DISCUSSION: Earlier today, a line of thunderstorms erupted over Austria and dropped decent sized hailstones all over the region. Videos shared to Facebook show golf ball sized hail impacting the southern part of Austria, however thunderstorms affected the majority of the country with heavy downpours and powerful winds as well. Hail forms when strong updrafts in a growing thunderstorm pushes liquid water above the freezing level in the cloud. The water droplets eventually freeze and begin to grow as more and more liquid water droplets attach to and eventually become frozen as well. Once the “ice ball” becomes heavy enough to overcome the updraft, it begins to fall to the surface where it reaches the surface as what we know as hail. Hail ONLY occurs in thunderstorms. Hail does NOT occur during winter storms, the frozen precipitation that sometimes falls during winter storms is known as sleet.
Looking at the two videos posted to Meteo Europe’s Facebook page you can clearly see the hailstones falling and making quite an impact. Austria is not new to severe thunderstorms, and according to meteorologists from the region they occur quite often in the month of July. This is the case because Austria is located near the battleground of cool stable air from the north, and warm moist air from the south. Here, with the help of topographical lift, helps thunderstorms to blossom and grow. According to one of the major climate news outlets in Austria, ZAMG reports that July 2016 has been one of the warmest and wettest, since observations began in the country 250 years ago.
No reports of damage or fatalities have emerged from the region, but thunderstorms are expected to continue to impact the country tonight and into the day tomorrow as well. To learn more about other high-impact weather events from across Europe, be sure to click here!
DISCUSSION: As strong to severe thunderstorms erupted once again today across parts of Western to Central Europe, some of these storms moved through atmospheric environments characterized by particularly high vertical wind shear (i.e., a change in the direction and/or the speed in the wind with increasing height in the atmosphere) as well as high convective instability (which supported the generation of very strong updrafts). As the storms encountered this stronger vertical wind shear as well as the stronger convective instability, this favored the development of discrete (and fairly photogenic) storms with the potential for tornadic development.
One such example is included in the video below (courtesy of Anja Horn) where an isolated, rotating storm formed near Wiehl, Germany and eventually generated a tornado. As you can clearly see in the footage below, there were several points during the tornado's existence during which you can clearly identify the presence of a number of very small-scale features which are scientifically referred to as suction vortices. Suction vortices are smaller funnels which are embedded within the larger parent tornado funnel and often cause the most violent destruction within the tornado. If you look closely, you can see how the suction vortices actually appear to "dance" around the periphery of the tornado as a result of the differential wind field changing within the confines of the parent tornado. This is certainly a classic example of very small-scale convectively-associated features causing havoc on society. To learn more about other high-impact weather events from across Europe, be sure to click here!
DISCUSSION: It’s not every day that people get a view like this! A passenger on an airplane flying over Sarajevo, Bosnia yesterday at around sunset filmed a time lapse of quickly maturing cumulonimbus clouds while cruising at an altitude of 37,500 feet (about 11,430 meters). In the beginning of the video, shown below, there are cumulonimbus clouds which exhibited neat structural changes in the form of moisture associated with its updrafts being fanned outward by strong upper-level winds, creating the flat and thin-looking features called anvils. Later on in this footage, low-level clouds as well as other developing cumulonimbus clouds were spotted. The favorable conditions which facilitated the development of these storms included plenty of moisture (i.e., most likely garnered from the Adriatic Sea), sufficient instability (i.e., from daytime heating), and lift (i.e., as a result of orographic enhancement due to the presence of geographic features such as the Dinaric Alps). To learn about other high-impact weather events across Europe, click here!
DISCUSSION: As strong to severe storms fired up within the warm-front sector of an intensifying low-pressure system across portions of Western Europe (just 3 days ago), some of these storms developed within regions characterized by particularly high convective instability as well as strong vertical wind shear. For those who are unaware, vertical wind shear is the scientific term used to reference the presence of winds which change with direction and/or speed with height. As a result of this change in the direction and/or the wind speed (i.e., between the surface and points well-above the surface), this can sometimes bring about the generation of rotation in the lower to middle portions of the atmosphere. As a result of these storms encountering stronger vertical wind shear, storms often tend to develop a rotating updraft core which is capable of producing strong downbursts, tornadoes, heavy rainfall, and frequent cloud-to-ground lightning. In the video below (courtesy of Krisztian Kiszely), you will denote the photogenic time-lapse footage of a supercell which developed in portions of Western Hungary on Wednesday afternoon (local time).
Note how in the time-lapse video below, you can clearly see the developing feature known as the "beavers tail" on the right side of the video as it evolves. This "beavers tail" is a consequence of the complex processes defined primarily by low-level convergence of both moisture and air-stream flow which results in rapid condensation of water vapor in the lowest levels of the atmosphere. Additionally, upon looking even closer (near the center), you can identify the episodic development of the wall cloud near the center which forms as a result of a number of complex processes (i.e., within the supercell thunderstorm); facilitating the lowering of the cloud base near the southwest portion of the supercell thunderstorm (i.e., near the feature known as the hook echo and statistically is the most probable location for tornadic development). Therefore, this is just one example amongst thousands of others which prove how even the most photogenic of time-lapse videos contains a multitude of interesting features and can often pose a significant threat to both life and property. For that reason, it is always critical to keep your eyes to the skies when severe weather is threatening. To learn more about other high-impact weather events from across Europe, be sure to click here!
QUITE A LIGHTNING SHOW ACROSS WESTERN/ NORTHEASTERN EUROPE IN THE PAST 24 HOURS! (credit: lightningmaps.org via Meteo Europe)
DISCUSSION: Over the past 24 hours, there has been an impressive onsalught of strong to severe storms; primarily focused across parts of Western as well as North/Northeastern Europe! Note the particularly high-density of lightning strikes observed and recorded across parts of Eastern France, many parts of Italy, and several countries across far Eastern Europe! This very concentrated lightning across far Eastern Europe was primarily generated by a strong line of thunderstorms which moved fairly slowly off to the east-southeast with time during the course of yesterday afternoon/evening! Though this is fairly common during the heart of the famous Summer-time convective season, it is still always impressive to witness (even from a long distance perspective) such intense (and widespread) thunderstorm events across the entire expanse of Europe. To learn more about this and other high-impact weather events from across Europe, be sure to click here!
PICTURESQUE DOWNBURST OBSERVED NEAR PUEBLA DE ALCOCER IN BADAJOZ, SPAIN! (credit: David Mancebo Atienza via Meteo Europe)
DISCUSSION: As strong thunderstorms erupted over parts of Central to Eastern Spain earlier in the day on Wednesday, some of these storms moved into regions which were dominated by what are referred to as low-level lapse rates and facilitates the development of strong downward motions within thunderstorms which are scientifically referred to as downdrafts. Last rates are simply a measure of the amount of temperature change measured every 1 kilometer vertically in the atmosphere. As a result of stronger low-level lapse rates, the thunderstorms that formed in certain parts of Spain such as this storm which formed over Puebla De Alcocer in Badajoz, Spain produced an atmospheric phenomena known as a downburst. A downburst occurs within a thunderstorm when there typically is a strong gradient in the temperature and/or the moisture content within or just below the base of storm which forces the rain-cooled air descending through the middle to lower parts of the storm to speed up towards the ground. This is often visually observed as a downburst such as that seen in the image below. Often times, downbursts can often be quite destructive as well as life-threatening in many situations (particularly in more densely populated areas where more objects can easily become hazardous projectiles under the circumstances of a downburst moving through a given region)! To learn more about other high-impact weather events from across all of Europe, be sure to click here!
DISCUSSION: As of earlier today, very strong thunderstorms moved through parts of Central to Eastern Europe. In doing so, a few of these storms produced life-threatening wind events known as downbursts. Downbursts occur as a result of rain-cooled air located within the middle-to-lower portions of a given thunderstorm rushing down towards the ground and spreading out violently. These thunderstorm-induced wind events are often capable of producing severe wind damage to homes and businesses due to any loose objects in the region quickly becoming air-borne and impacting surrounding structures. Note how in the video below you can clearly see the trees being whipped back and forth very quickly in the rapidly changing wind direction and speeds. To learn more about this and other high-impact weather events from across Europe, be sure to click here!
DISCUSSION: As of earlier yesterday afternoon, there were very strong thunderstorms which developed across Western and Central Spain. However, as a result of there not being much of any westward forcing mechanisms in place, these strong thunderstorms were very slow-moving. The result of their particularly slow propagation rate was the accumulation of incredible amounts of hail as seen in the image below courtesy of @Pedromad. This is not entirely unusual in this part of Europe since Spain often experiences strong storms capable of producing strong winds and comparably-sized hail. This climatological propensity for the development of stronger storms across Central and Eastern Spain during the earlier part of the summer is a consequence of warm fronts associated with incoming low-pressure systems off of the Northeastern Atlantic Ocean being ideally positioned with respect to Central and Eastern Spain. To learn more about other high-impact weather events from across Europe, be sure to click here!