Jet Streams

[mike Meehan]

Jet Streams were first suspected during the 1920's and during the first half of the 20th century there was further anecdotal evidence to suggest their presence but it was not until the advent of high flying jet air liners that we were really able to keep tabs on them to the extent that these aircraft will routinely seek them out or avoid them depending whether they will assist or detract from their ground speed.

 

The effect of Jet Stream is now much more in the public domain where they are often referred to when giving weather forecasts and we are informed that the jet streams separate warm and cold masses of air and that they spawn areas of low pressures.

 

Depending on the position of the jet stream in relation to the UK it can mean that we are in cold air if it is to the south, in relatively warm air if it is to the north and bloody wet if it is tracking straight towards us.

 

Sometimes it appears that these jet streams can get stuck in a particular position and nothing really moves them until such time as an increasing, or decreasing solar energy at the changes of the seasons can give them a nudge. 

 

This can lead to vast differences in the winter weather in the UK - if we go to the winters of 1947 and 1963, although the jet streams were not so well observed or documented at that time, I think it is pretty safe to say that they were to the south of us leaving us in a cold air mass which generally came from northerly and easterly quadrants and that these did become stuck, giving us several weeks of snow and ice.

 

During the last winter 13/14, they were pretty well coming directly at us, giving us the wettest period in living memory, whilst at the same time just north enough to ensure we remained in predominantly mild weather. This position, we are told, is because of disturbances originating in the area of Indonesia causing the jet to whisk in a north easterly direction across the Pacific, then south easterly bringing the majority of North America into the influence of cold polar air masses, hence the dearth of brass monkeys over there. Having travelled south east the jet then reached the Atlantic where it does a left turn to travel north east again with a pretty large temperature gradient between frigid North America and the relatively warm Atlantic and 'voila', it became macs and welly boots time in the UK with brollies blown inside out.

 

There is little doubt in my mind that global warming is intensifying these events because warmer oceans and air masses hold more water vapour and energy and that this type of weather will become more of a feature in our climate.

 

But snow lovers do not despair - it occurs to me that just as we ended up with a north easterly jet last winter, we could end up with a south easterly jet travelling to the south of us and with this persisting the likes of '47 and '63 could be repeated but alas this does not appear to be the case for this current winter which is now reaching its halfway point with the jets seeming to have found their home between Scotland and Iceland.

 

Keep living in hopes, it is bound to happen in another future winter.

Edited January 12, 2015 by mike Meehan