Western North Pacific, North Indian Ocean, and Southern Hemisphere Tropical Cyclones of 1997

The Pacific Meridional Mode and the Occurrence of Tropical 1 Cyclones in the Western North Pacific

30 This study investigates the association between the Pacific Meridional Mode (PMM) 31 and tropical cyclone (TC) activity in the western North Pacific (WNP). It is found that 32 the positive PMM phase favors the occurrence of TCs in the WNP while the negative 33 PMM phase inhibits the occurrence of TCs there. Observed relationships are 34 consistent with those from a long-term preindustrial co...

Effect of ENSO and the MJO on Western North Pacific Tropical Cyclones

Prior work has suggested that Rossby wave accumulation in the lower troposphere may be an important mechanism for the development of synoptic-scale disturbances in the western north Pacific in northern summer. This work examines the intraseasonal and interannual variability of wave accumulation by computing the barotropic wave activity flux divergence at 850 hPa for different phases of the Madd...

What Percentage of Western North Pacific Tropical Cyclones Form within the Monsoon Trough?

It is frequently stated that 70%–80% of western North Pacific tropical cyclones form ‘‘within the monsoon trough,’’ but without an objective definition of the term. Several definitions are tested here. When the monsoon trough (MT) is defined as the contiguous region where long-term (1988–2010) mean July– November 850-hPa relative vorticity is positive, 73% of all July–November tropical cyclones...

Influence of Western North Pacific Tropical Cyclones on Their Large-Scale Environment

The authors investigate the influence of western North Pacific (WNP) tropical cyclones (TCs) on their large-scale environment by lag regressing various large-scale climate variables [atmospheric temperature, winds, relative vorticity, outgoing longwave radiation (OLR), column water vapor, and sea surface temperature (SST)] on an index of TC activity [accumulated cyclone energy (ACE)] on a weekl...

Are Tropical Cyclones Less Effectively Formed by Easterly Waves in the Western North Pacific than in the North Atlantic?