New Zealand Climate Update 131 – May 2010

More frequent anticyclones (‘highs’) were located over and to the east of the North Island during April, resulting in a very dry month for much of the North Island and upper South Island. Drought was declared for Auckland, Waikato, Bay of Plenty, South Taranaki, South Canterbury and Otago in April, joining Northland which was declared a drought area in January. Even after some helpful rainfall at the end of the month, significant soil moisture deficits remain in many areas of the North Island (except for Taranaki, Gisborne, and the Kapiti Coast), as well as in Marlborough and Canterbury. In contrast, enhanced northwest winds affected the South Island, producing extraordinarily high rainfall in the southwest of the South Island.

During May-July, mean sea level pressures are likely to be below normal south of the country, with enhanced westerly flow over New Zealand. Temperatures are likely to be above average in the North Island, and average or above average in the South Island. Rainfall is likely to be near normal over much of the country, but normal or below normal in eastern regions and normal or above normal in the west and south of the South Island.