Monthly retrospective for July 2016

The month was slightly above average temperature wise but rainfall was again variable due to the showery nature of the precipitation although very dry in places, and sunshine was again rather below average almost everywhere away from the far north.

The (Hadley) CET mean temperature was near 17.0C, about 1.0C above average. Most parts of the north and west were very close to average but a few parts in the east and SE were over a degree above average. The pressure was 2-3mb below average across the northern UK but a few millibars above in the south.

The warmest mean maximum was at Gravesend (Kent) & at London Heathrow (Middsx) with 24.0C and the highest daily maximum was 33.5C at Brize Norton (Oxon).

The coldest mean minimum was at Eskdalemuir (Dumfries & Galloway) with 9.6C, the coldest absolute minimum by night was at Altnaharra (Sutherland) with 0.5C.

June was generally a rather dry or very dry month in the south & east, wettest in the north & north west. It was mainly drier than average in the south where Portland (Dorset) saw just 7% of its average rain but even as far north as Hereford saw only 8% of average. However places like Heathrow and Wattisham (Suffolk) saw near average amounts where heavy showery rain fell. However in Scotland amounts were generally well above average everywhere ranging from 130-200% and Fair Isle saw 216% of its average, although parts of the Scottish east coast were close to average.

Sunshine was somewhat below average almost everywhere away from the east coastal counties, Wattisham (Suffolk) saw average sunshine hours but Brize Norton (Oxon) for the fourth month running was one of the places with the greatest discrepancy from its expected sunshine hours and saw only 71%. However much of the south was with 10-20% of its expected amounts, so it was not all that dull really. Wattisham (Suffolk) saw one day with as much as 15.4 hours.

It was not a particularly stormy month with few windstorms of any note. Thunder was generally rather below average, esp in the first and third terciles.

By the end of July, despite the limited sunshine, sea temperature anomalies had risen to about 2C above average around most UK SW'ern, southern and eastern coasts, about a degree up on the average since June. Waters off NW Scotland were closer to average but whilst generally the central Atlantic was still a little below average, sea surface temperatures right across the Northern Hemisphere were well average.
Soil temperatures were almost uniformly slightly above average in the south & Midlands partly due to dry ground but generally nearer average in the north and soil moisture fell in the south during the month, this being especially noticeable in parts of the SW and SE but mainly rose in the wetter areas that received well above average rainfall further north.

Now looking at July in more detail.

The 2nd saw a chilly night in the far north after a wet day there. Altnaharra (Sutherland) fell to 0.5C and -1C on the grass. There was 39mm of rain in the 24 hours to 21Z at Achnagart in the western Highlands though. The 4th saw quite a chilly night in parts of N Scotland, Kinbrace (Sutherland) fell to 1.0C with 0C on the grass at Eskdalemuir and Shap (Cumbria). The 9th was very wet in part of north & west Wales with Capel Curig (Conwy) seeing 67mm in the 24 hours to 21Z. The 11th was again very wet in part of north & west Wales where Capel Curig (Conwy) saw a further 37mm in the 24 hours to 21Z & a grand total of 128mm in the 72 hours from 21Z on the 9th making it the wettest place to that date for all of Europe in the month. Further localised thunderstorms with some hail occurred across parts of the Home counties too. Farnborough (Hants) saw 22mm in a short period in the late afternoon. The 12th saw heavy showers develop in the afternoon across parts of Berks, London, Essex, Sussex and Kent with localised hail & thunder, giving Wych Cross (E Sussex) 25mm of rain.

The 15th saw Murlough, (Co Down) take full advantage of clearing warm sector conditions and being down wind from the Mourne Mountains served to give good sunny breaks, allowing it to reach 25.7C. The 16th was very warm in places with Writtle (Essex) reaching 27.1C. The 17th was again quite warm in places with both Heathrow (Mddlesx) and Writtle (Essex) reaching 27.6C. The 18th saw a warm airmass from the south advected northwards across much of the UK, giving a sunny day away from the far north where it remained cooler & wet in places. St James Park in central London reached 30.0C.

The 19th saw the key weather event of the month. A plume of exceptionally warm upper air extended north from Iberia & France giving some very high temperatures across much of the UK. The highest temperature on the mainland UK was 33.5C (92F) at Brize Norton in Oxfordshire, the warmest day in Oxon for 10 years with some very high dewpoints as well recorded, up to 21C in places. Guernsey recorded its highest July temperature on record (last set in 1962) of 32.6C and Maison St Louis Observatory in Jersey reached 35.2C, another July record for Jersey and the third highest on record (since records begun in 1894). With an east wind high temperatures were recorded in coastal west Wales probably from a foehn effect. Parts of east Cornwall & for example Brighton, (E Sussex) also saw a similar effect, giving unusually high temperatures in the low thirties there as well. Thundery showers developed in the NW later in the day. Heat buckled a rail in North Yorkshire, and speed limits were put in place on some rail lines due to "high rail temperatures". Great Western Railway said there would be a series of changes to timetabled services because track temperatures were expected to exceed 50C in parts of London London's ambulance service said it had received 300 more calls than usual.

The 20th saw a plume of hot air destabilise overnight producing bands of thunderstorms with heavy rain across much of NW Wales, northwest England and Scotland. In some parts of Cumbria 60mm fell in a three hour period causing localised flash flooding. Cockermouth School had to close because of "severe storm water damage". To the south it was an exceptionally mild night with temperatures no lower than 22.6C at Heathrow airport, giving probably the warmest night in 25 years. By 09Z it was exceptionally hot in parts of the far east again with 28C reached in places and London Heathrow reached 31.4C. The 21st was warm in places but wet in parts of northern Scotland though, Inverbervie (Aberdeenshire) seeing 35mm of showery rain in the 24 hours to 21Z. On the 22nd, although a few showers broke out in the south it was a fine day in many parts with 26.7C reached at Cavendish (Suffolk) & Brize Norton (Oxon) but more persistent rain affected the NW at times and West Freugh (Wigtownshire) was wet and saw 28mm.

The 23rd was a very pleasant warm day for many in the east & SE with 27.1C reached at Cromer (Norfolk) though the north & and NW was wetter with 20.4C at Kinloss.The 24th was also very warm and sunny in parts of the south & east and hot locally, in NW London, Northolt reached 28.7C. The 29th was very wet in localised parts of northern central areas, with Linton on Ouse (N Yorks) seeing 44mm in the 24 hours to 21Z, to the north however it was quite sunny, Glasgow seeing almost 15 hours.

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