Weather Radar Network Expansion

The Government has approved expenditure of $10 million to build weather radar installations in Taranaki, Gisborne/Hawke’s Bay and the Bay of Plenty as well as develop supporting infrastructure.

New Zealand currently has four weather radar installations operating near Warkworth, Wellington, Rakaia and Invercargill. MetService operates the radars, and has spent several years developing the infrastructure and forecasting tools to use the data they provide to improve weather forecasts.

Radar, which stands for radio detection and ranging, was refined during World War II to detect the presence of enemy aircraft and shipping. It sends out pulses of high frequency electromagnetic waves in the microwave spectrum and listens for evidence of the signal being reflected from solid objects. By repeatedly scanning across a selected field, the reflections received can be used to build up a picture of moving aircraft, vehicles and other objects. Apart from the obvious military and aviation applications, radar is also used in the less popular “speed traps” encountered by speeding motorists.

For some years, it has been known that radar also detected some meteorological phenomena. During the Kaikoura UFO incident in 1978, air traffic controllers commented on some of the radar images being due to weather phenomena. By the 1990s a practical application for weather radar to track moving bands of rain was developed, and the United States of America has invested heavily in the technology to improve their knowledge of weather systems.

New Zealand’s weather radar network has been in operation for about 5 years, being steadily refined with a major upgrade being completed about 18 months ago. However, the information provided by weather radar requires a great deal of interpretation and analysis as the density and temperature of the precipitation (including hail) can affect the quality of the reflected signal, and odd effects such as tunnelling and sea wave effects can give erroneous results. MetService has been improving its software and human analysis techniques to make the radar more effective.

The extension of the weather radar network will commence with the installation in Taranaki by July 2008. Two further installations in the Gisborne or Hawke’s Bay area and the Bay of Plenty will improve coverage of the North Island from 24% to 78%. Sites for these installations have yet to be finalised, and no date has been specified for their commissioning.

The installation in Taranaki is topical, following last week’s tornadoes which caused about $7 million-worth of damage. However, the new installation will not improve the direct detection of tornadoes coming ashore from the Tasman Sea.

But the good news is that the radar installation will dramatically improve the detection of thunderstorms off-shore in the Tasman Sea. Some of these thunderstorms create the conditions that allow tornadoes to form and, as MetService improves its observation of these thunderstorms, it is likely that they will be able to warn of possible tornado conditions. Warning time is expected to be of the order of an hour.

Being able to give up to an hour’s warning of a possible tornado presents authorities with a new set of problems, not the least of which is how to disseminate a warning to the public in so short a time.

The focus will again fall on the Ministry of Civil Defence and Emergency Management to develop and implement an effective official warning system on a nationwide basis. The Ministry’s policy of devolving front-line responsibility for managing local and regional disasters to the district and regional councils seems to have been effective in dealing with recent storms and floods. It is unproven in the event of a serious earthquake, and was shown to be seriously flawed during the Gisborne tsunami scare last year.

A national warning system existed during the 1960s and 1970s, and its function was drummed into much of the population, and printed in all of the nation’s telephone directories. “THE CIVIL DEFENCE WARNING SIGNAL FOR ALL EMERGENCIES is a series of intermittent siren or signal blasts of two or more minutes duration. This means tune into your nearest operating radio station and follow instructions.”

This universal warning signal was adhered to by civil authorities planning for tsunami warnings in coastal areas such as Gisborne, volcanic eruption warnings in the Bay of Plenty and even for warning of chlorine gas escape at the paper mill in Kawerau.

The system fell into disuse following the economic reforms of the 1980s which allowed public radio to be carved up and corporatised, the New Zealand Fire Service to set its own policy and council authorities to pursue their own plans. On a visit to Gisborne in the mid-1990s, I was stunned to hear the local fire siren go up 5 times as it called volunteers to the station. When I queried this, I was told that the siren consistently sounded 5 times when calling on volunteers. Being the only volunteer station in the city, there was no need for a coded sounding of the siren to distinguish the station from another nearby such as was the practice at Plimmerton and at Paekakariki and Paraparaumu.

The lack of a policy for warning of emergencies has resulted in local authorities coming up with their own sometimes bizarre solutions. A newly deployed network of sirens was tested in parts of the Bay of Plenty earlier this year, with some residents claiming the sirens couldn’t be heard. Gisborne plans to go door knocking to warn of a tsunami. One council on Auckland’s North Shore has developed an automated system which will ring local telephone numbers and play a recorded message. This last item is a doozy, as it assumes that people will answer their phones within a specified time; and it runs on the frail hope that the telephone network overloading that often follows earthquakes (and will accompany the signs of a possible eruption or news of a tsunami event) will allow the system to operate effectively.

Having adhoc local arrangements for warnings leads to confusion for visitors and new residents of an area and is a waste of money.

The Ministry of Civil Defence and Emergency Management needs to develop and enforce a standard for a national warning system that is universally understood and will work anywhere it is needed in New Zealand.

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