Winter of 2015-16: An Exceptionally Warm Winter That Strongly Correlated To Preferred Analogue Models

Winter of 2015-16 Over Southeast Lower Michigan

 

Strong Placement in Warmest Winters Ranking

 

The Winter of 2015-16 statistically went down as one of the warmest winters on record across Southeast Lower Michigan. The Winter of 2015-16 placed at the sixth warmest winter on record at Detroit; the second warmest winter at Flint and Saginaw. Reflecting on Chart -1 below; compare the EL NINO of 2015-16 to that of the other two preferred very strong El Nino winters in our analogue selection /1982-83 & 1997-98/. Even though the strongest and warmest El Nino's were preferred in the study; this past winter's El Nino was also expected to behave differently in its overall pattern as time wore on. The weakening influence of the El Nino along with a resilient strong Polar jet stream over northern and eastern Canada was expected to put a damper on the warm and historically, snowless winter. Mainly because of December's excessive warmth, the entire winter managed to place near the top warmest.

Strongest Placement for December's Warmth Across The Region

December's warmth secured a top billing for the warmest December ever...and at all three climate sites /Chart-2/! Never before had there been a December this warm over the entire region since record keeping commenced. This included both Detroit's and Flint's average temperature placing in the lower 40s. Above normal temperature departures ranged from between 11 to 12 degrees above normal at Detroit and Saginaw; to as high as 13.6 degrees above normal at Flint! The last time it was even "close" to this warm was back in December 2006 and that pales in comparison to December 2015 /see, chart-2 below/. The very strong El Nino analogue Winter of 1982-83 also made a very good showing with its December warmth in the warmest December chart with all three stations again, placing in the top 7 warmest Decembers. However; it's interesting to note that December of 1997, our other very strong El Nino analogue, never even placed in the top 20 warmest Decembers at any site.

                                        

Chart - 1

Comparing three strongest El Nino's /1982-83, 1997-98 & 2015-16/  and resulting winter temperature averages at Southeast Lower Michigan's climate stations. Top 20 Coldest/Warmest Winters in Southeast Lower Michigan
Rank	Detroit Area*				Flint Bishop**				Saginaw Area***
	Coldest		Warmest		Coldest		Warmest		Coldest		Warmest
	Temp	Year	Temp	Year	Temp	Year	Temp	Year	Temp	Year	Temp	Year
1	18.8	1903-1904	36.9	1881-1882	16.7	1976-1977	33.4	1931-1932	15.7	1962-1963	33.3	1931-1932
2	19.3	1874-1875	35.7	1931-1932	17.0	1962-1963	33.0	2015-2016	16.5	1917-1918	31.7	2015-2016
3	19.7	1976-1977	35.2	1889-1890	17.8	1958-1959	32.2	1982-1983	16.6	1919-1920	30.9	1997-1998
4	19.7	1917-1918	33.8	2001-2002	18.6	1978-1979	31.7	2001-2002	17.5	1978-1979	30.6	2011-2012
5	20.4	1962-1963	33.8	1997-1998	19.0	2013-2014	31.3	1997-1998	18.0	1977-1978	30.5	2001-2002
6	20.6	1977-1978	33.5	2015-2016	19.3	1977-1978	31.2	2011-2012	18.2	1976-1977	30.0	1936-1937
7	20.8	1919-1920	33.0	2011-2012	19.8	1993-1994	30.3	1932-1933	18.2	2013-2014	29.6	1982-1983
8	20.9	2013-2014	32.5	1982-1983	19.9	1944-1945	29.1	1952-1953	18.2	1958-1959	29.5	1920-1921
9	21.0	1935-1936	32.5	1879-1880	20.9	1981-1982	28.8	1936-1937	18.7	1935-1936	29.0	1918-1919
10	21.1	1892-1893	32.3	1918-1919	21.2	1935-1936	28.6	1948-1949	19.0	1993-1994	28.8	1932-19

Chart - 2

Top 20 Coldest/Warmest Decembers in Southeast Lower Michigan
Rank	Detroit Area*				Flint Bishop**				Saginaw Area***
	Coldest		Warmest		Coldest		Warmest		Coldest		Warmest
	Temp	Year	Temp	Year	Temp	Year	Temp	Year	Temp	Year	Temp	Year
1	17.8	1876	41.1	2015	16.1	1989	41.0	2015	16.2	1989	39.1	2015
2	18.0	1989	40.6	1881	16.6	2000	37.2	1982	17.2	2000	35.3	1923
3	19.2	2000	39.3	1889	17.4	1976	36.8	1923	18.8	1983	34.5	1982
4	20.8	1983	38.1	1877	17.8	1958	35.4	2006	18.9	1976	34.4	2006
5	21.5	1976	37.7	1923	20.1	1983	35.4	1965	19.0	1958	34.2	1931
6	21.8	1917	37.4	2006	20.5	1944	34.7	1931	19.1	1917	34.1	2012
7	21.9	1880	37.3	1982	20.8	1963	34.1	2001	19.5	1919	33.5	2001

Even with a very strong El Nino; Flint managed to capture the snowiest list this past winter, coming in at 15th snowiest /Chart-3 /. Areas north and northeast into the Thumb had even more snow in places (I explain why below in storm tracks). Chart -3 Top 20 Snowiest/Snowless Seasons in Southeast Lower Michigan
Rank	Detroit Area*				Flint Bishop**				Saginaw Area***
	Snowiest		Snowless		Snowiest		Snowless		Snowiest		Snowless
	Total	Year	Total	Year	Total	Year	Total	Year	Total	Year	Total	Year
1	94.9	2013-2014	13.4	1936-1937	83.9	2013-2014	10.9	1921-1922	87.2	1966-1967	7.7	1941-1942
2	93.6	1880-1881	13.7	1948-1949	82.9	1974-1975	16.0	1944-1945	83.5	1951-1952	18.5	1976-1977
3	78.9	1925-1926	15.1	1881-1882	82.8	2007-2008	16.5	1948-1949	80.0	2007-2008	20.0	1952-1953
4	74.0	1981-1982	15.2	1918-1919	78.6	1966-1967	18.5	1932-1933	79.4	2008-2009	21.0	1920-1921
5	71.7	2007-2008	15.4	1965-1966	76.6	1975-1976	20.7	1936-1937	76.2	2010-2011	21.9	1963-1964
6	69.1	1899-1900	15.8	1889-1890	75.3	1951-1952	21.5	1943-1944	75.4	2004-2005	22.7	1948-1949
7	69.1	2010-2011	16.6	1952-1953	73.0	2004-2005	21.6	1933-1934	75.0	1996-1997	23.6	1918-1919
8	67.2	1907-1908	17.1	1968-1969	72.9	1964-1965	23.4	1952-1953	68.4	1995-1996	23.8	1982-1983
9	67.2	1929-1930	18.0	1957-1958	72.8	2008-2009	24.2	1957-1958	67.2	2000-2001	23.9	1916-1917
10	65.7	2008-2009	18.0	1960-1961	72.1	2010-2011	24.4	1937-1938	65.8	1972-1973	24.3	1943-1944
11	63.8	2004-2005	20.0	1982-1983	64.9	1925-1926	28.2	1939-1940	63.0	1971-1972	24.5	1932-1933
12	63.1	1974-1975	20.9	1945-1946	63.4	1929-1930	28.3	1997-1998	62.2	1984-1985	25.0	1986-1987
13	61.7	1977-1978	22.8	1943-1944	62.9	1972-1973	28.4	1931-1932	61.9	1964-1965	25.1	1944-1945
14	61.6	1884-1885	23.0	1888-1889	62.2	1981-1982	28.6	1968-1969	60.6	1947-1948	25.6	1983-1984
15	60.9	2002-2003	23.4	1997-1998	61.8	2015-2016	28.7	1941-1942	60.3	2013-2014	26.1	1921-1922
16	60.2	1898-1899	23.7	1999-2000	61.5	1958-1959	28.9	1924-1925	57.0	1929-1930	26.5	1927-1928
17	60.0	1922-1923	23.8	1937-1938	60.1	1959-1960	29.5	1988-1989	56.3	1975-1976	26.9	1993-1994
18	59.9	1892-1893	24.1	2003-2004	55.9	2005-2006	29.5	1999-2000	56.0	2001-2002	27.5	1979-1980
19	58.6	1951-1952	24.8	1941-1942	55.4	1989-1990	30.5	1928-1929	55.9	1978-1979	27.5	1912-1913

Winter/Cold Season Temperature and Snowfall Comparisons and Results

Though the Winter of 2015-16 was warmer than what was projected by the analogues on average; the preferred and thoroughly discussed Winters of 1982-83 and 1997-98 were right in-line with this past winters. In addition; the overall pattern projected (fading El Nino influence, intermittently influenced by Polar jet and better snows than typically fall in a very strong El Nino) materialized where they were projected; north of metro Detroit over Southeast Lower Michigan. Normal to above normal snows were measured north of the Detroit Metro area into the Saginaw Valley and Thumb - NOT typical of a very strong El Nino but where intimated by the analogues.

The unseasonably warm December negated somewhat; my temperature departure number outlook for the entire winter. I wasn't warm enough for the winter on my above normal departures (up to four degrees above normal was stated) for all of Southeast Lower Michigan; as evidenced by the seven /6.9/ degrees above normal!  Had December been more in line with the warmer Decembers, the overall winter departure would have been much closer to my call. December's blow-out warmth was not expected though in my and the analogues defense; it was expected to be the warmest and largest above normal departure of the three winter months. Sticking with the above normal departure average on just the two preferred winters would have been much better in retrospect - my bad. The main reason I chose to be somewhat cooler than just the two analogue winters was; I expected the real warmth of the winter to run into trouble mid to late winter and thus, January and February not to average as warm as in 1983 and 1998 - which did happen. The mid and late winter was not as warm as its two warm analogue winters.

On a side note: in retrospect and commented on previously, this brings up the most common weakness seen in the analogues. While the sign (+, -, 0) of the departure may be a degree or more in the right direction (seen frequently), the magnitude remains probmatic at times and may be off a few degrees or more.

At the same time however: the way the winter's subsequent pattern unfolded was spot on with the analogue trend. Warmest weather relative to normal was expected to come early in the winter (predicted and materialized big-time in December). The bigger question was how the rest of the winter was to unfold after December? All research and subsequent analogues strongly suggested the entire winter would not behave as a typical very strong El Nino. In other words, previously dominant hemispheric patterns were expected to challenge "the new kid on the block" - El Nino.

From my Winter Outlook:

During the strong El Nino's of 1982-83 and 1997-98 the atmospheric characteristics and downwind affects really didn't peak until the winter period. Thus far, along the central and southern West Coast, the "wave-train" of storms has yet to materialize but if history is any indicator, next month should see things pick up some. Things have begun to change here in November though with some storms tracking further south into the West Coast, deepening on the lee side of the mountains and heading into the Great Lakes. However, this pattern is really not unusual for any late fall period so, nothing too El Nino-like.

At the same time; the Polar/Arctic jet has shown signs of expanding and phasing further south into the sub-tropical jet, typical for November. While the subtropical jet is becoming more active, so is the Polar/Arctic jet. This has created a combative, progressive rolling jet pattern across the country. I look for this pattern to continue into at least into early December as timing is always an issue this far out. While the Polar Vortex is expected to remain much of the time up in the Arctic; looking at my data and the past few winters, I look for it to be a player at times.

Temperatures: 

"I look for the winter pattern downwind to behave at times like a Hybrid or Modoki El Nino  rather than just the typical classic El Nino. Because of the other hemispheric patterns in place; I would expect more of a "roller-caster" type of temperatures pattern established especially going into the winter, as mentioned above and coming out; directly involving the El Nino, EPO and NAO.

In any event; look for a milder, less cold winter than the past couple with temperatures averaging around 2 to as much as 4 degrees above the established normals. 

Again, as it turned out even while predicting up to four degrees above normal which would have placed Southeast Lower Michigan in the Warmest Winter's listing as it were. What was warm enough for the winter were the preferred and strongest El Nino winters of 1982-82 and 1997-98. The Winter Temperatures chart below shows the average temperatures for winter months/season and departures. As you can see, the exceptionally warm December boosted the winter average temperature by several degrees and it alone was mainly the reason the winter turned out so warm. Both January and February were also warmer than typically felt but not to the extent of December.

1-TEMPERATURES

2-SNOWFALL

While the snowfall was expected to be at least around normal across the northern two-thirds of the landscape, it too was exceeded mainly around the Flint region into the Thumb. As expected, Southeast Lower Michigan became the battle ground at times between the Polar Vortex to the north and the moisture brought in by El Nino from the west and south. The central part of Southeast Lower Michigan was often "ground zero" for these battles, as mentioned in my Winter Outlook. Also, the snowfall chances were higher later in the season and this materialized as late as mid May - one of the latest observed.

"However, all is not lost snowfall lovers! Two winters contained normal snowfall at Detroit, one normal and two above normal at Flint and finally; two normal and three above normal at Saginaw. Therefore, the most obvious pattern seen in these winters is that the further north one goes in Southeast Michigan, the better chance for more snow. The same can be said for general precipitation across the region. The Winters of 1991-92 and 1972-73 saw the best snows across the entire region with normal to above normal. The Winter of 1940-41 saw the next best "snow showing" the entire region but still well below at Detroit /26.8/ to near 50 at Saginaw /49.7/. The actual snow pattern for this winter will be watched for updates". 

Snowfall Chart

Preferred Storm Tracks Verification

This also showed up and verified well in the preferred storm tracks across Southeast Michigan and also along the East Coast (which also was busy at times). Note the track I posted for Southeast Lower Michigan with the El Nino influence and phasing occasionally with the cold from the Polar jet. The storm track was estimated to cut right across the region with more snow to the north - matching the forecast. This track placement was too, a direct result of analogue preference for snow patterns in Southeast Lower Michigan.

All analogue winters comparisons including data from this past winter

 

Here is the entire set of analogue winters with the Winter of 2015-16 added at the bottom of the years, along with updated Winter types. As with any other image here; click on it to see a larger/better resolution.

Reflecting back on El Nino's strength this past winter

The Winter of 2015-16 was widely anticipated to be unseasonably mild mainly due to the projections of an El Nino in record territory. The El Nino didn't disappoint in that regard; it maxed-out with the two previous strongest El Ninos of 1982-83 and 1997-98 - but was it the strongest? A very good computation and summation of that question can be found from NOAA; written this past February when El Nino was clearly beginning to wane. However, there isn't much said on the comparisons to 1982-83 with 1997-98 and 2015-16 being the top contenders.

So is this the strongest El Niño on record, or what?

This is definitely one of the strongest three going back to 1950.  It’s hard to say definitively what single El Niño is the strongest, because there are a lot of different ways to measure strength.

The Oceanic Niño Index, the three-month-average sea surface temperature departure from the long-term normal in one region of the Pacific Ocean, is the primary number we use to measure the ocean part of El Niño, and that value for November – January is 2.3°C, tied with the same period in 1997-98. There are other areas of the ocean that we watch, though, including the eastern Pacific (warmer in 1997/98) and the western Pacific (warmer in 2015/16).

Also, don’t forget the “SO” part of the El Niño/Southern Oscillation (ENSO), which is the all-important atmospheric response. All that extra heat in the tropical Pacific Ocean warms up the atmosphere above it, leading to more rising air, which changes the circulation all around the globe. By one measure (the EQSOI), the El Niño-related changes in the atmospheric circulation in 1997/98 and 2015/16 are tied; by another (the SOI), 1997/98 was stronger.

There are other areas of the ocean that we watch, though, including the eastern Pacific (warmer in 1997/98) and the western Pacific (warmer in 2015/16).

El Nino SSTs and Subsequent Hemispheric Wind Jet Placement

What is just as important if not more for our interests, is where (latitude/longitude) El Nino peaked as far as SST departures over the Pacific. Were they mainly over the far eastern Pacific nearer to South America or more toward the middle Pacific? Actually both happened this past winter and this is also discussed in NOAA's analogy. They don't mention timing during the winter which I feel is important for the overall evolution of the winter weather hemispheric pattern.

In my Winter Outlook issued back in November, this was a main concern to me and how it would affect our evolution of our mild strong El Nino winter.

Hemispheric Winds Compared for Each El Nino

Below are the maps for each of the three El Nino's jet (and max wind speeds in the red highlighted regions). Note where each El Nino's jet maxed out: this past cold season /Nov-Mar/ it was over the far west Pacific. It's interesting also to note the troughing aided by the second weaker wind max over the eastern US. This is where the Polar Jet and El Nino subtropical jet interacted and thus; gave us more interesting and stormy weather than typically seen in very strong El Ninos. This was particularly significant at the start of the cold season /Nov/ and then again later in the season /Feb-Mar/. Also, important was the very weak to almost absence of the troughing out west, typically this is stronger and aids in bringing very mild air the entire season. Basically, the El Nino induced sub-tropical jet was displaced further north and one of the main reasons southern California remained drier (see precipitation maps down further).

Cold Season of  2015-16

During the cold season/El Nino of 1982-83 the strongest upper level winds were mainly over the west and central Pacific. Note the more defined trough over the western U.S. with very little jet action over the eastern U.S. This was especially true during December of '82, which mimicked our December of '15 much better than December of '97 for unseasonable warmth (see December comparisons further down).

Cold Season of  1982-83

During El Nino of 1997-98, like 1982-83, the max winds were out over the west and central Pacific with notable troughing again in the western U.S. These two combined to bring flooding rains to California that winter. Meanwhile, the troughing from northeast Canada is just about absent over the east while a second subtropical jet established further south.

Cold Season of  1997-98

Cold Season Composite Temperature Comparisons

The map shows widespread warmth over the north-central and northeast; while mild conditions existed elsewhere. However; it is very important to remember the map over the north and east is skewed warmer than existed the entire winter because of mainly one month, December.

2015-16

The cold season of 1982-83 below was much more typical of a strong El NIno with warm departures over the north and cooler departures over the south.

1982-83

Again; the cold season of 1997-98 was more typical of a strong El NIno with warm departures over the north and cooler departures over the south.

 

1997-98

December Comparisons

One can see the December temperature departure placement were more similar between the El Nino of '82 and '15 than El Nino of '97.

One of the most interesting examples of "very strong El Nino non-like precipitation" fell this past winter. First off; southern California was just about promised heavier rains, or at least more rain than normal - it never materialized with any needed regularity (note the drier the average conditions over that region). Heavier rains were deflected north and extended from northern California into Oregon and Washington State along with the main jet.

In addition further east; some places forecasted drier than normal were wetter, some MUCH wetter. This became even more pronounced and evident during the cold season /Non- Mar/. Also, note the subsequent verification maps from CPC below the precipitation maps. In addition; the temperature forecast/verification maps from CPC are displayed below the precipitation. Temperatures were much more in line with the forecast in the north but faltered somewhat in the south, where warmer than normal conditions also prevailed more than expected.

 

Polar Projection of the 500 Heights

Looking at the polar projection 500 MB heights for basically the climatological winter shows the very strong El Nino influence over the western/central Pacific; spreading out somewhat as she came inland on the West Coast with main jet deflected a bit north. In our neck of the woods; the bulge south of the Arctic/Polar jet shows up nicely as it intermittently nosed into the upper Midwest, Great Lakes into the Northeast.

500 MB HEIGHTS WINTER OF 2015-16

Next Up - That All Important Summer Outlook Due Out Shortly - I'm shooting for the first weekend of June. 

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