Twinned Bow - Bilfingen, Germany

Last updated on September 16, 2023

Twinned Bow - Bilfingen, Germany

On June 15, 2006, a remarkable atmospheric phenomenon known as a "Twinned Bow" was witnessed in Bilfingen, a town northwest of Pforzheim, Germany. This captivating event was captured by Michael Großmann and showcased the stunning beauty of nature's optical display. The weather that day began with clear and warm conditions. However, in the afternoon, a sudden stormy wind blew in, accompanied by a brief shower. Surprisingly, after just 15 minutes, the weather cleared up again, leaving behind an awe-inspiring sight that was the twinned bow.

A twinned bow is an intriguing occurrence where the primary rainbow appears doubled, creating two distinct arcs in the sky. It should not be mistaken for supernumerary fringes, which are additional bands of color observed within a single rainbow. Twinned bows are often associated with violent showers and are relatively short-lived phenomena.

The exact cause of twinned bows remains somewhat of a mystery. However, one theory suggests that the twinning effect may be the result of raindrops of different shapes and sizes interacting with sunlight in a unique way. It is hypothesized that small spherical raindrops and large flattened raindrops contribute to the formation of the dual arcs. The fact that the secondary bow does not exhibit splitting further supports this hypothesis.

While the phenomenon of twinned bows is fascinating, it is relatively rare to witness such an event. These atmospheric optical wonders tend to occur during intense and turbulent showers, making their appearance sporadic and unpredictable. Additionally, their fleeting nature adds to their allure, as they often vanish as quickly as they appear.

The twinned bow observed in Bilfingen serves as a reminder of the extraordinary beauty that can arise from the interplay between light and water droplets in our atmosphere. Nature constantly surprises us with its ability to create captivating visual spectacles that leave us in awe of its wonders.

In conclusion, the twinned bow witnessed in Bilfingen, Germany, on June 15, 2006, was a breathtaking example of atmospheric optics. This rare phenomenon, characterized by the doubling of the primary rainbow, is often associated with violent showers and lasts only for a short period of time. While the exact cause of twinned bows remains uncertain, the hypothesis of different raindrop shapes and sizes contributing to their formation holds promise. Witnessing such a unique event serves as a reminder of the mesmerizing beauty that can arise from the interaction between sunlight and water droplets in our atmosphere.

Twinned Primary, Single Secondary Rainbow imaged by Michael Großmann. ©Michael Großmann, shown with permission.

"The bow was seen June 15 2006 at Bilfingen, northwest of Pforzheim, Germany. The weather that day started clear and warm. In the afternoon a fresh stormy wind came up with a short shower. After 15 minutes the weather became clear again. It was the only shower that day"

Twinned bows are a doubling of the primary - not to be confused with supernumerary fringes. The twinning is often associated with violent showers and only lasts a short time.

We don't know for sure what causes them. The two bows might be produced by two types of raindrop, small spherical ones and large flattened ones. The lack of splitting of the secondary bow give some support to this.

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Reference Atmospheric Optics

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