11/27/24

Another Milder Winter In Store For Southeast Lower Michigan? - Is This Becoming a Habit - or Is It? Winter 2024-25 Outlook

 Part I

Current ENSO Conditions and Representative Winter Outlook & Analogues

Well, this Autumn over Southeast Lower Michigan has been what is generally expected over the region when a La Nina /ENSO/ is in the works. Dominating mild weather and more on the drier side when compared to an average fall. The only problem is; officially there was strictly no La Nina. Prevailing Neutral SST conditions slowly ebbing toward La Nina conditions are now what holds sway in the central Pacific. This is evidenced by the changing water temperatures in the official 3-month ENSO readings since the late spring into summer. Latest reading for the last ASO period in the chart below (not placed) continues a Neutral reading at -0.2; so ENSO continues to crawl  toward a weak La Nina.

Year

DJF

JFM

FMA

MAM

AMJ

MJJ

JJA

JAS

ASO

SON

OND

NDJ
20200.50.50.40.2-0.1-0.3-0.4-0.6-0.9-1.2-1.3-1.2
2021-1.0-0.9-0.8-0.7-0.5-0.4-0.4-0.5-0.7-0.8-1.0-1.0
2022-1.0-0.9-1.0-1.1-1.0-0.9-0.8-0.9-1.0-1.0-0.9-0.8
2023-0.7-0.4-0.10.20.50.81.11.31.61.81.92.0
20241.81.51.10.70.40.20.0-0.1

Current ENSO SST as of Nov 2024

Perusing over Maps 1 & 2 below; it does look like the developing La Nina is still somewhat in the works by the looks of the early and again, mid November data in the Pacific (in and around the equator /0' lat/). What remains to be seen is how well La Nina evolves (these particulars never seem easy, lately). Modeling SST forecasts ahead of the ENSO events (with the American CFS-v2 model anyway) have been too aggressive in ENSO development the seasons/months ahead. All latest expectations have now cut back on the below normal departures of the water temperatures /SST/. 

Before I go any further I must say (and I may regret it); I really don't see La Nina being much of an influencer this winter anyway and think it's probably too hyped. It's having a hard time taking off as it is and there are some negatives against it. If that's a decent assumption and bears out; the weather and systems should act more like Neutral ENSO conditions for the most part. 

Going with that regime; Southeast Michigan's winter season should be more influenced by the PDO (moderate - strongly negative), MJO, the NAO/AO (varying from positive - negative and also; where the oscillation is based), subsequent PNA and lesser extent, the AMO. I'll explore the PDO and others in the analogues more below but in keeping in the vein; continental air masses should be more of player this winter - which should only add to the volatility. 

 Note the Analogue Sea Surface Temperatures Map -1 below as of Nov 1st



         Now, the recent changes in Map -2 below as of Nov 24th

This time; the forming weak La Nina has backed-off slightly (weakened) while the negative PDO continues to form. 

 Current Oceans SST Anomalies 

 

 

3.4 SST Model Guidance

 
 
As mentioned above; what had been forecast by the model(s) was anywhere from a moderate or even strong La Nina this winter months ago; now has the water temperatures just slightly below normal and barely scratching the surface of La Nina territory. Therefore in keeping with the latest forecast; I adjusted my analogue category for winters under past Neutral - Weak La Ninas with similar timings and strengths but still; some with various local & hemispheric patterns beforehand. 
 

 Why the PDO (and EPO) are More Important This Winter

The Pacific Decadal Oscillation /PDO-/ has been trending this autumn to more negative with time. Why is this important - a picture (s) is worth a thousand words (below). How this plays out along with their frequency will be a main driver for the winter. If a positive /PDO+/ jet stream continues to intervene notably, the variance of temperatures will be apparent. Being the Pacific Ocean has influenced our weather this fall into winter we've seen both sides of this dominance (PDO+/PDO-) and not as much from the NAO/AO influence yet.

 

EPO graph

 

 

 

Note the numerical change in the PDO+ to PDO- in the last decade or so. The last few months are not in, in the bottom right.

The blue/negative numbers indicate a negative /PDO-/ has become more dominant the last few years. Also, the yellow/positive /PDO+/ from 2014-18 show the influx of the mainly positive state.



The graph /below/ of the PDO reflect those numerical numbers all the way back to the mid 1800s.

 


 
Current cold Phase of the PDO and weak La Nina show well in this recent SST scan on November 1st, 2024. 
 
 
 
 
Generally cold phases coincide with La Nina's or Neutral states and rarely El Nino states. It does happen and studies propose that when the PDO and ENSO are in phase, such as this Fall they tend to enhance the effects. When out of phase; which is a somewhat a rare event, that they may cancel out their known effects.
 
 

How Warm We've Been!

Again; here at Detroit and much of SE Michigan, we sit with a November average temperature that has blown away any warmest Nov in the past century (and then some) by averaging nearly 50 degrees (ave 49.6/+6.9 thru 22nd *Updated 11/26 @ 48.7/+ +6.7) Take note; the warmest Nov on record in Detroit being 47.8 in 1931! Of course; even with the colder snap that is taking shape for the last quarter of the month, we should still average near/at the top 20. By far however; the most shocking stat is how many warm Novembers and winters there have been since the '90s (or basically, the new norms period 1991-2020). At Detroit alone; nearly half of the Novembers (nine) are in the top 20 and another one is due at the end of this one)! Therefore; about half of the top 20 warmest Novs and winters at Detroit occurred the last 31 years /1994-2024/ including both 1994 & 2024. One more stat; add all those recent /9/ top warmest Novs since 1994 (excluding '24) and the ave is 45.9 (or near 7/8th place at 46)!
                                                        
Top 20 Coldest/Warmest Novembers 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 29.8 1880 47.8 1931 31.3 1951 47.3 1975 29.8 1951 47.1 1931
2 33.5 1976 47.6 2001 32.0 1995 46.6 2001 31.6 1995 45.9 1975
3 34.2 1996 46.9 1902 32.6 1996 46.4 2020 32.5 1959 45.6 2015
4 34.5 1875 46.8 1975 33.0 1959 46.2 1931 33.3 2019 45.4 2016
5 34.6 1951 46.7 2016 33.3 2018 46.0 2015 33.3 1976 45.3 2001
6 34.9 1894 46.6 2011 33.3 1976 44.6 2016 33.6 1933 44.6 2020
7 35.2 1967 46.0 2015 34.5 1936 44.4 1934 33.9 1996 43.2 2009
8 35.4 1936 46.0 1963 34.5 1933 43.8 1938 33.9 1955 43.1 2011
9 35.5 1995 45.7 2020 34.6 2019 43.7 2011 34.0 2018 43.0 1963
10 35.5 1911 45.7 1948 34.8 1967 43.3 1963 34.2 1989 42.4 1999
11 35.7 1910 45.5 1994 34.8 1955 43.2 1948 34.2 1967 42.4 1948
12 35.7 1892 45.3 2009 35.0 1947 42.8 1999 34.2 1950 42.2 1934
13 35.8 2019 45.2 1999 35.1 1929 42.5 2003 34.3 1947 41.8 1994
14 35.8 2014 44.9 1964 35.2 1950 42.5 1994 34.4 1986 41.8 1938
15 36.0 1933 44.9 1909 35.2 1921 42.4 2009 34.6 2014 41.6 1990
16 36.4 1903 44.5 1953 35.3 2014 42.4 1990 34.7 1949 41.6 1964
17 36.4 1901 44.3 2003 35.4 1986 42.2 1924 35.1 1943 41.6 1913
18 36.6 1959 44.3 1883 35.5 1997 41.8 1998 35.1 1925 41.5 1953
19 36.6 1891 44.2 1990 35.6 1943 41.8 1953 35.2 1926 41.4 1930
20 36.7 1950 43.9 1946 35.8 1949 41.6 1987 35.2 1919 41.3 1998
* Detroit Area temperature records date back to January 1874.

** Flint Bishop temperature records date back to January 1921.

*** Saginaw Area temperature records date back to January 1912.
 

Back to the Winter 2024-25 Outlook and Analogues   


My original nine winter analogues in chart (or table) below averaged slightly above the temperature normals of 1991-2020 for the 2024-25 winter. I look for the temperatures and weather to be more variable & possibly bordering on extreme at rarer times as Polar/Arctic jets vie for dominance over the obstinate Pacific Subtropical Jet. The latter should attach intermittently with warmer, moisture laden air from the Gulf of Mexico. A progressive but still; occasionally blocky upper wind jet / air stream will only add to the winter's variability. I look for both; a split flow but occasionally phasing of jets as much over the Central and Western US as in the East. This is the main problem for the winter outlook; how often the Polar/Arctic jets engulf the Great Lakes.
 
That being said; latest model extended guidance into early winter matches well with my dominant early winter analogues suggesting winter's cold will come down in spurts beginning late fall into early winter. While most analogue November's averaged normal-above (like this Nov and annotated with a/n/b next to analogue season on chart); Decembers had the best chance to average below normal or at least a notable period of cold (a far cry from recent Decembers). 
 
Arctic cold that charged up in the Polar Regions during the analogue falls  -our 2024 warm Neutral autumn not withstanding -  found it's way down into the Lakes Region with the majority of December's averaging below normal. In the past; out of the nine Winter Analogues; seven Decembers contained below normal temps, one on the low side of normal and one above. This doesn't mean there won't be notable mild periods and thus, the issue comes up; will the periods of colder weather be able to offset periods of milder weather during the winter. Obviously; this has been a major problem in many of our recent winters. Basically; when we did get the cold; it didn't last. 

The air masses 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/ which looks to be negative for the period. The overall Pacific Jet should continue to be active; a sort of a "layover" of sorts from the long dominant El Nino from mid 2023 to mid 2024. In addition; upper air ridging will have to be watched setting up west of Alaska to Alaska, the question arrives how often and long and thus, influential. This will be discussed in Part Two of my Outlook.
 
   ANALOGUE WINTERS FOR 2024-25 

Note; the two analogues /2001-02 & 2022-23/ at the bottom of the chart below are NOT strictly included in this winter's analogues. They were La Ninas at the end of an extended La Nina cycle (weakening not developing). In addition; they also contain a few developing or developed stronger solar flares like this fall into winter - and peaking solar cycle into 2025.
 
 
 ANALOGUE WINTER CHART FOR 2024-25


L










A

DETROIT

T

E

M

P

S


P

C

P

N

N

SEASON

DEC

JAN

FEB

WNT AVE

WINTER

NAO/P/SC

SEASON

DEC-FEB

WINTER

QBO

A

1942-43-n

25.6

21.7

28.0

25.1

1

N/P-

SC--

1942-43

7.19

1

*

L

1952-53-a

34.1

30.6

32.2

32.3

1

N/P

SC--

1952-53

4.66

1

E-

O

1964-65-a

30.4

25.5

26.6

27.5

1

N&N-P-

SC--

1964-65

8.42

1

E-

G

1966-67-n

28.7

29.3

23.8

27.3

2

N/P 

SC+

1966-67

8.15

2

W

U

1970-71-n

29.0

20.7

27.4

25.7

2

N-/P-

SC++

1970-71

5.32

2

E+/-

E

1983-84-n

20.8

18.0

33.3

24.0

3

N+/P+

SC-

1983-84

5.87

2

E

S

1995-96-b

25.6

24.3

26.0

25.3

4

N&N-/P 

SC--

1995-96

4.46

3

E-


2005-06-a

25.8

35.2

29.8

30.3

2

N&N-P

 SC-

2005-06

8.47

3

E+/-

N

2016-17-a/

29.1

32.1

38.0

33.1

3

N+/P

SC-

2016-17

6.89

3

W

E

BELOW: NOT INCLUDED:
IN ANAL STATS










U

2001-02-a

35.9

32.7

32.9

33.8

1

N+/SC++

2001-02

7.50


W-/+

T

2022-23-a

32.8

33.5

34.0

33.4

2

N+/SC+

2022-23

8.38


W-   

R












A

Ave

28.9

27.6

30.2

28.8



Ave

6.85


QBO

L

NORM 30Y

31.2

25.7

28.0

28.3

150yr

26.9

Norm

6.56


W


Dep

-2.3

1.9

2.2

0.5



Dep

0.29



I





-1.2








DETROIT

S

N

O

W

F

A

L

L


Oct

W

SEASON

OCT

NOV

DEC

JAN

FEB

MAR

APR

SEA TOT

SEASON

Sib snow

E

1942-43

T

4.4

9.2

18.4

2.7

2.9

6.8

44.4

1

*

A

1952-53

T

T

4.3

9.4

0.7

1.0

1.2

16.6

1

*

K

1964-65

T

2.6

8.4

7.1

15.8

12.9

2.4

49.2

2

*

 

1966-67

0.0

11.8

14.9

5.4

11.0

5.8

1.7

50.6

1

B

L

1970-71

0.0

1.7

9.8

8.7

5.9

8.7

0.6

35.4

2

B

A

1983-84

0.0

3.5

19.9

9.9

8.7

9.7

0.1

51.8

2

A


1995-96

0.0

1.3

4.5

6.3

3.6

11.8

0.1

27.6

3

B

N

2005-06

0.0

4.3

19.8

5.0

3.8

3.4

T

36.3

4

A

I

2016-17

0.0

0.1

16.8

11.8

2.2

6.9

0.1

37.9

5

B

N












A

2001-02

T

0.0

4.9

15.0

6.7

7.1

T

33.7


B

S

2022-23

T

2.5

5.0

11.7

2.0

15.8

0.1/T

37.1


%













I

Ave

T

3.3

10.7

9.9

6.0

7.8

1.2

38.9


%


30y Norm

T

1.9

8.9

14.0

12.5

6.2

1.5

45.0



2

Dep

0.0

1.0

1.8

-4.1

-6.8

1.6

-0.3

-6.1


Sib Snow

0






7



45

ther

*  N/A

2

Color

Temps

Degrees


Rain

Inches


Snow

Inches



4

Legend:

Below

1.0>


Below

1.00>


Below

<5.0

n


~


Normal

0.0-1.0


Normal

0.00-1.00


Normal

>-5.0<5.0



2


Above

1.0>


Above

1.00>


Above

>5.0



5












Some additional category explanations in the analogue chart for the entire winter
NAO: /N/ - The predominant phase of the North Atlantic Oscillation    N- (negative), N (neutral) or N+ (positive)

PDO: /P/   The predominant phase of the Pacific Decadal Oscillation   P- (negative), P(neutral) or P+ (positive)

SC :  Position of the solar cycle during that winter. 

Breaking it down
SC-- (opposite lowest sunspot cycle compared to the present, thus least similar) 

SC+ (sunspots moderate-high but waning and not approaching or at the highs/maximums like 2024-25.

Finally, SC++ where solar sunspot cycle was very close to the high cycle of 2024-25 and/or is at near the same incline; thus the best comparison and likeness to the upcoming winter.
           
QBO - W=West wind prevailed that winter or E=East wind prevailed. 

Trends: -/- (weak and weakening trend), -/+ (weak but strengthening), no sign  (steady trend, no change) + moderate and strengthening +/- strong but weakening. 

The closest analogues with QBO likeness years are the two with westerly and no change in trend; 1966-67 & 2016-17. Next is 2001-02, not officially an analogue.
          
 Sib snow - Siberian snow cover in October and rate of change. All previous analogues winters had mixed snow covers compared to this past October's/early November. Notations: A= above, B=below, % = equal to. 

A bit more on the solar cycle

Solar cycle actual effects on short term weather and longer term climate variability remain a controversial subject. I've read several articles which support or are against their shorter term winter relevancy. Some theorize that both natural solar cycles and man's influence affect our climate. I am in favor of the solar cycle being somewhat relevant and sometimes giving the present winter cycle a "little kick" in regard to hemispheric wind flow patterns and resulting temperatures.  Studies out of Europe for example, do in fact make the connection to wintertime effects.

"The Euro–Atlantic sector seems to be a region with a par-
    ticularly strong solar influence on the troposphere. In fact,
                significant positive correlations between solar activity and
    surface temperature in Europe have been reported in several
               papers (e.g. Tung and Camp, 2008; Lean and Rind, 2008;
             Lockwood et al., 2010; Woollings et al., 2010), although
        long records tend to give very weak signals (van Olden-
     borgh et al., 2013). We found a weak but significant change
     in the mean late winter circulation over Europe, which re-
     sults in detectable impacts on the near-surface climate. Fig-
     ure 9 suggests that during solar minima more cold air is ad-
     vected from the Arctic, thus resulting in a slightly increased
     probability of colder winters for large parts of the conti-
     nent. Sirocko et al. (2012) recently reached the same con-
  clusion after analysing 140 yr in 20CR, although their re-
     sults are strongly dependent on their selection criteria for
       the solar minimum composite (van Oldenborgh et al., 2013),
     which includes only one winter for each solar cycle".

 

Local Data Suggests

Temperatures: Normal to Above (-0.5 - +2.0)

Again; Our nine winter analogues in chart (or table) below averaged slightly above the temperature normals of 1991-2020 for the 2024-25 winter. I look for the temperatures and weather to be more variable & possibly bordering on extreme at times as Polar/Arctic jets via for dominance over the obstinate Pacific Subtropical Jet. 

Latest extended guidance matches well with my dominant early winter analogues suggesting the winter cold (below normal temps) will come in spurts beginning as early as late fall-early winter. While most November's averaged normal-above (like this Nov and noted with a/n/b next to analogue season); Decembers had the best chance to average below normal or at least contain a notable period of cold (a far cry from recent Decembers). In the past and present; Arctic cold that charged up in the Polar Region during the our notably mid-late warm Neutral (or weak La Nina) autumn; found it's way down into the Lakes Region with the majority of December's averaging below normal. Out of the nine Winter Analogues; seven Decembers contained below normal temps, one normal and one above. The issue comes up is when and where the notable cold manifested itself from late Nov into early Jan in early winter.
 
Check out this temperature analogue map for Decembers only
 

 
 

 

 

 

 

 

 

 

 

Winter 2024-25  Composite Maps

Despite my temperature table (or chart) above, averaging slightly above normal temperatures for the entire analogue winters; specific composite maps below; averaged the nine analogue winters slightly below normal temperatures. This is unusual but can happen when local analogues are near normal (in this case Detroit is just a 1/2 degree above normal). Looking at some of the warmer months, especially February I can see why locally the averages would be warmer than a national map. 

 


The analogue map is useful at this time since it shows where the cold blasts are intermittently likely this December and winter as a whole - from the Northern Plains, Upper Midwest into the Western Great Lakes and Ohio Valley. Local data doesn't show a continuation of cold nor warmth thus it's beneficial for areas likely to experience the Polar Express at times when revved up.  This of course relates back to the larger cyclical patterns discussed above.  

On the Precipitation side of things: Averaging around normal


The past chosen analogues paint a wet picture for the Pacific Northwest south into central California and eastward into the North and Central Rockies. 

Broadly; normal to above normal precipitation was found over a large area of the North & Central Plains into the Great Lakes/Northern Ohio Valley; then east to the East Coast. This also does indicates relatively active Great Lakes Lake Effect season along with the typical lee of the lakes snow squalls and snow showers. Of course; this will largely depend on the developing upper wind pattern and cyclical oscillations mentioned above. 

Like above discussion - Again; I really don't see La Nina being much of influencer this winter and think it's too hyped. It's been having a hard time taking off and there are some negatives against it. If that is a good assumption; the weather and systems should be more influenced by the PDO /negative/; NAO/AO, subsequent PNA and lesser extent, the AMO. Therefore; continental air masses should be more of player this winter - which will only add to the volatility.

Precipitation and Snowfall for Southeast Michigan:

Quite variable but generally averaging around normal with Lake Effect (Lakes Michigan and Huron -and certainly over the eastern Great Lakes) being more of a player than in many recent winters. Storms tracks will be determined by the above discussioned patterns. There were a few winters where the tracks held across SE Michigan and mixed precipitation was plentiful along with storms. 

In December in Part II; I'll take a look at model projections for the winter period along with observing prevailing jets and associated storm tracks forming. In addition; any shorter term weather related events.

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





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