CLIMsystems, Hamilton, New Zealand: Tracking Models for Tropical Cyclone Gita Show Possible Future Impact for New
Cyclone activity is ramping up in the South Pacific and New Zealanders are heightening their appreciation of how this
can impact the country. While there is a debate on when information should be shared with the public through the media
there are multiple sources freely available that all have something different to offer. From this information people can
and do make their own decisions on how to respond. That is the reality in the internet age. Every person, family,
community or business has a different risk profile and therefore information and its timeliness of delivery and actions
required will be uniquely theirs. But if and when a cyclone or extropical depression or any other extreme event is
imminent for New Zealand it is local authorities that are most relevant.
Some of the key sources of information are well-known such as the New Zealand Met Service, NIWA and Weather Watch. Other
useful sources include the Joint Typhoon Warning Center and the ExtendWeather South Pacific Cyclone Tracker. One of the
more useful sites is Cyclocane that provides access to graphs of the ensemble of cyclone tracking models. The current
release of tracks for Gita does show a range of possibilities and some do include New Zealand and hence there is at
least some risk but it is difficult to quantify at this point in time. Checking back regularly is critical as ensembles
of tracking do tend to tighten up and become more accurate as a possible storm event draws nearer.
The Extendweather South Pacific Cyclone Tracker is updated regularly and the speed that a cyclone or extropical
depression is making forward progress can be assessed. While there are multiple factors that enter into risk assessments
one important one is the speed at which depressions move past or across New Zealand. The rate of forward motion of a
tropical or extropical depression can influence the length of time with sustained rain and wind for a particular
location or coastline and number of high and low tide cycles that may be influenced, for example. This sort of
information can be factored into preparation planning.
The other issue to be considered is that Gita could potentially arrive following an already extensive rainy period for
some areas. This means that water tables are rising and streams and rivers are in some cases already running high. The
additional potential rainfall could pose an even greater risk when considered in the context of current conditions.
At CLIMsystems and Extendweather we advocate for awareness and resilience planning. The international scientific
community advocates for multiple lines of evidence to be considered in decision making and thus recommends the
processing of an ensemble of information. The scientific community offers online services and the public has increasing
access to this information without mediation from the media. If that leads to increased awareness and action toward
mitigating risk and raising resilience then a partnership between a better prepared and aware society and all levels of
government will hopefully evolve.