The phrase "intense thunderstorms" describes very strong and powerful storms that have loud thunder, heavy rain, and often strong winds. Full definition
A series of intense thunderstorms moved through southern California, southern Nevada and western Arizona during October 16 - 19, severely damaging roads and bridges owned by the U.S. National Park Service (NPS) and U.S. Fish and Wildlife Service (USFWS) spanning the three states. (transportation.gov)
It is this that leads to more intense thunderstorms: lightning only occurs if clouds are electrically charged, and this only happens if there are lots of ice crystals. (newscientist.com)
Hurricanes, called typhoons and cyclones in other parts of the world, are born when intense thunderstorms churn the atmosphere over an expanse of warm ocean water. (sciencemag.org)