Move over high pressure, low pressure is in the driver’s seat now.
For the first time in 2024, low pressure is dominating New Zealand for an entire week, bringing a variety of weather and a higher chance of cloudier, wetter conditions.
The large and slow nature of this low pressure zone means the weather won’t always be severe or majorly interesting – but the set-up is repetitive, much like when we have a high that is stalled over us.
Sometimes the easiest way to think of low pressure is to picture it as the creator, not the storm itself. Having low pressure parked over us doesn’t equal a storm – but it means rain events and instability will be part of the forecast for a week, normally reserved for only as a low passes by, or an active cold front comes in.
With the “creator” parked over the Tasman Sea for a week it will send various fronts, rain bands and showers into the NZ area and it’s these parts that can create the severe weather. Think of the low as a machine spitting out various daily weather and each day there will be a slight shift to the set-up.
This change is well overdue. So far, 2024 has been leaning drier than average for many places and while autumn and winter have seen some wet weather return there are several regions still in a rainfall deficit, so this will be helpful – but our mountains and ranges mean not everyone will get big totals.
If you look further into the week the weather maps are messy, with most modelling expecting this low to break apart and gradually lose energy. With high pressure expected south of the country over the week this may also shut down the colder southerly flow, meaning many regions may be milder than usual (please note that doesn’t equal being “warm”, but may mean the overnight lows aren’t so cold).
Speaking of cold, frosty weather has been back in recent weeks after taking a long time to get going for some. The South Island has been more exposed but seeing overnight lows back to -5 to -9degC recently reminded me of what used to be normal weather a couple decades ago.
New Zealand’s location on Earth means one large high can dredge up sub-Antarctic cold southerlies as it moves in and then pull down warm subtropical northerlies as it exits. So NZ can always buck the trend thanks to a couple misplaced air pressure zones, turning a month from colder than normal to warmer than normal. It’s why sometimes late autumn can be colder than the depths of winter. It’s all about those high pressure zones – and for now, they’re taking a break from dominating our weather.
Upcoming highlights:
• Low pressure to dominate the Tasman Sea area for over a week
• Rain and showers across NZ, mostly coming in from the west and north of both main islands
• Temperatures may be above normal (perhaps more noticeable overnight)
