Dr Kathleen Kozyniak
Principal Scientist Air
Hawke’s Bay Regional Council
Heavy sigh. April sees another month of below normal rainfall – the tally is now five consecutive months for areas such as the Heretaunga and Ruataniwha Plains, the Ruahine and Kaweka Ranges and the southern coastal area. At some of our sites in those areas, including Bridge Pa, the rainfall accumulations for the hydrological year are lower than those at the same time in the 2019-20 year.
April was the carbon copy of March in a couple of ways. Both months saw only 40% of average rainfall and both had very similar daytime temperatures – averaging approximately 20°C. That meant that April’s temperature was a mighty 2°C above average.
April’s river flows were very low across the region, averaging only 27% of normal, and the majority of groundwater wells we monitor were below normal for the month. Soil moisture levels ended April in the lowest 10th percentile of readings for the time of year at Bridge Pa and Crownthorpe and below median levels on the Ruataniwha Plains. It’s not a pretty picture and the longer it takes for rain to come, the uglier it gets.
The La Niña is almost history but seasonal forecast models show little change in the general pattern of weather. We still hang on to lower than normal pressure northwest of the country and higher to the southeast. We can expect a mix of northeast and southwest winds as a result along with a three month forecast on repeat – near or below normal rainfall and near or above normal temperatures. The first half of May is looking unsettled and we need it to deliver on its promise rather than be the fizzer that these unsettled periods have been to date.
Percentage of Normal Rainfall