Constraints in Dvorak Windspeed Estimates: How Quickly Can Tropical Cyclones Intensify?

The Dvorak technique is used operationally by meteorological agencies throughout the world for estimating tropical cyclone intensity and position. The technique consists of constraints that put a maximum threshold for which the Final T-number, which relates directly to intensity, can change during a certain time interval (6-hr, 12-hr, 18-hr, and 24-hr). There are cases when these constraints could be broken, especially during rapid intensification (RI). This research tests whether or not the constraints used for intensity change are needed or need to be changed. The hypothesis is that the constraints should remain the same. A database of cases with the largest intensity changes for 2000-2017 Atlantic tropical cyclones was compiled. A reconnaissance or scatterometer fix is required within 3 hours of both the beginning and ending of the timeframe for each case to verify the best track and to be included for analysis. Dvorak classifications from the Tropical Analysis and Forecast Branch (TAFB) are noted for each case which includes the initial and final T-numbers, CI numbers, and Data-T numbers. Statistical parameters, including correlations, intensity errors, absolute intensity errors, root-mean-square errors (RMSE), and significance tests are calculated and analyzed for each timeframe. Results suggest that the constraints for the 18-hr and 24-hr timeframes could be relaxed to a 2.5 and a 3.0, respectively. However, results also suggest that the constraints for the 6-hr and 12-hr time intervals should remain the same.