The ‘Beast From The East’ or the ‘Pest From The West’


Headline writers across Ireland and the UK have made numerous mentions of the ‘Beast from the East’ and how it could be set to return to our shores this month for the first time since the epic snowfalls of February 2018.  While it will turn noticeably colder by midweek next week, the current evidence suggests that severe cold is increasingly unlikely during January but remains a possibility for the beginning of February.

What is the 'Beast from the East'? When pressure is high over Scandinavia in winter, Ireland and the UK often experience a polar continental air mass.  Cold air is drawn in from the Eurasian landmass, bringing the cold and wintry conditions that give rise to the 'Beast from the East' label.

Ireland found itself in a blocked setup from December 27th through to last weekend whereby high pressure to our west prevented the more typical winter regime of Atlantic weather systems from approaching Ireland.  That cold spell, which brought overnight lows of -9c to parts of the midlands, was broken last weekend and since then, Ireland's weather has been under the influence of a tropical maritime airmass bringing wetter and milder conditions to most parts.  Eastern Scotland and northeastern England have continued to experience winter like weather with snowfall the result of Atlantic systems pressing up against colder air drifting off the continent there.

Lovers of cold weather in Ireland (there are many as the Weather Forum illustrates) will be well used to the prospects of much colder weather always looking like a 10-day wait away, known as Fantasy Island for keen observers of computer models.  In reality, the chopping and changing going on in computer models since the Sudden Stratospheric Warming (SSW) event of last week has brought the Fantasy Island period closer to 4-5 days such is the unpredictable nature of such events and their consequent impact on the weather in the northern hemisphere.  The models have caught on to a trend during the past 48 hours however.

It will turn colder from Wednesday next week as a north to north-westerly flow pushes down across Ireland bringing wintry showers of hail, sleet and snow to high ground in Connacht and Ulster in particular.  Temperatures will average up to 2-4c below normal (3-6c during daylight hours, subzero at night).  Boundary rain/snow events will be numerous as frontal systems encroach cold air over or close to Ireland.

A large area of low pressure centred between Scotland and the west coast of Norway will pull down the polar maritime air into the weekend.  This area of low pressure will pivot over the North Sea throughout the week due to a combination of high pressure blocking from Greenland to northern Russia and two other areas of high pressure, one in central Europe and the other over the Iberian Peninsula.   All the while areas of low pressure will track eastwards across the Atlantic towards Ireland and Britain.  

The Iberian high-pressure system is being consistently forecast to ridge further north diverting low pressure systems towards Ireland and Britain bringing milder and wetter conditions by the end of next week. A less progressive Iberian high would have a significant bearing on the prospects for more extensive cold but this has yet to materialise in medium range charts. Admittedly, this outcome is a lifetime away in forecasting terms but the recent trend is suggestive of this.

Earlier this month, Met Éireann launched a new bi-weekly updated monthly forecast.  In its updated monthly outlook issued today, Met Éireann has said temperatures over the next two weeks will be on average 1c below average with a more north-easterly regime taking hold in 10-14 days.  

In the opening week of February, Met Éireann says, temperatures are signalled to be colder than normal across Ireland and Britain, suggesting that a cold airmass originating from Scandinavia may influence our weather.  It adds, "Indications suggest precipitation will be higher than normal in the east and south in this airflow, with drier than normal conditions elsewhere, further reinforcing the indication of a mainly easterly airflow."

The uncertainty presented over the coming weeks is exemplified in the UK Met Office’s analysis of next week's weather.  It says, "The UK is on a fine line between being more frequently cold or more frequently mild."

In its monthly outlook, the Met Office says, "There are some strong signals for the low pressure track (which at the moment is displaced south in Spain and Italy) to return nearer to the UK, which would bring milder but wetter and windier weather. However, this comes with a rather large caveat: the polar vortex. This is a circulation of winds in the stratosphere, about 40-60 kilometres above the surface, and typically keeps cold Arctic air trapped at the pole. In early January, the vortex weakened and became displaced over Europe, and it's still overhead now. It usually takes a few weeks for the effects to reach the surface, so around mid-to-late January until early February we expect an increased chance of cold outbreaks."

According to IWO's Senior Forecaster Peter O'Donnell, "WEDNESDAY will be windy and cold; the offshore strong west to northwest winds will move onto land in the morning and spread through all regions by mid-day, reaching 70 to 110 km/hr. Bands of wintry showers will form over the Atlantic and move inland, turning increasingly to snow as they get further inland and especially so when crossing higher ground. Some hail showers may also be in the mix, but the east and south will have some sunny intervals. Morning lows near -2 C and afternoon highs 2 to 4 C but feeling more like -5 to -8 C in strong winds.

"THURSDAY will be similar except that the wind speeds will be down into a more moderate range of 50 to 80 km/hr, temperatures in a similar range (-2 to 3 C) and scattered bands of wintry showers with some snow accumulations possible on hills.   FRIDAY will be less windy but will remain cold, with sunny intervals and isolated wintry showers. Lows near -5 C and highs 1 to 4 C.

"SATURDAY remains a day of some mystery as model guidance ranges from a brief return to milder conditions with rain, to mixed bands of rain, sleet and snow from south to north, and also some scenarios of a wider snowfall event with strong east winds. Stay tuned on this one, it could go either way (I can predict who already said it will rain).  Temperatures will be determined by which outcome prevails, the all-rain scenario would see a quick rebound to the 8 to 10 C range, the mixed bands would run from that value in the south, to 1-2 C north, and the mostly snow and south coast sleet scenario would probably involve temperatures near or slightly above zero.

"By SUNDAY that disturbance, on whatever track it chooses to take, should be over Britain or northern France and colder weather would set in again briefly, with temperatures near 2 C and north to northeast winds. There could be some localized wintry showers with that. The OUTLOOK for the following week is somewhat uncertain but would most likely see a succession of lows crossing Ireland with mixed bands of precipitation ranging from rain in the south to snow in Ulster and north Leinster. This could shift a bit in either direction, but a lot of the guidance ends mid-week so there is only one model to consult for the second half of the week; that one was trending milder at that point. But the others looked like they might not necessarily follow that lead," Peter added.

A betting person would put their money on the Atlantic winning through and a zonal setup becoming the order of the day for the rest of the meteorological winter (today is the halfway point).  Why?  Because our weather is predominantly mild and unsettled in winter and it’s always a good bet.  A resurgent Atlantic is unlikely however.  Current indications suggest that the next 7-10 days will see Ireland in a transient setup where cold and milder south-westerlies are never too far away and airmasses may potentially interchange until a more settled patter of weather evolves.  IWO will continue to monitor  the weather prospects and Peter will have an updated forecast online tomorrow.