-tier snowfall pattern this winter with the heaviest amounts to the north along with an average chance for mixed precipitation the entire region. It will be interesting to see if these particulars bear out. (See more in: Storm Tracks)




Some Winter Dates:

Winter Begins early on:  December 21st,  2012 @  612 AM EST
Christmas:   Tuesday December 25th2012
Holiday Cold  Full Moon:   Friday December 28th, 2012 @521 AM EST
New Years:  Tuesday January 1st 2013
Ground Hogs Day:   Saturday February 2nd, 2013
Valentine’s Day:  Thursday February 14th, 2013













Next :

Active weather brewing for the last week of November?  

Look for the details late this week. Have a Happy Thanksgiving!






































Making weather fun while we all learn,
Bill Deedler -SEMI_WeatherHistorian














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