Rain won't be enough to break drought's back
New Zealand is braced with open arms to receive rain tomorrow, but it's unlikely to improve the drought situation, scientists say.
Yesterday, Minister for Primary Industries Nathan Guy announced the entire North Island was in a state of drought.
According to the National Institute for Water and Atmospheric Research (Niwa) water tables around the country are more than 100mm in deficit.
Victoria University Associate Professor of Physical Geography James Renwick said tomorrow's rain may generate some grass growth, but wouldn't come close to replenishing the soil.
"[It's] only a fraction of what's required. What we need is one of these storms every three days for a month."
MetService has forecast the remnants of ex-tropical cyclone Sandra to pass over much of the country tomorrow - bringing with it some heavy showers.
The rain would peter out over the following days, but most places in New Zealand would be lucky to see more than 20mm.
Meteorologist Daniel Corbett said the moisture supply from the tropical system could bring downpours in places.
A severe weather warning has been issued for Westland and a severe weather watch for Nelson and Buller.
On Monday, a cooler southerly flow was expected to bring another period of rain across most of the country.
Renwick said the situation at the moment was "extraordinary".
"The amount of rainfall in an event like this could be significant but maybe not in the places that need it the most.
"It's a pretty incredible situation to have the whole of the North Island in drought, and more than 100mm is going to need to fall before the drought is broken."
He said it looked as though the mountains west of Nelson and in the central South Island could get 100mm of rain or more.
"But on the lowlands where the farms are and where people live, rainfalls will be considerably less."
And with the ground considerably harder than normal, it was also unlikely all the rainfall would be absorbed.
"If the rain was to be heavier, the ground is at the kind of level where surface flooding could occur, but it's unlikely enough rain will fall for that to happen."
Meanwhile, police were urging motorists to take extra care as rain, mixing with a considerable amount of both dust and oils which would be on the roads, could make them more slippery.
Assistant Commissioner Road Policing Dave Cliff said after such a long dry period, the build-up of oily and other deposits on road surfaces will create a slippery film when it starts to rain.
"Roads will be extremely slippery for some time and drivers will need to be very careful about speed, following distances and distances it takes to stop."
Cliff said it's also important that people checked tyre pressure and tyre tread depth.
"We're asking everyone to take extra care on the roads when the rain does arrive," he said.