This study is motivated by the problem of extreme precipitation, which has been severe in the northeastern Pacific Basin. The goal was to calculate, for the core North American monsoon, the trend and return period (RP) of regional extreme precipitation not associated and associated with tropical cyclones (TCs) in teleconnection with the oceanic indices PDO, AMO, and ENSO indicators (SOI, MEI, and ONI). Daily precipitation observations from 48 weather stations were obtained from the CLImate COMputing (CLICOM) system for the time period 1961–2000. Using principal component analysis with oblique rotation, precipitation regions were determined. Extreme precipitation was calculated through the P95 and P99 percentiles. The following were calculated for the P95 and P99 percentiles: (1) non-parametric trend, (2) linear trend, (3) RPs, and (4) standardized precipitation anomalies (Z). The PDO, AMO, and ENSO indicators were obtained from the National Oceanic and Atmospheric Administration. Pearson (rP) and Spearman (rS) correlations between Z and the oceanic indices were calculated. The CNAM contained four precipitation regions. Only R1 had a positive linear trend of P95 not associated with TCs, at a rate of 2.75% decade−1. The +PDO (El Niño) phase influences Z-TCs in R4. Z-TCs in R1 and R2 are only influenced by –AMO (El Niño) phases. Only Z-no TCs showed inverse teleconnection with the +SOI phase in R3. MEI did not have teleconnection with Z. For the +ONI phases (El Niño), no significant Z-TCs were present in R1. From 2020 to 2050, the entire study area will have DEP > P95.
- Extreme precipitations