Relative contributions of environmental factors on different time scales to tropical cyclogenesis over the eastern North Pacific

The present study investigates relative contributions of large-scale environmental factors on interannual, intraseasonal, and synoptic time scales to tropical cyclone (TC) genesis over the eastern North Pacific (ENP) during TC seasons of 1979-2013 from the perspective of TC genesis time and position. Conditional sorting displays that the synoptic component is more important in the contribution of lower-level vorticity and mid-level specific humidity to TC genesis compared to interannual and intraseasonal components. The convection contributes to TC genesis mainly through synoptic and intraseasonal components. Synoptic-scale tropical disturbances mainly obtain barotropic eddy energy from climatological mean flows. TCs appear most frequently when vertical wind shear anomalies are between 0 and 3 m s(-1), in which interannual and intraseasonal westerly wind anomalies make a positive contribution due to climatological easterly wind shear. When total SST exceeds 28 degrees C, the interannual component of sea surface temperature (SST) is positive, and then it has a positive contribution to TC genesis. In addition, there are notable differences of relative contributions of different time scale components of large-scale factors among the ENP, northern Atlantic Ocean, and western North Pacific.

Automated summary

This study explores the relative contributions of large-scale environmental factors to tropical cyclone (TC) genesis in the eastern North Pacific (ENP) from 1979 to 2013. It finds that the synoptic component plays a key role in the contribution of vorticity and specific humidity to TC genesis, while convection mainly contributes through synoptic and intraseasonal components. Additionally, the study highlights notable differences in the contributions of different time scale components among different ocean regions.