On the violation of gradient wind balance at the top of tropical cyclones

Yair Cohen*, Nili Harnik, Eyal Heifetz, David S. Nolan, Dandan Tao, Fuqing Zhang

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


The existence of physical solutions for the gradient wind balance is examined at the top of 12 simulated tropical cyclones. The pressure field at the top of these storms, which depends on the vertically integrated effect of the warm core and the near surface low, is found to violate the gradient wind balance—termed here as a state of nonbalance. Using a toy model, it is shown that slight changes in the relative location and relative widths of the warm core drastically increase the isobaric curvature at the upper level pressure maps leading to nonbalance. While idealized storms return to balance within several days, simulations of real-world tropical cyclones retain a considerable degree of nonbalance throughout the model integration. Comparing mean and maximum values of different storms shows that peak nonbalance correlates with either peak intensity or intensification, implying the possible importance of nonbalance at upper levels for the near surface winds.

Original languageEnglish
Pages (from-to)8017-8026
Number of pages10
JournalGeophysical Research Letters
Issue number15
StatePublished - 16 Aug 2017


  • gradient balance
  • gradient imbalance
  • tropical cyclone upper level dynamics


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