The three storms are three weather events occuring in the film.
Siberia Storm Edit
The storm freezes everyone in sight including a mamoth with food in it's mouth as well as people who get to close to the storm. The storm then goes to Ulaanbaatar and then Beijing before going to Tokyo. This storm freezes most of east Asia.
Scotland Storm Edit
The storm in Scotland freezes the fuel lines of 3 military helicopters going to airlift the royal family before killing everyone inside. The storm later kills professor Terry Rapson and his colleagues. The storm then heads down to London, Paris, Berlin, Warsaw and Chrisinau before going through Europe.
Northern Canada Storm Edit
This storm starts in Canada killing a photographer, it then goes to Ottawa and Toronto where it kills some more people. In then arrives in New York where it devastates Manhatten. Jack and Sam hall barely escape from this storm but others such as an NYPD officer and the group from the library aren't as lucky. The storm then heads down to Atlanta and stops there.