Here is an explainer on the difference between the rain radar imagery and rain forecast imagery available on metservice.com and how to use them.

Rain radar

Written by John Law, Meteorologist

Sitting out in the middle of the ocean, New Zealand is vulnerable to extremes of weather from all directions; from the remains of tropical systems barrelling in from the north, to cold winter southerlies bringing a blanket of snow.

As New Zealand’s designated national meteorological service to the World Meteorological Organisation (WMO), it is MetService's responsibility to provide clear, concise and timely warnings of severe weather that is likely to affect New Zealand.

What defines severe?

On Saturday 17 September 1921, the deciding test of the first Springbok Tour was played at Wellington’s Athletic Park. New Zealand had won the first test 13-5 at Carisbrook and South Africa the second test 9-5 at Eden Park.

We had an enquiry from an astute member of the public asking about the comings and goings of rain.   They had noticed that in southerly weather the rain has a tendency to "come in bands (e.g., 20 minutes rain, 20 mins dry, 20 mins rain etc.) rather than as a more constant rain that comes with northerlies". They were wondering why this was. This is a good question and I will try to answer it here.  

There was a lot of rain in many parts of New Zealand over the last two weeks of May 2010. One of the few places to escape this was the sunny West Coast of South Island - the days are clear and stunning there when the flow is southeasterly. If you had been following the surface weather maps during May you would have noticed a lot of low pressure over the Tasman Sea and northern NZ, and periods of relatively high pressure farther south.