Mainly fine weather was felt across the nation to kick off the school holidays, but as we near midweek, MetService is forecasting heavy rain and strong winds to put an end to the sunny spree.

Today, settled weather is widespread across the nation thanks to high pressure that moved in during the weekend. However, as we move into Tuesday more cloud will be seen across the skies; northeasterly winds will pick up and some rain starts to fall around the southwest of the country.

MetService meteorologist Lewis Ferris warns, “Wednesday and Thursday are the main risk period for severe weather and Heavy Rain Watches are already in force for western and northern parts of the South Island. It’s likely some of these will be upgraded to Orange Warnings and areas in the North Island may be added.”

This potentially severe weather is brought about by a low pressure system approaching from the Tasman Sea which drags some warm and humid air across our shores. While this does mean some warmer than average temperatures it also increases the chance of heavy rain as the system passes over. Strong northeasterly winds will also be seen before the rain arrives.

The Bay of Plenty has been rather dry throughout September, especially Whakatāne which has had about 30% of their average September rainfall. The prolonged and potentially heavy rain due from Wednesday night through Thursday could bring more rain to parts of the region than they’ve seen this month.

While most of the North Island will be covered by the warm and humid air, there is some cold air being dragged across the southern half of the South Island. This means Thursday brings the risk of snow falling down to around 500 metres for inland Otago and southern parts of Canterbury. Prolonged rain is also possible around these areas and severe weather forecasts might be issued.

It’s a good idea to stay up to date with the latest forecasts this week as the weather from Wednesday will be very different to now and severe weather may impact numerous regions.

Note for Cantabrians:

Canterbury will be getting a new and improved weather radar. While we complete this work, the current radar is offline and is expected to be back in service by mid-December. During this upgrade, we’ll use radar data from Wellington, Otago, and Westland to provide partial coverage in the Canterbury area. For more information on this project visit our website: Canterbury Radar Replacement and Upgrade

Understanding MetService Severe Weather Warning System 

Severe Thunderstorm Warnings (Localised Red Warning) - take cover now:

• This warning is a red warning for a localised area.
• When extremely severe weather is occurring or will do within the hour.
• Severe thunderstorms have the ability to have significant impacts for an area indicated in the warning. 
• In the event of a Severe Thunderstorm Red Warning: Act now!

Red Warnings are about taking immediate action:

• When extremely severe weather is imminent or is occurring
• Issued when an event is expected to be among the worst that we get – it will have significant impact and it is possible that a lot of people will be affected
• In the event of a Red Warning: Act now!

Orange Warnings are about taking action:

• When severe weather is imminent or is occurring
• Typically issued 1 - 3 days in advance of potential severe weather
• In the event of an Orange Warning: Take action.

Thunderstorm Watch means thunderstorms are possible, be alert and consider action

• Show the area that thunderstorms are most likely to occur during the validity period.
• Although thunderstorms are often localised, the whole area is on watch as it is difficult to know exactly where the severe thunderstorm will occur within the mapped area.
• During a thunderstorm Watch: Stay alert and take action if necessary.

Watches are about being alert:

• When severe weather is possible, but not sufficiently imminent or certain for a warning to be issued
• Typically issued 1 - 3 days in advance of potential severe weather.
• During a Watch: Stay alert

Outlooks are about looking ahead:

• To provide advanced information on possible future Watches and/or Warnings
• Issued routinely once or twice a day
• Recommendation: Plan

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