Weatherwise with Gordon Currie - Flaming June? More a damp squib

Children brave the rain

Children brave the rain

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Already in the first half of this year we have experienced two months with excessive rainfall totals, namely April and June.

The month just ended is the second wettest June in my 64 year span of records, with total rainfall of 171.3 mm (6.85 ins.) which is still some way below the total of 192.7 mm. ( 7.70 ins. ) recorded in June 2007.

It is interesting to hear the current climatic comments from scientific sources to the effect that our rainfall behaviour may be becoming more extreme and inconsistent between the months, year on year. The record of June 2007 was preceded by a very wet January 101.4 mm. ( 4.01 ins. ) and a very dry April, 8.9 mm. (0.35 in). However, these are very short term comparisons, from which no definite trends can be concluded. Looking through my records, we have experienced 14 wet Junes since 1946 (with rainfalls exceeding 75 mm (3 ins ). Five of these occurred between 1948 and 1963, followed by a 14 year gap of drier months until 1977. Four more occurred in the 1980s, followed by a 9 year gap of drier Junes between 1988 and 1996.

Since then, the trend has certainly been for wetter Junes up to the present one. The final word on rainfall figures concerns the cumulative half-yearly total, January 1 – June 30 which this year has reached 457.6 mm (18. 30 ins) which represents 75 per cent of the average annual total, but is still below the record wettest first-half yearly total of 571.4 mm (22.85 ins) recorded in 2007.

The temperature figures for this June are equally disappointing, with a mean overall value of 57.1 F (13.9 C) against the long term normal, 59 F (15C). The consistent coolness of the month can be reflected in the average daily maxima, 62.5F (16.9 C) the lowest in any June since 2000.

Six Junes in the past 12 years have been cooler than average.

At the other end of the scale, the most outstanding month in terms of heat was June 2003, with a mean figure of 63.2 F (17 C) and an average daily maxima of 73.4F (23 C).

If we take a closer look at the failings of June’s weather, the fundamental fault can be found in the dominating synoptic pressure pattern throughout the month, centred upon four cyclonic spells, between June 8 – 9, June 14– 17, June 21 – 22 and finally, June 27 – 28. All these periods featured noteworthy low pressure centres, or depressions moving in from the South Western Approaches, travelling north-eastwards, eventually crossing Northern England and ending their journeys off the East Coast of Scotland. The last one of the series took a more westerly route tracking up the Irish Sea and over Scotland, dragging extra tropical air on southerly winds from southern Spain across England.

All these depressions had two common features, the tendency to slow down in their movement across Northern England, andtheir circulations involving high humidity air-masses drawn from the sub-tropical Atlantic.

These were subjected to convergence, causing high instability as they crossed our region in the case of the first three cyclonic periods.

The results of these caused some violent thunderstorms especially on June 15 when there was an explosive development of a super cell storm, just to the north of Ripon between Leeming and Northallerton.

This super cell structure occurs when the main cumulonimbus cloud begins to spawn separate storm cells around it which eventually coalesce into one gigantic centre.

Intense rainfall and hailstones accompanied this storm.

Another storm was associated with the depression of June 21, when cumulonimbus clouds were embedded within the layers of thick Atlantic rain bearing clouds.

Prospects for week ahead

Hopes for an improvement in early July’s weather quickly faded with the continued resolute tracking of depressions and fronts from fairly low latitudes of the Atlantic across the British Isles. The fault of this summer’s pattern lies in the positioning of high pressure centres near Greenland ( cold polar type ) and the Azores High, far too far south of its normal location. Between the two, this leaves an atmospheric weakness in mid-Atlantic which creates an alignment for the passage of depressions, heading with no resistance for this country. Little change is expected in the coming week, with one or two intervening ridges of high pressure in-between the frontal systems.

Temperatures, 64 – 70F (18 – 21C).