NWC REU 2021
May 24 - July 30



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Diurnal Variability in Tropical Cyclone Tornado Occurrence

Ivan Sloan and Benjamin A. Schenkel


What is already known:

  • Tornadoes tend to occur on the eastern side of tropical cyclone track primarily near the coast
  • The number of tornado reports peak during the late afternoon
  • Tornadoes in the outer periphery of the tropical cyclone have stronger diurnal variability than those in the inner core

What this study adds:

  • Diurnal variability is stronger in inland tornadoes compared to coastal tornadoes with a pronounced late afternoon peak
  • Tornadoes in the outer portion of the tropical cyclone also have stronger diurnal variability than inner-core tornadoes with a late afternoon peak as well
  • As their distance from the coast increases, tornadoes increasingly occur in the outer eastern half of the tropical cyclone during the afternoon.


This study investigates the relationship between the diurnal variability of tropical cyclone (TC) tornadoes and their location. Observed TC and tornado data are used to characterize how the diurnal cycle of tornadoes varies with distance from the TC center and distance from the coast. Our results show that TC tornado occurrence quickly increases in the late morning, peaks in the late afternoon, and sharply decreases thereafter. The largest diurnal variability is associated with tornadoes located on the eastern half of the TC within 100– 500 km from its center. Our analysis also showed that the diurnal variability of tornadoes becomes larger with increasing distance from the coast. Specifically, there is an order of magnitude more inland tornadoes during the late afternoon than at any time during the night. Our study also considered the diurnal variability jointly associated with TC-relative and geographic location finding that: 1) inland tornadoes typically occur during the late morning and afternoon within the outer region of the eastern half of the TC and 2) coastal tornadoes largely occurred throughout the day in the northeast quadrant. These results may aid forecasts of TC tornadoes and, more fundamentally, deep convection as TCs move inland.

Full Paper [PDF]