The meteorological winter season, 2021/22, began on Wednesday. However, some wintry weather conditions continue to be present in Europe throughout the week. The weather pattern is dynamic and progressive and will continue into the next week. A powerful North Atlantic storm Barra will be heading towards Ireland and the UK with potentially damaging winds and major waves.
Monday’s large and deep trough, which is located over the North Atlantic, will cause a rapidly deepening, fast-moving surface low. It will be moving from eastern Canada towards Western Europe. The low will tend to explode cyclogenesis before reaching Ireland’s coast early Tuesday morning.
This deep frontal storm will be called Barra, the second named storm in the winter season 2021/22, and it is expected to bring severe weather conditions to the UK, Ireland, Scotland and Wales starting Tuesday and continuing through Wednesday. Travels will be disrupted locally by powerful winds and rain storms. The Scottish Highlands will be blasted to the north by a lot of snow.
Barra is an Irish name that made the list for season 2021/22, which includes 22 names. Since 2015, the Irish Met Éireann and the Met Office (UK) have been working together on the storm names partnership to help raise awareness of the potential impacts of severe weather and were joined by KMNI (Netherland) in 2019.
The first one this year was a storm Arwen, a powerful extratropical cyclone that was part of the 2021–22 European windstorm season. It impacted the United Kingdom, Ireland and France, bringing snow and strong winds at the end November (25-27th). Wind gusts reached a peak speed of 177 km/h (110 miles per hour), with the lowest recorded pressure at 973 mbar. Storm Barra is forecasted to be even stronger.
Storm Arwen resulted in at least three deaths and widespread power outages throughout the affected areas. People were killed by falling trees. Around 120 trucks were stranded on a motorway near Manchester because of the deep blowing snow. Trains between Newcastle & Edinburgh were cancelled. The storm’s worst-hit was for parts of the north of England, Scotland, and Northern Ireland from late Friday and early Saturday.
Before we go into more detail about the storm Barra, let’s take a look at how the exploding cyclone and a strong windstorm will affect western Europe.
Winds are expected be strong, locally damaging, with possibly hurricane-force winds along the western-southwestern coastline of Ireland. Also, destructive waves up to 40+ feet high are possible.
This system will be known as classic bombogenesis, a term that meteorologists around the world use. These cyclones are formed when a cold and warm air mass collides. Bombogenesis is the process that forms a rapidly strengthening surface low. This is what is known as a bomb cycle.
BOMB CYCLONE BARRA – WHAT IS IT AND HOW SUCH STORM FORMS?
The storm Barra will intensify quickly in its final stages before it reaches western Europe. It is possible that we will see a huge conveyor belt wrap around the deep low with a strong warm seclusion Monday evening. This will lead to the formation of a powerful/destructive windfield near the center.
Weather models are consistent with the pressure drops once the low enters its rapid intensity overnight to Tuesday. bomb cyclone phase. An example of a bomb cyclone can be seen in the satellite below – this is the powerful Atlantic storm Dennis in mid-February 2020.
Note: A bomb cyclone is a deep low that is caused by a system intensifying rapidly. Bomb cyclones are formed when explosive cyclogenesis, also known as bombogenesis, occurs. This is when the system’s barometric pressure rapidly drops. To be classified as a bomb-cyclone, the system must experience a minimum of 24 hours of atmospheric pressure (a millibar means atmospheric pressure).
Like a normal extratropical storm, a bomb-cyclone’s energy is generated by temperature variations. This includes the temperatures at the Equator and Arctic regions, as well vertically throughout the atmosphere. This type of cyclone differs from tropical cyclones which derive their energy from the extremely warm sea surface temperatures in tropical regions.
The North American continent’s east coasts are ideal breeding grounds for cyclones during the colder months. A cyclone can rapidly develop or explode because of the interaction between cold continental air, warm, humid ocean air, and moist ocean air.
Bomb cyclones are very common in winter months of the North Atlantic. However, they can also occur throughout the year, including systems that quickly reform from a decomposing tropical cyclone when they travel north towards Europe.
Every year, there are around 70 bomb cyclones. About 50 (two-thirds), are located in the Northern Hemisphere. They are particularly concentrated off the east coasts and North Atlantic of the U.S., as well the northwestern Pacific around Japan. Australia also experiences several bomb cyclones each year, although they don’t tend to intensify as rapidly as the North Atlantic or Pacific storms.
PROGRESSIVE WEATHER PATTERN FOR EUROPE IS ESTABLISHED
The very dynamic weather pattern over Europe continues this weekend. A large and deep upper storm is sweeping the continent’s central parts. Another snowstorm is sweeping the Alpine region and central Europe. The majority of the snowfall is located over Austria, but also partly over Czechia and Slovakia.
The large low is visible in the North Atlantic. However, a wave which will become storm Barra has already been seen to the east coast of Newfoundland.
Progressive weather patterns mean that we are experiencing unpredictable weather conditions with changing and dynamic weather conditions. Frontal systems disturbances travel across Europe several times a week, which means we are experiencing unpredictable weather conditions. This has been happening since mid-November thanks to the Azores and northern Europe’s well-established blocking highs.
This means that we often have more severe zonal flow winds patterns across the North Atlantic. These wind patterns deliver air masses roughly from West to East. A deep trough and lots of cold air mass at the mid-upper levels further north towards Arctic region means that deep cyclones or frontal systems are formed over the Atlantic. These systems travel towards Europe colliding with already cooler conditions across the continent.
Recent reports have shown that there has been some snowfall in the UK, Northern Spain, Central Europe, the Alps and even Scandinavia. There has been a lot of snow accumulation along the southern Alpine flank, some as high as 100-200cm.
Further north, Fennoscandia, which is home to a huge amount of very cold and seasonally extreme temperatures, has overtaken most of Scandinavia. Temperatures have been pushing down to nearly -35 °C in the most exposed area, especially over the Lapland region across northern Sweden, Finland, and Norway.
The attached maps below show the Sunday morning temperatures. Extreme cold continues across Lapland. This is even 10 degrees Celsius below the normal temperature in early December. The cold temperatures in northern Europe are expected to persist for at least another seven days.
A NEW WEEK STARTS NOW, WITH A RAPIDLY DEVELOPING STORM BARRA DIRECTING THE IRELAND & UK
A wave will begin to eject from eastern Canada on Monday morning and it will be moving very fast across the North Atlantic towards Europe. A second intrusion of the colder air mass from Greenland to the North Atlantic will cause a South Lobe of the Polar Vortex circulation to create an organizing surface depression somewhere in middle of the Atlantic.
The general weather model consensus suggests that the surface pressure will fall rapidly as the pressure drops by 15-20 mbar within 12 hours. This is because the pressure drop in the atmosphere will be rapid. The surface pressure will drop to 955 mbar by Tuesday afternoon or late morning near the western coast Ireland.
This is a result of almost 45-50mbar change in approximately 24-30 hours. It’s an extremely rapid pressure fall to say the least. It is enough to give a bombogenesis classification. The following chart shows how storm movement and pressure fall are changing.
Monday evening will see the pressure rise to the low 970s at night. There will be a well-defined frontal structure, intense rainfall, and high pressure. Storm Barra will get even more organized overnight and into Tuesday morning, moving slowly towards Ireland with intense rain/wind gusts before daylight. The main front squalls across Wales and southwestern England will begin once the center of Barra has reached Ireland.
Barra, a North Atlantic storm, will bring a lot of rain to western Europe, particularly in Ireland, the western UK, Scotland and Wales. Some areas could receive as much as 80-120 mm of rainfall through Wednesday night. Rivers could cause flooding.
Below is the ARPEGE and ICON EU comparison chart. Both show a similar picture of the strongest and most extreme rainfall amounts.
Behind Barra, an enormous pool of much colder atmospheric mass will spread across Atlantic and slowly push towards southwestern Europe through Wednesday & Thursday.
Notice also how the extreme cold remains in place across northern Europe, with temperatures about 8-10 °C below normal from the Baltic region into Sweden, Norway, and Finland. Temperatures will continue to stay well below zero for days, with mornings below -30 °C in Lapland.
After the storm Barra has ended at mid-week, some cold weather will spread across western Europe and last into the weekend. Barra’s southern portion will lead to a secondary low that will form towards central Europe and northern Mediterranean. This will create a winter storm with new deep snowpack.
STING JET CAN PRODUCE HURRICANE FORCE WIND GUSTS OF UP TO 200 KM/H
Due to the system’s rapid intensification and bombogenesis on Monday night, violent, hurricane-force winds will likely develop with it. The highest wind gusts will be above 160 km/h, possibly even up to near 200 km/h within the so-called phenomenon – a sting jet. These rapidly developing surface cyclones in North Atlantic often produce a wind maximum.
A stingjet is a narrow, violent zone that originates from within the mid-tropospheric clouds of explosive cyclogenesis. The jet’s descent increases the strength of the stingjet, drying out and evaporating the precipitation.
This evaporative cooling causes the air inside the jet to become denser. This accelerates the downward flow towards cyclone center tip, which is where the clouds head wraps around the tip. Below is a satellite that shows the typical appearance of a Sting Jet with Atlantic Cyclon Jorge at the end February 2020.
The aforementioned sting jet wind maximum will develop on Monday night into Tuesday. It will then spread across the long swath of the storm Barra until it reaches its peak before the severe impact on the Irish coast on Tuesday. The jet is predicted to generate winds of nearly 200 km/h according to high-resolution modeling. These are impressive gusts of 125 mph and could even reach the Irish coast.
Although it is uncertain how intense and where exactly the stingjet will develop, most of the high resolution weather models, including those from the global GFS or ECMWF, are aiming at its development once explosive bombogenesis begins Monday night.
Below are additional comparison tables by the ICON model (in addition to the ARPEGE models above), showing the slightly different track and direction of the Atlantic storm Barra. This shows the extent of the strongest hurricane force winds. However, the cyclone is expected to be much deeper than we can see from the charts above, possibly in mid 950s. This will mean that winds will be strong and violent in many parts of Ireland and the UK on Tuesday.
The winds along the southern portion of the storm Barra will be the strongest from Monday afternoon through Tuesday noon until the system reaches Ireland. Normally, winds are at their strongest during the bombogenesis phase when the central pressure is deepening rapidly and intensely.
Storm Barra will display the typical appearance of an extratropical hurricane of the same intensity and scale as those being simulated over the next few days.
Barra is also at risk from large swells and waves that will hit western and southwestern Europe. As a powerful low forms on the Atlantic along the wave heading from Newfoundland toward Ireland, the large area with strong westerly winds will cover nearly the entire northern half the North Atlantic.
These types of North Atlantic storms typically generate a stronger, longer-lasting swell for days. The strongest waves will likely blast west and southwestern Ireland. However, they could also be very high once the front reaches northwestern France (Brittany), on Tuesday.
Images in this article were provided courtesy of Windy and Wxcharts.
Source: Severe Weather