There's some rain around this weekend, but it's been a notably dry March up to now, and that drier weather will return next week. The effects of the recent Stratospheric event have been delayed and we may have to wait until April for a pattern change.
March has been notably dry and sunny for much of the country, especially in most of England and Wales. A substantial area of England and Wales has already exceeded the normal amount of sunshine for the entire month, and we are only on the 22nd. Conditions have been less exceptional in Scotland and Northern Ireland, but even there, most sites have recorded above-average sunshine.
Most regions have also recorded less than 20% of the normal rainfall for March. The main exceptions are northern Scotland, which has experienced more frontal rain, and some eastern coastal parts of England, which were heavily affected by showers during the colder spell in the second week. Nonetheless, even these areas have generally been drier than normal – in an average March, 60 to 70% of the normal monthly rainfall would have occurred by this point. The very dry weather has extended as far north as the Central Lowlands of Scotland and the east of Northern Ireland.
Rainfall so far this March
The main cause has been frequent high pressure centred to the south and/or east of Britain. This positioning has been favorable for clear skies over most of England and Wales, especially eastern England, but is often associated with more cloud further north and west, while also keeping rain-bearing low-pressure systems away. A colder spell in the second week of March mainly brought sunshine and scattered showers, resulting in relatively limited rainfall totals and further sunshine.
As is often the case in dry, sunny Marches, maximum temperatures in England and Wales have generally been between 1 and 3C above the long-term normal so far, but minimum temperatures have widely been 1 to 2C below normal. This is due to temperatures often dropping quickly with clear skies and light winds. At this time of year, the increasing strength of the sun helps to raise daytime temperatures in sunny anticyclonic conditions, but the nights are still relatively long, which results in temperatures dropping overnight, and in high diurnal ranges. The highest mean temperatures relative to normal have generally been in Scotland, where more cloud and wind have tended to keep temperatures relatively mild by night, while frequent tropical maritime air masses have kept temperatures high by day.
Despite a recent disruptive stratospheric warming event, which traditionally tends to promote relatively high pressure to the north and a more southerly tracking jet stream, the generally dry theme looks set to continue for most. High pressure is expected to remain close by to the south and south-west, and will sometimes ridge across the southern half of Britain.
This weekend is set to be relatively wet, with low pressure over the country today. Persistent rain will cover a large area of Scotland and northern England, with some heavy, locally thundery showers further south.
However, this will be just a temporary interruption, with high pressure again set to build early next week.
Sunshine is likely to be more variable than earlier in the month, with some weak fronts moving across the country and bringing more cloud at times, but there will still be some sunny and dry weather in between. The north-south split also looks set to continue, with England and Wales generally seeing more sunshine relative to normal than Scotland and Northern Ireland. With predominantly westerly winds in the north, eastern Scotland will probably also be mostly dry and sunny.
After a generally dry week, low pressure again looks set to move in next weekend, but it looks probable that the emphasis will be on sunshine and scattered showers, rather than cloudy and wet weather. That will take us through to the end of March.
The recent stratospheric warming event will probably eventually result in a blocked pattern with high pressure to the north of Britain and relatively low pressure in the south-east, but it now looks probable that this will not arise until early April. The medium-range forecast models have been predicting this pattern for some time, but its onset has kept being delayed, and it currently looks unlikely to develop until after the end of March.
Current guidance from the 42-day long-range forecast model from ECMWF suggests that this pattern with northern blocking may establish by the second week of April. However, high pressure to the north will probably have a larger influence on our weather than lower pressure to the south-east, suggesting the potential for much of the country to remain drier than normal for the foreseeable future.
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