WeatherHistorian-SeMI: Nov 19, 2019

Autumn across the Great Lakes had an extended summer feel weather-wise with most areas experiencing above to well above normal temperatures into mid October. But like many other falls, October's weather did an about-face late in the month with sharply colder weather invading the premises. So much so, that temperatures that were averaging several degrees above normal through much of October; just managed to squeak out a degree or so above normal by month's close.

November's opening weather continued the chill and took on an early winter-like appeal with readings generally in the 30s and 20s; or more like Christmas in the offing rather than Thanksgiving. Then; Mother Nature has the nerve to throw us a big curve snowball on Veterans Day with a big snowstorm on top of it all - and it's still a 1/2 a month before Climate Winter even begins! With record snows and record cold temperatures has Mom Nature already shown her hand for the entire winter - or just faked us out? Well that's the past and current what about the future?

Winter Outlook for the Winter of 2019-20

Local Research and Hemispheric Data suggests:

Temperatures - Normal to Below

As with the majority of winters especially ENSO Neutral; look for temperatures during the 2019-2020 winter to be quite changeable under a fluctuating jet stream. The ongoing pattern recently experienced this fall was also telegraphed for the Winter for 2018-19. In fact; the similar cold and snowy weather experienced last November has even more aggressively repeated this November.

In my research; I’ve found Neutral ENSO patterns in the Pacific generally have little effect on the weather patterns in the Great lakes and Southeast Lower Michigan. This winter's analogues are strongly suggesting normal to below normal temperatures this winter with the clear majority pointing in that direction (see Analogues, below).

I expect this winter to be more typical of the "old fashion winters" seen in these parts with snow and cold breaking for a typical thaw before resuming and playing out the rest of the winter into early spring. And; the thaw wasn't always in January; a significant amount of December analogues /7/ contained above normal temperatures (some significantly - and that will be more understood when discussing the storm tracks toward the end).

In the final analysis; I look for Southeast Lower Michigan winter temperatures to average between 1.0F to -3.0F of normal. While last year's winter averaged in the warmer part of that range; this years winter should average colder.

Precipitation (Rain & Snow Water Equivalent) - Above

Unlike last winter; this year’s set of analogues and storm tracks suggest a wetter and snowier winter across Southeast Lower Michigan. The majority of patterns that evolved in the analogue winters were both front and back-end loaded winters with a notable break or two in between (the preferred).

In the end; most areas should see average to above average snowfall; especially areas just north of the main storm track. When and where are discussed in the Analogue section and storm tracks. All snow seasons in the analogues do in fact range from below normal- to normal - to above and thus; it's more of the dominant trend in the analogues that will represent this winter's snowfall. With the higher amounts of precipitation; mixed precipitation will be included.

Note: Below normal precipitation; more than /- 1.0"/ of the winter average water equivalent. Normal precipitation; +/- 1.0" of the winter average water equivalent and above normal precipitation; better than /+1.0"/ of water equivalent above the average.

Below normal snow; more than / 5.0"/ below the season snow average. Normal snowfall; +/- 5.0" of the winter average and above normal snowfall; better than /+5.0"/ of the normal snowfall.

Hemispheric Discussion - ENSO

Researching through several periods of oscillating weak El La Nina-Neutral-weak El Nino left a very wide range of winter weather solutions for this winter. This is complicated by the questionable but narrow current Sea Surface Temperatures /SST/ and computer projections for the winter. The current ENSO 3.4 area continues to vary from a weak La Nina - Neutral - weak El Nino. The area of ENSO 3.4 is seen on the diagram below.

Note the recent Pacific SST's and variability along the equator...

Computer projections of SST's for the next several three month periods

Note how SST's hover around Neutral throughout the winter (encased in the yellow square).

Though generally a Neutral ENSO is projected and accepted into the winter; the more "fine-tuned" weak El Nino to Neutral shown here was preferred in the analogues.

Running 3-Month Mean ONI values

Added to the annotated strong and weak El Nino's and La Nina's on the chart, are the Neutral winters included in this year's set of analogues winters from 1950 on.

Southern Oscillation Index /SOI/

The Southern Oscillation Index /SOI/ below shows the La Nina's and El Nino's from 1880 to 2016. Remember; a negative SOI is indicative of a positive SST and ONI - or El Nino. This scaling comes into play especially pre-1950 for analogue research.

1880-2016

2000-2018

Very little additional time will be spent on the ENSO this Winter Outlook since it is expected to have the least, if any effect on our winter weather. It was used as a starting point for the analogues only and for that; it served its purpose. On to the more pertinent winter effects....

North Atlantic Oscillation/Arctic Oscillation - NAO/AO

This should be one of the important, if not the most important meteorological influences for this winter. In the last few years, it's had an on and off again effect on our weather, working with Stratospheric warming and the EPO (more later). Refreshing our memory on this little number shows WHY the major influence with our weather.

Generally when the NAO/AO index is in the positive phase; more zonal winds dominate as the polar vortex lifts up toward or over it's home, the North Pole region. However; when in a negative phase; the cold vortex or wind flow is more meridional and thus; cold Polar or Arctic air is readily pushed south from the Pole; down into the eastern half of the U.S. (among other Northern Hemisphere areas). Many times ridges of higher pressure develops in conjunction on the North American west coast and/or into Greenland.

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. However, this is also one of the most elusive oscillations to predict for more than a week or two. One of the most impressive seen this year is the NAO/AO pattern has been primarily in a negative phase since the summer. While the NAO has been more negative; the AO has held in a fairly tight range around neutral.

Note the drop "off the cliff" the AO forecast projected mid month. This jived well with the Arctic cold that has been over the eastern half of the country mid month.

Pacific Decadal Oscillation /PDO/ and associated subset EPO

The warm phase of the Pacific Decadal Oscillation is represented on the left side of the following example and the cold phase on the right.

Warm Phase of the PDO Cool Phase of the PDO

Latest SST's (below) seemed to have evolved into a cool phase recently. Note the above or well above normal SST's around Alaska and south over the mid Pacific. Relatively cooler anomalies have formed further inland along the West Coast.

The warmer SST's further off the West Coast south of Alaska; generally encourages high pressure ridging which may help at times, deliver Polar and Arctic air from the northern Canadian regions into the Lakes. This was especially true during the hard, snowy winter of 2013-14 where the NAO was not always negative.

A negative Eastern Pacific Oscillation /-EPO/ is displayed below along with its cold affects it can have downwind on North America. The Winter of 2013-14 was one cold, bitter winter along with exceptionally heavy amounts of snow across Southeast Lower Michigan. The brutal cold delivered to the region on many occasions was either the cause or was aided by a strong -EPO helping to build a strong high pressure ridge on the West Coast which in turn; slammed our region with a deep low pressure trough filled with cross polar air from Siberia and North Pole.

Likewise; a positive Eastern Pacific Oscillation /+EPO/ pattern is displayed below along with its mild affects it can have downwind on North America.

A three-way indices pattern /NAO, AO and EPO/ evolving together can have interesting weather for the eastern half of the country as stated below;

Pacific/North American /PNA/ Pattern

The above oscillations help create the Pacific/North American /PNA/ pattern. A negative PNA generally reflects a trough over the western portion of the US with ridging and warmer weather in the East. A positive PNA is reflected by a broadening trough and influx of colder air into the center and subsequently, the eastern portion of the US.

-PNA

+PNA

Solar Cycle Relevance

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 particularly 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 Oldenborgh et al., 2013). We found a weak but significant change in the mean late winter circulation over Europe, which results in detectable impacts on the near-surface climate. Figure 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 conclusion after analyzing 140 yr in 20CR, although their results bare 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 is a possible influence only and not a major contributor. While the solar cycle was in various modes, the tendency is for Neutral winters to occur during the mid to lower part of the cycle or during an overall, weaker cycle. This season's El Nino analogues resulted in about three quarters in the lower part of the sunspot cycle.

Longer Term Solar Sunspot Activity since 1750 (includes this season's Winter Analogues)

This year's solar sunspot cycle; at the bottom of the 24th cycle.

Siberia/Eurasia Snow Cover

One of the newer studies by Dr. Jonah Cohen uses October snow-cover over Siberia/Eurasia to aid in projecting out the main phase of the NAO and likely corresponding temperature pattern for the winter. Recently, early November is also considered in the comparisons.

The snow accumulation study over Siberia and northern North America over Canada. Both of these have been above normal, especially late October into November. The study is mainly concerned with October's snowfall. The best data goes back into the 1990s which doesn't help our analogues much since (see analogue Siberia snowfall column) only one exists in that time period but it's certainly notable to look at for recent winters. These charts go back to the Winter 2005-06 and also then, would encompass some notable winters locally.

The red line represents this fall on both charts thru 11/17/19. While snow over Eurasia is now just about average; the snowfall over North America had surged to near record amount (for this time period since 2005-06) recently with the expansive snowcover last week before a pull back the last few days.

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 and 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 a lighter westerly wind to gradually shift to a light easterly QBO. The set of maps below show the differing influences of the QBO dependent on phase and trend. The QBO is presently in the weakening westerly and trending into a weak easterly (closest being maps in sequence; C then A).

QBO and WinterTemperatures Trends

WINTER 2019-20 ANALOGUES

If the month of November was all that the analogues had to project, we'd be looking great with over half colder than average and 12 out of 15 snowier than normal; some substantially above normal - like this year. The actual Winter Outlook via analogues into early spring is generally quite diverse but with a trend suggested on the Temperature and Precipitation stated at the beginning of this forecast. Also with the variance in temperatures; mixed precipitation will be quite likely.

Decembers
-There is also a strong conflict in December temperature results with 7 above normal and 7 below
normal and only 1 normal. Not surprising; the sum and average of all; leads to a normal or
average temperature for December. Therefore; the analogues concluded anything goes for
December, temperature-wise and...
-Snowfalls too, were quite variable and averaged on normal but with quite a few below normal and
almost as many above. Again no preference.

Januarys
-While temperature patterns showed colder weather dominated with 8 out of 15 colder than average; still a notable 5 Januarys were warmer and just a few normal. I suspect several of the warmer Januarys contained thaws. Therefore; it was concluded a notable thaw or two seem more plausible and likely - like many winters .
-Snowfalls in January were quite variable -like the winters on the whole- but the sample averaged below normal by a couple of inches, giving a bit more credence to a lighter January and thaw.

Februarys
The coldest of the winter weather is projected during the second half - January into February or February-March. One of the more definitive patterns seen is the evolution of this colder weather with time with February having the best chance of below normal temperatures and...some hefty snowfalls and extremely light ones averaging out to normal.

March/April
-Snowfalls picked up late in the season; averaging above in April.

WINTER 2019-20 ANALOGUES

(click to enlarge)

Some additional analogue conclusions and category explanations in the analogue chart

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 2019 low level. Finally, S++ where solar sunspot cycle is at or very close to the low cycle of 2019-20 and/or is at the same decline with 2019...the best comparison and likeness. There are several this time at 8, one of the highest likes - meaning the sunspot phase of the sun is very close to 8 other analogues out of the 15.

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 2019 is W-, a light west wind and weakening and subsequently, should become light east /E-/. This fits with all the analogue winter's that contained a light westerly to easterly QBO. Those winters were the Winter of 1898-99, 1926-27 and to a lesser extent 1946-47.

Sib snow - Siberian snow cover in October and rate of change. Only one previous analogue winter had below compared to this past October's/early November since the data only goes back to the late 1990s. Notations are this fall compared to analogue fall: WA=Way above, A= above, B=below, % = equal to.

Letter n /next to the analogue winter years at Detroit/ - A cold November preceded these winters in all of Southeast Lower Michigan - like this present November 2019. Interesting, out of the 15 analogues; more than half /8/ were also preceded by a cold November - a solid number. In, the other winter years; the temperatures in November were normal or above normal temperature.

Snowy November was almost a given in the analogues!

-Another very notable category was included; the prevalence of snowy Novembers at the largest analogue sample, Detroit - 15 analogues. The above normal snowfalls are highlighted in yellow. The well above normal snowfalls (better than 3x the normal )were highlighted in green. An outstanding 12 out of 15 Novembers contained above normal snow and out of those 12; half or 6 contained well above normal snowfall, like this November. Clearly this is a winner this season already.

-Snowy November didn't always mean a snowy winter

Extrapolating the well above normal snowfalls in November did not always translate to a snowy (above normal snow) for the winter. Out of the 6 well above normal snowy Novembers; half continued to be a snowy winter with the other half /3/ having one normal and two below normal.

Comparing the analogue year 500 anomalies to the ENSO Neutral years shows some interesting comparisons.

Generally; the negative anomalies are further northwest in the analogues as opposed to the general neutral years. In addition; blocking in the analogues is a bit further south of Greenland than over Greenland.

Here are the composite maps of the specific analogue chosen and general neutral years. Note the scales are slightly different (analogue 1/2 degree and -5/+5 departure as opposed to Neutral years 1/2 degree and -3/+3 departure).

Note the coldest of the weather is centered further west in the analogue temperatures compared to general neutral years but overall the patterns are similar.

Analogue Temperature Projections

General ENSO Neutral Years Temperature Projection

In the composite precipitation maps; the analogue years show the core of the heavier snow and rainfall further north and west toward the Upper Ohio Valley and occasionally Lower Lakes as opposed to the general neutral years further south. This would imply more Ohio Valley Lows to the East Coast rather than Tennessee Valley systems to the East Coast. Both would be indicative of some Gulf/Texas Lows.

Analogue Precipitation Projection

General ENSO Neutral Years Precipitation Projection

Mean 500 MB Flow from Analogue Years

Trough situated further west over eastern Canada & Lakes

Mean 700 MB Flow forecast from computer CFSv2

Trough projected further east over North Atlantic

Subsequent Storm Tracks

Storm tracks should focus from western Canada southeast into the Upper Great Lakes to Southern Plains and Gulf States. Besides the typical Polar/Arctic storm track across the northern Lakes; two other storm tracks across the western Lakes and the eastern Lower Lakes will determine our rain or snow. These originate over the southern plains/Texas/Arkansas area and potential lies for classic Gulf lows deepening on sharp trough orientation up the Ohio Valley or East Coast.