Covering period of Mon 20 – Thu 23 November – MetService has issued a Severe Thunderstorm Watch for the risk of downpours in the Auckland, Waikato, Coromandel and western Bay of Plenty regions this Monday afternoon and evening. Widespread rain continues to fall in the eastern areas of the North Island while the majority of the South Island remains relatively settled until a frontal system arrives on Thursday.
The remnants of a low pressure system is lying across the North Island to start the week. This system has brought warm and humid air in around the northern half of the North Island, which is increasing the chance of thunderstorms this afternoon and evening. The highest risk is for the Auckland, Waikato, Coromandel and western Bay of Plenty regions where there’s sufficient likelihood of downpours (rain exceeding 25mm/hour) for a Severe Thunderstorm Watch.
MetService meteorologist Lewis Ferris mentions: “The Watch covers the potential of severe thunderstorms, if we observe one on our radar network then we will issue a Red Severe Thunderstorm Warning, this means that impacts are likely and people should avoid the area if possible.”
Heading south, there is a risk of thunderstorms for inland areas between Kahurangi National Park and Otago.
Persistent, and sometimes heavy, rain is streaming onto eastern regions of the North Island, with Watches and Orange Warnings for heavy rain currently in force until Tuesday.
Eastern areas of the North Island will continue to be impacted by onshore winds until Wednesday, which means overcast days with rain, more persistent about higher ground.
The upper half of the North Island and inland areas of the South Island will have light winds and clear skies this week, however during the afternoons showers could pop up with the potential of thunderstorms sprinkled in the mix.
Temperatures will broadly be on the balmy side for most this week, with Christchurch forecast to reach 26°C on Thursday; that’s around 6°C warmer than their average daytime maximum for this time of year. However, Cantabrians will need to wrap back up on Friday as we’re forecasting a high of 14°C due to an outbreak of cooler air from the Southern Ocean.
The arrival of the cool air is preceded by rain setting in on Fiordland on Wednesday. This band of rain quickly zips northward on Thursday and moves across the North Island on Friday. This system brings a big dip in temperatures, a burst of heavy rain, and there could be some quite blustery southerly winds in places. We recommend keeping up with our forecasts surrounding this system so you don’t get caught underprepared.
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
