Archive for the ‘General Interest’ Category

Jenny Island - Antarctica

Wednesday, February 6th, 2019

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Jenny Island, Marguerite Bay, near Rothera - Antarctic Peninsula - weather4expeditions.com(c)

Jenny Island is situated in Marguerite Bay, almost 20km South of Rothera, the BAS bas on the western side of the Antarctic Peninsula. This picture is taken from a BAS Twin Otter approaching the Rothera runway from the South (1997).

This pretty spectacular formation of Orographic Stratus is a result of a rather strong Northerly wind towards Jenny Island - in this flow a lot of moisture is evaporated from the sea into the adjacent air. As this air is pushed upwards along the Northern slopes of the island it cooles, saturates and forms orograhic Stratus. On the leeside the Stratus mixes with the drier air and the clouds dissipate again. In this situation the risk for severe turbulence at lower levels along the leeside of the mountains is at least 30 to 40 percent - this turbulence is also known as rotor waves.

Early morning in Union Glacier

Wednesday, February 6th, 2019

Early morning in Union Glacier

Early Morning in Union Glacier, Antarctica - weather4expeditions.com(c)


When the katabatic winds stop blowing from the South, local wind systems start to develop. These local winds are very complex and hard to predict; however most of the time there is an easterly component.

This soft easterly breeze brings moisture from the Ronne ice Shelf into Union Glacier and generates mist, fog and low clouds. This can ruin a whole days flight plan!

In general during the second part of the month of December and also during the month of January the risk is largest. During this period a lot of open water is present over the Weddell Sea and due to evaporation moisture is pushed in a Northerly flow over the Ronne Ice Shelf. When this moist air flow touches the cold surface of the ice shelf, it cools till it reaches saturation. At this point condensation takes place, hence fog or stratus is formed.


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