The effect of translation speed upon the intensity of tropical cyclones over the tropical ocean

Abstract

During the past several decades operational forecasts of tropical cyclone (TC) tracks have improved steadily, but intensity forecast skills have experienced rather modest improvements. Here we use 40 years of TC track data to show that storm intensity correlates with translation speed, with hurricanes of category 5 moving on average 1 m s−1 faster than tropical storms. This correlation provides evidence that the translation speed of a storm can exert a significant control on the intensity of storms by modulating the strength of the negative effect of the storm‐induced sea surface temperature (SST) reduction on the storm intensification (i.e., the SST feedback): Faster‐moving storms tend to generate weaker sea surface cooling and have shorter exposure to the cooling, both of which tend to weaken the negative SST feedback. Consistently, there exists a minimum translation speed for intensification and its value grows with TC intensity, resulting in a minimum translation speed for the existence of a TC in each intensity category. Furthermore, a composite analysis of satellite‐based SST measurements reveals that in the tropical region the average strength of the storm‐induced sea surface cooling can be explained by the superposition of an effect due to the storm intensity and an effect associated with the translation speed, and implies that the variability of upper ocean stratification may not be an important factor in this region. Our results suggest that progress in the prediction of TC tracks, particularly in the translation speed of storms, should lead to improved storm intensity prediction.

Observed near‐surface flows under all tropical cyclone intensity levels using drifters in the northwestern Pacific

“…Table 1 shows slowly moving storms (F r < 1) are fewer in category-4 and À5 (18%) than in weaker storms (23 and 28%). Therefore, our data here roughly agrees with the result of Mei et al [2012].…”

Observed strong currents under global tropical cyclones

“…The mean of translation speed is calculated for each bin of wind speed. Mei et al (2012) found a net increase of U h with TC category from global TC data. In this study, the mean U h also correlates closely with the maximum sustained wind speed (The correlation coefficient R = 0.96 in the NH and R = 0.94 in the SH).…”

Effects of the Representation of Convection on the Modelling of Hurricane Tomas (2010)

“…Another aspect to note from the overall analysis is the relationship between the translational speed of the protohurricanes and their degree of intensification, an idea pointed out by Mei et al [38]. Although our simulations do not use the 1D model option for ocean mixed-layer representation and hence do not incorporate wind-induced SST cooling with its negative feedback to the storm, yet, intriguingly enough, our results show that the simulations creating the most intense proto-Tomas perturbations, the groups KF-KF and NGE-NGE, are also those that bring the system furthest from their origin and so create the fastest translational speeds.…”