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A depression is a low pressure weather system.   Air in this system rotates around the centre and is sucked inwards and upwards.   Depressions are also commonly known as "lows".   Deep depressions can be recognised by the concentric circles drawn on weather maps.   The closer together the lines are drawn, the stronger the wind is.

When strong winds cross a mountain range, they sometimes become exceptionally strong downwind from the mountains.

Tropical cyclones form in the tropics during summer and early autumn and can move south towards New Zealand.   When this happens, tropical cyclones sometimes change into deep depressions, bringing heavy rainfall to some areas and gale force winds to others.

In a tropical cyclone, the strongest winds are near the centre.   In a deep depression that has formed from a tropical cyclone, the strongest winds are often hundreds of kilometres from the centre.   These depressions usually affect the North Island more than the South Island.

Strong winds which come from "lows" forming in the Tasman Sea or south of New Zealand, usually affect the South Island and the lower half of the North Island, especially in late winter or early spring.

Tornadoes

Tornadoes are narrow funnels of violently spinning air which descend from the bases of cumulo-nimbus cloud.   They often last only for a few minutes and the path of destruction may be only 50 metres wide.

Tornadoes develop very quickly, often without warning – except for the presence of giant towering clouds.

Storm surges

Gale or storm winds blowing directly from the sea to land can sometimes cause the sea to invade the land.   The effect is worse where the sea bed is shallow for a long way offshore and when there is a spring tide.   Low air pressure associated with a deep depression, will also help to raise the sea level.

Severe wind warnings

A severe wind warning is issued when winds of more than 70 km/h are expected over land.

The warning is issued by the National Weather Forecasting Centre in Wellington to the Police and the Ministry for Emergency Management.   The Police then warn radio stations, and Civil Defence organisations are warned by the Ministry for Emergency Management.

The National Weather Forecasting Centre also provides the news media with daily weather forecasts.

If strong winds cause danger to the public, a civil defence emergency may be declared.   This occurred in Taranaki in March 1988 during Cyclone "Bola".

Develop a family plan so that each person knows:

	what to do to survive a storm
	what to do if a storm prevents them from returning home.

Help your neighbours to develop a plan for getting help during a storm.   Talk to your Civil Defence organisation about this.

Storm hazards

Severe Winds

• roofing iron may be torn off houses and fly free
• motor vehicles can be blown off the road
• telephone boxes, bus shelters and walls can be blown over
• trees and branches may snap
• power lines can be blown down
• large panes of glass may break.

Tornadoes

• objects in its path may be shredded
• items torn free may become fast moving missiles

Storm surge

• the sea will be higher than usual and may flood sections near the beach

Emergency Preparedness

Right Now:
Check your disaster survival kit at home and at work. Check the civil defence pamphlet Your Disaster Survival Kit for items that you should include in the kit.

Check:

• Batteries in torches and radios in case the power supply is lost during the storm
• Food and emergency water supplies
• The first aid kit
• Important documents such as insurance papers, birth certificates and passports
• Essential medicine supplies
• The roof, for loose iron sheets and tiles – fix these.
• The exterior television aerial – secure it to the roof.

When a strong wind warning is received

• Keep listening to your radio for information.
• Bring pets inside.   Move stock to shelter.
• Pick up rubbish outside and put smaller rubbish bins indoors.
• Secure outdoor furniture, fittings and lightweight garages.

• Put tape across very large windows to prevent them from shattering.

During the storm

• Stay inside. Don’t walk around outside – you may be hit by flying debris.
• Don’t go driving unless absolutely necessary.
• Listen to the nearest operating radio station for information. Be sure to use a battery powered radio since power may be cut.
• Close the curtains – this will slow down flying glass or other loose objects.
• Stay away from doors and windows. If the wind becomes destructive, shelter further inside the house.   If you can move a mattress, use this for added protection.
• During an electrical storm, stay away from metal and electrical fixtures in your house. These can act as lightning conductors.
• If your house or building is severely damaged by the wind, contact your local council.
• Open a window on the side of the building away from the wind – this will help relieve pressure on the roof.  
• Be prepared to take essential items with you if emergency services ask you to evacuate.

After the storm

Avoid dangling and broken power lines. Report these to the nearest electrical authority.
Contact your local council for advice in cleaning up debris from wind damage.

REMEMBER ...

You will need to know in advance how to contact your local civil defence organisation for assistance during an emergency. Contact your organisation through your local council and find out what they would prefer you to do.