Pacific basin volume had a smaller nine-month ENSO correlation advantage in 2000-2019 than in 1980-1999

We tested a reported decrease in the lead of Pacific warm water volume over ENSO temperature. We used fixed NOAA GODAS volume and CPC ERSSTv5 Nino 3.4 records. Each 20-year window has 222 common start months for lags from zero to 18 months. The basin correlation at nine months minus its correlation at zero months fell from 0.462 to 0.058. The change was -0.405, with a 95% interval of -0.894 to -0.003 from 36-month blocks. After linear trend removal, the change was -0.380 and the interval was -0.851 to 0.017. The fitted peak lag fell from seven to four months, but its bootstrap range included no change. Western volume did not have a resolved change in the fixed contrast. The overlapping 2005-2024 window gave a basin peak at five months. These results show that a smaller long-lead correlation advantage and an uncertain peak-lag change can occur together. Few ENSO cycles, revised data, fixed time windows and method choice limit inference. The test does not identify a physical cause or measure forecast skill.

ENSO · warm water volume · lead time · block bootstrap · replication · GODAS