Sunny and dry in the south these days, and a bit windy at times. Prime conditions for dust storms.
On 26 April 2015 there were several source areas.
On 28 April 2015 there were several source areas visible also, from Ölfus to Jökulsárlón.
Note that it looks like there are two wind direction governing the dust east of Mýrdalsjökull; small stroke due south, and other ones to the south-west.
This figure shows the meteorological observations in the area at 17:00 on the 28 May 2015. Looks like different wind direction at nearby location is not unlikely.