Climate & Weather - Meteorology

 

References


Anon (1990)  Giant hailstones!  Sligo Champion 9 March 1990.


Anon (2012)  ‘Twister’ strikes at Rosses Point.  Sligo Champion 9 May 2012.


Burkitt, J.P. (1917)  Notes.  Zoology.  The effect of the 1916-17 winter on birds.  Irish Naturalist 26:172.


Cadée, G.C. (1988)  Bottles crossing the Atlantic Ocean.  Irish Naturalists' Journal 22(11):499 .


Connolly, J. (2003)  Northern Lights: Solar storm brightens the night.  Irish Times 30 October 2003 (Front page).


Cotton, D.C.F. (1987)  Correspondence.  A case of Atlantic crossing by passive transport.  Irish Naturalists' Journal 22(5):213-214.).


Cotton, D.C.F. (2004)  Fish Notes.  A fall of sand eels Ammodytes tobianus L. in Co Sligo.  Irish Naturalists' Journal 27(10):407-408.


Crisp, D.J. (1964)  The effects of the severe winter of 1962-63 on marine life in Britain.  Journal of Animal Ecology 33(1):165-210.


Cruikshank, J.G.; N. Stephens & L.J. Symons (1962)  Report on the hurricane in Ireland on Saturday, 16th September, 1961.  Irish Naturalists' Journal 14(1):4-12.


Dixon, F.E. (1987)  Early Irish weather records.  Pages 59-61 in: Shields, L (ed.)  The Irish Meteorological Service.  The First Fifty Years 1936-1986.  The Stationery Office, Dublin.


Kilgannon, T. (1905)  Kilgannon’s Almanac for North Connaught.  T. Kilgannon, Printer and Publisher, Sligo.


Kilgannon, T. (1926)  Sligo and its Surroundings: a descriptive and pictorial guide to the history, scenery, antiquities and places of interest around Sligo.  Kilgannon & Sons Limited, Sligo.


Kinahan, G.H. (1860)  March 4, 1859.  On the remarkable destruction caused among birds in Kerry by the winter of 1854-55.  Proceedings of the Natural History Society of Dublin (for the sessions 1856-1859) 2:147-149.


Murphy, M.E. (1980)  Management of Sand Dune Areas in the West of Ireland : a neglected aspect of Land Reform.  Unpublished M.Sc. thesis, The New University of Ulster.


Rohan, P.K. (1987)  The Climate of Ireland.  2nd edition.  Stationery Office, Dublin. (1975 1st edition).


Wood-Martin, W.G. (1882)  History of Sligo, county and town.  Volumes 1-3.  Hodges, Figgis & Co., Dublin. (Appendix K : rainfall data pages 485-489).


Wynne, J. (1860)  June 15, 1855.  On the effects of severe frost on plants in the neighbourhood of Sligo.  Proceedings of the Natural History Society of Dublin (for the sessions 1849-1855) 1:39-40.

Positions of nearest synoptic stations to Sligo & Leitrim for which there is a long run of data (Northern Irish synoptic stations are not shown)


1 Belmullet

4 Claremorris (replaced 1996 by an AWS)

5 Clones (replaced 2008 by an AWS)

9 Malin Head

The Northern Lights or Aurora Borealis over Benbulbin

(Photograph shown here with permission of James Connolly - all rights reserved)

Published in Irish Times (Connolly 2003)

Weather-related phenomena


Severe winters

Years in which the winter was severe were :


                                                    1946-47

                                                    1962-63

                                                    1978-79

                                                    1981-82

                                                    2009-10

                                                    2010-11





Giant hailstones

Hailstones with a diameter of up to 27.3 mm and weighing up to 5.70 grams fell at Lisduff, Calry on 28 February (Anon 1990).  Such events are rare this far north and are associated with unstable air conditions such as in large thunderstorms.

Source of data :  Modified from: Met Éireann at http://www.met.ie/climate/30year-averages.asp

Synoptic Stations


Claremorris

For many years the nearest synoptic station to the Sligo and Leitrim region was at Claremorris which is inland and about 70 km south-west (No.4 on map).  This weather station is situated on the main Galway road about 2 km to the south of Claremorris town, Co. Mayo (53°42'40"N 8°59'29"W and 71 m above mean sea level).  The station opened on the 13 November 1943 and was closed in 1996 when Knock Airport weather station became operational.  An Automatic Weather Station is now operating on the Claremorris site.  At a distance of 70 km away this station is not representative of weather in the more mountainous or coastal areas of Sligo and Leitrim.


Belmullet

The Belmullet station (No. 1 on the map) was opened in September 1956 when it replaced the station at Blacksod Lighthouse, 16 km to the SW.  The weather station is located 1 km to the east of Belmullet town at Carne, Co. Mayo (54°13'40" N 10°0'25"W and is 11 m above mean sea level).    The station is regarded as being particularly important because of its location on the western fringe of Europe.  It is also of interest to people living in Sligo and Leitrim because it gives some idea of the weather coming our way when the weather systems are approaching from the west.  In 2012 Belmullet went automatic.


Malin Head

Lies on the coast at the very northern tip of Ireland, 144 km north-north east of the Sligo region (No.9 on the map).  It is mentioned here because it was the nearest station to the north of this region, and it is coastal.  However, it is a long way away and is not representative of weather or climate in the Sligo region.  Like most other weather stations it was closed as a manual station and replaced with automatic recording equipment in 2010.


Clones

83 km east (No.5 on the map) was far away from the sea and lay in the north midlands of Ireland.  It was closed in 2008 and replaced by an automatic one nearby at Ballyhaise.



As can be seen from the map, Sligo and Leitrim were not served well by any of these stations.  In fact, when one considers the collection of meteorological data, the Sligo Region was probably the least well represented area in Ireland.

Historical data


Knowledge of the weather of the Sligo-Leitrim region has a special place in Irish meteorological history because a weather station was established in 1824 by Edward Joshua Cooper in association with his astronomical observatory at Markree Castle near Collooney in Co. Sligo.  This station has produced a continuous run of weather data since 1833.


In common with three other astronomical observatories where weather records were collected; at Dunsink (1788), Armagh (1790) and Birr (1845); the data are historically important because of their reliability and continuity from very early dates (Dixon 1987).  The only other Irish place with such a long run of data is the Botanic Gardens in Dublin that has collected data since 1800.


Severe winters that affected wildlife in County Sligo are described in several notes and papers.  Kinahan (1860) and Wynne (1860) describe the winter of 1854-55; Burkitt (1917) the winter of 1916-1917; and the impact of the severe winter of 1962-63 is described in Crisp (1964).  Robert Warren also made reference to hard winters in some of his ornithological notes.


The lowest air temperature ever recorded in Ireland was -19.1oC at Markree Castle on 16 January 1881.


John Wynne of Hazelwood also collected some meteorological data which is now deposited in Sligo County Library, but it only covers a short period of time.


Wood-Martin (1882) presents a table of rainfall data on pages 485-489.


A summary of meteorological data collected at Markree for the year 1905 is published in Kilgannon (1906).  Kilgannon also gives three pages of information about the climate of Sligo and how to make meteorological measurements (Weather Table pp17-19).


The modern age of meteorological data collection and analysis began in 1936 when the Irish Meteorological Service was established (now called Met Éireann) http://www.met.ie/

Wind-pruned tree in the Bricklieve Mountains

Prevailing wind direction

The Northern Lights or Aurora Borealis are occasionally seen from Sligo.  Conditions favouring sightings are peaks of sunspot activity, a view of the northern horizon, a clear night sky, and to be away from sources of light pollution.  The Northern Lights are caused by solar wind during sun spot activity that excites nitrogen and oxygen gases in the ionosphere (above 80 km in height) and causes them to glow (red and green for oxygen and blue for nitrogen).  A tremendous image of this atmospheric phenomenon was taken by James Connolly (Picsell8) on 29 October 2003 and was reproduced the next day on the front page of the Irish Times newspaper (Connolly 2003).

Blowing sands

Wind is the main force that builds sand dunes after sand has been fed onto the shore by water currents and waves.  Once the sand is deposited as hills the vegetation stabilises the sand and prevents it blowing further inland.  Sand dunes are very fragile environments and excessive use by people can cause the vegetation to die back and the dunes can suffer blow-outs.  This appears to be what happened along the Sligo coast in the early 1800’s from Mullaghmore, to Ballyconnell and Strandhill when huge amounts of sand blew on to adjacent agricultural land (Murphy 1980).


In 1837 Samuel Lewis wrote “on the eastern shore, about half a mile from the village (of Raghly) are the ruins of the old castle of Ardtarmon, now deeply buried in sand, the ancient residence of the Gore family.  The blowing sands of Knocklane extend northwards from the village, and are about two miles long and two broad; they have already covered a great tract of good land and about 150 cabins, and are constantly in motion, giving a dreary and desolate appearance to the country around.”  It would seem that at Ballintemple 280 hectares of the Ecclesiastical Commission’s property and another 200 hectares belonging to other proprieters were covered in up to 3 m depth of sand.  A similar situation occurred at Strandhill where the original village had to be abandoned when it became buried in wind blown, shifting sands, and was moved to higher ground (Murphy 1980).  The ancient parish church of Killaspugbrone was nearly covered with sand according to Lewis (1837).

Wind pruning

The prevailing direction of winds in the Sligo-Leitrim area are from the south-west and west.  One effect of continuous strong winds is to shape and stunt the growth of trees and hedgerows in exposed places like on the coast and mountain sides facing the sea.  This process is called wind-pruning and it is primarily caused during the winter when the windward side of the plant has its buds dried and killed, or its twigs on the windward side are snapped off.

Stream of the Height (Sruth an Áird)

An unusual phenomenon that can be observed in Glencar happens when a south-westerly wind is blowing (Force 7 or higher) and the ‘Stream in the Face of the Height’ (Sruth in Aghaidh an Áird) is blown back up to the mountain plateau.  From a distance this looks like smoke from a fire (see photograph shown below).  This stream also marks the boundary between counties Sligo and Leitrim.  This, or a similar ‘peculiarity’ is described by Samuel Lewis (1837 reprint page 15) under the name of Glenduff.

Wind-pruned tree at Lissadell

Damage to Forestry

Strong winds are a notable feature of the weather all along the west coast of Ireland.  From time to time these winds exceed gale force 8 and become storm force 10 or even hurricane force 12.  One such hurricane force wind was experienced over the west and north-west of Ireland for a 10 hour period on 16 September 1961.  Gusts above 160 km hr-1 were recorded from a southerly and south-westerly direction which at the time were the strongest winds in Ireland since records began 35 years earlier.  Severe damage was caused to property, agricultural crops and forestry.  In Sligo and Leitrim vegetation was desiccated by the wind and several plantations of Sitka spruce saw up to 5% of the trees being lost.  Plantations of young trees were least damaged but trees of 9-12 m high were snapped off at about 3-4 m above the ground (windsnap) and trees planted in peat or in soils where peat overlay poorly drained clay-till, were damaged by windthrow.  Glenfarne forest in Leitrim was particularly badly affected with 44,000 trees being lost, and a plantation at Glenwood, Lugnadeffe in the Ox Mountains was also severely damaged (Cruikshank et al. 1972).  Hurricane force winds are very rare but even storm force winds can easily cause windthrow in conifer plantations on peat soils in exposed locations.  It is therefore a pity that conifers continued to be planted in such situations in the Ox Mountains where they may never produce a commercial crop and yet the undisturbed blanket peat was a special ecological habitat.

Wind and water erosion of sand dunes at Trawalua Strand in January 2010

Heavy growth of lichens encouraged by high humidity on hawthorn tree at Glenade, CoLeitrim

Tornado

On 19 April 1999 at 15:00 hrs a tornado lasting only about a minute struck the village of Ballygawley.  Trees were uprooted and several houses lost parts of their roofs and gardens were flattened.  The event was associated with a thunderstorm that went through the area with heavy rain a short time earlier and was followed by a showery airflow of strong south-easterly winds causing a tornado effect.




Water spout

In recent years water spouts have been noted over Sligo Bay on two occasions; on 07 May 2012 (Anon 2012) and on 18 December 2013.  These are undoubtedly more frequent than records indicate but are either not recognised for what they are by most people or are not recorded.



Coastal erosion and deposition

An effect of wind on the coast is to cause the erosion and deposition of sediments.  Wind is a force of erosion in its own right but it also causes swells and waves on the sea that buffet the coast.


The hurricane force wind of 16 September 1961 was reported to have caused exceptionally rough seas and damage to most harbours (Cruikshank et al. 1972).


The last week of 2013 and the first week in 2014 saw a succession of deep low pressure systems being steered across the Atlantic Ocean by the Jet Stream.  The one depicted in the screen grab below occurred on 05-06 January 2014 and had a central pressure of below 950 hecto pascals.  Its land-fall coincided with spring tides and it caused a great deal of damage on the south and western coasts of Ireland but County Sligo got off lightly apart from some sand dune erosion (see also photograph shown below).

High humidity

The west coast of Ireland has regular high rainfall which leads to high humidity.  It is these humid conditions that have encouraged organisms that are adapted to damp conditions to flourish.  This can be appreciated on a large scale when one looks at the way in which peat bogs blanket the hills and mountains, and on a smaller scale when we see lichens, mosses, liverworts and ferns doing so well.

Trans-Atlantic voyagers

Various items have been picked up on Sligo’s beaches that have crossed the Atlantic Ocean through the action of winds and surface water currents.  One that I published (Cotton 1987) was of a plastic bottle containing a message that was thrown into St. John’s Harbour, Newfoundland on 13 September 1985 and was found washed up on the shore at Raghly, County Sligo on 18 January 1986.


On this occasion the flotsam travelled 2960 km (re-calculated as 3125 km from St. John’s, Newfoundland, Canada (Latitude 47o34’N; Longitude 52o42’W) to Raghly, Co. Sligo (Latitude 54o19’N; Longitude 08o39’W) in 127 days; an average speed of 24.6 km d-1


This note attracted the comments of Cadée (1988) who described experiments using glass bottles that indicated it takes between 200-300 days for drifters to cross the Atlantic Ocean from Newfoundland or Nova Scotia to Europe.  The passage time of the bottle described here falls well short of the predicted time period which can be explained by the fact that this was a plastic bottle which sat high in the water and would have been wind assisted in its passage.




Biological organisms including tropical seeds, jellyfish, by-the-wind-sailors, Janthina, buoy barnacles, goose barnacles, turtles also wash up and these are dealt with in Miscellaneous beach finds.

Fall of sand eels

One of the most amazing weather-related natural phenomena was a fall of sand eels. which was published by myself in Irish naturalists’ Journal (see Fall of Sand Eels)

National Roads Authority (NRA)


A network of 54 weather monitoring stations set up along national roads are part of the ‘Ice Detection and Prediction System’.  Information from these weather stations and road sensors is directly relayed to Met Eireann to be used to give forecasts about icy road conditions. The forecasts are then automatically relayed to local authorities to aid them in planning their road salting and snow ploughing programmes.

There are 6 NRA weather monitoring stations in the vicinity of this region viz. 

N15 Bundoran (= Tullaghan, Co. Leitrim G764571)

N16 Manorhamilton (= Gortnagrelly, Glencar, Co. Sligo G732421)

N4 Collooney By-pass (= Drumfin, Co. Sligo G707207)

N5 Charlestown, Co. Mayo (G4501)

N61 Elphin

N59 Ballina


Data from them can be accessed within minutes by anyone with an internet connection by visiting http://www.nra.ie/RoadWeatherInformation/

Irish Weather Network

This independent network of weather enthusiasts has brought together over 70 people who own an Automatic Weather Station (AWS) and who put their results up ‘live’ on the internet.


At the time of writing this there were stations submitting data from Charlestown, Co. Mayo (but just over the border from Sligo);


Ballycroy (Lagduff Fishery), Co. Mayo

Westport, Co. Mayo

Offline

Ballymote, Co. Sligo

Castlebaldwin, Co. Sligo


http://www.irelandsweather.com/index.php




Northern Ireland

The nearest meteorological station to the Sligo-Leitrim area that is over the national border is at St. Angelo Airport, Trory, Enniskillen, Co. Fermanagh (54°2355N 007°3907W) which is  5.6 km North of Enniskillen.

NRA weather monitoring station at Tullaghan, Co Leitrim (above and detail above right)

NRA weather monitoring station at Glencar, Co. Sligo

Photograph Jean Dunleavy

Deep low pressure system (cyclone) approaching Ireland on 05 January 2014.  Winds in excess of 100 km per hour were experienced on the south coast of Ireland but not in County Sligo.  Source of map : http://earth.nullschool.net/

The M4 weather buoy was originally placed much closer to land in April 2003 but was moved further offshore in May 2007

Wave heights and surfing

On 13 December 2011 the M4 weather buoy recorded a wave 20.4 m high which at the time made the news because it was the largest ever wave officially recorded in Irish waters (http://www.met.ie/news/ accessed 29 December 2011).  Then on 26 January 2014 the record was broken again when a wave height of 23.4 meters was recorded at the same location (http://www.met.ie/news/display.asp?ID=237 accessed 30 January 2014).  It is these big waves that attract surfers from other countries who make special journeys to Mullaghmore where the large and dangerous waves may be ridden.  On this occasion surfers flew in from Germany, Portugal and the USA.

Peter Conroy surfing a record height wave off Mullaghmore Head, January 2013.   Photograph: Roo McCrudden

Erosion of dunes at Yellow Strand after the storms of December 2013 and January 2014

For the more regular surfers the coastline of County Sligo is particularly good because Donegal Bay often focuses waves created by westerly winds on to these shores.  Places favoured by surfers include Lislary, Strandhill, Dunmoran Strand, Trawee and Easky in part because these places provide good safe access.

Sruth an Áird (Stream of the Height), Glencar, Sligo & Leitrim

Synoptic, Climatological and Rainfall Meteorological Stations in Counties Sligo and Leitrim

Modern Data


The term ‘weather’ refers to conditions that are current like the weather of the day, week or year.  Climate on the other hand is an average of conditions over a longer period of time.  Typically, climatic data is analysed on a 30 year rolling average which by convention starts with a year ending in a one.  The current 30 year period 1991-2020 will have its data set completed at the end of 2020 and a new 30 year period for 2001-2030 will begin.  Data for the previous period (1981-2010) was published by Met Éireann in 2013.


There are three levels of sophistication in the collection of meteorological data :


Synoptic Stations are run professionally by the Meteorological Service and take wide range of measurements every hour of the day, and every day of the year;


Climatological Stations are often run by institutions, but may be serviced by keen amateurs, and collect meteorological data at 09:00 UTC (GMT) every day;


Rainfall Stations are more numerous and are mainly run by amateurs, but in the past were largely serviced by Garda Stations, and collect data on the amount of rainfall on a weekly basis.

Since 1996 the situation has greatly improved with the addition of two synoptic stations close to this region; namely Knock Airport just out side of this area to the south and Finner Camp just outside this area to the north.  Then in 2007 an Automatic Weather Stations (AWS) was established at Markree Castle which upgrades the site from Climatological status.


Knock Airport

During the early 1990’s, a computerised automatic weather system (AWS) was installed at Knock Airport with data download to the main computer at the meteorological office in Dublin.  In 1996 staff from Claremorris were relocated to Knock Airport and for a number of years collected data manually in conjunction with the automatic weather system.  The manual operation of a synoptic station has continued.


Finner Camp

The Synoptic station at Finner Army Air-camp is between Bundoran and Ballyshannon, Co. Donegal (54°30'N 08°14'W and 45 m above mean sea level).  It was opened in 1996.


Markree Castle

The weather station at Markree Castle collected data of a variable quality and continuity for 174 years.  It was founded by Edward Joshua Cooper in 1824 and from 1833 right up to 1998 it produced a continuous run of data, being serviced by various members of the Cooper family.  An amusing anecdote from one of the family members claimed that as little boys it was not unknown for them to occasionally pee into the rain guage ;-) hence the variable quality comment.  In 2007 the establishment of an AWS at Markree means that Sligo now has a synoptic station and this is situated half-way between Knock Airport and Finner ArmyCamp.

Current synoptic stations (2014) are :


2  Ballyhaise Agricultural College AWS

3  Belmullet AWS

6  Claremorris AWS

11 Finner Army Camp AWS

14 Knock Airport manual station

16 Malin Head AWS

17 Markree Castle AWS

20 Newport AWS



See Met Éireann for more information

Ballyhaise

Ballyhaise Automatic Weather Station (AWS) was opened in 2003 and is situated in the grounds of the Ballyhaise Agricultural College, Co. Cavan (54.051°N 7.31° W 67 m above mean sea level).  This AWS replaced an existing climate station which was opened in 1931.  Since April 2009 the station has replaced the synoptic station at Clones, Co Monaghan.

Description of Climate


Most of the climatic data for the Sligo Region has to be extrapolated from maps that have been compiled from data collected at the nearest synoptic stations by the Meteorological Service (published in Rohan 1975 & 198?7).  This is not a satisfactory situation for anyone requiring more precise data because there are many local variations in climate that can not be accurately predicted. The Irish climate is noted for its degree of uniformity, having relatively small seasonal fluctuations compared with the continent of Europe.  This is caused by the proximity of the ocean which has the effect of moderating temperature extremes and providing a regular supply of rainfall.  The influence of the sea is enhanced by a prevailing west to south-westerly airflow and by the North Atlantic Drift (NAD) which is a warm water current that leaves the Gulf Stream and passes up the west coast of Ireland.  Thus Ireland has a maritime-temperate climate with warm damp summers and cool wet winters.  The influence of the ocean is even more pronounced in the Sligo region which gives the area a reputation for having a very mild and damp climate.  Sea temperatures haven't been measured in the region but extrapolating published data would suggest an average surface temperature of just over 9oC in January and 13.5oC in July; however the lowest temperature may be expected in February and the highest in August.  The average air temperature in January varies from 5.5oC on the coast to 4.5oC inland whilst in July it is 14.5oC.  The average daily minimum air temperature in January is 2.5oC on the coast and 1.5oC inland, and the mean daily maximum air temperature in July is 17.5oC on the coast and 19oC inland.  These figures show that the effect of the sea is to keep coastal temperatures cooler in the summer and make them warmer in the winter within this small region.  As would be expected, the number of days with air frosts is very small on the coast (less than 10 per year) but the inland parts of the region may have up to 40 or 50 days per year with air frosts.


A spectacular way of demonstrating how the ocean currents modify the climate of western Europe can be seen in the following example.  Sligo and Leitrim span a latitudinal range of between 53o48' and 54o29' N which on the other side of the North Atlantic the Labrador coast of Newfoundland; and also a part of Hudson Bay further west; are at the same latitude.  As stated, the average January temperature in Sligo and Leitrim it is at about 5oC whilst on the Labrador coast it is at or below -15oC.on the other hand the summer temperatures are very comparable :


                                            Sligo and Leitrim        average July 14.5oC

                                            Labrador                    average July 13oC


Rainfall

The distribution of rainfall in the Sligo Region is very closely correlated with topography.  The highest rainfall of 1600-2000 mm per year occurs on the very highest mountains in the Ox and Benbulbin/Dartry ranges.  The rest of the high ground has an annual average of 1000-1200 mm.  Allied to these figures is the fact that there is an average of more than 200 days with more than 1 mm of rainfall in the mountains whilst in other parts of the Sligo region this average is between 200 and 175 days with rain.  The monthly variation in Sligo's rainfall is quite small, and as data from Markree Castle show (see Table) the driest months are from March to May whilst the wettest are October to January.  Snow is relatively infrequent except in mountainous areas and is rarely prolonged or severe.

Mean monthly rainfall (mm) and number of days with more than 1mm of rainfall as measured at Markree Castle, Co. Sligo (1931-1960)(after Rohan 1975).

People living in the area of north Sligo / north Leitrim will be very well aware that the weather along the coast from Lissadell up to Mullaghmore is endowed with less rainfall, more wind and is sunnier with milder temperatures than the nearby mountain valleys like Glencar.  The rainfall aspect of this is confirmed by data collected by the climatological station at Ardtermon run by Charles Henry since 1985 and the rainfall station at Glassdrumman, Glencar run by Brendan Rooney since 1993.  These stations are only 18 km apart but their data shows that Ardtermon gets between 55% and 65% of the rainfall experienced at Glassdrumman.



Rainfall chemistry

There are no data on the acidity of rainfall in the Sligo Region, but published data indicate a general increase in the acidity of rainfall over Ireland with "acid rain" (pH of less than 5.6) having been recorded at Belmullet on a number of occasions (Shields 1987).  It can be assumed that acid rain sometimes falls in the Sligo Region but this is not going to be a problem where there is limestone rock, or glacial till containing limestone, as is the case for most of the region.  It could be a problem in areas such as the Ox Mountains or Curlew Mountains where the more acid geology offers no buffering capacity.



Sunshine

Data on the average daily sunshine also show the coastal areas of Sligo to have less cloud cover with figures of more than 3.5 hours per day for the coast but less than this value for the rest of the region.  Direct observations of the cloud cover in the region substantiate the data just presented.  For example it is very common to see the Mullaghmore-Streedagh-Raghly coast in sunshine whilst the mountain tops are blanketed in a layer of stratus cloud.  It is also common to see the Ox Mountain chain with low cloud spilling over from the south-west making the coast around Aughris Head dull whilst the northern parts of County Sligo are in sunshine.  On the other hand, during very calm weather in late summer or autumn the coast and inland parts of County Sligo can be enveloped in sea fog and fog around the lakes but if one drives over the Curlew Mountains into south Leitrim the sun can be shining brightly.  Another interesting feature is the way in which air rising to pass over Ben Bulben can actually be seen forming cloud.  This happens because as moist air rises, the pressure and temperature fall resulting in the ability of the cooler air to hold less moisture than the previously warm air so water vapour begins to condense into cloud.



Wind

The predominant wind directions of the west coast of Ireland are south-westerly and westerly.  Sligo gains some protection from south-westerly winds by the mountains of County Mayo and the Ox Mountains.  However, westerly gales blow straight on to the Sligo coast and create high seas in Sligo Bay.  This can also cause large waves on west-east orientated lakes such as Lough Melvin and Lough Gill which funnel the wind.  Inland parts of Sligo and Leitrim are generally less windy because of the shelter given by the coastal mountain ranges.

Climatological Stations


Climatological Stations are little more than Rainfall Stations but with one or two additional  measurements.  There are 3 within this geographical region and one just beyond the area at Ballina, Co Mayo (see red dots on map shown above).


Ardtermon House, Ballinfull

In addition to rainfall data this weather station records air temperature and grass minimum temperature at 09:00 GMT every day.  Daily readings have been taken since 1985.


Sligo Airport, Strandhill


Creevy Ballinamore


Ballina


There is also a climatological station at Ballyshannon, County Donegal run by the Electricity Supply Board.






Rainfall Stations


Rainfall is one of the most difficult meteorological parameters to measure.  If you think about it, meteorologists are depending upon measuring the amount of precipitation that falls within the rain guage’s circular collector, traditionally with an diameter of 127 mm.  It would take 79 such rain guages to collect precipitation from a square metre. This result is then multiplied up by 79 millions to calculate how much rain might have fallen in a square kilometer and trillions when 100 square kilometers are being represented.  In the 1970’s the meteorological service had about 770 rainfall stations in the Republic of Ireland and this network was in part established using Garda stations around the country to gather data.  In the Sligo area stations at Aclare, Coolaney, Inishcrone, Easky, Gorteen, Skreen and Tobercurry were involved.  However, this network had ceased by the 1990’s and In 2014 there were 419 rainfall stations nationally of which 9 were in Sligo and 10 were in Leitrim.  This geographical area has always been under-represented by rainfall stations.  The longest running station in the area of Sligo and Leitrim is that at Drumshanbo that has been in operation since 1893 (see table shown below).  The station near Easky Lough, Cloonacool now has an autographic rainfall recorder.

Sea Forecast Areas and Marine Weather Stations


Buoys

Weather buoys were deployed around Ireland in the early 2000’s in order to improve weather forecasts; especially gale and swell warnings for shipping bulletins that would increase safety at sea.  The project is a joint collaboration between the Marine Institute, Met Éireann, the UK Met Office and the Irish Department of Transport.  Parameters measured by the buoys are: wind speed and direction, atmospheric pressure and tendency, air temperature, relative humidity, sea surface temperature, wave height and periodicity, wave direction, maximum wave height and speed, salinity and configurable wave spectra.


The buoy most relevant to Donegal Bay is “M4” which was originally positioned in April 2003 at 81.5 km offshore (at 54 40 N, 09 04 W), but was moved on 03 May 2007 further offshore to 83 km west-northwest of Rossán Point (55 00 N, 10 00 W) (see map shown below).  The original location was found to be recording a wave climate characteristic of its position rather than giving a more representative picture of the wave climate offshore in the north-west.


A new generation of wave buoys with the ability to measure maximum wave height was introduced in June 2011 with the M4 and M2 (in the Irish Sea) first to be replaced.


Data from the M4 buoy may be accessed at :

http://www.marine.ie/home/publicationsdata/data/buoys/Observations.htm

Synoptic Stations are of the greatest value in the short term when making weather forecasts, but they also generate vast amounts of precise data that is used to build up a long term picture of the climate of an area.  Typically climatic data is analysed on a rolling 30-year average.  The table shown below presents the average data for the period 1961-1990 but there will already be 30 year average data for 1971-2000 and average data for the period 1981-2010.