Being Careful not to predict cold too quick

Written by on November 19, 2018 in Rest of Europe, United Kingdom & Ireland with 0 Comments

I know I keep going on about this but I feel strong about this. There has been a great deal of hype and buying into individual ‘cold model runs’ lately. Do that was caution at this early stage, especially when the models see big cold blocking patterns but with little PV disruption.

While there has been a heck of a lot of hype with regards to the coming cold, I can already see all this backing off as we approach the period. My reason for my doubts is based on a fairly strong polar vortex and to get these big cold spells including November 2016, comes with weak, displaced vortexes. We do not have that this year. Another issue is timing. Remember that when the PV does weaken, displace, collapse or whatever, there’s a lag between the cold going from stratosphere down towards the lower troposphere. This ‘cold’ is pretty much business as usual for the time of year, nothing more.

Negative AO/NAO’s do occur in November, remember the last two straight November’s were very cold, backed up by weak PV’s. This year, it’s been warm and now we’re going to normal. To get an extremely negative AO/NAO, it typically occurs mid and late winter and with a strat warming event. The November 2010 event was rare and extreme compared to normal, driven by a solar minimum. Sure we have a very low solar but not a weakened vortex so any blocking shouldn’t last particularly long or deliver extreme cold.

Note the NAO ensemble has a less deep negative compared to late last week.




So, do we have major cold for the time of year coming? I don’t see anything particularly anomalous brewing YET for the UK anyway. I will be watching the behavior of the PV as there is a chance it weakens late this month. Low solar years do increase the potential for strat warmings, -AO/NAO’s and colder winters but I believe it will be mid and late winter when we could revisit some of the conditions we experienced in 2009 and 2010.

I definitely believe some of the longer range models with strong blocking and a cold winter. The Christmas period could be interesting, especially if we see PV disruption late this month or early next.

I like the below MO forecast.

Met Office


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