Spatial Analyses of Climatological Effects on Hurricane Intensification Rates

The aim of these studies is to determine spatial climatological effects on hurricane intensification rates. Previous studies have noted that the skill in predict a hurricane's track has improved at a much greater rate than the skill to predict its intensity. There is even less research concerning hurricane intensification rates, let alone research done spatially and climatologically. Therefore, the research herein aims to understand what drives hurricane intensification rates. This is done by using spatial climatological analyses to determine the effects that intensity, sea surface temperatures (SSTs), ocean heat content (OHC), El Niño--Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), Madden--Julian Oscillation (MJO), and the Pacific Decadal Oscillation (PDO) have on hurricane intensification rates. Using both equal-area hexagons and raster techniques, hurricane track data is plotted spatially. SST, ocean salinity, and OHC values are also represented on a spatial grid. Finally, climate variables are represented temporally as mean yearly values. A generalized linear model from a gamma family and a logarithmic link function, as well as a full probability model are used to determine the effects that the variables of interest have on hurricane intensification rates. It is found that intensity has a positive effect on hurricane intensification rates with an average increase of 0.024 ± 0.0032 m s⁻¹ in intensification for a 1 m s⁻¹ increase in intensity. SST is also found to have a positive effect on intensification rates with an average increase in hurricane intensification of 16% for a 1° C increase in mean SST. It is also found that decreased salinity may have a positive effect on hurricane intensification rates by inhibiting vertical mixing. In the North Atlantic basin, it is found that the NAO has a negative effect on intensification rates of ‒0.18 m s⁻¹ h⁻¹ per 1 SD, while ENSO and MJO do not have a statistically significant effect. In the Eastern North Pacific basin, it is found that both the NAO and ENSO have a positive effect on hurricane intensification rates, while the MJO and PDO do not have a statistically significant effect. Finally, in comparing the largest intensification rates during the most extreme NAO events in the North Atlantic basin, as well as the most extreme ENSO events in the Eastern North Pacific basin, it appears that rapid intensification (RI) may simply be normal intensification occurs over a longer time period. These studies confirm the previously held idea that warmer SSTs will lead to higher intensification rates. Along with this is the finding that the NAO has a negative effect on hurricane intensification rates in the North Atlantic basin. This was not something that was previously mentioned in the research. Finally, the idea that RI may not be due to small thermodynamic processes but instead normal intensification over a longer amount of time is an intriguing notion that deserves further analysis.