NIWA’s Silver Climate Jubilee: Celebrating 25 Years Of Seasonal Forecasting

The
Seasonal Climate Outlook (SCO) is one of NIWA’s most
popular services. It provides temperature, rainfall, soil
moisture and river flow predictions for Aotearoa for the
coming three months.

The first SCO was released in
1999, just before the turn of the millennium. This was when
computers still used dial-up internet and the first mobile
phone with digital camera (at a measly 0.11 megapixels)
wouldn’t be sold until the following year.

NIWA’s
Chief Scientist for Climate, Atmosphere and Hazards Dr
Andrew Tait says our methods to create the original SCOs
were quite old-school.

“Computers were starting to
become the mainstream way of interpreting data from
ground-based measurements and satellites. But it was a
transition period; sharing between worldwide climate centres
was not common, and much of the modelling was still done by
hand.

“We’d sit in our respective offices and dial
in using an old teleconference phone to share our scribbles.
We’d look at what happened during similar conditions in
the past and interpret the results. Then, by spoken
consensus, would agree upon our predictions for the climate
of New Zealand in the coming months”, said Dr
Tait.

Back then, those predictions were published on a
4-page leaflet that was sent by post to the media and anyone
else who wanted to subscribe.

Today, the SCO is
accessed online and generally covers more than 4 pages. It
is also supported by an extensive code base, running on
NIWA’s powerful supercomputer that can perform up to 1.4
trillion calculations per second. It is also a lot more
objective, with data collated from more than 9 general
circulation models (GCMs) worldwide, and aggregated and
tailored for Aotearoa New Zealand.

But it still is, as
it was in the olden days published every
month.

It’s a little
complicated…

So, what does the SCO tell
us?

SCOs are not weather forecasts. Weather forecasts
are highly accurate, real-time updates of the weather for a
short-time period – think: do I need to take my umbrella to
the park tomorrow?

However, it is not possible to
predict daily weather variations months in advance for
specific locations. Therefore, SCOs are a statistical
summary of the average weather conditions expected over a
three-month period – think: what are the chances my heating
bill going to cost more because it will be a colder winter
than last year?

Specifically, NIWA’s SCO gives
percentage-based regional guidance on rainfall, air
temperature, soil moisture, and river flows expected over
the next three months. The country is divided into six
regions based on geography and similarities in their
long-term climate: the north, west, and east of the North
Island and the north, west, and east of the South Island –
guidance is provided for each region.

NIWA
meteorologist Ben Noll says this general and probabilistic
information is given due to the chaotic, non-linear nature
of the atmosphere and the longer timescales used.

“For
an SCO, forecasters make predictions based on climate
drivers, which are features that steer the wheel of Mother
Nature’s car. These include El Niño and La Niña, which
many Kiwis will be familiar with, the Southern Annular Mode,
regional sea surface temperatures, and lesser-known
influences like the Madden-Julian Oscillation,” said Mr
Noll.

The climate drivers can “nudge” the system in
different ways. A marine heatwave, for example, can increase
the chances for above average air temperatures. A La Niña
can increase the chance for above normal rainfall in the
north and east of the North Island.

“Due to New
Zealand being surrounded by vast oceans, La Niña/El Niño
has always been a focus of the SCO. Although this climate
driver occurs over 5000 km away in the equatorial Pacific
Ocean, it can shift patterns of rainfall and thunderstorm
activity which has flow-on effects for areas of high and low
pressure nearer to New Zealand,” said Mr Noll.

The
process to create their SCO predictions is a complicated
one, taking lots of time, care and thought. Climate drivers
have varying lifespans, intensities, and effects, meaning
forecasters are in the unenvious position of trying to
decipher when and how they will interact and must deal with
the fact that no two climate driver interactions are the
same.

Blame it on the weather
man

Communicating the SCO has always been
vital to NIWA – disseminating the information in a clear and
engaging way improves trust and facilities informed,
appropriate decision making.

These days, our
meteorologists take advantage of the technology at hand.
Social media channels such as Instagram and Twitter allow
the team to provide daily updates and interact with people
from all over the world. You can watch them on Facebook Live
as they give a breakdown of that month’s outlook, with
live chat functions allowing real-time questions. Multimedia
graphics make the information way more accessible, and the
share functions of social media mean the content can reach
audiences beyond those of just local weather
enthusiasts.

However, back in the 90s and early 00s,
it was different story. Instead, our meteorologists would
jump in a car or on a plane and physically travel around the
country to deliver public seminars to disseminate the data
of the latest SCO. Every single month. Think of the time,
money and fossil fuels that would have taken!

Despite
their best efforts to make accurate predictions and
communicate that information to the world, forecasters often
find themselves at the centre of public
frustration.

“The immense complexity of what goes into
creating outlooks and the domain knowledge needed to clearly
break the information down can sometimes be lost or
forgotten because we almost take forecasting for granted
these days. And while the adage of ‘blame it on the
weather man’ is something my colleagues and I are very
familiar with, forecasting and our methods of communicating
have vastly improved over the decades,” said Mr
Noll.

The importance of climate
outlooks

For the everyday person wondering
whether to book a festival over a summer predicted to be
wetter than average, climate forecasting can be of mild
interest. But beyond that, they can be quite literally
lifesaving.

SCOs are vital for media, businesses,
government, and the primary industries to plan and adapt.
The outlooks can prove helpful to water managers,
particularly those involved in the South Island hydro power
schemes. They can also help farmers understand if irrigation
may start early or if extra feed is needed to cope with a
particularly dry summer. The health sector may be wondering
about heat stress, which is of growing concern as our
climate warms. Coastal scientists may be wondering how long
a marine heatwave might last as part of an assessment of
krill behaviour and its impact on penguins. These are just a
few of the types of questions that the SCO can help
answer.

NIWA is also not constrained by borders,
providing seasonal outlooks for the Pacific Islands through
the Island Climate Update, which is also celebrating its 25
th birthday this year.

There, seasonal outlooks of
rainfall have been coupled with health data to derive a
malaria risk outlook for the Solomon Islands. Dam levels can
also be estimated to determine the chance for water
shortages in Samoa. These types of outlooks highlight the
intelligence that can be generated when sectoral data
intersects with climate data.

“Weather and climate can
literally make or break a season for people that depend on
it for their lives and livelihoods. Therefore, the
implications of an accurate and well-communicated seasonal
outlook can be significant,” said Ben.

What
the future holds

Ben has several ideas and
dream scenarios for the future, including a personalised
app.

“In my dream world you would have an app which
gives you not just the specific weather for the next 5 days,
but a prediction of weather “themes” for the next month and
three months, translated into regionally relevant impact
statements that are generated using the latest forecasts and
AI.

“An example of an impact statement could be:
‘there is a high chance for above average winter
temperatures in Auckland, so you may not need to run your
heater as much and you could consider wearing lighter
clothing” or “there is an elevated chance for a heavy
rainfall event in 2 to 3 weeks in your area that may cause
flooding, so please plan accordingly,” said
Ben.

Ben’s vision for the future could easily be
made possible thanks to the fact that many international
forecast centres, called global producing centres (GPCs),
are now providing open access data at a global scale. NIWA
is not a GPC, but it uses data from GPCs to create outlooks
that are regionally relevant to New Zealand.

“We’ve
entered a golden age of data availability toward better
seasonal predictions. And with the rise of artificial
intelligence, forecast skill continues to improve. Our deep
understanding of the physical science is being married with
decades of dense data collection and AI output, which, when
combined, exponentially grows our ability to recognise and
predict climate patterns,” said
Ben.

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