| Summary: | By defining cyclone growth as a logarithmic change in absolute vorticity of the surface center, we investigate growth rates of a ten year sample of cold-season (1 October through 31 March) extratropical cyclones in the North Pacific Ocean basin. Strong growth is frequent in coastal regions near Japan and in the East China Sea. In contrast to the conventional deepening rate intensification parameter, frequency distributions of maximum 24-h growth are found to be more Gaussian in character. To investigate possible physical processes acting to enhance growth, composite sea surface temperature (SST) anomalies are computed for groups of cyclones which deepen maximally in the vicinity of the Gulf Stream and Kuroshio Currents. Comparison between groups of similar deepening revels stronger growth is generally associated with warm SST anomalies and with weaker upper-level support for intensification. Composite latent and sensible heat flux fields computed from observations support this finding.
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