Winter 2013-14 Outlook for Southeast Lower Michigan
William R Deedler; Southeast Michigan Weather Historian
This being my 17th year of issuing season outlooks reminds me of how quickly the time has past, how variable and many times exciting the winters have been but most of all, how enthusiastic I still become at the challenges forecasting the upcoming season.
This upcoming season looks to be a more exciting season than the past few (especially 2012-13). The winter of 2012-13 was a boring, slow season with hopes of snowstorms for snow lovers dashed frequently. And, while the Winter of 2012-13 started in that same vein, it did make up for the slow start with an active late season. On to the Winter of 2013-14...
Local Data and Hemispheric Patterns suggest:
Temperatures:
Considering the lack of Pacific Ocean influences across the country this
upcoming Neutral ENSO Winter (more
below), I look for a more variable temperature winter. That being said;
dominant trends of upper hemispheric pattern the past few recent seasons along with
selected winter analogues (also below), suggest generally normal to below normal
temperatures (but not exclusively) throughout the winter. In addition; winter analogues and resulting
final statistical data strongly suggest a colder than normal winter. I look for the final winter statistical departure to range between -1.0 to -4.0 across Southeast Lower Michigan when compared
to the 30 year 1981-2010 normals (also included on
analogue charts).
While the
analysis of my winter analogues show mainly below normal
(very similar to our recent summer analogues), it is felt the coldest
of analogues are too cold and
thus, skewing the average down
some. However, at the same time, some of the cold outbreaks seen this winter will rival some of the outbreaks seen in recent milder winters leading to a normal to above normal amount of below zero days.
Expanding on this “normal” idea, it is interesting to note that the 100 year winter mean temperaturefor Detroit
is approximately 26.7 degrees
with a one standard
deviation spread of 3.5 degrees either
side of that 26.7. Statistically speaking, based on this data the temperatures could average as low 23.2 degrees
or as high as 30.2 and still be considered within a “normal” range
of the mean under one standard deviation. Basically, this just supports
the idea that winter temperatures in these parts, by nature,
have a wide statistical range
and this winter should be no exception!
Snowfall and Rainfall:
Snowfall patterns
this winter - as with most across Southeast Lower Michigan - will be mainly a
result of the dominant synoptic storm tracks evolving and a lesser result of
Lake Effect snows. However, it should be noted that considering the pattern expected
to evolve; this should be a fairly active lake effect season for the Great
Lakes as a whole.
As would be somewhat expected in a Neutral ENSO winter, snowfall amount
ranges were more extreme in the analogue
years with some of the snowiest to snow-less seasons included this season. Overall, however snowfall means in the analogue years tended to hug the lower
end of the normal ranges. Southeast
Michigan was clearly in the sweet spot for heavy snows in first analogue of 1880-81 (snowiest
winter on record) and ironically about 100 years later for #3 snowiest in
1981-82.
Overall, I look for a wider range of snowfalls this winter across the
region. Generally normal (to locally above) snowfalls are possible over the
southern sections of Southeast Lower Michigan (generally along and south I-69); while normal to below normal snowfalls
can be expected across the northern areas (more specifics
can be found in the analogue section). This would be primarily be a result of storms passing near and to the south of the region. This is a difficult call this early since if the dominant storm tracks were to travel a bit further north, then heaviest snow would also be further north into northern areas. At this time though, recent patterns and analogue data suggest chances are higher to the south and updates will be issued if needed.
Snowfall should average near to above
normal (or near normal to 12"above of the normal) across the south
half of the region and normal to 12” below across the northern sections. Keeping in mind
that the range considered in the normal category is 6”+/- of the normal statistical value).
Broad Scale Discussion
As we move toward
the winter of 2013-14;
the near normal or neutral sea surface
temperatures /SST/ that dominated the past several seasons
are expected to continue to hold sway over the Pacific waters. A brief recollect; the Neutral ENSO pattern expected this winter is a reflection of near normal Pacific sea surface temperatures.
In addition, this will be the second Neutral ENSO winter in a row to play out over the Pacific, a major fact considered in analogue selection.
Therefore; like
last winter, little if any influence is expected from the Pacific via La Nina or El Nino with an overall, Neutral pattern. Therefore the region will be dominated
by the phases of the North Atlantic/Arctic Oscillation /NOA, AO/, the Pacific Decadal
Oscillation /PDO/, the Pacific and North American /PNA/ pattern and the sub-tropical flow from the southwest and south.
Neutral ENSO
Checking out the Pacific water temperatures in Nino 1+2, 3 and 4 (Fig-1a,
b), show the
regions
highlighted (1a) and the stable very weak negative to zero SST anomalies (1b). For
scientific purposes, area Nino 3.4
is used to determine officially, whether or not a
Neutral phase exists.
As one can see, the SST’s in area 3.4
have returned right to the
0c anomaly (Fig-1b). Various model projections for the next several seasons are under
Fig -1c, all basically being Neutral through the winter.
Fig - 1a
Fig -1b
The latest
weekly (11/11/13) SST departures are:
Niño 4 0.3ºC
Niño 3.4 0.0ºC
Niño 3 -0.1ºC
Niño 1+2 -0.4ºC
Fig -1c
Patterns of ENSO are shown here for the past century, note where more El Nino's and La Nina's prevailed. Recent data shows were are entering a new La Nina dominated period ( Fig-2a, 2b)
Fig-2a
Fig-2b (note pattern is flipped with La Nina on the bottom)
NAO/AO
One of the most important
ingredients in this winter’s weather (like most others)
is the trend of the North Atlantic Oscillation/Arctic Oscillation throughout the winter.
Of course, this is the biggest
challenge to the
forecast and potentially, has the biggest
bust potential. While some
weather trends with La Ninas and El Ninos are seen (and even these aren’t always consistent), the NAO pattern remains highly elusive and generally, trends
are seen only a week or two out. Our colder winters in the study surely reflect
a predominately negative NAO/AO.
The long term trend of the NAO (Fig-3 a, b), clearly shows the oscillations (long and short term) from positive
to negative to positive
and just recently, settling
toward neutral and negative. Note the negative dominant trend of the 1950s, 60s and 70s seem to be returning.
Fig 3a
Fig 3b
The latest trace of the NAO (Fig-3c)
reflects the pattern
since July 2013. The summer pattern was basically neutral with the cycles meandering about the 0 line. This allowed a more comfortable, near normal to below temperature summer. Since the summer,
the NAO oscillations have been more a neutral (1,-1) to negative. This trend change has allowed more below normal temperatures to dominate the past month with near normal the past three (see maps below).
Fig - 3c
Fig - 3b
Oct 10 - Nov 10, 2013 Aug 10 - Nov 10, 2013
The
Pacific Decadal Oscillation
The Pacific
Decadal Oscillation (PDO) (Fig - 4a,b) is the long-term ocean fluctuation of the Pacific Ocean. The PDO waxes and wanes approximately every 20 to 30 years.
Most scientists think we have just entered the “cool” phase (see Fig -5, below).
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 in the late 1940s, lasting into the
late 1970s. There is evidence that during the cooler phase, La Nina’s tend to be more commonplace and last longer
(now, compare the current
evolution of the PDO pattern to the likeness of the ENSO, NAO phases resembling those
of the 1950s -1970s). It will be interesting to see how close our winter weather
patterns of the next few decades
resemble those of the 1950s-70s.
Fig - 4a
Fig - 4b
The cool water anomaly in Fig-4c shows the dominant effect of La Niña
patterns back since
2000. The broader
area of cooler than normal water temperatures off the coast of North America from Alaska (top center) to the equator is a 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).
Fig-4c
The Winter 2013-14 Analogues
These selected analogue winters below, followed a similar
sequence of events (though timing
may vary a bit) that were recently
observed over the Eastern
Pacific during the past several seasons. Neutral conditions prevailed for well over a year from at least the previous autumn, winter, spring, summer and again into the second autumn. All winters were selected upon second Neutral winter conditions for just a home base. After that; previous summer and autumn's temperature and precipitation patterns were examined and compared to this past seasons. Many, many seasons resembled the past six monthly with temperatures normal to below and precipitation normal to wet. Even some years monthly patterns were strikingly similar. I also included the ongoing solar cycle (sc) at the time of the analogues and compared it to the cycle threshold we are presently in (see bottom of Analogues in Legend).
As stated in my Autumn 2013 Outlook; this fall's analogues showed a wide range of temperature patterns for September and October with mainly normal conditions pevailing. The real only subtle pattern that materialized were notable cold spells (stronger than average) turning up sometime in October into November. November itself had the best chance to be below normal and an overwhelming number of Novembers were just that...cold.
November's Foreboding
In this analogue data set, the Novembers where scrutinized for similarity to our ongoing November, mainly because of the overwhelming colder than normal winters that followed in the data set and basic curiosity. I was amazed to find out that when temperatures averaged normal to below in eleven of the Novembers (most were below) ALL the following winters were below normal. In the remaining four warmer than normal Novembers, two were again followed by a colder winter (for a total of 13 colder winters) with only the remaining two warmer Novembers followed by a warmer than normal winter (see more about this under the upper air section below).
Though this November's temperature departure is well from being decided at this mid junction, early indications are the temperature departure will range from normal to below. I will have to say though; these cold strong polar highs coming out of Canada so early in the season this November have been impressive!
Temperatures:
In one of the strongest below normal signals I've seen in the 17 years of Outlooks; you'd think it'd be a slam dunk but not always. Granted most of the time when a temperature trend was even close to this strong, it turned out to be in the right direction. I can recall a few winters however, where that
backfired and the minority ruled. One thing that has me concerned is there were no normal temperature winters in the Detroit sample. The two past trends were cold or mild..no normal or average. More often than not this tells me either a cold trough dominated or very infrequently, a flat ridge (or zonal flow) prevailed. I can't go against a cold signal this strong and dominant nor from what I'm seeing this fall, therefore below normal it is. Best below normal chances would be at Detroit but that's only because of the inflated heat island norms.
As far as timing, while on the whole all months averaged below normal, scattered about each month's column were a few above normal Decembers, Januaries and Februaries. December had the second best chance for an above normal average after the many below normals prevailing. The Decembers that were on the milder side were followed by some brutally cold Januaries and/or Februaries. There also a strong likelihood of a few mild periods or thaws during the winter given the upper air pattern expected (see in Upper Air/Storm Track section) and the scattering of mild analogue months. Of course, timing will be the issue for milder weather but there is enough of evidence to indicate breaks in the dominant cold. This variance would also be supportive of an amplified upper wind pattern that would be at least, somewhat progressive.
Snowfall:
Now this trend result, the analogues are not so kindly instructive with snowfall amounts ranging from well below normal to well above. In the Detroit sample alone; two of our snowiest winters are matched against several "snow-less"! What to do? Well let's attack this first from what we do see...and that's trend and location.
First off; The analogues are suggesting a back-end loaded winter as far as snowfall with averages hinting toward an above normal February & March. In fact; there were some hefty snowfalls in some Januaries, Februaries and Marches with even some notable late season snows in April and even May...let's hope not! On the flip side; in many other analogues there were seasons with light to very light amounts of snow. Given this mixed snow amounts picture and averages falling in the normal to below normal category, I'm inclined to go overall normal (locally above) to below snowfalls for the snow season.
Secondly; Best snowfall averages (highest) this season focuses on the southern sections of the region. This would include areas along and south of 1-69...or mainly from the Flint and Port huron areas south throuh Ann Arbor and Metro Detroit to the Ohio border. See below for estimates...
Overall,
I look for a wider range of snowfalls this winter across the
region. Generally normal (to locally above) snowfalls are possible over
the
southern sections of Southeast Lower Michigan (generally along and
south I-69); while normal to below normal snowfalls
can be expected across the northern areas of Southeast Lower Michigan including the Saginaw Valley and areas well away from Lake Huron. This would be primarily a result
of prevailing storm tracks passing over and to the south of the region.
This is a difficult call since if dominant storm tracks were
to travel just a bit further north, then heaviest snow would also be further
north into northern areas. At this time though, recent patterns and
analogue data suggest heavier snow chances are more to the south and updates will be
issued if needed.
Snowfall should average near to locally above
normal (or near the statistical normal to locally 8" above of the normal) across the south
half of the region; and widespread normal to 8” below the statistical norm across the northern sections. (Keeping in mind
that the range considered in the normal category is 6”+/- of the statistical normal value - located on the bottom of analogue data).
Upper Air and Resulting Storm Tracks
After a positive NAO/AO and resultant ridging dominated the eastern half of the country during the Winter of 2011-12 and then again, early in the Winter of 2012-13; there was a distinct change in the upper pattern since mid Winter of 2012-13. A more neutral to negative NAO/AO phase took hold at that time and has prevailed since, resulting in more troughing over the eastern half of North America. I look for this to prevail during the up coming winter which would encourage blocking in the upper air pattern and thus, aid in delivering colder air to the region.
Using my analogue winters upper air reanalyzed patterns and comparing it to recent trends leaves me with this conclusion; a predominantly neutral to negative NAO/AO for the Winter of 2013-14. In Fig- 5a below, there is little doubt of the prevailing cold upper level trough extending from the Arctic south over the Eastern half of North America
Fig -5a
In Fig 5b; here will see the dominant upper air jet streams to be key players in the upcoming winter based on past and present observations.
Fig -5b
It's very interesting to note, that this experimental NOA/AO projection also supports the analogue set for the winter.
Projected Prevailing Storm Tracks
First off; lets look at the anomalies (departure from normal) of the upper air patterns averaged out for the analogue winters and see if there are similar patterns noted at the present time. In Fig - 6a, one of the first items noticed is the strong above normal heights extending from western Alaska southwest out over the northern Pacific and over Greenland; both representing dominant upper air high pressure or ridging. The other notable feature is the broad troughing extending from Canada southward into the northern half of U.S.
Fig - 6a
Expected Prevailing Storm Tracks for the Winter of 2013-14
Three main storm tracks are expected to cross the United Stated this winter.
-The first in order of precedence is the Alberta Clipper type systems bringing the Arctic
air crossing the southern prairie lands of Canada and northern Plains of the US into the
Great Lakes and East.
-The second in precedence involves several main tracks; The clippers that travel further
south into the Midwest and Ohio Valley and intensify over the Mid Atlantic region. The
British Columbia/Pacific Northwest impulses that drive south-southeast into the US
heartland and Southern Plains (Kansas/Texas Hookers-Panhandle Lows) on there way to
the Great Lakes. Also; The Pacific Ocean driven impulses which ride over the Rockies and
also energize Southern Plains low centers.
-The third storm tracks in order of precedence; the Ohio Valley Low taking shape over
Arkansas/southern Missouri and deepening as it moves toward the eastern Great
Lakes and finally, the Gulf Low that moves into the Ohio Valley/Lakes or up the East
Coast.
Winter Temperature Analogue Composite Map: Dec - Feb
Winter Precipitation Analogue Composite Map: Dec - Mar (March included for possible better snowfall representation - especially in normally snowfall regions).
Look for storm and cold alerts during the winter along with updates and possible changes.
Making weather fun while we all learn,
Bill Deedler -SEMI_WeatherHistorian
