Summer 2017 Outlook for Southeast Lower Michigan (and a look back at the warm Winter of 2016-17)

SUMMER OUTLOOK 2017

 

Spring 2017 Brief Synopsis

As we move into the summer months; a distinctive yet tolerable cool trend has dominated the weather across Southeast Michigan during May into early June. Temperatures have basically averaged normal to slightly below - a degree or less since the start of May - yet the entire spring itself averaged above normal fueled by a warm April.

It was a fairly wet spring across the land, especially around Metro Detroit where all three months averaged above normal. Early to mid spring was generally the wettest elsewhere with a notable drying trend taking place later spring across the Saginaw Valley into the Flint and Thumb region.

 

SUMMER 2017

 

TEMPERATURES

I look for overall normal during the summer with any "heat waves or warm periods" to be routinely tempered by cooler air pushing south out of Canada. I'm looking for an occasional -NAO to help deliver the cooler weather as discussed in Hemispheric Patterns below and in the Analogue section. On specific temperature departures; I expect temperatures to average from +1.5 to -1.5 of normal. 

 

RAINFALL

Latest model and atmospheric trends agree with Summer Analogues for generally below normal rainfall this summer as heaviest rains generally fall west and southeast/east of the region.  Of course; there will be pockets of heavier rains with convective activity but overall, below normal rains are expected.

 

HEMISPHERIC DISCUSSION

SST AND ENSO'S PRESENT STATE

 
ENSO's neutral state should have minimal effect on our summer's pattern. The outlook for the summer /JJA/ is one of neutrality to persist with just a slight edge toward the weak El Nino side of the equation. So basically, very little effect even if a weak El Nino did develop later since the downwind affects are not only negligible but the lag time would push any influence into autumn.

Interestingly, as a side note, the Hurricane Center also see any possible weak El Nino in the Pacfic as a non-event as better formed El Nino's tend to suppress activity in the Caribbean and Atlantic. They actually see an above average season for hurricanes and tropical storms in spite of a weak El Nino:

“The outlook reflects our expectation of a weak or non-existent El Nino, near- or above-average sea-surface temperatures across the tropical Atlantic Ocean and Caribbean Sea, and average or weaker-than-average vertical wind shear in that same region,” said Gerry Bell, Ph.D., lead seasonal hurricane forecaster with NOAA’s Climate Prediction Center.

Strong El Ninos and wind shear typically suppress development of Atlantic hurricanes, so the prediction for weak conditions points to more hurricane activity this year. Also, warmer sea surface temperatures tend to fuel hurricanes as they move across the ocean. However, the climate models are showing considerable uncertainty, which is reflected in the comparable probabilities for an above-normal and near-normal season.

Present Pacific SST's and Computer Projections

Jet Streams

The overall Jet Stream (Pacific, Polar) and the basic trend of the NAO will definitely lead the summer influence, as it has this past winter into spring with little affects from ENSO. Admittedly, the summer months bring weaker jets and NAO cycles but there has been a notable dominance of the Pacific jet stream the past several months with the -NAO (negative) actually becoming more of a player later this spring (and thus, our cooler weather). The $50K question is, will this continue or will this fade for the summer? More investigation is needed to make an educated forecast this summer.

Here is the NAO trend since February 2017:

Latest CFSv2 Jet projections at 10K FT /700 MB/  suggest ridging this summer over the Great Plains and Mississippi Valley to intermittently extend east and hook-up with the Bermuda High. This is a typical upper air summer pattern. At the same time however, troughing across eastern Canada is intimated to shift west and east through the summer, aided by the NAO cycle. How far west the troughing shifts at times during the summer will dictate our temperature pattern in conjunction with the movement of the ridging. At this time; there is agreement between many models and Local Analogues for a generally normal temperature summer with a slight negative departure bias.

SUMMER 2017 ANALOGUES  AND  SUMMER MODEL OUTLOOKS

TEMPERATURES:

Interestingly; Analogues and CPC's experimental model ECCA agree on a comfortable summer overall with temperatures normal to below. This would also give credence to a more intermittent -NAO this summer rather than the +NAO that dominated up until May, as seen on the graph above. Meanwhile, CPC's general public summer outlook goes for a better chance of above normal temperatures this summer (see further down on the page) siding against the ECCA model and the more typically used; the CFS model for temperatures.

Trends  in Analogues

Trends in the analogue summers show June has the better chance to average normal to above out of the three summer months for temperatures; while July and/or August has the best chance of averaging normal to below. Note; none of the July's were "hot' with well above normal temperatures and that also holds basically true for August with only one out of the nine analogues containing a hotter August - back in 2001. Overall; analogues depict a normal but the cooler side of the normal with departures /-1.1/ overall. This is nearly identical with the experimental ECCA below which also depicts close to normal but with a slight preference for a negative departure over Southeast Lower Michigan. The analogue months show on the monthly temperatures and departures and not intra-monthly. This is important since meteorological patterns reflecting upper wind cycles, come infrequently packed neatly in monthly trends. It's best to use summer months as trends and not hold any one month for specific numerical value.*

*For an example; looking at the Summer of 1890 we see June was a warmer than normal month, followed by a cooler than average July and then, a much cooler August. Therefore; you might interpret the trend of that summer was warmer than average at the beginning (but not necessarily June itself) followed by a normal, then a below normal temperature pattern mid and/or late summer. There may very well have been predominantly above normal readings the first six weeks of the summer (first half) and colder than normal the next six weeks (second half) to create that three month temperature pattern.

 E C C A Experimental Model  

              E C C A Experimental Model                       

The ECCA uses Canonical Correlation Analysis (CCA), an empirical statistical method that finds patterns of predictors (variables used to make the prediction) and predictands (variables to be predicted) that maximize the correlation between them. The most recent available predictor data for different atmospheric/oceanic variables are projected onto the loading patterns to create forecasts. The ensemble refers to forecasts produced by using each predictor separately to create a forecast. The final forecast is an equally weighted average of the ensemble of forecasts. The model is trained from 1953 to the year before the present year to create the loading patterns.

Predictor Selection :
The pool of possible predictors used in the forecasts are:

200mb global velocity potential global sea surface temperatures sea level pressure (north of 40N) The predictors selected to be used in the ECCA are based on factors such as : a) which climate signals/atmospheric variables play a large role in US temperature/precipitation for a certain season (ie. soil moisture is included in summer forecasts b) status or strength of climate signals that impact US temperature and precipitation. For example, seasons with current or expected relatively strong ENSO years typically include sea level pressure as one of the ECCA predictors because of its ability to represent the ENSO signal.

 SUMMER TEMPS /CFS/

CPC SUMMER 2017 TEMPERATURE OUTLOOK

PRECIPITATION:

The past analogues for the summer strongly suggest a drier summer overall with six drier summers, one normal summer and two slightly (less than an inch) above normal. The drier summers were so pronounced that they skewed the average rainfall of all the summers down to more than two inches below normal /-.2.25/. The analogues seem to suggest a notable dry spell mid to late summer, fairly typical of most summers yet more pronounced than usual. July and/or August has the best chance for the drier weather this summer but all three months averaged below normal rainfall. Only the Summer of  '51 contained rather steadily accumulating, plentiful rains.


Our CFS Climate model for summer monthly rainfalls would seem to agree with the analogues; calling for each month to contain below normal rainfall. 

 SUMMER PCPN /CFS/

The CPC favors Equal Chances for rainfall however; giving equal weighting to above, below or normal rainfall - therefore no rainfall preference forecast.

Reiterating:

TEMPERATURES

I look for overall normal during the summer with any "heat waves or warm periods" to be routinely tempered by cooler air pushing south out of Canada. I'm looking for an occasional -NAO to help deliver the cooler weather as discussed in Hemispheric Patterns and in the Analogue section. On specific temperature departures; I expect temperatures to average from +1.5 to -1.5 of normal. 

RAINFALL

Latest model and atmospheric trends agree with Summer Analogues for generally below normal rainfall this summer as heaviest rains generally fall west and southeast/east of the region.  Of course; there will be pockets of heavier rains with convective activity but overall, below normal rains are expected.

_____________________________________________________________________________

A Look Back....

Winter of 2016-17: The Roller-Coaster Ran Full Throttle!

Obviously all seasons have their ups and downs in the temperature department but last winter was quite variable month to month and intra-month. In the end; a very mild winter was had by all with temperatures averaging well above normal. After a relatively normal start to the winter in December; readings jumped to well above normal for both January and February.

One thing that was persistent through the winter was the exaggerated roller coaster of temperatures with the above normal readings winning out. December by far was the snowiest and most "normal" of the winter months.

TEMPS						SNOWFALL			RAINFALL
DETROIT	DEC	JAN	FEB	WINTER
NORM 30Y	30.1	25.6	28.1	27.9		NORM 30Y	42.5		Norm	6.44
AVE	29	32.1	38	32.9	8th Warm	TOTAL	37.9		Total	6.89
DEP	-1.1	6.5	9.9	5		DEP	-4.6		DEP	0.45
FLINT
NORM 30Y	27.5	22.5	24.9	25.0		NORM 30Y	47.4		Norm	5.03
AVE	27.8	28.9	34.5	30.2	8th Warm	TOTAL	39.4		Total	7.14	16th Wet
DEP	0.4	6.5	9.6	5.2		DEP	-8		DEP	2.11
SAGINAW
NORM 30Y	27.4	22.3	24.5	24.7		NORM 30Y	44		Norm	5.10
AVE	27.1	28.9	34.5	29.4	9th Warm	TOTAL	37.4		Total	5.88
DEP	-0.3	5.7	9.1	4.7		DEP	-6.6		DEP	0.78

No one has to be told we've had some extreme winters in the past couple of decades since 2000,  just look at the frequent placements in the warmest or coldest winters with the warmest ahead in total.

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	32.9	2016-2017	19.9	1944-1945	30.2	2016-2017	18.2	1958-1959	29.5	1920-1921
9	21.0	1935-1936	32.5	1982-1983	20.9	1981-1982	29.1	1952-1953	18.7	1935-1936	29.4	2016-2017
10	21.1	1892-1893	32.5	1879-1880	21.2	1935-1936	28.8	1936-1937	19.0	1993-1994	29.0	1918-1919
11	21.4	1904-1905	32.3	1918-1919	21.3	1969-1970	28.6	1948-1949	19.2	1916-1917	28.8	1932-1933
12	21.5	1978-1979	32.2	1952-1953	21.4	1985-1986	28.5	2012-2013	20.0	1961-1962	28.5	2012-2013
13	21.7	1880-1881	31.6	1877-1878	21.5	1961-1962	28.3	1930-1931	20.1	1944-1945	28.3	1952-1953
14	21.8	1911-1912	31.3	1948-1949	21.6	2008-2009	28.2	1991-1992	20.2	1969-1970	28.0	1930-1931
15	21.8	1878-1879	31.2	1920-1921	21.6	1983-1984	28.2	1949-1950	20.3	1981-1982	27.8	1974-1975
16	21.9	1981-1982	31.1	1875-1876	21.6	1947-1948	28.1	1974-1975	20.7	1947-1948	27.6	1948-1949
17	22.4	1969-1970	31.0	1953-1954	22.0	2014-2015	28.0	1953-1954	21.2	2008-2009	27.2	1998-1999
18	23.0	1958-1959	30.8	1949-1950	22.2	2010-2011	27.8	1998-1999	21.3	2002-2003	27.1	1986-1987
19	23.2	1876-1877	30.7	2012-2013	22.4	1942-1943	27.7	1986-1987	21.4	1942-1943	27.1	1953-1954
20	23.3	2014-2015	30.6	1932-1933	22.5	2002-2003	27.7	1940-1941	21.6	1985-1986	27.0	1991-1992
* Detroit Area temperature records date back to November 1874. ** Flint Bishop temperature records date back to January 1921. *** Saginaw Area temperature records date back to January 1912.

WINTER 2016-17 ANALOGUES

How did the Analogues do this past winter?

Lousy. The actual raw analogues has called for a normal to below temperature winter and one of the few times the direction for temperature (warmer/colder) was wrong. Fortunately, I disagreed with the analogues and went for a warmer winter, mainly due to the ongoing pattern. 

In the end, the Pacific Jet was more dominant, especially mid-late winter reflecting at times, a psuedo El Nino. This pattern was actually more like an El Nino across the entire country than our actual El Nino was the year before (Winter of 2015-16). The analogies weren't completely without merit however, there were a few mild to warm winters, especially 1889-90 where the that exceptionally warm winter with an average temperature of 35.1 at Detroit (3rd warmest). 

However; an even better analogue winter to dig further into was the Winter of 1998-99 after the very strong El Nino of 1997-98 and not unlike the ENSO trend of our past two winters of 2015-16 and 2016-17. The successive Winter of 1998-99 (like this past winter) also averaged above normal in temperatures /30.4/,  just missing our 20th warmest winter ranking. Back then, only one winter month /January/ out of the three contained normal temperatures; while December and February were considerably above normal. Of course, this past winter it was December that contained more typical or normal temperatures while January and February were warmer than normal leading to an average of 32.9 degrees /8th warmest/.

The SOI 's of the similar winters also were similar in trend.


Winter 2016-17 SOI:

 

Comparing the SOI between 2016-17 and 1998-99 (highlighted in yellow) shows a similar pattern overall. The reflected weak La Nina after the strong El Nino of 97-98 (below) was a bit more pronounced and persevered longer than our past La Nina of 2016-17 (above).


Winter 1998-99 SOI

 
Winter Outlook 2016-17 

While I deviated from my analogues for the Winter Outlook by going for a normal to above normal winter, I didn't go warm enough regarding the numerical departures (+2.0F). Actual departures were 4-5.0F above normal; placing it in the top 20 warmest winters.

From the Winter 2016-17 Outlook...

Temperatures:  Normal to Above

Expect temperatures during the 2016-2017 winter to be more variable than usual with conflicting data in research. This will be due to a variable upper wind jet stream. I look for both a split flow and phasing of jets as much over the Central and Western US as in the East. Guidance and Analogues suggest the heart of the winter /Jan-Feb/ seeing the most of the action (though that doesn't mean there won't be any, other times) but winters tended to start somewhat later than average (see more in Analogues). This will be guided by the anticipated weak La Nina to Neutral state interacting with the North Atlantic and subset Arctic Oscillation /NAO, AO/. Just as important this winter will be the Pacific Decadal Oscillation /PDO/ and associated Eastern Pacific Oscillation /EPO/.

In the final analysis, I look for the Southeast Lower Michigan winter to average around normal to above normal.  Temperature departures should average from -1.0F to + 2.0F.

WINTER 2016-17 SNOWFALL

 DETROIT

NORM 30Y	42.5
TOTAL	37.9
DEP	-4.6
FLINT
NORM 30Y	47.4
TOTAL	39.4
DEP	-8
SAGINAW
NORM 30Y	44
TOTAL	37.4
DEP	-6.6

From the Winter 2016-17 Outlook...

Snowfall and Rainfall:  Normal to Above depending on location

Because of the temperature variability and associated storm tracks observed in many of the analogue winters, snowfall in those winters ranged widely from above normal to below. This would be expected since the variance of temperatures hint at the variability of the upper atmospheric patterns and storm tracks. Therefore, pinpointing the perceived prevailing storm tracks this winter will make a significant difference in regard to seasonal snowfall. 

Using the expected dominant storm tracks for the upcoming winter, it is likely much of the region will experience normal to above normal precipitation with above normal snowfall /5.0"+/ around Detroit's northern and western suburbs north into the Flint and Saginaw Valley; to around normal /within 5.0"/ over the far Southeast corner of Lower Michigan (south of Detroit). Mixed precipitation events seem to be a higher than normal risk.

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