Part - 1
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.
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.
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).
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).
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.
|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
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.
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 region…or 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
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