Medium to Longer Term Thoughts & Analysis – 24th Feb 12

24 Feb

Well it goes without question that February 2012 will go down as a month of extremes and producing a large variety of conditions.  The first half of the month, or so, was clearly dominated by cold conditions and temperatures dropping to between -10C and -15C quite frequently.  However, yesterday’s maximum temperature of 18.7C shows that the UK can produce some significant extremes of conditions within a matter of weeks…so what does the remainder of February and March have in store…

Well I want to start with the following image, which I produced a day or so ago which is relevant to next week;

The primary reason the  UK has been bathed in very mild air from the south-west in recent days is due to the above synoptic situation within the mid and upper levels of the atmosphere and of which, is forecast to repeat itself next week.  In the above image I have highlighted an area of high pressure not only at surface levels but also within the upper atmosphere at the 300mb level, the height of the jet stream.  Now this area of high pressure situated just to the south of the UK is the primary reason for allowing such mild and moist air to advect into the UK from the south-west.  The strong jet stream forecast on the above image for next week helps to reinforce the high pressure and aid in the advection of some very mild air from the south-west.  Last nights 120hr FAX chart ties in nicely with the above image;

Note how pressure is higher to the south and south-west of the UK, whilst low pressure is dominant to the north-west.  Also note how the surface low pressures and frontal zones align nicely to where the jet stream is forecast to be early next week.  A significant and extensive warm sector is forecast across the UK early next week in particular with once again the air mass originating from the Azores.  So in summary next week looks to be another mild or very mild week with temperatures well above the seasonal average.  With high pressure dominant just to the south of the UK in some shape or form, than many southern areas of the UK are likely to have a predominantly dry week whilst Scotland and Ireland are at greatest risk of more unsettled conditions at times.

So what does the end of February and more particularly the first half of March have in store.  Well there has, and continues to be, good model agreement and consistency for high pressure to remain a persistent feature of the weather to the south or perhaps south-east of the UK, whilst low pressure dominates to the north-west.  This can be seen on the below image as well which highlights the 500mb means in terms of where pressure is likely to be higher (orange/reds) and where pressure is likely to be lower (blues).

 

Clearly the important features here is the ridge just to the east of the UK and the associated orange colours and also the deep trough to the east of Canada and the blue colours.  What this pattern is suggesting is that many southern and eastern areas of the UK are likely to remain predominantly dry throughout the next 7 to 10 days at least and I believe this pattern will continue out to 14 days as well.  In contrast more northern and western areas of the UK are at risk of more unsettled conditions at times, but what does seem highly likely is that temperatures across the UK will remain generally above average throughout the next 7 to 14 days at least.

The ECM ENS and GFS ENS mean at 240hr highlight the expected pattern well also;

The GFS ENS mean does have pressure higher across a large portion of the UK, but the broader pattern is similar with high pressure to the south or south-east of the UK and lower pressure to the north-west and the ECM ENS chart (top image) in particular is a good representation of what I expect the weather will be generally through the rest of February and into early March.

The latest longer term data, including the latest EC 32 day is signalling a similar pressure pattern as we progress through March with higher pressure dominant to the south of the UK and low pressure dominant to the north or northwest.  As a result there is the potential for further mild or very mild conditions through the first half of March and perhaps with further predominantly dry conditions with below average rainfall across England and Wales.  Things may well change beyond mid-March to a more unsettled and cooler regime but this is a long way off as yet.

So, expect further mild or very mild conditions in the weeks ahead and also predominantly dry conditions away from northern and western areas of the UK.  The end of winter is certainly going out on a whimper and with some confidence I can say that there is little risk of any cold and wintry weather returning to the UK within the next 10 to 14 days at least.

Have a good weekend all!

Regards,

M.

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