A Study of the Constraints of the Dvorak Technique

The Dvorak Technique for estimating the intensity of tropical cyclones (TCs) has been used world-wide for several decades. It includes a methodology for quantifying the cloud patterns associated with TCs, along with a set of constraints (rules) that govern how quickly the intensity estimates can change over periods of 6, 12, 18, and 24 hours. The constraints are a somewhat controversial topic, as 1) how they were originally derived is unclear, and 2) several TCs appear to have developed at faster rates than the constraints allowed. This study examines the constraints using best track data from the Atlantic basin during times where aircraft reconnaissance was available to provide ground truth intensities. The results suggest that in the vast majority of cases, TCs have developed and weakened at rates that fall within the Dvorak constraints, with less than 2% of aircraft-observed intensity changes falling outside the constraints. The results suggest that, at least in the Atlantic basin, the Dvorak constraints are good and do not require significant modification.