Variability of Tropical Cyclone Rapid Intensification in the North Atlantic and Western North Pacific

The paper uses long-term observations to investigate rapid intensification (RI) variability of tropical cyclones (TCs) in the North Atlantic and the western North Pacific, and the relationships with large-scale climate variations. RI is defined as a TC intensity increase of at least 15.4 m/s in 24 hours. In the North Atlantic, RI displays both interannual and multidecadal variability. The top three climate indices showing high correlations with RI are the June-November ENSO and Atlantic warm pool indices, and the January-March North Atlantic oscillation index. It is found that variability of vertical wind shear and TC heat potential is important for TC RI in the Atlantic hurricane main development region, whereas relative humidity at 500-hPa is a factor responsible for TC RI in the eastern tropical North Atlantic. In the western North Pacific, RI events have exhibited strikingly multidecadal variability. During the warm (cold) phase of the Pacific decadal oscillation, the RI number is generally lower (higher) and the average location of RI occurrence tends to shift southeastward (northwestward). Such multidecadal variations of RI are associated with the variations of large-scale ocean and atmosphere variables such as sea surface temperature, TC heat potential, relative humidity and vertical wind shear in the western North Pacific.