This shows the Sunrise and Sunset for the station in question.
http://dateandtime.info/citysunrisesunset.php?id=6620749&month=6&year=2014
Not clouds...quite the opposite, actually.
Using 2.75*30 = 82.5 hrs of total sunlight possible (average), they are noting a 14.3% exposure relative to the normal 8.97% amount of sunlight.
They are still predominately overcast by that estimation. However, the amount of cloud cover went down, along with the frequency of snowfalls.
Average winds fell to ~22km/h (from 35)...so it wasn't "windless".
But examine some of these facts from the end of the translation:
The wind blows 115 days a year to more than 100 km / h and approaches or exceeds annual 200 km / h. The record speed was recorded May 23, 1988, gusting to 245 km / h. The station is not located in a corridor terrible katabatic winds (from the Greek [katabatikos], "go down"). These winds, which originate from [the] cold, dense air mass, descend [from] the slopes of the high Antarctic plateau due to its own weight, [and] can reach 300 km/h on the coast. They mostly occur in the passage of disturbances in the autumn and spring periods of
strong thermal contrasts between the sea air and continental air.
Those are some hefty speeds. Yet, it is that "thermal contrast" which catches my attention. The exchange which the air performs along the coasts is a vital factor in this anomaly, I suspect.
The cartoon in my head is still qualitative, but I can't help noticing the peculiar pattern of clouds and winds when I look at a time lapse animation of them.
Alluring puzzle, it is, mmmm yes!
http://www.weather-forecast.com/maps/Antarctica?over=arrows&symbols=none&type=cloud