tropical storm vs vortex

tropical storm

noun
  • A cyclone within the tropics, typically having its thunderclouds organized in a spiral shape with wind speeds on the surface between about 30 and 75 miles (60 - 120 km) per hour. 

vortex

noun
  • A whirlwind, whirlpool, or similarly moving matter in the form of a spiral or column. 

  • Anything that involves constant violent or chaotic activity around some centre. 

  • Anything that inevitably draws surrounding things into its current. 

  • A supposed collection of particles of very subtle matter, endowed with a rapid rotary motion around an axis which was also the axis of a sun or planet; part of a Cartesian theory accounting for the formation of the universe, and the movements of the bodies composing it. 

  • Any of numerous species of small Turbellaria belonging to Vortex and allied genera. 

verb
  • To mix using a vortex mixer 

How often have the words tropical storm and vortex occurred in a corpus of books? (source: Google Ngram Viewer )