How does a Central American migrant caravan form?

SAN SALVADOR, El Salvador (AP) — “When does the next caravan leave?” ”Can I go? I’m from Guatemala.” ”What papers do I need for my kids?”
The questions pile up on the phones of hundreds of Central Americans, all with the same goal: Get as many details as possible before leaving their country.
Costly phone calls with relatives and friends in the United States to work out the route or find the best smuggler are a thing of the past for many Central Am