NZ Weather Forum

Am I losing my memory or is there a giant lack of summer time sea breeze convergence in the upper north island over the past roughly 5 years? There also seems to be less afternoon thunderstorms over these recent years.
If my memory is serving me well, what is the driver behind this.
Climate change I believe is really starting to alter the climate and weather patterns where I live. Summer today is a lot different to what summer was 15-20 years ago. Rainfall stats show this. Temp stats show this.


On a side note……
The change in climate is really starting to mess with a dairy farm system that has stood the test of time, but now is now becoming too challenging. I’m having to make big changes to the system to survive summers. It all costs.
I read an article of how sudden and lengthy extreme droughts or even climate change killed off the Mayans. They couldn’t adapt fast enough to the changing climate.


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warmer ocean temperatures might be part of the problem
i,e the marine heatwaves
makes the sea breeze not as strong

Our upper atmospheric temps I believe have increased markedly which has then in turn made our atmosphere more stable over the summer months.

There have been several examples when Australia has had a heatwave, and the same blocking ridge that was responsible for it moves over NZ the warm air that got trapped in the mid to upper levels just sits there and creates a nice big inversion which hinders all convection from forming.

-16*C at 500hpa is generally a good ruleset (taking moisture and SFC temps into account) for the atmosphere to be cool enough for decent Summertime storms, but our atmosphere is trending very warm (-8 to -10*C @ 500hpa is becoming far more common than it used to).

For storms to form round those temps at 500hpa our climate would need to turn tropical.

I think this is strongly related to global warming, our summers are becoming hotter with less dispersion of rainfall over the summer months.

The typical driving forces of our weather (the roaring 40's) are less and less pronounced over the summer months as that jet subsides further and further south.

that seems to tally alright

It has been an active Summer over eastern Australia. Certainly in recent years the Summers here have been much more stable with long dry periods.

The easterly sea breeze in Chch has been less strong this year, probably again due to the higher ocean temperatures and despite the weaker westerlies. However, there have been a number of days this summer with inland convergence showers/storms likely aided by orographic forcing from the Southern Alps and foothills. The upper air over the South Island has been warmer this year though, I can't recall any temperatures below about -23/-24C when we can get -30C 500mb air crossing over at times with associated severe hail risks.

When I went to live in Wellington in Jan 99 for first job out of Uni, I noticed that some days were cool to cold to a degree that was very foreign for time of year, but on the positive side, when did get a fine day often got a really blue sky that lasted all day. Had only lived in Waikato and Auckland before then where by my recent memory in summer it was very rare for it to not cloud over by midday and for cloud to come/go during afternoons. The change that seemed to suddenly happen since about summer 2017/2018 is it's happening all the time up here now too, staying almost cloudless all day even on warm days in summer. The 4th Jan just been, being the most stark example recently.

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The upper North Island has become a sweet spot of Summer ridging.

There's been quite a reduction in the number of storms here in the last 10 years along with cooler summers.