Storm Chase Analysis: Observing Spectacular Thunderstorm Cloud Structures and Tornado Development over the M25
Introduction:
On [10/05/2023], I embarked on an exhilarating storm chase, which yielded mesmerizing encounters with various awe-inspiring thunderstorm cloud structures. These remarkable meteorological phenomena included anvils, shelf clouds, and low cloud bases. The pinnacle of this extraordinary chase was witnessing the development of a funnel cloud, evolving into a full-fledged tornado, over the M25 region. This analysis will delve into the meteorological intricacies behind these captivating storm features, using advanced terminology to enhance the understanding of the atmospheric dynamics at play.
Anvils:
During the storm chase, I observed a multitude of anvil clouds, an iconic feature commonly associated with mature thunderstorms. Anvils result from the rapid vertical growth of convective updrafts, driven by strong updraft velocities and the presence of a stable layer aloft. As the updrafts reach the tropopause, they encounter a region of colder air, causing the ascending air mass to spread horizontally. The resulting anvil-shaped cloud formation extends in the direction of the prevailing wind, which helps to illustrate upper-level wind patterns. The presence of these expansive anvils indicates the vigor and maturity of the thunderstorms encountered during the chase.
Shelf Clouds:
One of the most visually striking phenomena witnessed during the storm chase was the presence of shelf clouds. These menacing formations often precede the arrival of a severe thunderstorm and are indicative of strong, gusty winds associated with the approaching storm. Shelf clouds form along the leading edge of a thunderstorm's gust front, where cool, downdraft air from the storm's outflow collides with warm, moist inflow air ahead of the storm. This collision initiates the lifting of warm air, leading to cloud formation along the gust front. The resulting shelf cloud appears as a low, wedge-shaped cloud structure, typically characterized by a turbulent and billowing appearance.
Low Cloud Bases:
Throughout the storm chase, I frequently encountered thunderstorms with remarkably low cloud bases. Low cloud bases are indicative of highly unstable atmospheric conditions, allowing the thunderstorm to develop closer to the ground. Several factors contribute to the formation of low cloud bases, including high moisture content, intense surface heating, and steep lapse rates (a rapid decrease in temperature with height). These conditions promote vigorous updrafts, enabling the thunderstorm clouds to grow and extend closer to the surface. The presence of low cloud bases suggests a high potential for severe weather, including strong winds, heavy rainfall, and the possibility of tornado formation.
Funnel Cloud and Tornado Development:
The highlight of the storm chase occurred over the M25 region, where I observed the development of a funnel cloud, subsequently progressing into a tornado. A funnel cloud is a rotating column of air that extends from the base of a cumulonimbus cloud but does not reach the ground. It represents the initial stage of tornado formation. The formation of a funnel cloud requires a combination of favorable atmospheric conditions, such as wind shear (a change in wind direction and/or speed with height) and a strong updraft within a supercell thunderstorm. As the updraft intensifies, it begins to stretch and rotate the horizontal vorticity present in the storm's environment, eventually leading to the formation of the funnel cloud.
