11/18/17

Winter 2017-18 Outlook for Southeast Lower Michigan - Some surprises along the way?

While the past several months have had some notable weather; to a large extent the summer into mid autumn was fairly tranquil with just the occasional upset in the pattern. We are beginning to see a busier and more contrasting and subsequently, conflicting pattern rev-up as we head into the latter part of the year. What's been somewhat gratifying yet a bit uneasy for me is how well the present mid fall pattern fits into the upcoming winter pattern I found for this; my 21st Winter Outlook.

Some changes in my Outlook are in store for the beginning of my third decade of season outlook forecasting. They include an even more thorough analogue chart including previously mentioned patterns in the past such as: Arctic Oscillations, Solar and QBO cycles along with Siberian/Eurasia October snow cover (available since 1998) during the previous analogue winters. This in turn is compared to the upcoming Winter of 2017-18's observed or projected patterns. Therefore, much of the information discussed is there for the reader to quickly scan on the chart. I still will provide a brief summary of each indicator but limit the amount of description, while still occasionally connecting the reader to the corresponding website. The overall, Winter Outlook format remains the same as presented in the past. Now on to the Outlook...


Winter Outlook for the Winter of 2017-18

 

Occasionally in my past Winter Outlooks, I've eluded to Mom Nature 'tipping her hand' as to what the upcoming winter will bring. This appears to be the case this time as one casts one eye on the recent autumn pattern change and the other eye on this winter's analogues and general upper and surface weather pattern - which actually agree strongly with computer guidance. Of course, sometimes even though the overall general pattern verifies well; the final winter statistics may differ from the forecast - this too I could easily see being the outcome with this winter's projected pattern with the wild fluctuations.

Local Data Suggests 


Temperatures: Normal to Below 


Expect temperatures during the 2017-2018 winter to be quite changeable as opposing air masses vie for dominance under a fluctuating jet stream. This is not only a developing trend seen the past month or two but it's well displayed in the Winter Analogues for 2017-18 and finally; the computer guidance for the upcoming winter. While this is a typical La Nina pattern, my research shows and I believe again this winter the Pacific jet will be more of a key player against the typical La Nina pattern. The basic difference this winter from last winter is all data that I research is intimating a notably colder winter than last winter. This is likely due to a preponderance of polar/arctic air masses.

In the final analysis, I look for the Southeast Lower Michigan winter to average around normal to below normal.  The outlook for temperature departures will be of a wider range than generally forecast; averaging from -3.0F to +1.0F.

Precipitation: Above


Because of the parade of conflicting air masses diving in from the north and west, with temperature variability and associated storms and storm tracks ignited; above normal precipitation is likely for the Winter of 2017-18. This trend is supported by many of the analogue winters, along with model output for the winter and recent autumn trends. With the discussed storm tracks below; mixed precipitation is at a higher risk this winter. I do look for the alternating extended wet and dry periods to persist into the winter from the autumn.

Snowfall: Around Normal to Above 


The especially tricky part of this forecast is how much of the expected precipitation will be snow and/or mixed precipitation? In the analogues: snowfall in the 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. This is similar to last year's La Nina and is strongly suggested in model output. Remember; an above normal precipitation winter does not necessarily mean above normal snow...even with a colder winter! It's been awhile since we've had a cold winter but with below normal snowfall. The state of the atmosphere when the precipitation becomes available is the key and this looks especially relevant this winter. Leaning on the analogues; I look for generally normal, or an average winter's snowfall (+/- 5" of the norm) across much of extreme Southeast Lower Michigan. This is a winter however where below normal snows could certainly occur especially in this area if the storm track rides further north. The better chance for above normal snow expected further west and north away from that region. Therefore; best chance for above normal snow will lie in an arc from the Brighton/Howell area /I-96 area/ east northeast across Flint and Port Huron /I-69/ and points north/northwest into the Saginaw Valley/Thumb Region.

Below Normal snowfall; less than /- 5.0"/ of the winter average snowfall  
Normal snowfall; +/- 5.0" of the winter average snowfall
Above Normal snowfall; better than /+5.0"/ of snow above the average.


Hemispheric Discussion 


In case you haven't surmised by now; the upcoming winter is expected to be, like last winter, a La Nina winter. In addition; this winter's La Nina is likely to be generally similar in strength to last year's; albeit possibly a bit stronger and may reach borderline moderate at -1.5 departure. I also look for this winter's La Nina to have more of an influence on our weather than last winter's; mainly due to the atmosphere's stronger resultant La Nina pattern reaction (not dominant last winter) along with the cool Pacific Decadal Oscillation in place.


 ENSO Regions in the Pacific

 

 

 

Current ENSO SST anomalies as of mid November

 

 

Current ENSO map conditions as of mid November


 



The Oceanic Nino Index /ONI/ 1950 - mid 2017 below; shows all the El Nino's and La Nina's strong and moderate - weak are not depicted except for last winter's.

  ONI


 SOI


The Southern Oscillation Index /SOI/ below shows well the recent negative corresponding values in conjunction with our recent strong El Nino of 2015-16. Remember; an above normal SST is reflective of a negative SOI. This comes into play especially pre-1950 for analogue research.


 

North Atlantic/Arctic Oscillation - NAO/AO 

Most winters; the phase of the NAO/AO is one of the most important ingredients to the type of winter to be-had over the central and eastern part of the country; and even parts of the mountainous areas of the west at times. This is one of the most elusive oscillations to predict for more than a week or two out.

SNOW-COVER 

One of the newer studies uses October snow-cover over Siberia/Eurasia to aid in projecting out the main phase and likely corresponding temperature pattern for the winter. In my analogues; I've included this past October's coverage (and looking at the rate of coverage) that has been researched since 1998. In the analogues; you will notice minus signs and a plus sign for this October. Simply put; this October had the most snow-cover over that region for all the analogue years. The analogue years since 1998 are less than this year /-/ and this October is /+/ for the greatest relative to those analogue years. As a matter of fact; this past October 2017 had one of the snowiest overages by the end of October relative to any year since 1998 with only a few non-analogue years that equaled it. This study suggests a more -NAO/-AO likely to prevail this winter and thus; colder temperatures (see map below). The research and up to date discussions can be found here on Dr. Jonah Cohen's pages.

Mr. Cohen has a nice update here every week on current and expected trends.


From his discussion 11/20/17...

"October Eurasian snow cover extent was above normal, Arctic sea ice extent is well below normal and will continue to be below normal for the entire winter.  Also, strong blocking was observed this fall across the high latitudes.  All three factors favor colder temperatures across at least parts of the Northern Hemisphere (NH) mid-latitude continents during the winter months".

  Snow-cover as of Nov 20th 2017

 


Pacific Decadal Oscillation /PDO/ and associated subset EPO


The previous warm phase Pacific Decadal Oscillation recently switched to a cool phase this year. A cool phase of the PDO is represented on the right of the following example and compare it to the current state.

 





                             Warm Phase of the PDO                    Cool Phase of the PDO






The recently evolving cool phase of the PDO and weak La Nina are displayed well in this recent Global SST scan on November 16th, 2017. 





Generally warm phases coincide with El Ninos or Neutral states and rarely La Nina states while cool phases coincide with La Ninas, as in the present state. Studies propose that when the PDO and ENSO are out of phase; which is a somewhat rare event, that they may cancel out their known effects. This isn't expected to happen during the upcoming winter.

"When SSTs are anomalously cool in the interior North Pacific and warm along the Pacific Coast, and when sea level pressures are below average over the North Pacific, the PDO has a positive value. When the climate anomaly patterns are reversed, with warm SST anomalies in the interior and cool SST anomalies along the North American coast, or above average sea level pressures over the North Pacific, the PDO has a negative value" (Courtesy of Mantua, 1999).


Recent PDO values 



YYYYMO VALUE
201612  0.55
201701 0.10
201702 0.04
201703 0.13
201704 0.52
201705 0.29
201706 0.18 
201707 -0.54 *
201708 -0.64
201709 -0.26
201710 -0.60















*The notable change from positive to negative values are shown

"The Pacific Decadal Oscillation (PDO) is a pattern of Pacific climate variability similar to ENSO in character, but which varies over a much longer time scale. The PDO can remain in the same phase for up to 20 to 30 years, while ENSO cycles typically only last 6 to 18 months. The PDO, like ENSO, consists of a warm and cool phase which alters upper level atmospheric winds. Shifts in the PDO phase can have significant implications for global climate, affecting Pacific and Atlantic hurricane activity, droughts and flooding around the Pacific basin, the productivity of marine ecosystems, and global land temperature patterns. Experts also believe the PDO can intensify or diminish the impacts of ENSO according to its phase. If both ENSO and the PDO are in the same phase, it is believed that El Niño/La Nina impacts may be magnified. Conversely, if ENSO and the PDO are out of phase, it has been proposed that they may offset one another, preventing "true" ENSO impacts from occurring". 


http://jisao.washington.edu/pdo
http://www.john-daly.com/theodor/pdotrend.htm




Last winter, the ENSO (La Nina) and PDO (warm phase) were out of phase and the winter was indeed notably warmer than what is generally seen in a La Nina winter. This was mentioned in last Winter's Outlook and one of the reasons noted that may interfere with the normal LA Nina winter jet and temperature pattern.


SOLAR CYCLE /SC/


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.  Numerous recent studies for example, do in fact make the connection to our climate and solar activity including wintertime effects. One of the studies stated the following:

 


"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 continent.
 Sirocko et al. (2012) recently reached the same con-
 clusion after analyzing 140 yr in 20CR, although their results
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".



Comparing solar cycles of the past analogue winters to the present as a possible influence only and not a major contributor. While the solar cycle was in various modes, the tendency is for these La Nina's to Neutral winters to occur during the mid to lower part of the cycle or during an overall, weaker cycle (like the ones we have entered below on the Sunspot chart - only three winter's at opposite ends of the solar sunspot spectrum were noted in our La Nina analogues.

Recent Sunspot chart since the new millennium





Longer Term Solar Sunspot Activity since 1849 (includes the Winter Analogues)





 THE QBO INFLUENCE



The QBO, or Quasi-Biennial Oscillation, is an oscillation in the wind direction in the stratosphere within about 15 degrees of the equator. Over a roughly two-year period, winds tend to oscillate between westward and eastward, with the switch between west and east winds starting high in the stratosphere and then shifting lower in altitude with time. The QBO is the result of waves propagating vertically in the atmosphere that then interact with the mean flow to slowly change wind speeds and direction. These changes influence the overall global circulation patterns, which in turn influence winter weather patterns across North America. 



The amplitude of the easterly phase is about twice as strong as that of the westerly phase. At the top of the vertical QBO domain, easterlies dominate, while at the bottom, westerlies are more likely to be found. At the 30mb level, with regards to monthly mean zonal winds, the strongest recorded easterly was 29.55 m/s in November 2005, while the strongest recorded westerly was only 15.62 m/s in June 1995 (Wikipedia).

If you notice on my analogues; I included the QBO's for each available winter and compared it to the upcoming winter's QBO phase and trend. The present and expected QBO this winter is for an easterly QBO (recently switching from west since the summer shown below as a negative wind speed) and also increasing in amplitude. The set of maps below show the differing influences of the QBO dependent on phase and trend.The QBO is presently in the negative and trending more negative phase (first map).




2017:     14.92   14.78   14.35   13.88    8.01   -3.18  -10.48  -14.42  -15.28  -16.79
  

 
QBO and WinterTemperatures Trends



WINTER 2017-18 ANALOGUES - SOUTHEAST MICHIGAN


         
    

                        CLICK ON TO ENLARGE


 Some additional category explanations in the analogue chart from left to right

AO/SC

AO - The predominant phase of the Arctic Oscillation during that winter. AO- (negative), AOn   
         (neutral) or AO+ (positive).
SC -  position of the solar cycle during that winter. Breaking it down (see solar cycle chart):   
          SC-- (opposite high cycle compared to the present, least similar) SC+/- (sunspots 
          waning but not near minimum or 2017 low level. Finally, S++ where solar sunspot cycle is  
          at or very close to the low cycle of 2017 and/or is at the same decline with 2017...the   
          best comparison and likeness.
          
QBO - W=West wind prevailed that winter or E=East wind prevailed. Trends: -/- (weak and    
            weakening trend), -/+ (weak but strengthening), s (steady trend, no change) +       
            moderate and strengthening +/- strong but weakening. Note that the trend now in the fall  
           of 2017 is E/+, a moderate east wind and still strengthening. This fits with all the winter's
            that contained a easterly QBO. Those winters were the Winter of 1917-18 (also  
            increasing)1950-51 (weak and weakening further), 1984-85 (strong but weakening), 
           2000-01  (moderate  easterly and steady) and finally 2011-12 (weak but increasing).  

Sib snow - Siberian snow cover in October and rate of change. All previous analogues winters
                  had less snow cover than this past October's. There have been a few winters not in
                  the analogue list that had roughly equal to and one of two that had more snow cover
                  but a clear majority had less snow cover.

WINTER ANALOGUE SUMMARY 


Temperatures 

One of the first things one notices about this winter's analogues is the wide-ranging temperatures and snowfalls. That is clearly NOT surprising; one look at the dominant atmospheric players for the winter, the subsequent jet streams and storm tracks explains exactly why the variable analogue results, in spades. This winter will not be a clear-cut La Nina influenced; mainly because of the influential strong Pacific jet tempering results at times. This shows up mainly in the variable jet stream/storm tracks, temperature patterns and resulting snowfall amounts. As an example; though on average Decembers averaged below normal, there were still a notable amount above /Detroit; 4 out of 14/ all in the later years since the 1970s. At the same time; if the Decembers were mild, then the Januarys were generally cold or below normal. Looking across the board at the three cities, there were a predominance of normal to below normal winters (also my forecast) with a few above normal. Generally; these winters were early to middle loaded with the preponderance of storms roughly from mid December into mid February with later winter, average to below. However; colder weather tended to hold on into at least early spring...not surprising in these parts. By the way; severe weather buffs should note that the spring looks to be busier than the past several years.

 

Precipitation


Total precipitation and snowfall also widely ranged from below to above. However; a definite trend was seen in normal to above precipitation (matching well with all guidance, La Nina winters on average and recent trends) while a dry winter was least likely. There again though, there were enough drier winters that made a showing not to eliminate that possibility. With the storm tracks created this winter (see below); the risk of mixed precipitation is higher.  In other words: a normal to below normal temperature winter with below normal rain and snow is not out of the question reflecting back in previous analogue years...and it's been a while since we've had a "cold but relatively dry winter". 

 

Snowfall

The snowfall category by itself is quite interesting with a wide amount of snow totals and where those snow amounts fell.  First off; it was close to an even split for below, normal or above normal snowfalls across the Southeast half of our concerned region. This area extends from the Flint to Port Huron area; south to the Ohio border. There were significant below normal snows ranging in the 20s (inches) across Detroit and 20s and 30s into Flint, constituting a good third of the sample. On the higher side of normal; there were just as many above normal snowfalls into the 50s and 60s around the Detroit region and 50s to even a few in the 70s across the Flint region. I'm sure the reader here can see why snowfall for a season can be such a tough call...and where.

 

The only region where snowfall truly showed a trend (above) was across the northern third of Southeast Michigan; the Saginaw Valley and Thumb region. This are had 7 above normal snow winters and 4 normal - there were no below normal. Above snowfalls ranged from around 50" into the 70s. In fact; the average snowfall for the analogue winters at Saginaw was a foot above normal. Where as Detroit and Flint settled in the normal range.

 

Below are the maps from the analogue winters for Temperature departures, 500MB Low placement and subsequent likely storm track placement (Dec-Mar). Note the time period encompasses March also (still a winter month in my book)

 

TEMPERATURES 

 

 500 MB LOW PLACEMENT




STORM TRACK PLACEMENT 


 

 Latest Model Output for the Winter of 2017-18 with a few surprising models.

CFS /American/

TEMP
 PCPN

ECMWF /EUROPEAN/

TEMP


PCPN

UKMET /BRITISH/

TEMP
PCPN

METEO FRANCE 

TEMP
PCPN


Look for more write-ups through the winter involving notable weather events, major storms and comparing the Winter Outlook trends and actual weather trends!

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

 

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