January and February CETs Relating to December and a volcano theory

[Timmytour]

The December just gone has been what I would consider to be relatively mild (defined hereon as being with a CET of 5C or above).

Many will be hoping for a cold (defined as a CET of 3.5C or below for winter months) January and February.

(NB. Definitions are not official....used for the purpose of this thread only)

However, CET stats would indicate it will be an uphill struggle! 

Following the mild Decembers since 1987, only on one occasion has the ensuing January been mild (2001, 3.2C) and only on one occasion has the ensuing February been cold (1994, 3.2C).

In that same time-frame there have now been 19 out of 33 such Decembers, including the one just gone

Remarkably however December 1980 to 1989 saw 7 such Decembers, a return of 70% compared to just over 50% for the thirty Decembers since. More remarkably perhaps, four of those Januarys were cold (1980, 1985, 1986,1987, respectively 2.3C, 0.8C, 3.5C and 0.8C) and four of those  February were cold (1981, 1984, 1985, 1986, respectively 3.0C, 3.3C, 2.1C and -1.1C) .

It's not something that happened much at all during the last century, but when it did it seemed to occur in groupings, with another cluster occurring in the mid fifties.

So why is this?  Of course global warming is a factor though its interesting to note that if you go back to the Decembers between 1910 to 1919, 70% of them were warm and in only one of the years were the ensuing Januarys and Februarys cold...(both 1919...2.9C and 1.9C respectively).

Of course, there was an epidemic taking place in December 1918, so perhaps history might repeat itself in the midst of another pandemic!

But I wonder if a bigger factor is the relative lack of significant volcanic action?  During the 20th century there were relatively frequent eruptions of a Volcanic Explosivity Index (VEI) of 5 or above  - 13 to be precise.   But since the eruptions of Mount St Helens (1980) and  El Chichon (1982) - maybe behind the cluster of warm Decembers cold Jans/Febs mentioned earlier? -   and Pinatubo and Hudson in 1991, there has only be one such eruption in 29 years...the Chilean  Puyehue-Cordón Caulle in 2011  (after which we did experience some cold months!).

Sooner or later we will get a significant volcanic eruption.  Maybe next time it won't be as isolated as the Chilean eruption which looks like an outlier in terms of the number of years both before and after it that have passed without a fellow eruption of a similar strength! I feel the time that the warming climate reduces our cold and snow chances to virtually nil are still some distance away.  This decade  I predict we will experience at least two volcanic eruptions of VEI 5 or above.  And thereafter those models showing Narnia in ten days time will start becoming nailed on!   

Just maybe not this winter!.... :)

 

 

 

 

 

  

 

 

[Timmytour]

Revisiting this I can see a typo early on where I've inadvertently used the word "mild" instead of "cold". Corrected below...

Quote

Following the mild Decembers since 1987, only on one occasion has the ensuing January been cold (2001, 3.2C) and only on one occasion has the ensuing February been cold (1994, 3.2C).

 

Usually when I stick a thread like this up, it's busted the same month!  So I thought noting that we'd just had the 19th mild December of the last 33 years, but only one of the previous 18 had been followed by a cold January, was sure to bring about a cold January!

Of course that is still possible,, but this time last week with the way the models were shaping up it looked more than probable!  With the way they are shaping up now, I'm more inclined to believe that one of eighteen is on the cusp of becoming one out of nineteen! 

 

Edited January 17, 2021 by Timmytour

[Timmytour]

So we get only our second January with a CET falling below 3.5C  (3.1), that has followed the 19 "warm" Decembers we have had since 1987 (defined as CET of 5C or above).

The way the models are shaping up we could even manage to get the second February of the same type to follow such Decembers, and the first when both following months have been cold.

It would have looked a lot better if I'd put this post up after the 18th warm December!!!!

[North-Easterly Blast]

It is very true that the Januarys and Februarys of the 1990s and 2000s were mostly mild, whereas overall for these two decades December was often not far from average.  In actual fact some of the colder Decembers in this period were also followed by mild Januarys or Februarys or both (Dec 1992 3.6, Jan 1993 5.9 (mild), Feb 1993 4.6), (Dec 1996 2.9, Feb 1997 6.7 (very mild), Dec 2001 3.6, then a very mild rest of the winter; then we had the exceptionally cold December 2010 at -0.7, then a very mild Feb 2011 (6.4).  It was certainly true that the 1980s featured a number of relatively mild Decembers followed by much colder Januarys or Februarys or both, a pattern which has become almost extinct since then.  The 1950s also saw a number of milder Decembers followed by a colder rest of the winter.

[Timmytour]

Maybe winters come in patterns that take place over a numbers of years and we are returning to a previous one?

[Timmytour]

Well I honestly thought after I put up this thread that I had put the curse on the theory that I was laying out. After 18 mild Decembers since 1987 (ie a CET => 5C)  had only produced one cold January ( =< 3.5C ) and one cold February, which occurred in separate years,  I felt confident that our chances of seeing a cold January and February following on from the 19th such mild December was slim.

Lo and behold January came in cold, followed by what looked like it was going to be a freezing cold February.  But of course the turnaround in February has been amazing!  To think it now could end up being the warmest month of the winter is little short of astonishing.....who would have been brave enough to forecast that as we went into the first weekend of the month???!!! 

So despite picking a year to outline something that hadn't happened for 19 years, only to see it then happen, I remain confident that, in our current climatic pattern, the theory that a mild December will be followed by two winter months that are not particularly cold is one that still holds water.  What was a 5.5% frequency over the last 33 years has now  just under 8% in the last 34 years, but  it certainly remains low enough for me to lean towards erring on the mild side of my CET predictions for  the first two months of the year, if the preceding December has come in mild. 

Unless we get an explosive volcanic eruption in the meantime!