Abstract This study investigates the diversity of the impact of the North Pacific Meridional Mode (NPMM) on western North Pacific (WNP) tropical cyclone (TC) genesis during June–November from 1961 to 2024. We consider preceding springtime NPMM events driven by tropical and extratropical forcings, and classify them as successive and stochastic events, respectively. In successive positive NPMM years, TC genesis changes only slightly over the entire WNP. In successive negative NPMM years, significant increases (decreases) in TC genesis are observed over a region spanning 20°–140°E, 0°–20°N (140°–160°E, 0°–20°N). In stochastic NPMM years, there are significant increases in TC genesis over a region spanning 135°–160°E, 5°–25°N. These changes in TC genesis can be explained by the anomalous environmental conditions in different NPMM years, which can be further linked to the NPMM’s strength as well as sea surface temperature anomalies over the tropical western Pacific.
Observations from the Little Bunker
Last updated: November 30, 2025 04:25 AM
Atmospheric CO₂
426.8 ppm
+18.1
ppm/year
Atmospheric CH₄
1927.61 ppb
+2.73
ppb/year
Global Temperature
+1.48 °C
Peak: +1.73°C
World Population
8.1 billion
+67
million/year