Appareance In Satellite Data

Depending on the synoptic situation, bora sometimes occurs with clouds gathering on the hilltops and moving towards the sea with rain or snow. This type of bora is usually reffered to as a "dark bora". On the other hand, a "clear bora" is a bora with clear skies, which is the more frequent case.

Since bora is a wind phenomenon it is not directly visible in satellite images, but there are different cloud structures typical to bora cases. In strong, deep-layer bora cases, lee clouds can develop all across the Adriatic Sea, reaching the Italian coast. The effects of bora on cloud formation are most clearly seen in HRV images or RGB combinations of IR 10.8 µm and HRV images.

10 February 2015/13.00 UTC - Meteosat 10 RGB image (HRV, 10.8, 10.8)

In the loop of HRV-IR images lee waves can be seen forming all across the Adriatic towards the Italian coast. It is easy to notice how the wind there is channeled through the mountain passes, which also influences the lee wave formation.

Fibres of cirrus clouds can also be seen stretching over the Adriatic. A cloud "cap" consisting of mid-level clouds is often seen trapped on the Velebit and Biokovo mountains. In the image loop the effect of clouds dissipating all along the coastline, a very frequent consequence of bora, is seen clearly. A wave-like cloud formation of the trapped waves is also seen here on the upwind side.

09 April 2015/04.45 - Meteosat 10 RGB image (HRV, 10.8, 10.8) - 15 min loop

08 April 2015/09.45 UTC Modis TERRA RGB image (0.65 µm, 0.55 µm, 0.46 µm)