Numerous trees were felled, containers in ports flipped, at most 12 people died, and many residents were injured. That’s the toll of a historic Storm Eunice, the strongest Atlantic cyclone in decades that brought destructive havoc to western Europe on Friday. Although it will take days to recover, the weather is not kind to the region. On Sunday night, Frankin, another potentially powerful windstorm, will blow across Ireland and UK, with hurricane force winds again. Then, on Monday, another bomb cyclone follows it as Polar Vortex over us is unusually intense.
Violent windstorm Eunice battered Ireland, Wales, England and the English Channel into northern France. It also left many 100.000 homes without electricity in the UK. The transport network was severely disrupted by Eunice’s destructive winds of up to 200 km/h (125 miles/h).
The UK Met Office issued a rare Red Warning, while our forecasters gave a HIGH RISK for strong winds on Friday. High winds caused school closures, flight cancellations, and at least one death.
The Isle of Wight saw a record-breaking wind gust of 122 mph = 196 km/h in England. This was higher than the previous record of 120 mph (190km/h) set in 1978 at Gwennap Head in Cornwall. Many areas reported gusts of 150-180 km/h.
Looking at the satellite image this Saturday afternoon, we can see a quite similar pattern is developed as it’s been with the Dudley and Eunice storms a few days ago. Eunice is leaving the Baltic region, while a large upper wave disturbance is developing over the Atlantic Ocean.
To the north of this front zone, an Arctic cold blast is spreading from Canada across the Labrador Sea into Canada. This disturbance is clearly visible by the cloud patterns at its front edge. With the zonal flow to its north, the Azores High, warmer air is being drawn towards Europe.
Analysis of the surface patterns shows that a large depression is forming south of Greenland. The frontal baroclinic area extends southwest all the way to Gulf of Mexico and is 3000+ km in length. This setup is likely to lead to another dangerous weather system in the region.
The NOAA Ocean Prediction Center has declared hurricane-force winds as the cyclone moves closer towards Iceland. The central pressure will drop to around 15-20 mbar by Sunday morning, before the low takes a sharp turn towards southeast and heads towards western Europe. Northern Ireland and, in particular, western Scotland Sunday night.
This system will be our main focus from Monday morning. After destructive storm Eunice and a severe windstorm in western Europe, the upcoming Franklin could again be a very strong and potentially dangerous windstorm for parts of western Europe. Through Sunday night, violent, hurricane-force winds of up to 100 mph are expected. There will be major 15m waves in Ireland, Northern Ireland and western Scotland.
Below is a quick overview of the Franklin as it develops and the bombogenesis that occurs over the Atlantic. The first Franklin will be seen in western Europe within the next 48 hours. A monster for Iceland will follow on Monday night. This air mass will be relatively mild so no significant winter weather is forecast. For areas affected, the main threats are intense rain and wind gusts.
The impact of both storms on the marine traffic in the corridor between northwestern Europe and eastern Canada and the Northeast U.S. is quite significant. Additionally, we can expect to see additional tree damage, power outages, and traffic disruptions at the areas where the strongest winds are expected.
As was the case with the recent storm Eunice it is likely that the North Atlantic’s very active weather pattern is responsible for the development and emergence of powerful cyclones. These cyclones are triggered by the Polar Vortex, a feature also known as the Arctic Storm. Before we go deeper into the latest forecast regarding storm Franklin and another violent low near Iceland, let’s quickly learn why it is important to understand the background of the Polar Vortex.
THE POLAR VORTEX THAT DRIVES ALL OF THESE EVENTS
When we look at how the Earth’s atmosphere is made, six layers are visible. The lowest two layers, known as the troposphere or stratosphere layers, are where most of the weather-related phenomena that affect our lives happen.
The lowest one sitting on the Earth’s surface layer is the troposphere, this is where all the weather changes we encounter take place. The troposphere layer extends from the surface to approximately 12 km up in the sky. The depth of the layer can vary from 8 km to nearly 20 km depending on where you live. The troposphere, which is located above the equatorial zone, is thickest and it gets thicker above the North- and South poles.
The stratosphere is the layer that lies just above it. The stratosphere layer is approximately 10-50 km deep, and the air within it is also very dry. This layer also contains the Ozone layer, the one that has a vital role in the protection of our planet’s life against the storms from the Sun.
The stratosphere is home to the most important component that triggers all weather dynamics. It is called the Polar Vortex. The Polar Vortex is a huge, three-dimensional ring that generates powerful winds high above our heads. It surrounds both the North and South poles, grazing the air at about 20-50 km above the Earth’s surface.
The Polar Vortex is strongest during winter months in both Northern and Southern hemispheres. It is exceptionally strong this Winter Season 2022/22. The Polar Vortex affects winter weather every year from October to March.
The troposphere and stratosphere layers are both crucial for the climate in which we live. The Polar Vortex covers the majority of the atmosphere’s bottom half. It extends from the middle of Earth’s troposphere up into the stratosphere layer. As you can see, the Polar Vortex plays the most important role in winter weather across high and middle latitudes.
The Polar Vortex spins above our heads but is still connected to the lower atmosphere. It acts as a large hemispheric circulation, giving our weather shape in many ways. The Polar Vortex has been responsible for all the dynamic systems we have observed this winter.
How does the Polar Vortex form?
The northern hemisphere’s polar regions begin to see less sunlight from the autumn months. This is the consequence of the stronger inclination of the Earth’s axis, as the North Pole is sent into the position that it starts cooling down. The result is that polar nights can last several months and days without sunlight.
While the polar regions are becoming colder, the atmosphere layers in the equatorial areas to the south are still warmer than the regions further north. These regions receive more sunlight and energy, which creates a high temperature contrast between them.
As the poles get cooler, this is also affecting the surface pressure. This is actually a very similar weather process that also occurs in the stratosphere layer over it. The temperature difference between North pole and equatorial areas rises. This results in the formation of a large low pressure cyclonic circulation through the polar stratosphere. This is why we call it The Polar Vortex.
All these facts combined, the Polar Vortex acts as a large and thick cyclone. It extends from the North Pole to the mid-latitudes. It is the same in the southern hemisphere, too. If you look at the chart, it shows an example of the Polar Vortex at around 30km (18 miles) altitude, which is close to the top of stratosphere during winter season.
This year’s unusually intense and active Polar Vortex has been the main driver behind the recent storms Dudley & Eunice. It will also be the driving factor of storm Franklin and the new storm next Wednesday. As is the norm, the Arctic Canada-based leading upper wave disturbance draws the cold air into North Atlantic, and the response is rapid cyclogenesis toward Europe.
This often leads to a combination Arctic cold and intensifying winter storm ejecting east North America. This creates the conditions for significant deepening in the Atlantic. The central pressure will be rapidly increasing, and we often see a bomb cyclone. This meteorological term is used when the central pressure of a system falls very quickly. You will notice that the storm is stronger the lower the pressure.
What is a Bomb Cyclone and How Does It Form?
The typical criteria that will indicate that the system is a bomb cyclone is the pressure shift that we see in the forecast charts for Monday through Tuesday in North Atlantic, and around Iceland. This means that the surface cyclone will intensify rapidly, with its central pressure falling very quickly (or even for a while).
As the developing low’s barometric pressure rapidly increases, this is when explosive cyclogenesis (also known by bombogenesis) will be spoken of.
A system that experiences a minimum of 24 millibar pressure drop within 24 hours must meet the criteria for being classified as a bomb-cyclone. It is a purely tropical system, also known extratropical cyclone. This system develops rapidly from low-pressure systems. The satellite image above shows a typical example of a bomb cyclone. This is a classic Nor’Easter bomb storm along the U.S. East Coast from a few years ago.
Extratropical storms in the North Atlantic can grow to be very large and often dominate large portions of the ocean (or sometimes the North Pacific). These systems move towards the northeast due to the Coriolis force. They are extremely large and produce hurricane-force winds. You can also expect to see large waves, coastal flooding, or even severe winter storms that bring a blizzard across the country.
A bomb cyclone, which is very similar in appearance to an extratropical low, is fueled primarily by fluctuations in temperature. Interactions occur between the warmer air mass at the Equator and the Arctic region’s colder temperatures. These processes also occur vertically throughout the atmosphere.
These types of Atlantic storms, despite looking like tropical cyclones from satellite imagery, are very different to hurricane-season systems. Extremely warm sea surface temperatures are what hurricanes use to get their energy.
Meteorologists track these systems with annual statistics. The east coasts of North America are well-known as the ideal breeding ground for these types of cyclones in the late fall and winter months. They can cause severe winter storms in parts of Canada, the Northeast United States, as well as a continuation into the North Atlantic and Europe as strong storms.
This is because the combination of Arctic cold continental mass from Canada and warm, moist tropical air near to the Gulf Stream provides tons of energy that allows a cyclone develop explosively over the warmer waters.
We will often see bomb cyclones during winter months in the North Atlantic, the same with the Nor’Easter storms. These cyclones are possible all year. On average, there are 60-70 bombs forming annually on Earth. About 50 of those are located in the Northern Hemisphere. The Atlantic and east coasts of the U.S.
Let’s now focus on the upcoming severe threats, we will take a deeper look the Sunday’s storm and then the bombogenesis following behind on Monday.
POLAR VORTEX DRAGS FRANKLIN TRAIGHT TO WESTERN Europe SUNDAY NIGHT
The deadly Eunice is leaving Europe, but the North Atlantic is chomping at the air masses, creating more danger for western European residents. A plume of Arctic air keeps the southward flow of cold intrusions going strong thanks to the Polar Vortex’s southern lobe. It seems like the Arctic plume is not ending as it continues to fuel the region by bringing in deep troughs of the north.
This is what happens most often. It triggers more storms and helps them to rapidly deepen as they move towards Iceland or western Europe. The new, potentially dangerous windstorm Franklin is the first system in a line.
The Arctic cold is again present in stark contrast to the subtropical air that is much warmer. The warm air is sweeping across southwestern Europe and western Europe, but it is followed by much colder air by large waves. This is how Franklin will turn east-southeasterly with the strong Azoric high to the south and the deep Icelandic low to the west.
Storm Franklin will likely intensify significantly through Sunday, possibly to 955 mbar in early morning hours, before reaching its mature extratropical high phase. This is the main concept of this system. It matures into a very large storm and generates a larger size. It should have a greater impact with both major waves and violent winds.
Franklin will move southeast through Sunday night. The pressure gradient will become very tight across Ireland and Northern Ireland. This is a sign that violent winds will develop. Below is the sequence that storm Franklin traveled from the south to Iceland, through Scotland Sunday night, and finally reached Denmark on Monday morning. It has gradually increased central pressure but remains intense.
Weather models predict that there will be severe weather in western Europe, with heavy rain and severe winds squalls to south of the main cold front. It is possible that Graupel showers could be mixing with the Atlantic’s cooler maritime air mass.
VIOLENT, HURRICANE-FORCE WINDS EXPECTED FOR IRELAND, NORTHERN IRELAND AND SCOTLAND
Keep in mind that the central pressure will be in the mid 960 mbar when we have such a low. It will travel across Scotland so it will no doubt cause some very violent winds in the most exposed areas. This is particularly true in western Scotland and northwestern North Ireland, where the strongest pressure gradient will be.
The wind gusts that reach the highest heights could reach 80 mph or more (160-200 km/h locally), just off the coast to west-northwest.
The wind fields generated by such large and intense winds will also produce huge waves that will likely exceed 16m at the center of the maximum wind speed. The system will gradually spread southeast, while it advances towards Scotland and North Sea Sunday night.
Waves of great height will sweep the entire western coasts of Scotland, Northern Ireland, & western Ireland. These waves could reach up to 12-14 metres, causing erosion and damage to the coastline.
Although the winds will be intense and persistent, the rainfall amounts won’t be too high. Rainfall peak are expected to be in the terrain-induced precipitation areas. These include Wales, western, northern England, and western-central Scotland. These areas should see 30-70mm of rain from Monday morning.
The temperatures are relatively warmer this time so snow is only expected for the highest elevations. Northern England and the Scottish Highlands, possibly even the highest areas of Wales. Below are the forecasts for snowfall and rainfall.
Once Franklin crosses the North Sea, Denmark and Sweden on Monday, it intensifies again on its way to the Baltic Region. It will be a strong frontal system with a decent amount snow and near-blizzard conditions in southern Sweden and Finland. This will also affect the Baltic countries Monday through night.
The strongest winds should exceed 120 km/h, especially along the Baltic coast of northern Poland.
On Monday, the dangerous wind threat will slowly decay across western Europe. Meanwhile, the North Atlantic will be producing a new violent system. It will be a classic bomb-cyclone, as we discussed earlier.
ANOTHER MONSTER STORM – A BOMB CYCLONE HEADS FOR ICELAND AND FAROE ISLANDS ON MONDAY NIGHT
It is actually quite similar to the Atlantic end-of-January explosion. A textbook example of a bomb cycle is triggered by the continuation of the Arctic plume cold air above the Polar Vortex. The P.V. has been so particularly strong this Winter Season 2021/22, it just doesn’t stop dragging outbreaks of very cold, often frigid cold Arctic air mass across the North American continent into the Atlantic Ocean.
This is the perfect recipe for the Polar Vortex, which can again trigger extratropical storms. The satellite image of the geocolor spectrum satellite from Saturday shows an impressive example of the developing storm induced by Arctic air.
The huge frontal zone that extends from the southern tip Greenland all the way to the tropical region, Gulf and Mexico, is striking. The two large airmass reservoirs of the Arctic cold and the warmer, moist subtropical air will clash on Sunday. It will lead to the literal explosive development of a bomb storm.
A typical process for this type weather setup will see the low go through a significant bombogenesis phase over the next 24 to 36 hour. This will begin Sunday morning with the new wave forming off Newfoundland. It is expected that it will mature into a powerful extratropical hurricane by Monday morning. Its structure at its peak intensity will be quite spectacular, we can expect.
Satellite images often show the appearance of cloud bands that are symmetrically wrapped around a tightening core. The following example is a similar system, taken back in October 2020, when Hurricane Epsilon was also visible close to Bermuda.
The NOAA Ocean Prediction Center’s (OPC) forecast map for Sunday shows that this new system will have an average pressure of 988mbar, centered east of Newfoundland, Canada. A strengthening High along the U.S. East Coast causes the baroclinic zone to drag east and south.
The NOAA’s chart reveals the rapid intensification process is forecast within the following 24 hours, from Sunday morning through Monday morning. According to the OPC forecast, the low should increase from the upper 980s to close to 950 mbar. As Iceland approaches, hurricane-force winds are possible. Also notice the huge pressure difference over the Atlantic, 1040 mbar high over the Azores and 950 mbar below the Icelandic low.
It will cause heavy freezing spray with violent winds in the system’s wake, blasting the Newfoundland and the southern Labrador Sea up to southern Greenland all day on Sunday. This will cause severe problems for the marine traffic traversing this region from Sunday to Monday. They will need to battle dangerous conditions like freezing spray, violent winds, and massive 10-12 meter sea waves.
The system will start at 06 UTC on Sunday off the New England, USA. There, the central pressure is around 1002mbar. The system will sink to 974 mbar in the first 24-hour period (Monday 06: UTC), and then drop to 952 by Monday evening (18 UTC).
That’s a 28-mbar drop within the first 24 hour, followed by a 22-mbar pressure drop over the 12 hours. Remember the criteria to determine if there is a bombogenesis pressure drop of 24 mbar over a 24-hour period. These criteria will be easily broken by this system, which is a common occurrence in bombogenesis storms. That’s a really explosive development at its finest!
The central pressure will continue to rise from Monday night into Tuesday. However, the rapid intensification period will come to an end before the night. When the system wobbles in Greenland and Iceland, pressure should settle at 945 on Tuesday. It will bring about wild winter weather in Iceland and southeast Greenland as well as the Faroe Islands, Monday night through Wednesday morning.
The cyclone is expected to produce violent, hurricane-force winds during the rapid intensification process. It will be heading towards Iceland on Monday and will likely reach peak wind gusts of over 160-180 km/h. These will be the result of a stingjet we discussed earlier as a common occurrence with bomb cyclones this week.
Iceland and the Faroe Islands will also be affected by the winds. This is due to the storm approaching these countries on Monday night into Tuesday. Iceland will be particularly vulnerable to wind gusts, with winds up to 200 km/h on the country’s complex terrain.
As it’s well seen on the chart above, another wind maximum is forecast to be in the Denmark Strait between Iceland and Greenland, once the low retreats back north-northwest after occluding on Tuesday morning. Winds will be significantly increased due to the very strong pressure gradient that exists between the Greenland High High and Icelandic low. Peak gusts can reach 200 km/h across strait when this happens.
Because of the Atlantic’s wide winds, there are likely to be significant waves. These systems are known for producing large waves. The largest waves will be found to the south of the center low, and will likely reach 12-15 meters. Waves will move northeast between Scotland and Iceland on Tuesday. The worst waves will be between Faroes Islands and Iceland.
Monday night will bring heavy snowfall to Iceland and southeast Greenland. It is possible to get 30-50 cm across Iceland. The internal mountain ranges may have closer to 1 meter. Similar across southeast Greenland. Similar distances of 15-30 cm are also found in parts of Faroe Islands.
Blizzard conditions are also expected to develop, as the combination heavy snow and powerful winds will make it ideal for extreme driving conditions and snowdrifts. Driving across Iceland’s majority of the country on Monday night or Tuesday will be dangerous. Many areas will experience whiteout conditions and visibility that is close to zero.
The conditions will improve by Tuesday night with weakening winds, but the Arctic cold will continue to dominate the North Atlantic. The cold maritime airmass will cause widespread showery weather with many snow and graupel showers.
This cold air will also be reaching Ireland, Northern Ireland and the UK on Wednesday. This should bring snow showers, some accumulations, and rain through Thursday. In addition, the Arctic cold flow will continue into the Atlantic through mid-week, which could lead to more intense extratropical thunderstorms.
Weather models suggest a new one for Iceland on Thursday or Friday, and another deep monster over the weekend.
CLASSIC WARMSECLUSION APPERANCE IN THIS CYCLONE
A warmer air mass will move into western and southwest Europe ahead of the North Atlantic’s active weather pattern. This will provide a typical zonal warmth. The Arctic cold air mass will be dragged into Northwest Atlantic by the northwesterly wind, while the Atlantic low is in its wake.
This creates a very didactic fluid dynamics presentation on chart, we can see the large-scale processes working together while the Polar Vortex lobes above trigger weather system.
The above temperature contrast image is a great example of the powerful extratropical lows in North Atlantic. Extremely cold Arctic air can be found in eastern Canada with frigid low temperatures that extend southeast into the northwestern Atlantic.
The violent force of an exploding tropical low will cause the opposite effect further east. A strong warm advection subtropical air mass from the north will move the center low to the north again. This will create a classic comma-shaped temperature map. This is called warm seclusion and it is the sign that the mature phase in the extratropical cycle lifecycle is near.
Warm seclusion could be characterized by cloud-free features that look like eyes on satellite imagery. It can sometimes be reminiscent of tropical storms. It indicates that the system’s warm-core center is surrounded by hurricane-force winds, along the bent-back warm front. Once the warm seclusion has been completed, the mature phase of a cyclone begins and the system’s decaying process is complete.
These weather patterns and systems are very common during winter months in the North Atlantic. They occur after strong Arctic outbreaks from Greenland and Canada, which penetrate into the warmer sea water. Strong winds and waves are usually produced by warm-seclusion storms. Often, winds are particularly violent with hurricane-force speeds in a very narrow area to the south-southwest of the cyclone’s core.
The main driving factor to force these destructive winds is known as the sting jet wind maximum, forming inside the cloud head into the frontal‐fracture region of a Shapiro-Keyser cyclone.
WHAT IS A STING JET?
As you may have heard, Storm Eunice is a meteorological phenomenon that is often blamed for producing powerful (hurricaneforce) winds. These destructive winds are called a stingjet. This extremely strong windstorm can often lead to peak wind speeds well above 150 km/h. In some cases, gusts can even exceed 200 km/h. A Sting jet is a narrow area of extremely severe winds that originates from the mid-tropospheric clouds head in the explosive cyclogenesis, or bomb cyclone.
A textbook extratropical Cyclone is composed of two frontal zones: the warm front and the one following it. The cold conveyor belt is a strong wind flow of cold mass that develops into the cyclone before the warm front. Following behind the main cold front, a much cooler and also drier air mass, very often originating from the Arctic region, flows into the cyclone’s core. The dry intrusion forms towards the core of a deepening storm, usually from the southwest.
The cold conveyor belt generally brings cold and moist atmosphere towards the center of the extratropical thunderstorm, along with rain and snow. The dry intrusion is cooler and also more dry, and it brings the cyclone’s center air. The precipitation that falls from the cold conveyor belt to the dry air within a dry intrusion leads to droplets quickly evaporating, which further cools the air mass through a process called evaporative cooling.
As the air is drying out, the strong winds are intensifying as they descend towards the surface. The winds are literally grazing the air and vaporizing the layers on the nose of the descending jet. This clears the path through the precipitation. Evaporative cooling causes the jet to become denser, which in turn accelerates the downward momentum. The winds are pushed to the tip of the cloud head, when it wraps around cyclone dead center.
These processes with the stingjet occur at altitudes of 3-4 km above sealevel and can lead to very severe wind gusts. These gusts can easily exceed 90-100 mph (150-161 km/h), or even more than 125 mph (200km/h) in the evening with the strongest cyclones. A developed sting jet wind maximum is fairly easily recognizable as the cloud, hooked just like a scorpion’s tail. This is what gives the violent wind region its name.
The composite satellite image above hints at how well the shape of a textbook cyclone with a sting jet looks like with a scorpion’s tail layered above. This is quite amazing. A sting jet typically affects a small area, usually between 100 and 200 km in diameter. It is also smaller than the parent large-bomb cyclone. Although it usually lasts for several hours, it can reach land areas and cause destructive winds.
We can expect to see the typical satellite appearance of the cloud heads that are associated with bomb cyclones carrying sting jets when we see storms erupting over the Atlantic Ocean. As we saw above, the cloud head is strongly curved into the cyclone, that is why it will look like a scorpion’s tail and stinger alike shape.
Also note, that these cloud bands disappear quite sharply on the jet’s front edge due to the effect of evaporation in the dry air of the dry intrusion.
Images used in this article came from Windy, TropicalTidbits (Wxcharts), and Windy.
Source: Severe Weather