They have been advising a "go-bag" for the past 7 or 8 years.
It is an (as usual) too-late reaction to Hurrican Katrina in the US. When that happened, thousands of JWs were relocated to other states, sometimes hundreds of miles away, and they were ill-prepared for it.
Not to mention that congregation activities were disrupted. Imagine, there were dozens of congregations that did not submit their field service reports on time! The horror!
And further not to mention, it was the perfect opportunity for "faders" to completely disappear off the radar screen of their congregations.
To avoid such mishaps in the future, the WTS now requires each congregation to have a "diaster plan". Part of that plan is to encourage every family to have a "go bag", containing food, water, medicine, etc. for several days. The idea is that in case of some sort of emergency requiring evacuation, the JWs just grab the "go bag" and jump in their car and go.
This "disaster plan" is ostensibly for the good of the congregation members. And of course it is rather a good idea for those who live in high-risk areas to prepare for emergencies, part of which preparation should be such a "go bag".
But given the WTS' history, as I intimated above, the "congregation disaster plan" appears to be primarily a way for the congrgation to still remain under the autonomy of the WTS branch.