Watching the images roll into social media on Friday evening, I thought to myself that I’ve seen these kinds of pictures before. But usually they’re from North America or Asia, or maybe Europe. But this was New Zealand’s largest city. Nowhere is safe from extreme weather these days. James Renwick, Atmospheric scientist, Victoria University of Wellington, writing in The Conversation
Over ten inches of rainfall fell on the City of Auckland in New Zealand in just hours. That is a new record in New Zealand and is more rainfall in just one day than falls in the entirety of a typical summer. The event is again a warning that our infrastructure is not ready for climate change-enhanced natural disasters.
It should be a shot across the bow of billionaires that they can ride out the apocalypse in New Zealand while the rest of the world burns. Nowhere is safe.
The Washington Post:
More than 10.3 inches of rainfall was observed within 18 hours in Albany, a northern suburb. Within just two hours, Auckland Airport received over 5 inches of rainfall — more than half its record-setting total of 10.2 inches for the day, according to the country’s MetService.
The torrential rains come during what is typically a dry stretch of the year on much of New Zealand’s North Island, home to its most populous and developed areas, with about 1.7 million residents in the Auckland region. About 2.8 inches falls in an average January in Auckland, according to the MetService, while fall and winter are typically wetter; average July rainfall there is about 5.3 inches.
Scientists expect that climate change will mean less annual precipitation for the Auckland region and northern and eastern parts of the North Island, but an increase in “very extreme” precipitation events for the entire country, according to a government report based on data from the Intergovernmental Panel on Climate Change.
Rainfall in the Auckland area is not expected to ease for another week, so total rainfall is likely to rise.
James Renwick writes in the creative commons, The Conversation.
The torrential rain came from a storm in the north Tasman Sea linked to a source of moisture from the tropics. This is what meteorologists call an “atmospheric river”.
The storm was quite slow-moving because it was cradled to the south by a huge anticyclone (a high) that stopped it moving quickly across the country.
Embedded in the main band of rain, severe thunderstorms developed in the unstable air over the Auckland region. These delivered the heaviest rain falls, with MetService figures showing Auckland Airport received its average monthly rain for January in less than hour.
There will be careful analysis of historical records and many simulations with climate models to nail down the return period of this flood (surely in the hundreds of years at least, in terms of our past climate).
How much climate change contributed to the rainfall total will be part of those calculations. But it is obvious to me this event is exactly what we expect as a result of climate change.
One degree of warming in the air translates, on average, to about 7% more water vapour in that air. The globe and New Zealand have experienced a bit over a degree of warming in the past century, and we have measured the increasing water vapour content.
But when a storm comes along, it can translate to much more than a 7% increase in rainfall. Air “converges” (is drawn in) near the Earth’s surface into a storm system. So all that moister air is brought together, then “wrung out” to deliver the rain.
A severe thunderstorm is the same thing on a smaller scale. Air is sucked in at ground level, lofted up and cooled quickly, losing much of its moisture in the process.
While the atmosphere now holds 7% more water vapour, this convergence of air masses means the rain bursts can be 10% or even 20% heavier.
New Zealand's South Island is in the midst of a marine heatwave.
WELLINGTON, Jan 16 (Reuters) - Waters around New Zealand’s South Island are as much as 6 degrees Celsius (42.8 degrees Fahrenheit) warmer than normal due to climate change, the weather phenomenon La Nina and a series of high pressure systems, according to scientists.
Metservice oceanographer Joao de Souza, who is part of the Moana Project, said that waters around the southern South Island were all well above normal for this time of year with temperatures in Fiordland 6 degrees warmer than normal.
The Moana Project said that water temperatures on the West Coast of the South Island are currently 4 degrees above average.
These temperatures are going to have significant consequence for an eco system that is built or adapted to cold waters, he said.
From billlaurelMDin the comments:
In that Reuters article (and I went to it and checked), they miscalculated the equivalent degrees Fahrenheit (6oC * 9/5 = 10.8oF). But regardless, from the surface to 100m depth around the NZ South Island is an ENORMOUS heat source!