The 2011 southeast Queensland extreme summer rainfall: A confirmation of a negative Pacific Decadal Oscillation phase?

The devastating southeast Queensland (SEQ) flood and the associated extreme rainfall in January 2011 were accompanied by an extraordinarily strong La Niña. The regional summer rainfall is affected by the El Niño‐Southern Oscillation (ENSO) cycle, but modulated by the Pacific Decadal Oscillation (PDO) or the Interdecadal Pacific Oscillation (IPO). What does the recent flood tell about the status of the PDO‐IPO? Using three lines of supporting evidence it is proposed that the SEQ 2011 austral summer rain constitutes a confirmation of a transition to a negative phase of the PDO‐IPO. Firstly, the 2011 summer saw large SEQ rainfall and SOI values that historically occur only in a negative PDO‐IPO phase; secondly, there was an associated re‐establishment of an ENSO‐SEQ rainfall teleconnection; and finally, the decadal‐circulation state, particularly the tropical convection, has developed toward a state similar to that during other negative PDO‐IPO periods. The results imply an increased chance of high summer rainfall events over the region during La Niña in the upcoming decade or so. Key Points The 2011 floods are a line of evidence for a transition to a negative PDO phase The negative PDO provides favourable dynamic conditions for extreme floods There is an higher chance of extreme flooding in the next decade in Queensland