The Tasman Tempest takes its toll – time to tally up
MEDIA RELEASE
MONDAY, MARCH 13, 2017
The Tasman
Tempest takes its toll – time to tally up
As the Tasman Tempest headed east off New Zealand today, it’s time to look at the statistics and see how many records it washed away.
NIWA meteorologist Ben Noll says among other
milestones this weather pattern produced:
More rain than
typically falls for the whole of March
Instances of 1 in
100 year rain
A tie for Auckland’s wettest March
hour
Widespread flooding.
The Tasman Tempest strengthened off the east coast of Australia a week ago and churned very slowly to the northwest of the North Island over the Tasman Sea for days on end. Warmer than average sea surface temperatures east of Australia contributed to the storm’s strength and duration.
In fact, the structure of the Tasman Tempest was similar to a tropical cyclone, Mr Noll said.
Tempest totals
Here are some of the Tasman Tempest's most impressive records:
Whangamata received 260mm of rain in 24 hours from
Tuesday into Wednesday. That was 156% of the normal March
rainfall in one day.
From Tuesday 7 Mar to Sunday 12 Mar,
Whangamata recorded 475 mm of rainfall, the highest total at
any one location from the Tasman Tempest. This was 112% of
the normal rainfall for the entire autumn
season.
According to NIWA’s High Intensity Rainfall
System, the 225mm that fell in 12 hours on Tuesday
night-Wednesday in Upper Hunua exceeded a 1 in 100 year
event.
Between 3am and 4am on Saturday 11 Mar, Kaitaia
had its wettest March hour on record (44.6 mm) since hourly
records began in 1962.
Auckland (Mangere) tied its
wettest March hour on record with 27.6 mm between 5pm and
6pm on Friday since hourly records began in 1965.
Between
9am on Friday 10 Mar and 9am Saturday 11 Mar, Auckland
(Mangere) recorded its wettest March day on record (100 mm)
since 1959. This was also the 3rd wettest autumn day on
record in Auckland (Mangere).
Hamilton observed its 4th
wettest March day on record (since 1907) on the 10th with 77
mm.
Kaitaia had its 2nd wettest March day on record
(since 1948) on the 10th with 104 mm.
With all the rain,
Kaitaia is already on track for a top-4 wettest March on
record with 216 mm since the beginning of the month (267% of
the March normal).
Paraparaumu recorded its 2nd wettest
March day on record (since 1951) on the 11th with 74
mm.
In the Auckland suburb of New Lynn, it is estimated
that 60mm fell in two hours on Sunday afternoon, causing
flash flooding. The return frequency on such a rainfall is
approximately 1 in 30 years.
Kumeu recorded 41.4 mm of
rain in one hour on Sunday 12 Mar, which is a 1 in 20 year
event according to NIWA’s High Intensity Rainfall
System.
Whangaparaoa is on track for its wettest or 2nd
wettest March on record since 1948. 226 mm have fallen since
the 1st of the month, which is 317% of the March normal and
84% of the entire autumn normal.
But is it climate change?
While no one weather event is caused by climate change, all events are influenced by climate change since the atmosphere is now warmer and moister than it was in the past. Climate change increases the likelihood of extreme rainfall, given the appropriate weather setup. Research suggests that there will be up to 8% more intense rain for every 1°C of warming.
Goodbye Tempest, hello sunshine
High pressure will build over New Zealand this week, causing much calmer conditions across the upper North Island and country as a whole. The humidity that the Tempest brought will be replaced with typical crisp autumn mornings, though afternoons will be filled with sunshine and comfortable warmth for many.
For those looking to have some late-season beach days, next weekend is looking pretty fabulous across the upper North Island, Mr Noll says.
And here’s the silver lining: the Tasman Tempest caused some warming of the sea temperatures around the northern portion of the country as warm winds blew from the north for many consecutive days.
Through to the end of the month, high pressure will be favoured to the west and over the country, leading to long stretches of dry weather and sunshine with temperatures near or above average.
ends