Meteorologist's Commentary

Storm Arwen to bring cold & windy spell - 25th November 2021

Named by the UK Met Office, Storm Arwen will track southwards along the east coast of Scotland on England through Friday and Friday night. For Ireland, Storm Arwen will introduce strong northerly winds and a cool polar maritime air, with the strongest winds expected along northern and north-western coasts on Friday, and later in the Irish Sea.

Met Éireann have issued yellow wind warnings for counties Donegal, Sligo and Mayo for Friday afternoon into Friday night, with strong gale force 9 winds expected along northern and eastern coasts, and storm force 10 winds in the Irish Sea on Friday night. The Met Office has issued a yellow wind warning for Northern Ireland through Friday and Saturday.

Met Éireann meteorologist, Elizabeth Coleman, said “It’s going to be a cold and very windy day on Friday. We’ll see north to northwest winds peaking late Friday afternoon . Gale to strong gale force winds are forecast along north facing coasts, generating large coastal waves and spray overtopping, with northerly storm force 10 winds developing in the Irish Sea on Friday night. Strong northerly winds over land in the north and northwest could bring down some trees and power lines with travel distribution possible.

Forecast pressure and airmass chart for Saturday 27th November showing cold northerly winds (blue) across Ireland

Elizabeth continued: “This system will generate high seas too, in the north and west through Friday, with the storm force winds and high seas transferring to the Irish Sea on Friday night”.

Storm Arwen – Named by the @metoffice, #StormArwen will bring a spell of cold & very windy weather to the UK on Friday & Saturday.

It’ll be cold & windy for Ireland too, especially across northern areas where we have yellow wind warnings in place

https://t.co/XGJxZFd5UU pic.twitter.com/UxcYvDR3wj

— Met Éireann (@MetEireann) November 25, 2021

Met Éireann have forecast blustery scattered showers on Friday, which will turn to sleet, mainly parts of the north with snow possible over the hills. Daytime temperatures will be limited to around 6 to 9C, but feeling colder with an added wind chill factor from the brisk northerly winds. Overnight temperatures are expected to fall close to freezing with frost expected in some areas.

It will continue cold through Saturday with winds easing later in the day with long spells of sunshine and while most areas will stay dry, there will be a few wintry showers in the north and towards the west coast.

Although it may feel like winter has arrived, milder conditions will move up over the country through Sunday and for the start of next week bring rain or showers at times but generally frost free nights.

#BeWinterReady

The unique risks brought by winter can occur suddenly and unexpectedly. Make sure you and your family are prepared for whatever the weather may bring during the winter months ahead. Visit winterready.ie or see #BeWinterReady and make sure to visit met.ie for the latest weather forecast and warnings. Follow us on Twitter and Facebook for extra weather and climate content. You can also listen to the latest national forecast on our daily podcast.

Whatever the weather please follow the public health advice and help keep everybody safe from COVID-19.

Turning colder and windier later this week - 23rd November 2021

On Friday a complex area of low pressure will move down over the northern tip of Scotland which will open the door to strong winds and cool polar air set to sink down over Ireland, with the strongest winds especially affecting areas in the far north.

Met Eireann meteorologist, Mark Bowe, said “It’s going to get noticeably colder from Friday as the low pressure system over Scotland will allow very cold northerly winds to blanket Ireland on Friday and into Saturday. There is a risk of wintry showers for areas in the far north with sleet and snow possible over the hills. This will mainly affect the northern half of the country with showers and some sunny spells expected elsewhere”

Met Eireann have forecast a windy day on Friday with frequent showers. Daytime temperatures will be limited to around 6 to 9C, but the brisk northerly winds will make it feel colder. Overnight temperatures are expected to fall close to freezing for many areas with frost expected.

Forecast pressure and airmass chart for Saturday 27th November showing cold northerly winds (blue) across Ireland

Mark continued: “It will be windy too with strong winds and gales on exposed coasts and hills likely on Friday before easing then again on Saturday”

The Met Office has issued a yellow wind warning for Northern Ireland through Friday and Saturday, as this low pressure system is expected to bring the strongest winds to the northern part of the island. Met Éireann forecasters are keeping a close eye on the development of this system for later in the week.

#BeWinterReady

Whatever the weather please follow the public health advice and help keep everybody safe from COVID-19.

Turning colder this weekend with the first frost on the way for many – 19th Nov 2021

After a rather mild November so far, temperatures will turn noticeably colder over the weekend with the return of overnight frosts.

On Saturday a cold front will push across Ireland introducing a much colder polar maritime airmass. This will bring daytime temperatures generally in single figures on Sunday and through next week, along with some cold nights and an increased chance of frosts.

Airmass and pressure chart for Sunday 21st November 2021 shows cooler airmass across Ireland (light blue) along with high pressure building from the Atlantic.

Met Éireann meteorologist, Liz Walsh, said:

“Tomorrow (Saturday 20th November) will start mainly dry in the south and east with some bright or sunny breaks, but it’ll be a damp start in the north and west with cloud and rain associated with a cold front. It’ll be a reversal of fortunes for the afternoon as the cold front clears the north and west, turning brighter and colder with just a few showers, but as this cold front makes its way across the country it’ll bring cloudier and wetter weather to southern and eastern areas.

“Sunday will be a cold and blustery day with some sunny spells and showers. Temperatures will be around 6 to 9 Celsius, though it’ll feel chillier in the brisk northerly winds. On Sunday night we’ll see the first widespread frost of this autumn so far, as temperatures fall close to or below freezing across the country.”

Commenting on the start of next week, Meteorologist Liz Walsh continued: “Through Sunday a large area of high pressure will build across Ireland and this will bring a good deal of dry, bright and crisp weather on Monday. Tuesday will still be a dry day though there will be more cloud in places, especially over the northern half of the country, and a few patches of drizzle. It’ll be another chilly night, though frosts will be largely confined to southern areas where clear spells are most likely.

The milder than average November temperatures we’ve been experiencing of late will be displaced by noticeably colder temperatures later on Saturday.
Daytime highs will be generally in single figures Sunday & next week with an increased risk of night-time frosts. pic.twitter.com/33MiU4Po38

— Met Éireann (@MetEireann) November 18, 2021

Chance of wintry weather next week

Commenting on the forecast into the middle of next week, Liz continued:

“It looks set to turn unsettled and colder still from around midweek. We’re keeping a close eye on some low-pressure development between Iceland and Norway which could bring windy and wet weather to Ireland later on Wednesday and perhaps the chance of some wintry showers Wednesday night and into Thursday. While it’s not unusual to get these types of weather conditions in late November, it will be a bit of shock to the system because our weather has been generally mild and benign lately.”

#BeWinterReady

Turning cooler for Halloween Weekend with a mixed weather in store - 29th October 2021

After a mild and wet week so far, it’ll turn cooler and drier over the first half of Halloween weekend, followed by some wet and windy weather on Sunday.

Commenting on the weather over Halloween weekend, Met Éireann meteorologist Aoife Kealy said: “Today (Friday 29th) will see a mix of bright spells and scattered showers, these will be heaviest and most frequent across western areas with brighter and drier weather across the eastern half of the country. Tomorrow (Saturday 30th) will be a bright day with good sunny spells and plenty of dry weather and just a few light showers.”

“However, through Saturday night it’ll turn wet and blustery as a low pressure moves close to Ireland.” Aoife continued: “It’ll stay unsettled on Sunday with some heavy showers or longer spells of rain around – and it’ll be a windy day too which could blow away a few witch’s hats!”

As we head into the start of November it’ll feel chillier than recent weeks with much more seasonal temperatures of around 8 to 10 Celsius and the chance of frosts increasing as temperatures overnight fall close to freezing.

Forecast pressure and airmass chart for Sunday 31st October 2021, showing low pressure centred over Ireland along with a cooler airmass

Whatever the weather please follow the public health advice and help keep everybody safe from COVID-19.

For the most accurate and up to date forecast for your area on the Island of Ireland go to met.ie. The latest weather advisories and warnings for Ireland are on the Met Éireann Warnings page. These services and more are available on our free app – available from the App store for iPhone, and Play store for Android. Follow us on Twitter and Facebook for extra weather and climate content. You can also listen to the latest national forecast on our daily podcast.

Spells of wet weather this week with some impacts possible - Tuesday 26th October 2021

Low pressure will bring spells of heavy rain across parts of Ireland this week, with impacts from local flooding possible.

Met Éireann has issued a Yellow Rain warning for southern and eastern parts of the country, starting early on Wednesday and lasting until Thursday morning.

Yellow Rainfall warning for Wednesday 27th October

Meteorologist Paul Downes said: “A slow-moving band of rain will bring spells of persistent and heavy rain tonight and through tomorrow, especially across southern and eastern parts of Ireland. Around 20-40mm rain is expected, with southern and eastern areas potentially seeing higher totals – particularly the higher ground of Cork and Kerry. These high rainfall accumulations may lead to impacts in some areas, such as tricky driving conditions, delays to public transport and localised flooding.

Forecast rain from Tuesday 26th to Friday 29th October, ECMWF

Paul continued: “Further spells of wet weather are expected tomorrow night and through Thursday with another 30-50mm rain possible, once again the greatest amounts are expected across southern and eastern areas. As well as the possibility of rivers flooding locally, at this time of year the risk of surface flooding can be increased due to fallen leaves blocking drains.”

It’ll also turn a little fresher later in the week as a cooler airmass gradually pushes in across Ireland, and while the winds will generally ease later in the week, current indications suggest it may become quite unsettled again over the weekend with a spell of wet and possibly windy weather crossing the country on Sunday.

Whatever the weather please follow the public health advice and help keep everybody safe from COVID-19.

Wet & mild spell before settled and fresher weather arrives next week – Thurs 7th October

Met Éireann have issued a yellow rain warning for western parts of the country through Thursday and Friday, as prolonged and heavy rain will likely lead to localised flooding and tricky driving conditions.

Met Éireann meteorologist, Paul Downes, said: “Whilst eastern part of the country will see some showers or rain over the next few days, it is the western half of the country that will see a spell of very wet weather with prolonged and often heavy rain. Mountainous regions in the west and southwest of the country will see the heaviest rainfall, with in excess of 70mm falling in some of these areas within 48 hours. This will lead to some localised surface and river flooding especially for hilly areas, with some disruption to transport and tricky driving conditions possible.”

A stream of tropical air will bring mild and wet weather

The reason behind the wet weather is due to a slow-moving weather front from the remnants of ex-Hurricane Sam. This weather front will stall over the western half of the country bringing a spell of prolonged rainfall to western counties, but it could edge over eastern areas at times bringing some spells of rain to eastern counties too.

Meteorologist Paul Downes continued: “Friday evening in particular will see the heaviest rainfall, although this will mainly be focused across western areas before spreading east overnight. Saturday will see another cloudy and damp start but it’ll gradually brighten up from the west as the weather front clears into the Irish Sea, with cooler, drier and brighter conditions following in the east by Saturday afternoon.”

Temperatures on Thursday and Friday will be very mild around 16 to 20°C, the average October temperature in Ireland is around 10°C. Thursday and Friday night will be mild too with temperatures around 12 to 16°C. This mild tropical airmass will be replaced by a fresher polar maritime airmass through Saturday, with temperatures returning closer to normal for the time of year as well as cooler nights.

High pressure building next week

An area of high pressure will gradually build through the weekend bringing more settled and drier weather into next week. There will still be some rain and drizzle around at times, especially in the north, but for many it’ll be dry next week with some spells of Autumn sunshine.

Whatever the weather please follow the public health advice and help keep everybody safe from COVID-19.

An unsettled week in store before high pressure returns next week - 4th October 2021

Low pressure will keep our weather unsettled this week with spells of heavy rain at times, however there are signs of more settled conditions on the way next week, as high pressure builds over the weekend.

Monday will see spells of heavy rain developing across the southern half of the country, before clearing through Tuesday morning. Tuesday will be bright and breezy with scattered showers, though turning drier through afternoon. Temperatures on both days will be around average, but it’ll turn much milder and more humid from Wednesday, due to warmer air moving across Ireland associated with ex-Hurricane Sam.

Met Éireann meteorologist, Elizabeth Coleman, said: “Currently off the east coast of the U.S., Hurricane Sam will move north-eastwards towards Iceland over the next few days, weakening as it does so. The path of ex-Hurricane Sam will allow a very mild, tropical maritime airmass to move across Ireland, bringing temperatures well above average for the time of year from Wednesday onwards.”

Location of Hurricane Sam at 00 UTC Mon October 4th on Met Éireann’s airmass and pressure analysis chart

Temperatures from mid-week onwards will be around 15 to 19 Celsius, the average maximum temperature in October is around 10°C.

Forecaster Liz Coleman continued: “The remnants of ex-Hurricane Sam will remain to the far west of Ireland, however the tropical airmass will bring a good deal of dull, cloudy and drizzly weather with mist and fog affecting hills and coasts. Some brighter spells may develop in the east at times. However, a weather front with waves will become slow-moving over western parts of Ireland on Thursday and Friday bringing some persistent falls of rain and the likelihood of local flooding – we have issued a Weather Advisory for some western areas where rain is expected to be heaviest.”

Looking ahead to the weekend, forecaster Liz Coleman continued: “The front is expected to move eastwards over the country on Friday night and Saturday before clearing into the Irish Sea. It will be followed by an area of high pressure building across Ireland for the rest of the weekend bringing more settled conditions and it will gradually turn a bit cooler again. Next week looks fairly settled with seasonal temperature values and high pressure generally dominating, though a little rain may affect some northernmost parts at first.”

Forecast path of Hurricane Sam as of October 4th 2021. Source: NOAA

Provisionally the warmest September on record

Whilst October so far has seen fairly typical Autumnal weather, the month of September was provisionally the warmest September month on record for Ireland, with mean temperatures 2.1°C above their long-term averages (LTA 1981-2010).

Munster and Leinster had their warmest September on record, with mean temperatures of 15.6°C and 15.1°C respectively. Connacht had its joint highest, matching 2006, with 14.7°C. While Ulster had its second highest 14.3°C, its highest was in 2006 with 14.4°C.

A new station temperature record of 27.9°C was recorded at Shannon Airport (in a record going back 75 years), whilst Phoenix Park in Dublin had its warmest September in 122 years, with a mean temperature of 15.8°C (2.4C above its LTA).

Dr Sandra Spillane of Met Éireann’s Climate Services said: “September 2021 has been a notably warm and dry month across the island of Ireland, with mean temperatures well above average and below average rainfall. Much of September was characterised by periods of high pressure which often brings dry and settled weather, before conditions turned more Autumnal towards the end of the month as low pressure moved across Ireland.”

The latest climate projections for Ireland signal a warming trend across all seasons into the future. More details on September 2021 in our Monthly Statement.

Rainfall, temperature and sunshine data for September 2021

Whatever the weather please follow the public health advice and help keep everybody safe from COVID-19.

More seasonable weather on the way - 24th September 2021

After a very mild September so far, temperatures will take a noticeable dip early next week as a cold polar maritime airmass arrives across Ireland.

So far this month it has been very mild, dry and calm, with all weather stations across Ireland reporting temperatures 1.5 to 2.7°Celsius above the September average. The above average temperatures will continue into the weekend due to a mild, tropical maritime airmass, however through the second half of Sunday a much cooler, polar maritime airmass will push in across Ireland, introducing more seasonal temperatures.

Forecast pressure and airmass chart for Monday 27th September 00 UTC showing colder air (green) pushing in across Ireland

Met Éireann meteorologist, Andrew Doran-Sherlock, said: “This weekend will see the last of the above average temperatures, with some places reaching around 20 degrees Celsius. However, from Monday we’ll see a significant change with a much more autumnal feel to our weather, as temperatures dip to a cooler 12 to 15°Celsius.”

“Along with lower temperatures, it’ll turn quite unsettled too with spells of rain and heavy showers along with some windy conditions, which current indications suggest will persist through much of next week.”

Met Éireann are encouraging people to keep a close eye on the forecast this weekend and into next week as spells of heavy rain and showers could lead to hazardous weather conditions in some areas, with the potential for some localised flooding and tricky driving conditions.

Why the change in weather?

Currently the jet stream – the core of strong winds that lies over the boundary between the warmer air to the south and the colder air to the north – is lying to the north of Ireland. As a deep depression develops in the mid-Atlantic later this weekend, the jet stream will wrap around the south of the depression, allowing colder air to sink down from the north over Ireland.

Andrew continued: “The change in weather from next week will be quite noticeable given conditions have been rather warm and settled so far this month – it may be time to dig out the autumn layers, hats and scarves as it is going to feel much chillier.”

Whatever the weather please follow the public health advice and help keep everybody safe from COVID-19.

For the most accurate and up to date 7-day, hourly forecast for your local area on the Island of Ireland go to met.ie. The latest weather advisories and warnings for Ireland are on the Met Éireann Warnings page. These services and more are available on our free app – available from the App store for iPhone, and Play store for Android. Follow us on Twitter and Facebook for extra weather and climate content.

Warm spell to end with thunderstorms - 8th September 2021

The first half of this week brought warm and dry weather across Ireland, however the second half of the week will turn more unsettled and less warm along with the chance of thunderstorms.

Temperatures this week peaked at 28.3°C in Durrow, Co. Laois on Tuesday – this is provisionally the first time a temperature above 28°C has been recorded in Ireland on a September day in 30 years. The last time temperatures reached 28°C was on 5^th September 1991, with 28.4°C at Valentia, Co. Kerry. Temperatures of 28°C or higher have only occurred three times in September since Met Éireann’s digital records began in the 1960’s.

The average maximum temperature for Ireland during September is around 17°C, while the average minimum temperature is 9°C. The highest September maximum temperature on record in Ireland is 29.1°C, recorded on 1st September in Kildare on Saturday 1 September 1906.

Around 10 weather stations across Ireland provisionally recorded new September maximum temperature records on Tuesday, including Sherkin Island, Claremorris and Shannon Airport.

Airmass Analysis chart from 00 UTC Sept 8th 2021

However today (Wednesday 8^th) brings a change in weather conditions as the warm airmass and high pressure is replaced by a less warm, more unstable airmass. Met Éireann meteorologist Matthew Martin said: “We’ll still see temperatures reaching into the low 20’s Celsius in some areas over the next few days, but later this week and into the weekend temperatures will fall to around 16 to 19°C, which is more average for the time of year.”

“We also have a more unstable airmass moving in over the country and this will bring the chance of some heavy showers and thunderstorms through the rest of the week, though pinpointing when and where the thunderstorms will occur can be a challenge.

“Whilst many areas may avoid the heavy showers and thundery downpours, where they do occur it could lead to the risk of localised flooding and disruption to transport. We’re therefore encouraging people to stay up to date with our forecasts and warnings, as well as our radar so they can keep an eye on thunderstorm development.”

Met Éireann has issued a nationwide Yellow thunderstorm warning valid from today until midday on Thursday 9^th, where scattered heavy downpours and thunderstorms could lead to localised flooding in places. The Met Office has a thunderstorm warning in place for Northern Ireland on Thursday.

Status Yellow – Rain & Thunderstorm warning for Ireland

Scattered heavy downpours & thunderstorms are expected in some areas today, tonight & for a time on Thursday. Localised flooding may occur where rainfall is heaviest

Valid: 09:04 Wed 08/09/2021 to 12:00 Thurs 09/09/2021 pic.twitter.com/4adkDUFvrj

— Met Éireann (@MetEireann) September 8, 2021

Commenting on the forecast for the weekend, Matthew continued: “At the moment it looks like we’ll see a mix of sunny spells and scattered showers on Saturday and Sunday, although these showers aren’t expected to be as heavy as what we can expect over the next few days.

“There are signs of high pressure returning next week which could bring a more settled spell, however there’s still a good deal of uncertainty in the forecast at this early stage.”

Whatever the weather please follow the public health advice and help keep everybody safe from COVID-19.

A very warm start to the week – 6th September 2021

Today (Monday 6^th) and tomorrow will see temperatures rise into the low to mid-twenties across Ireland, before turning less warm from Wednesday.

An area of low pressure to the west of Spain has allowed very warm air from north Africa to push up across Ireland, bringing above average temperatures for September. In mid-summer this type of airmass would result in temperatures exceeding 30 Celsius in parts of Ireland, but as we approach the autumn equinox and the days are shorter – there is less time for heat to build.

Airmass Analysis chart from 00 UTC Sept 6th 2021

Met Éireann meteorologist, Matthew Martin, said: “Along with a warm southerly airmass, Ireland is influenced by high pressure over the next few days helping to keep weather fronts largely at bay. This means most places will enjoy long spells of sunshine today and tomorrow, though mist and fog may linger across some southern and eastern coasts through the day.

“Temperatures will reach around 25 Celsius today and possibly up to 27 Celsius tomorrow, with these highest temperatures expected in the midlands.”

“Not everywhere will be sunny and warm today though as parts of Ulster and Connacht will stay rather cloudy with some patchy light rain too, however tomorrow these areas will join the rest of the country with long sunny spells.”

It’ll stay quite warm overnight through the week with temperatures not falling below 15 or 16 Celsius in some places.

The average maximum temperature for Ireland during September is nearly 17°C, while the average minimum temperature is 9°C. The highest September maximum temperature on record in Ireland is 29.1°C, recorded on 1st September in Kildare on Saturday 1 September 1906.

Commenting on the forecast for the rest of the week, meteorologist Matthew Martin continued: “Wednesday will be another warm day with temperatures in the low to mid-twenties. However some heavy, scattered showers are likely to develop as an area of low pressure moves towards Ireland bringing more unstable air.

“Thursday and Friday will see the sunny spells and scattered showers continue, these could be heavy and thundery and possibly turn quite widespread, especially on Thursday. It won’t be as warm by the end of the week with temperatures falling back to around 17 to 20 Celsius.”

UV levels will be moderate in sunshine this week, be #SunSmart and follow the advice from Healthy Ireland:

Whatever the weather please follow the public health advice and help keep everybody safe from COVID-19.

Meteorological summer to end dry, sunny and settled - Thurs 26th Aug 2021

High pressure will continue to bring a spell of settled weather to end meteorological summer, with largely dry conditions and long spells of late summer sunshine.

Meteorologist Paul Downes said: “With high pressure firmly in place over Ireland, low pressure systems are being kept well away, maintaining the dry, warm and settled period.”

“Today (Thursday 26th August) will be the warmest day of the week with highs of 21 to 26 degrees. A weakening cold front to the northeast of Ireland will track close to eastern coasts tonight and tomorrow, introducing a slightly cooler east to northeasterly airflow for Friday and the weekend. Temperatures will still be in the high teens to low twenties generally through the weekend with good sunny spells for the most part giving a very pleasant end to the summer.”

Paul continued: “Although it’ll be dry for most this weekend, some cloud may develop along with a spot of drizzle or light shower, especially in northern areas. It’ll also feel a little cooler on exposed coasts.”

The long spells of late summer sunshine will continue well into next week, however early next week temperatures will fall closer to normal with highs in the mid to high teens due to a slightly cooler airmass originating in Scandinavia.

Analysis chart showing pressure and airmass from 06 UTC Thursday 26 August

How long will the settled spell last?

While a breakdown of the high pressure across Ireland does look to be on the cards later next week, there is still some uncertainty as it very much depends on what is happening in the Equatorial Atlantic. The global weather connection can clearly be linked as development in the tropical Atlantic region can have knock on effects in the higher latitudes, such as northern Europe. While there is currently no indication that developing storms may impact Ireland directly next week, the indirect implications can alter our weather patterns, as tropical systems take heat from the warm sea surfaces of the tropics, and release it into the atmosphere. This acts to nudge the flow and alter the speed of the jet stream, which would influence our weather patterns for northern Europe.

Satellite image showing weather developments in the Atlantic on Thurs 26th August. Source: NOAA

The sun is still strong in August and early September and UV levels will generally be moderate to high, so follow the Healthy Ireland #SunSmart steps:

Healthy Ireland SunSmart Steps

Is this an Indian Summer?

An Indian Summer is a term sometimes used to refer to a spell of warm and calm weather in autumn months, usually September to November. As we are still in meteorological summer, this current spell of weather is simply summer weather, with meteorological autumn starting on September 1.

Whatever the weather please follow the public health advice and help keep everybody safe from COVID-19.

A warm & settled end to summer - 24th August 2021

The last full week of meteorological summer brings a spell of warm and largely dry and sunny weather across Ireland.

Explaining the reasons behind the warm and settled spell, Met Éireann meteorologist, Aoife Kealy, said: “The jet stream has been displaced to the far north of Europe allowing a large area of high pressure to settle across Ireland and keeping weather fronts and low pressure away from us.

“This means we’re going to see a warm, dry and settled week with temperatures reaching widely into the low 20s Celsius, with some areas possibly seeing 25 to 26 Celsius on Wednesday and Thursday.”

Analysis chart showing pressure and airmass from 00 UTC Tuesday 24 August

This week will also see long spells of late summer sunshine, especially across inland and western areas. However, areas along eastern coasts will be cloudier at times, especially during the mornings and evenings as low cloud, mist and fog drift in from the Irish sea due to a light easterly breeze.

The sun is still strong in August and UV levels will generally be moderate to high this week, so follow the Healthy Ireland #SunSmart steps:

Healthy Ireland SunSmart Steps

Commenting on how long the warm and settled spell will last, Aoife, continued: “The area of high pressure will stick around until at least this weekend and even into next week, so it looks like this settled spell will take us into the early days of meteorological autumn, though indications suggest that temperatures next week will be closer to average, in the high teens or low twenties.”

Is this an Indian Summer?

Whatever the weather please follow the public health advice and help keep everybody safe from COVID-19.

Heatwave - July 2021

For the latest Weather News story on the heatwave please see Met Éireann news.

Turning warmer and more settled this weekend - 27th May 2021

After a notably chilly May so far, temperatures are on the rise this weekend reaching into the high teens and possibly low 20’s Celsius in places.

Daytime temperatures across Ireland have been below average so far this month, with many stations 2°C below the May average. However, as we head into the weekend, much of Ireland will enjoy a spell of settled and warmer weather to end the month.

Met Éireann meteorologist, Aoife Kealy said: “Whilst there’s some wet weather across southern & western areas today (Thursday 27th), northern and eastern areas will enjoy a largely dry and bright day, though rain will eventually move here later this afternoon and evening. This system will gradually clear through Friday, followed by high pressure becoming well established for the weekend.

“We’ll also have southerly winds which will bring warmer air and this, in combination with the strong sun at this time of year, means we’re going to see higher temperatures into the high teens and low twenties Celsius in places.”

The highest temperature reached so far this year is 21.2° Celsius, recorded on April 1st at Valentia, Kerry. With warmer weather in store this weekend we could see temperatures come close, especially on Sunday.

Surface pressure chart for Saturday 29th May showing high pressure across Ireland

Saturday will be generally cloudy to start with patchy drizzle mainly affecting some western areas and the northeast coast. Cloud will break up through the afternoon as sunny spells develop and it’ll become dry apart from isolated showers. Temperatures will reach around 16 to 19 Celsius, possibly 20 Celsius in the best of the sunshine across eastern areas.

Sunday will be another warm and largely dry day with sunny spells for many, temperatures reaching around 17 to 21 Celsius. The highest temperatures are expected in the midlands and east in the best of the sunshine, whereas areas further west and southwest will see cloudier skies and temperatures not quite as high.

UV levels will be moderate to high over the weekend, especially in strong sunshine. You can keep an eye on the UV index for your region here and remember to take care in the sun.

On Monday rain and drizzle will push east across the country, bringing a cooler and cloudier day with highs between 13 and 17 degrees. However, it should stay and warm dry for eastern and southeastern areas with sunny spells and temperatures reaching 18 or 19 degrees. Certainty then decreases as we move into next week but current indications suggest that it will stay warm with sunny spells, though showery rain will affect some areas at times also.

But whatever the weather please follow the public health advice and help keep everybody safe from COVID-19.

Weather for the Bank Holiday Weekend - 30 April 2021

A spell of unseasonably wet and windy weather is on the way this Bank Holiday Monday, as an active low-pressure system moves across Ireland.

Ahead of this system which will arrive in the early hours of Monday morning, Saturday and Sunday will see a mix of scattered showers and sunny spells, with temperatures below average for the time of year. An unstable northerly airmass extends across the country on Friday and Saturday, feeding in cold air and leading to some overnight frosts. On Saturday, slow-moving, scattered showers will develop through the afternoon and these could turn thundery at times along with the risk of hail. In between showers there will be good sunny spells with temperatures of 9 to 12 degrees Celsius expected. Most showers will ease through Saturday night with temperatures dipping under clear spells to around -1 to +3 degrees Celsius, leading to a frost in a few places along with mist patches.

Forecast airmass chart for Saturday 1st May showing the cold northerly airflow over Ireland. Blue colours indicate a cold airmass.

On Sunday a westerly airflow will establish across Ireland along with a slight ridge of high pressure, leading to a good deal of dry weather but still a few scattered showers could pop up in places – though these aren’t expected to be as heavy as Saturday. Temperatures on Sunday will still be on the cool side around 9 to 13 degrees Celsius, but it could feel quite pleasant in long sunny spells.

Commenting on the transition to more unsettled weather on Bank Holiday Monday, Met Éireann forecaster, Andrew Doran-Sherlock, said: “Later on Sunday night cloud will push in across the country, heralding a change to much more unsettled conditions as a low-pressure system makes its way towards Ireland from the Atlantic.”

“Monday will start wet and blustery across Ireland with unseasonably strong winds developing quite widely, along with the potential for gale or near gale force winds across coastal areas. There may also be a risk of localised flooding in areas expected to see the heaviest and most persistent rain, particularly across Atlantic and northern counties.”

Andrew continued: “The low-pressure system will clear eastwards away from Ireland later on Monday, with a northerly airflow re-establishing across Ireland. This will keep temperatures below average next week, around 8 to 12 degrees Celsius and it’ll stay on the unsettled side too.”

But whatever the weather please follow the public health advice and help keep everybody safe from COVID-19.

A cold weekend ahead

A spell of unseasonably cold weather is forecast across Ireland this weekend, with daytime temperatures well below average and some very cold nights and widespread frosts ahead.

Met Éireann meteorologist Emer Flood, said: “We’re seeing another spell of cold weather this weekend as an arctic airmass re-establishes across the country through Friday, bringing the chance of scattered wintry showers of sleet, hail and snow over the weekend. Temperatures today (Friday 9^th) will reach around 6 to 10 Celsius, followed by a very cold night with a widespread sharp frost as temperatures overnight fall to around -3 in places.

“Saturday will be another cold day with temperatures limited to around 5 to 9 Celsius, once again falling to around -3 in places overnight and another widespread frost with the risk of icy stretches.”

Forecast chart for Saturday 10th April showing a cold northerly airflow across Ireland (blue colours) that will bring below average temperatures, along with the chance of wintry showers of hail, sleet and snow.

Along with bright spells of sunshine over the weekend, the cold Arctic airmass will bring the chance of scattered wintry showers of sleet and hail, especially on Saturday. There’ll also be a risk of thunderstorms, as well as snow showers over the hills and mountains. Showers will be lighter and less widespread on Sunday.

Sharp frosts at this time of year can cause problems for gardeners, so take care to cover vulnerable plants and protect from frost damage. The cold weather can also pose challenges for farmers and so we’re encouraging farmers to keep an eye on our farming commentary.

Looking ahead to next week, meteorologist Emer Flood continued: “Later on Sunday conditions will turn less cold, as northerly winds are replaced by slightly milder westerly winds. Monday will be a cloudier day with rain spreading from the west to most areas during the day. Temperatures will be slightly up from the weekend too, with highs of around 7 to 10 Celsius.”

But whatever the weather please follow the public health advice and help keep everybody safe from COVID-19.

A tale of two halves this Easter Weekend

The weather in the lead up to Easter weekend will be largely dry and settled with sunny spells for most. However later on Easter Sunday we’ll see a big change as much colder air arrives across the country, introducing the chance of wintry showers of hail, sleet and snow.

Met Éireann meteorologist, Matthew Martin, said: “High pressure will establish across Ireland in the run up to Easter, allowing a spell of settled weather lasting until the first half of Easter Sunday.

“It’ll be largely dry with sunny spells for most, though there’ll be a bit of a temperature contrast – today and Good Friday we could see highs of around 15 to 18 Celsius across southern and western areas in the best of the sunshine, whereas northern and eastern areas will be notably cooler as easterly breezes keep temperatures at around 10 to 12 Celsius. These coastal areas may also see low cloud lingering through the first part of the day. Saturday will be another dry day with good spells of sunshine and temperatures of around 10 to 13 Celsius, still feeling cooler though along northern and eastern coasts.”

Commenting on the forecast for Easter Sunday and the change to colder conditions, Matthew continued: “Easter Sunday will start dry with sunshine for most and whilst southern areas will continue to enjoy a dry and bright day, a cold front will introduce cloud and rain across the northern half of the country through the afternoon – it’s this cold front that opens the gates to very cold air from the Arctic from Easter Sunday night and through much of next week.”

Forecast chart for Monday 5th April showing a colder, northerly airflow across Ireland (blue colours) that will bring wintry showers of hail, sleet and snow across the island.

The cold airmass will introduce the chance of wintry showers of hail, sleet and snow on Easter Monday and Easter Tuesday, with temperatures limited to around 3 to 7 Celsius. Temperatures overnight will widely fall close to freezing with a touch of frost in places, which could cause problems for gardeners so take care to cover vulnerable plants and protect from frost damage.

The cold snap could also pose challenges for farmers and so we’re encouraging farmers to keep an eye on our farming commentary ahead of the cold conditions arriving later this weekend.

But whatever the weather please follow the public health advice and help keep everybody safe from COVID-19.

Vigorous depression to bring severe winds with a cold and unsettled weather regime to follow

Update on Wednesday 10 March 15:00

A vigorous depression will track to the northwest of Ireland tonight with very strong south-westerly winds developing over Ireland, veering westerly overnight. Gales will develop around all Irish coasts with Storm Force winds expected for a time in south-western sea areas. Status Orange wind warnings are in operation for County Kerry and County Cork from 8pm today (Wednesday 11^th March) until midnight with a Status Yellow Weather Warning in operation for much of the rest of the country through until 7am Thursday 11 March. See full details on our weather warnings here: https://www.met.ie/warnings/today

(Fig 1: Position of depression at 00UTC 10 March, centred to the southwest of Ireland with a central pressure of 967hPa. The low pressure system will track to the northwest of Ireland tonight bringing a swathe of very strong winds across Ireland with some severe gusts in the south and southwest expected)

In the wake of the vigorous depression a cold and unstable westerly air-flow will follow over Ireland with showery conditions and brisk winds. There will be widespread showers on Thursday, Friday and Saturday with a risk of hail and some thunderstorms. A cold polar maritime air-mass will lie over Ireland and this will allow for some wintry showers over high ground, especially on Saturday.

(Fig 2: A cold and unstable westerly air-flow will become established over Ireland on Thursday 11 March with heavy showers embedded in the flow)

(Fig 3: Many of the showers that follow will be heavy with a risk of hail and lightning. The above chart shows the risk of lightning across Ireland on Thursday 1200UTC forecast by IREPS)

Early indications are that milder weather will begin to move in for Sunday and next week with some rain or showers with a trend for high pressure to become established near Ireland by the middle of next week allowing for drier and more pleasant weather conditions to develop.

(Fig 4: Early indications are that high pressure will build in over Ireland for St. Patrick’s Day but there is still some uncertainty in the forecast)

Monday 08 March 15:00

After a rather quiet start to meteorological spring, conditions will turn much more unsettled this week with spells of wet and very windy weather on the way.

High pressure has brought largely dry and settled weather since the start of March, but as the jet stream moves over Ireland in the next few days this will steer a succession of Atlantic low-pressure systems towards us.

Met Éireann meteorologist, Paul Downes, said: “Today (Monday 8^th) will be the last day of the current spell of settled weather, before conditions turn widely unsettled from tomorrow with spells of wet and windy weather expected through the rest of the week.

Image: Forecast chart for 1800UTC Wednesday 10th March showing deep low to the NW of Ireland

“Although tomorrow (Tuesday 9^th) will start dry, rain and strong winds will push east across the country from tomorrow afternoon, becoming widespread by early evening. Further wet and very windy weather is expected on Wednesday as a deep low-pressure system tracks to the northwest of Ireland – bringing very strong south-westerly winds and spells of heavy rain through Wednesday afternoon and Wednesday night.”

Met Éireann has issued a nationwide yellow wind warning from 12:00 on Wednesday, to 07:00 on Thursday, where mean wind speeds could reach 50 to 65 km/h and gusts could reach around 100km/h in exposed locations, with damaging impacts possible.

Meteorologist Paul Downes continued: “During the early hours of Thursday this low-pressure system will clear away from Ireland, introducing a colder and more unstable airmass. However, it will remain very windy into the weekend along with blustery showers, these possibly turning wintry over high ground.”

Image: Forecast chart for Friday 12th March showing cooler polar maritime airmass over UK & Ireland

But whatever the weather please follow the public health advice and help keep everybody safe from COVID-19.

Cold Snap Forecast Update – 8 February 2021

Updated by Matthew Martin on 08/02/2021

Monday-Wednesday: Risk of snow showers, frost and ice

A cold easterly air-flow has now become established over Ireland and over the next few days the risk of snow showers will increase with eastern counties at greatest risk. The risk of snow accumulations will increase tonight (Monday night), through tomorrow (Tuesday) and for a time on Wednesday before the main focus for snowfall risk turns to the attempted frontal breakdown from the Atlantic on Thursday and Friday.

Sea-effect snow showers

The risk of wintry showers over the next few days will be driven by what is termed the ‘sea-effect’. Similar to lake-effect snowfall that is common place in North America during winter, sea-effect snow is a term used to describe the mechanism by which showers develop over the sea during winter. Sea/Lake effect snow occurs when cold polar or arctic air flows over relatively warm water, generating convective bands of showers downwind from the body of water. These shower bands can at times become quite narrow and intense giving significant falls of snow in very localised areas whilst some adjacent areas receive very little snowfall. Convective snow showers or bands are enhanced by lift due to frictional convergence and orography over the leeward shore and other factors such as wind fetch play a critical role in determining the intensity and extent of the sea-effect snow showers or bands. In Ireland, the Irish Sea is often the origin for many of our wintry showers during an easterly or north-easterly air-flow, however, they can also form in northern sea areas and in the Celtic Sea.

Typically, the temperature difference between the water surface and the lower atmosphere (850hPa) must be at least 13°C to support convective sea-effect shower formation over the Irish Sea. At present sea-surface temperatures are around +8°C whilst forecast 850hPa temperatures are around -10°C, resulting in a 18°C differential which should be sufficient to create some snow showers over the coming days.

Fig 1: ECMWF Sea Surface Temperature forecast for Monday 00UTC February 8th 2021

Fig 2: ECMWF Forecast chart of 850hPa temperature for Monday 1200UTC February 8th 2021

Areas at greatest risk of seeing snowfall are highlighted in the white/green shades in the ECMWF forecast charts below. However, this is a rough guide and showers are likely to be more widespread than highlighted in these graphics.

Fig3: ECMWF Forecast snowfall risk Monday night to Wednesday

Thursday & Friday: Frontal snow risk

On Thursday, frontal rain-bands in the Atlantic are forecast to move towards Ireland and as they encounter the cold air in situ over Ireland further snowfall is predicted. However, there is some uncertainty as to how far these frontal bands track north-eastwards over Ireland as high pressure over Scandinavia is dominating and acting to weaken these fronts as they move into the cold air. However, current projections indicate a spell of sleet and snow spreading north-eastwards over Ireland on Thursday and into Friday bringing accumulations of snow to many areas. However, the snow may transition to rain in some southern and western parts as milder air attempts to move in from the Atlantic.

Fig 4: Forecast chart for Thursday 1200UTC 11 February 2021 shows low pressure in the Atlantic and high pressure positioned over Scandinavia. Over Ireland, there is a boundary between very cold air to the east and northeast and milder air from the Atlantic with a spell of snow expected

Fig 5: Forecast rain, sleet and snow on Thursday 0600-1200UTC 11 February 2021

Fig 6: Forecast rain, sleet and snow on Thursday 1800-2359UTC 11 February 2021

At time of writing, a weather advisory is currently in operation and weather warnings are likely to be issued in the coming days.

As always, you can stay up to date with Met Éireann’s weather and warnings by monitoring the following pages on our website and please sign up for weather warning notifications on your smartphone Met.ie app.

https://www.met.ie/forecasts/national-forecast

https://www.met.ie/warnings

By Meteorologist Liz Walsh, 4th Feb 2021

Our weather is expected to turn progressively colder from early on Sunday 7th February, with the cold spell now looking likely to last well into next week. The origin of the cold air over Scandinavia will bring a northeasterly or easterly component to the wind-flow over Ireland. That wind will be especially noticeable on Sunday and Monday with gusty east to northeast winds likely to produce a significant wind-chill factor.

00z Run ECMWF from 4th Feb.
Wet Bulb Potential Temperature forecast from Sunday 7th – Wednesday 10th February.
Indicates temperatures at around 1.5km (850hPa) up in the atmosphere. Below zero with precipitation = snow likely at surface.

Daytime temperatures are expected to struggle in the low single figures, generally 1 to 3 degrees Celsius, which means any frost or ice that forms at night will be slow to clear, if it clears at all, so the risk of icy roads and footpaths will increase.

ECMWF Forecast Daytime Maximum Temperatures on Sunday, Monday & Tuesday (l-r)

Snowfall is expected in the form of showers from Sunday onwards, but more especially later on Monday and during Tuesday. Any showers are likely to be restricted to eastern parts of Leinster and Ulster initially, but a few may push further inland during Tuesday.

Forecast snow for Midday Tuesday 9th Feb over 3 consecutive runs of the ECMWF model. Latest run on the left – earlier runs from Monday 3rd Feb on the right.

There is still a high degree of uncertainty in the forecast from Wednesday 10th February onwards, but it looks as though Atlantic frontal systems will attempt to push milder air in from the south to displace the cold air in situ over Ireland.

It is still too early to predict how energetic or vigorous these frontal systems will be, and that has a downstream effect on the impact that this clash of mild and cold air may have over Ireland. If the frontal feature is vigorous, for example, it would likely make quick progress northeastwards over the country and any associated snowfall would be a transient affair with rain following behind. However, if the frontal system has less energy as it comes towards us and starts to become slow-moving either on its approach or as it tracks over us, we could end up in a situation where some parts of Ireland could see more significant and lasting snowfall.

Whatever the case snow-ice and/or low temperature warnings are likely in the coming days for conditions from Sunday through Tuesday, and forecasts for the latter part of next week will be updated and fine-tuned as we move closer to the time.

As always, you can stay up to date with Met Éireann’s weather and warnings by monitoring the following pages on our website:

https://www.met.ie/forecasts/national-forecast

https://www.met.ie/warnings

But whatever the weather please follow the public health advice and help keep everybody safe from COVID-19.

Unsettled weekend ahead as the battle of warm and cold air poses multiple risk-29th Jan 2021

by Paul Downes, Meteorologist.

Wet and windy weather tonight, gradually getting colder Saturday with the risk of sleet and snow increasing.

Over the coming days Ireland will lie between colder air to the north and an active zonal Atlantic pattern to the south that will feed in several lows bringing rain sleet and snow at times as well as blustery east winds.

ECMWF: WBPT, 1000-500 thickness, MSLP and 6h rain chart for Sat 06Z

River and Surface Water Flood Risk

Soils are mostly waterlogged countrywide, or at least in saturated conditions. Rivers are already elevated in the Northern half of the country, in response to appreciable rainfall over the last week. Over the coming days, multiple separate spells of precipitation will further exacerbate the flood risk across the country. Localised flooding is expected over the weekend and into next week, particularly in the Northern half of the country.

Coastal Flood Risk

We are in a period of Spring (High) Tides. The combination of Spring (High) Tides, strong onshore winds and storm surge associated with the low pressure systems to the south-west of Ireland tonight and into Saturday, is likely to increase the risk of localised coastal flooding, particularly in flood-prone areas along the East Coast (when coincident with High Tides and strong onshore winds).

Becoming wet and windy tonight. Status yellow rainfall warning issued.

The first deep area of low pressure will begin to track to the south of Ireland tonight bringing a band of rain northwards across the country. A status yellow rainfall warning will come into effect from 3am for Wicklow and Wexford with heavy rain bringing accumulations of 30 to 40mm and a risk of localized flooding overnight.

Further to this easterly winds will increase fresh to strong and gusty overnight, while there is a status yellow gale warning in effect from Valentia to Loop Head to Slyne Head. While the winds will generally remain below Status Yellow level overland they will be very strong for the less common and often less sheltered easterly direction.

Becoming cooler on Saturday with sleet and snow on higher ground.

With cold air to the north in close proximity and moving southwards gradually on Saturday morning, precipitation will turn to sleet or snow over higher ground with accumulations possibly building quite quickly. This will lead to hazardous condition, especially through the Wicklow Mountains.

The precipitation will clear southeastwards during the afternoon and the winds will ease.

Saturday night starts off cold and frosty with rain sleet and snow moving in from the west by morning.

While Saturday night will start off cold with some clear spells and an early frost, leading to icy patches, in many northern parts, a further spell of rain, sleet and snow will cross the country early on Sunday.

Greatest risk of snow in northern parts

The northern half of the country looks likely to see the greatest risk of sleet and snow with some accumulations, however warmer temperatures in the south will slowly move northwards with sleet and snow gradually transitioning back to rain in most areas. It will be a cold day however with afternoon highs of just 1 to 4 degrees in most areas, while Munster will remain warmer.

While an advisory has been issued for the weekend, further weather warning are likely and our warnings page should be monitored for updates.

But whatever the weather please follow the public health advice and help keep everybody safe from COVID-19.

A Sudden Stratospheric Warming (SSW) - January 2021

By Climatologist Paul Moore

The stratospheric polar vortex (SPV) is a rotating vortex of cold air high up in the stratosphere over polar regions. It forms every winter in the Northern Hemisphere and the strength of the Northern Hemisphere SPV has a significant influence on the Northern Hemisphere mid-latitude weather patterns. When the SPV is in a strong symmetrical state, it helps to maintain westerly momentum in the troposphere over polar regions and in the mid-latitudes, leading to our typical winter pattern of a strong west to east North Atlantic jetstream, bringing storms and weather fronts over Ireland from the west or southwest and keeping it mild and wet. When the SPV is in a weakened or non symmetrical state, it can lead to the weakened jetstream behaving more like a meandering river with blocking high pressure forming in our region, bringing the possibility of colder, drier weather.

When a weakened SPV goes through further disruption, it can lead to what is know as a Sudden Stratospheric Warming (SSW) event, which refers to the reversal of the zonal winds in the Stratosphere from westerly to easterly, along with a rapid jump in temperatures in the winter polar stratosphere that leads to a complete breakdown of the SPV. A SSW is now defined to have happened when the mean zonal wind (ZW) at 60°N and 10hPa (approx. 30km high) reverses to easterly. A SSW event usually has a significant impact on the tropospheric weather patterns in the mid latitudes. Following a SSW, there can be an equatorward shift of the tropospheric jetstream with associated cold conditions over northern Europe and these impacts can be long lasting. Every SSW is different and less than half of them lead to colder conditions in Ireland. For example, the SSW in February 2018 led to the ‘beast from the east’ and storm Emma, whereas the SSW in January 2019 had no significant impact here, due to the easterly winds not propagating down into the troposphere from the stratosphere. See more about the 2018 SSW event in a report on Storm Emma here.

The current state and forecast for the SPV

The SPV has been below average strength through most of December 2020 (pink line—left panel below) and is forecast to continue weakening (orange line –left panel below) to below zero m/s, which means changing from westerly to easterly. This signifies a technical SSW. The mean zonal winds at the bottom of the stratosphere have also been at very low levels (pink line— right panel below), and are forecast to decrease to record low levels over the next week (orange line– right panel below). This has been, and continues to be a contributing factor in the blocking high pressure systems we have seen in our region lately. The lack of westerly momentum at the bottom of the stratosphere helps to slow down the North Atlantic jetstream in the troposphere and leads to it meandering like a river, north to south, resulting in a more blocked pattern in the mid latitudes. https:// acd –ext.gsfc.nasa.gov/Data_services/met/ann_data.html#ncep_clim_stats_nh

What this reversal looks like can be seen in the below charts. These show the zonal mean wind averaged around the globe at each latitude line. The orange and red colours signify westerly winds and the blue signify easterly winds, with the numbers on each contour showing the m/s value. The values on the x-axis represent latitude, with EQ meaning the Equator. The values on the y-axis represent height in hPa. For example 10 hPa is approximately 30km high and is in the stratosphere, where as 200 hPa is approximately 10km high and is the top of the troposphere. On the 29th December 2020 (left panel below) the zonal winds high up in the stratosphere between 60 and 90N were between 20 and 60 m/s westerly and the sub-tropical jetstream, at 30N and 200hPa height was at 40m/s westerly. The forecast for the 5th January 2021 (right panel below) show the polar stratospheric winds have reversed to between 20 and 40 m/s easterly and are beginning to propagate down into the lower stratosphere. The sub-tropical jetstream averaged around the whole globe has intensified to 50 m/s. https://www.geo.fu –berlin.de/ en/met/ag/strat/produkte/winterdiagnostics/index.html

In the below charts, looking down from a northern hemisphere point of view at the 10 hPa height level (at the same times as above) the temperatures are represented by colours, with the °C values on the left and the geopotential height is represented by contours. On the 29th December 2020 (left panel below), the already weakened polar vortex, with its low pressure centre just to the northwest of Scandinavia, is surrounded by tightly packed height contours representing the strong westerly winds rotating anticlockwise around the vortex. The ZW at that stage was 25.2 m/s and can be seen at the bottom of the chart. There is already a strong warming signal over Siberia represented by the red colours. On the forecast chart for the 5th January 2021 (right panel below) the warming signal and associated high pressure has worked its way around and is penetrating into the polar vortex, pushing it further away from the north pole and almost splitting it. The more this high pressure pushes in over the north pole, the more the ZW changes from westerly to easterly. The ZW has reversed to easterly at this stage, shown by the -3.2 m/s at the bottom of the chart.

It is uncertain how this will affect our weather in the coming weeks as we are already in a very blocked setup. It could kick-start the westerly momentum in our region, at least temporarily, as the SPV is pushed over Scandinavia, leading to a strengthening of the North Atlantic jetstream, resulting in a more typical winter weather pattern for Ireland. It could also prolong and intensify the high latitude blocked setup leading to cold polar air masses flooding south into northern Europe or elsewhere in the mid latitudes.

Monthly Weather Forecast

Met Éireann are now issuing monthly forecasts twice a week, at 5pm every Tuesday and Friday, beginning 5th January. It will be available here in the Forecast menu. Monthly forecasting covers the time range of around 10 to 40 days ahead and is really more correctly described as sub-seasonal or extended-range. It is a time scale in between medium-range weather forecasting (10-day)* and seasonal forecasting (3 monthly).