The University of Wisconsin-Madison's Cooperative Institute for Meteorological Satellite Studies revealed that satellite-based Visible Infrared Imaging Radiometer Suite (VIIRS) sensors showed lightning streaks, gravity waves, mesovortices inside the super typhoon's eye.
According to the U.S. National Aeronautics and Space Administration (NASA), atmospheric gravity waves form when buoyancy pushes air up, and gravity pulls it back down. Studies have shown that tropical cyclones generate gravity waves.
Mesovortices, meanwhile, are rotating bodies of air found inside storms and the eyewall of tropical cyclones.
Five areas were placed under storm signal number 5. These are Cagayan, Isabela, Kalinga, Apayao, Northern Abra and Ilocos Norte.
This is the first time state weather bureau PAGASA issued a storm signal number 5.
The rest of Abra, Ilocos Sur, Mt. Province, Ifugao and Calayan Group of Islands were placed under storm signal number 4.