Dust surges can happen at any point in the year and seem to be most prominently associated with easterly wind surges from Africa, of which tropical waves can be one marker. They are generally thought to be related to rainfall over the Sahel region of north Africa. There's still a lot we don't know in that regard, however.

Dust surges generally have negative effects upon tropical cyclone formation and intensification if the cyclone is embedded in or near an outbreak. If it is on its periphery or if it is a particularly weak dust surge, these impacts may be reduced somewhat.

As for the last question, I would say not particularly but with the qualifier that I haven't followed that region of the basin all that much yet this year. I do know that in the spring rainfall had been above average there to date, so perhaps their frequency may be somewhat limited later this season. Again, however, there's just not enough data or knowledge to say for certain.