Hello. It’s the Snowy Hibbo back for another year of sub-Seasonal forecasting for the European Alps. This year, I will be producing model based outlooks, like last year. I will also be adding climate driver based outlooks to the outlooks, to give more meaning to the models, and the signals that they produce. Anyway today I will be reviewing all the information for the winter season forecast. So let’s get into it!
The CPC(Climate Prediction Center of the American NOAA) has finally declared a La Niña. As explained in the last couple of blog updates, we are going for a Weak La Niña.
Above is a ENSO forecast, from ECMWF. It shows a weak-moderate La Niña forecast for the winter period. ENSO is so far away from Europe, it doesn’t have a large effect on the continent. However it does have an effect on the AO (Arctic Oscillation) and NAO(North Atlantic Oscillation). La Niña is correlated with a +AO, which means a warmer Alps region. The NAO and ENSO relationship seems rather confusing, from the various papers I have read over the years. But based upon the AO and NAO relationship, a La Niña is likely to correlate with a +NAO.
We are currently in a negative or easterly phase of the QBO. The QBO is basically the measurement of the stratospheric equatorial jetstream at 30mb. A Easterly phase of the QBO matters, as it correlates with more SSWs(Sudden Stratospheric Warmings), which in turn creates a -AO. This means a colder Alps region.
Snow and Ice
There are two major regions of snow cover in the Northern Hemisphere, Siberia and North America. The Siberian Snow Cover is currently larger than normal. This correlates with a weaker polar vortex, more SSWs and a -AO. The North American Snow Cover, which is at it’s largest in a decade, has a much weaker correlation with the AO. However, it may equal a colder Arctic, which means a +AO. But this is weak and not fully proven.
Secondly, the ice in the Arctic also has a link with the AO. The Barents-Karas Sea Ice has the highest correlation with the AO. It is currently lower than average, which equals a -AO and a colder winter for the Alps.
You can see from today’s snow & ice chart, that there is lots of Siberian snow and not a lot of ice in the Barents-Karas Sea region.
We are currently are going into a period of less activity from the sun, or a solar minimum. You can see this from the following sunspots chart.
This means there is an increased chance of a -AO and -NAO.
The AAM or Atmospheric Angular Momentum, which is basically a measurement of the relationship between the winds around the world and the earth’s rotation, has been in a negative phase for several months now. This trend may continue into winter. The GEFS 16 day forecast shows that the GWO is going into Phases 1 & 2, sending the AAM into it’s negative phase. This is correlated with a -AO.
Recent history of the AAM and GWO.
Current GFS forecast for AAM.
Now I am going to have a look at the seasonal model output.
Firstly the output from the ECMWF model(known as the best weather model in the world)….
December 500mb anomaly.
January 500mb anomaly.
February 500mb anomaly. December and January show the Alps, particularly the Western Alps under a troughing signal. February shows a ridging signal over e Alps.
Next the CFS….
The CFS model shows a ridging pattern over the Alps during winter.
The CanSIPS model also shows a similar setup to CFS, with a ridge over the Alps.
So the NMME models show a ridging pattern for winter, but EC shows a more troughing pattern early-mid winter. The climate drivers are mostly going for a -AO setup, which means a colder and more snowier Alps region. The exception to this is the La Niña, that goes for a more +AO setup… My punt is on a slightly above average snow season for the European Alps. This isn’t taking into account MJO, and other shorter term drivers… Others may think differently, but it should be an interesting winter.
Thanks so much for reading.
Seasonal outlooks tend to have bias and errors, due to the fact that these forecasts are so far out. So don’t use these outlooks to make important decisions. These outlooks is meant to be interesting information, that can help to see what the season might be like.
This took a lot of work, so I appreciate your support. Starting in December, my long range outlooks for the European Alps will start! They will be produced every 2-3 weeks, looking out into the range of 10-30 days out. This season, I will explore climate Drivers as well, including the AAM, MJO and others. Stay tuned.
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