début de la tempête
"First of the Storm."
This is actually not a very good translation of the Arabic original. And I believe the Arabic original is where we really need to focus our interpretive energy to possibly determine their future planning.
The Arabic original of their threat is that [the Paris attacks are]:
أول الغيث (awwal al-ghayth)
A better English translation would be:
"First of the Heavy Rain."
But the important point in understanding their threat is that this phrase is a quote from a well-known Arab proverb:
أول الغيث قطرة (awwal al-ghayth qaTrah)"The first (thing) of a heavy rain is a (single) raindrop."
This is a proverb roughly equivalent to, for instance, "Every journey must begin with the first step."
Native speakers of Arabic who hear "أول الغيث (awwal al-ghayth)" likely know the proverb and its true meaning.
The normal word in Arabic for "storm" is:
The fact that the communique does not use the normal word and instead quotes this proverb may be telling. The proverb is not focusing so much on the severity and intensity of the storm itself, but rather on the abundance of the raindrops.
If the Paris attack is but the first drop of a heavy rain shower, the communique seems not to be threatening more severe attacks. Rather, it is threatening abundant attacks, even small ones, all of which will add up to an "abundant rain."