review of spring 1985 over the northern hemisphere

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REVIEW OF SPRING 1985 OVER THE NORTHERN HEMISPHERE MARCH On-the monthly mean 500mbar chart there were vortices over the Canadian and Siberian Arctic. There was a very strong flow over almost the whole of the north Pacific especially in central and western parts. The jet stream was further south than usual over eastern north America with the Canadian trough east of normal at about 55"W. There was also a well-defined upper trough near 5"E. On the monthly mean surface chart the Asian high was much stronger than usual with an anomaly of 12mbar near Moscow. The easterly flow on the south side of this high resulted in unusually cold weather over southern USSR from the Ukraine eastwards to the Aral Sea with warmer than average temperatures in north and west Russia (anomalies up to +6degC). Spain, France and the UK were also colder than usual with monthly mean anomalies of -3degC in France. Over most of Europe except Iberia it was wetter than usual but in the USSR the area from the Black Sea north-east to the Ural Mountains was relatively dry. The Iceland low was displaced to south of Greenland resulting in unusually cold and wet weather in north-east Canada but over almost all the rest of the north American continent the weather was warmer and drier than usual especially in the prairie provinces of Canada (anomaly up to +SdegC). An area around the Great Lakes extending south-west to Mexico, however, had above average rainfall, as did Alaska. Over India and the Sahel regions of Africa monthly mean temperatures were nearly 2degC above normal. Notable weather events included avalanches in Switzerland resulting in eleven deaths early in the month, a sharp cold spell in western Europe around mid-month (giving heavy snow in many parts of Britain, while snow fell as far south as Rome) and severe storms towards the end of the month in the Bay of Biscay - again with considerable loss of life. Central England Temperature 4.9"C (-0.7degC) England and Wales Rainfall 65mm, 110 per cent (provisional) APRIL The 500mhar monthly mean chart bore a considerable resemblance to that of March but the European trough at 5"E was absent. The flow was generally zonal with very strong winds in the north Pacific between 40" and 50"N and the Canadian trough remained close to 55"W. On the corresponding surface chart the Arctic high was well- developed with a +8mbar anomaly north of the Bering Strait. In middle latitudes the flow was very westerly both in the Pacific and in the AtlantdEuropean sector. Pressure was below average over all Europe but especially in the north (anomalies -4mbar over the UK, -10mbar over north-west USSR). Most of the Arctic together with the area from east Greenland to Scandinavia and north-west USSR had mean temperatures up to 3degC below average but temperature anomalies over most of Europe were small. Almost all of the USA and also the Canadian prairies were warmer than usual (anomaly +3/ +4degC) but temperatures were below average in Alaska (-1 1°C) and north and east Canada. Most of India except the west continued warmer than usual. The rainfall pattern reflected the zonal flow with most of Europe and the USSR being wetter than normal (2001300 per cent in Scandinavia, 150/200 per cent in France and Germany) whilst further south over most of the Mediterranean and Greece dry weather predominated. Over north America the same zonal pattern occurred, with Canada (except the maritime provinces) rather wet and USA mostly drier than average, except in the region between 35/40"N and 9511 I0"W. 254

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Page 1: REVIEW OF SPRING 1985 OVER THE NORTHERN HEMISPHERE

REVIEW OF SPRING 1985 OVER THE NORTHERN HEMISPHERE

MARCH

On-the monthly mean 500mbar chart there were vortices over the Canadian and Siberian Arctic. There was a very strong flow over almost the whole of the north Pacific especially in central and western parts. The jet stream was further south than usual over eastern north America with the Canadian trough east of normal at about 55"W. There was also a well-defined upper trough near 5"E.

On the monthly mean surface chart the Asian high was much stronger than usual with an anomaly of 12mbar near Moscow. The easterly flow on the south side of this high resulted in unusually cold weather over southern USSR from the Ukraine eastwards to the Aral Sea with warmer than average temperatures in north and west Russia (anomalies up to +6degC). Spain, France and the U K were also colder than usual with monthly mean anomalies of -3degC in France. Over most of Europe except Iberia it was wetter than usual but in the USSR the area from the Black Sea north-east to the Ural Mountains was relatively dry. The Iceland low was displaced to south of Greenland resulting in unusually cold and wet weather in north-east Canada but over almost all the rest of the north American continent the weather was warmer and drier than usual especially in the prairie provinces of Canada (anomaly up to +SdegC). An area around the Great Lakes extending south-west to Mexico, however, had above average rainfall, as did Alaska.

Over India and the Sahel regions of Africa monthly mean temperatures were nearly 2degC above normal.

Notable weather events included avalanches in Switzerland resulting in eleven deaths early in the month, a sharp cold spell in western Europe around mid-month (giving heavy snow in many parts of Britain, while snow fell as far south as Rome) and severe storms towards the end of the month in the Bay of Biscay - again with considerable loss of life.

Central England Temperature 4 .9"C (-0.7degC) England and Wales Rainfall 65mm, 110 per cent (provisional)

APRIL

The 500mhar monthly mean chart bore a considerable resemblance to that of March but the European trough at 5"E was absent. The flow was generally zonal with very strong winds in the north Pacific between 40" and 50"N and the Canadian trough remained close to 55"W. On the corresponding surface chart the Arctic high was well- developed with a +8mbar anomaly north of the Bering Strait. In middle latitudes the flow was very westerly both in the Pacific and in the AtlantdEuropean sector. Pressure was below average over all Europe but especially in the north (anomalies -4mbar over the U K , -10mbar over north-west USSR).

Most of the Arctic together with the area from east Greenland to Scandinavia and north-west USSR had mean temperatures up to 3degC below average but temperature anomalies over most of Europe were small. Almost all of the USA and also the Canadian prairies were warmer than usual (anomaly +3/ +4degC) but temperatures were below average in Alaska (-1 1°C) and north and east Canada. Most of India except the west continued warmer than usual.

The rainfall pattern reflected the zonal flow with most of Europe and the USSR being wetter than normal (2001300 per cent in Scandinavia, 150/200 per cent in France and Germany) whilst further south over most of the Mediterranean and Greece dry weather predominated. Over north America the same zonal pattern occurred, with Canada (except the maritime provinces) rather wet and USA mostly drier than average, except in the region between 35/40"N and 9511 I0"W.

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Page 2: REVIEW OF SPRING 1985 OVER THE NORTHERN HEMISPHERE

There were several more accidents in the Swiss Alps as a result of avalanches.

Central England Temperature England and Wales Rainfall

8.5 "C ( + 0.5degC) 66mm, 114 per cent (provisional)

MAY

The 500mbar monthly mean chart again featured unusually strong winds in the north Pacific between 40" and 50"N with the Canadian trough remaining near 55"W. However there was a weak ridge at 20"W in the Atlantic and a weak trough neai the UK. On the monthly surface chart there were negative pressure anomalies over much of Europe and also over North America but north of 60"N higher than usual pressure predominated.

The Arctic regions were mostly colder than usual as were the uK, France (-1 SdegC), Iberia, the western Mediterranean and most of central USSR.

East and south-east Europe and western USSR had mean temperatures above average. Most of north America was also warmer than usual (anomaly +3degC west of 90"W) but Alaska, Labrador and the Canadian maritimes had below-average temperatures.

Rainfall over Europe was mostly near or above normal but it was relatively dry in the central Mediterranean and southern Scandinavia. The USA south of about 38"N was drier than usual along with western Canada but Alaska and an area west of the Great Lakes had above-average rainfall.

The long drought was broken in Ethiopia but continued over the Sahel region of Africa. A tropical cyclone affected 400 km of coastline in Bangladesh destroying 35 km of embankments. At least a million people were affected and there were probably nearly IOOOO deaths.

At the very end of the month a series of at least 20 tornadoes caused widespread destruction and about 85 deaths in north-east USA and Canada. The Whitsun holiday weekend was exceptionally wet in Britain.

Central England Temperature England and Wales Rainfall

1 1.1 "C (-0.2degC) 72mm, 108 per cent (provisional)

SPRING AS A WHOLE

The most notable feature was probably the persistence of positive temperature anomalies over most of North America (except the Canadian maritime provinces, which were persistently colder than usual). Over western Europe the season was unsettled with alternations of very contrasting types.

Central England Temperature England and Wales Rainfall

8.2"C (-0. IdegC) 203mm, 110 per cent (provisional)

R. A. S. RATCLIFFE

RECENT ADVANCES IN METEOROLOGY AND PHYSICAL OCEANOGRAPHY

Recently published by the Society, this is a collection of reviews presented at a meeting in October 1983 to celebrate the centenary of the granting of the title 'Royal Meteorological Society' by Queen Victoria in 1883. There are seven contributors, all past presidents of the Society. The book will be sent to members free of charge, and sold at f 10 to nonmembers, post paid. Copies may be ordered from the Executive Secretary, James Glaisher House, Grenville Place, Bracknell, Berks RG12 IBX.

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