Medium & Longer Term Outlook (Mid-Late Feb 12)

10 Feb

It goes without question that the weather over the last 2 weeks or more across the UK have been markedly different from earlier in the winter.  Without diverging away from this main topic, the primary reason being has been changes within the stratosphere which were acknowledged at the end of December and into early January.  Gone has the prolonged +NAO pattern with low-after-low steaming into the UK and clearly we have been experiencing a far colder and more blocked pattern.  As an example the following chart highlights the pattern in the last week or more;

High pressure has been dominant to the north-east of the UK and we have been experiencing a persistent feed of cold air from the near continent which clearly has been combining with low pressure and frontal systems from the west to bring a far more wintry spell of weather.  So what does the remainder of February have in store?…

The outlook for the remainder of February is now more changeable.  The least ECMWF 32 day forecast is signalling a far more progressive and changeable pattern from week to week through the rest of February and into early March.  This model has been excellent all winter and has picked up on patterns a good number of weeks in advance.  Unfortunately what the changeable signal does bring however is uncertainty, specifically uncertainty over the details of the synoptic evolution as each week ticks by.  What can be said however is that more unsettled conditions are predicted by the ECMWF 32 day model, but without returning to a ‘proper’ zonal Atlantic.

We can see the variation in conditions during the course of next week and into next weekend on these 2 charts which are the GFS ENS mean;

Again despite uncertainties over the details the weather is about to change.  The significant block to the east and north-east of the UK is on its way out and we now turn our attention more towards to the west and north-west during the second half of February.  Next week is likely to deliver a temporary northerly air mass during Tuesday and Wednesday but as can be seen on the first chart the block to the west isn’t stable enough to support any prolonged cold weather.  This is then likely to collapse down into the UK before a potential ‘re-load’ scenario develops by next weekend.

In fact there is model agreement for next weekend (18th-19th) to be potentially quite snowy for some given an unsettled north-westerly air mass which is forecast to be quite cold, take the 850mb temperature ensemble mean from the GFS ENS as well;

Towards the latter half of next weekend (at the moment) the 850mb temperatures are at or below -5C across a large portion of the UK and as ever this is often a reasonable indicator for wintry precipitation.  So a changeable and more mobile weather pattern is forecast to develop during next week and into the following weekend with some rain, showers and also sleet and snow in places as cold north-westerly winds develop.  This is backed up by the ECM ENS mean as well;

The signal for this changeable pattern to continue then follows into the final full week of February with again the majority of the weather coming from a westerly quadrant.  Low pressure is likely to be a feature to the north of the UK in some shape or form as high pressure persists to the west or south-west.  At the moment there is little sign for any significant height rises across Greenland and I do believe and suggest that any significant northern blocking within this area is unlikely to happen during the remainder of February, despite perhaps temporary ridges of high pressure to the west and north-west.

So in summary the middle and latter half of February is set to see a change, a change away from the continental blocked pattern to a far more changeable setup.  Some milder days are forecast, particularly compared with of late, but equally there is still a clear sign for colder weather as well from potential north-westerly or northerly winds at times which may well bring further wintry precipitation, particularly seeing that it is likely to become more unsettled with it. 

Have a good weekend all.

Regards,

M.

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