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18-10-2019, 13:56   #1006
sryanbruen
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I am going to be posting about October 1993 here.

October 1993 was the second consecutive notably colder than average October at the time following on from the very cold October 1992 which was the coldest in Ireland since 1981 which may not seem that notable at first sight. We have not seen any October to be as cold as 1992 or 1993 since. 1992 was more about the persistence of lower than average daily temperatures whilst 1993 produced some notable severe frosts mid-month and some of the lowest October temperatures since 1926.

The month started off on the unsettled side but it was not your average unsettled period following on from a very wet September in the south and east of Ireland. Through early October, low pressure systems tended to progress in the same regions resulting in an unusually dry month to the north and west.

This 500mb height synoptic on 5th October 1993 is indicative of the unsettled period up to the 9th. An evident anticyclone is to the southeast of Greenland with low pressure centered over southern Ireland with northeasterly winds on the northern flank of the low. It was very wet at times in the east and south particularly on the 4th-6th; some daily falls at synoptic and climate stations below:

Warrenstown, Co. Meath - 60.2mm on the 6th
Ardee, Co. Louth - 58.0mm on the 5th
Dublin Airport - 44.6mm on the 5th
Sherkin Island, Co. Cork - 32.1mm on the 4th
Derrygreenagh, Co. Offaly - 28.2mm on the 6th

Markree Castle, Co. Sligo in comparison had a maximum monthly fall of 10.5mm on the 3rd with the month total being 23.1mm, only 20% of its average October rainfall. Unusually, Warrenstown was the wettest station with 122.1mm during October, 142% of average; although nearly half of this fell on the 6th alone. Even Maam Valley, Co. Galway which is normally one of the wettest stations in Ireland, had only 81.3mm during October 1993.

This split in rainfall reflected the very easterly nature of October 1993.

Belmullet, Co. Mayo had the monthly absolute max for October on the 4th with 16.5C.



It became drier generally from the 10th onwards but further rain showers continued for a few days along eastern and southern coasts with northeasterly winds gusting to gale force. These showers merged to heavier and more persistent falls on the 12th/13th with the air becoming more unstable as air pressure lowers. Maximum temperatures stuck at 8-10C in eastern regions generally.



A northerly attempted to bring cold air down towards Ireland on the 13th and although it did become colder, we escaped the worst of the airmass with the -8C isotherm getting as far south as northern Scotland on the 15th. High pressure ridged in from the Atlantic on the 14th and 15th giving lots of sunshine and feeling cold with maximum temps only 8-12C. Both nights got down to at least -2C somewhere.







On the 16th, high pressure collapsed from Greenland over us so cut off the northerly flow. However, cold air has been established over Ireland from the northerly and with widespread clear skies, there was severe frosts. Plenty of crisp autumn sunshine with only a few coastal showers on the 17th in the southeast corner. The air temperature fell to -6.0C at Straide, Co. Mayo and Markree Castle on the 17th, a new October record for Straide and lowest at Markree Castle since 1926. Markree Castle recorded -6.0C on the 18th also (and -5.6C on the 16th). Meanwhile, Derrygreenagh had a grass min of -14.0C on the 16th.

Even some coastal regions got down to -1 or -2C on the 17th.





The high began to drift away on the 19th allowing milder and cloudier conditions to occur from the southwest although most had another severe frost during the morning.



A cold front spread southwards on the 20th with clearer skies returning from the north behind it. Light showery rain associated with the front. The severe frosts returned with sunny days for most away from the north on the 22nd and east on the 24th. Fog tended to form in the east on the 24th. Markree Castle had an air min of -4.1C on the 22nd. Days felt chilly but maximum temperatures only slightly below average or on par for late October for most in the 9-14C range.





Anticyclonic gloom for the final week of October 1993 with light easterly winds. Some brighter conditions to the south on 29th/30th. Maximum temperatures stuck at 8-11C for most under persistent cloud for days but no frost.



Data from Met Éireann.
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14-11-2019, 17:18   #1007
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November 1919 (99 years ago) recorded one of the most extraordinary cold spells in the history of the UK and Ireland. The fact the cold spell occurred in mid-November (not even the end of the month) says it all really. The November 1919 cold spell is my second favourite weather event to research or discuss about after November/December 2010 as I find it so fascinating how it could be as cold as it was then (Autumn 1919 in general was extremely intriguing, not November alone). Just goes to show how cold it can get in mid-November if the setup is there.

The pattern of November 1919 was similar to that of November 2010. There was blocking over Greenland with anomalous below average heights to the southeast of the UK driving winds in from the northeast with air coming from Scandinavia. The 500mb height anomaly reanalysis of November 1919 below shows this.

The first ten days of November were rather cold already with some overnight frost and light easterly winds at first, gradually becoming windier. The easterlies led to a lack of sunshine for many especially to the south of the UK and east of Ireland. These days were just damp, quiet and chilly.

The cold spell really took hold on the 11th (my birthday ) with northeasterlies dominating. There was plenty of snow showers. There was reports of thundersnow including for Blackpool in the northeast of England. A snowstorm occurred overnight into the 12th in Scotland as a secondary low passed within the severely cold air. Villages were cut off by the snow. There was a foot of snow (30cm) at Dartmoor, 17 inches (44cm) at Balmoral and 8 inches (20cm) at Edinburgh. At Balmoral, this snow continuously laid on the ground from the 8th to 30th November. The snow showers continued for a few days up to the 16th.

Light northeasterly winds and pressure rising led to bitterly cold temperatures being recorded. The snow cover acted as an excellent insulator in further dropping the temperatures to abnormally cold levels for mid-November (probably unprecedented) especially over Scotland. Braemar got down to a whopping -23.3c on November 14th! That is an exceptionally low temperature in the middle of Winter, never mind mid-November. This is the November record low temperature for the UK to the present day when writing this. November 14th 1919 is the earliest a minimum temperature of -20c (AND -15c!) has been recorded in the UK. This is such a phenomenal figure in many ways as you can see. On the same day, Perth got down to -21.7c. Balmoral recorded afternoon maximum temperatures of -10c on the 14th and -12c on the 15th. The temperature fell again to -22.8c on November 15th at Balmoral, the second earliest -15c/-20c temperature in the UK and the second lowest November temperature on record. The maximum at Carlisle, Cumbria in England on November 14th was only -2.7c whilst England's lowest minimum was -12.8c at Scaleby on the 16th. Lisburn in Northern Ireland recorded a minimum of -12.2c on November 15th, Northern Ireland's November record low to this day. 2010 got close at -11.9c on the 28th but not quite beating the 1919 record.

After the 17th, the weather turned more changeable with day to day variation of mild and cold. There were further instances of snow, sleet and hail from the 20th-23rd. Was the extraordinary cold going to become a distant memory or would Winter 1919-20 continue the cold? Winter 1919-20 was unsettled and mild so the November cold was to become the coldest weather of the whole season.

Lowest minimum temperatures of November 1919 for various Irish stations (via the UK Met Office monthly weather report).

StationCountyMinimum temperatureDate(s)
Markree CastleSligo-11.1*14th
Blacksod Pt.Mayo-1.714th/15th
MallaranyMayo-1.713th/15th/30th
DunfanaghyDonegal-3.914th
Malin HeadDonegal-1.114th/15th
LisburnAntrim-12.215th
DonaghadeeDown-1.717th
Armagh ObservatoryArmagh-8.315th
NewtownforbesLongford-8.315th
Dublin CityDublin-3.915th/30th
GlasnevinDublin-6.115th/16th/30th
Phoenix ParkDublin-9.415th
Trinity CollegeDublin-6.715th
RanelaghDublin-5.616th/30th
NewcastleWicklow-2.29th/16th
Birr CastleOffaly-9.414th/15th/16th
MountmellickLaois-6.714th
KilkennyKilkenny-8.912th
GortmoreWaterford-5.612th
Training CollegeWaterford-7.212th
Seskin, Carrick-on-SuirWaterford-4.411th/13th/15th
CahirTipperary-9.412th
FoynesLimerick-5.615th
Mungret CollegeLimerick-10.615th
KillarneyKerry-6.715th
Valentia ObservatoryKerry-4.412th
BallinacurraCork-6.712th
Roches PointCork-2.212th/13th

*The -11.1c temperature at Markree Castle on November 14th 1919 was the record low November minimum temperature for the Republic of Ireland until 2010 when it was beaten at -11.5c by Clonroche, Co. Wexford.

At a CET of 3.3c, November 1919 was the equal 7th coldest on record back to 1659. Just 4 years before, November 1915 was the second coldest on record with a CET of 2.8c (the coldest being 1782 at 2.3c). The coldest CET we've seen since 1970 was November 1985 at 4.1c in comparison. November 1915 was persistently cold and frosty whilst November 1919 had an extreme cold spell but was moderated later.

Data comes from the UK Met Office.
100 years ago today, Markree Castle recorded -11.1C which would be the lowest November temperature in Ireland until 2010 and thanks to Century Ireland, we finally have some photos of the snowfalls in November 1919 in Ireland:







https://www.rte.ie/centuryireland/in...-change-denied
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