An occluded front moving down the upper North Island crossed southern areas of the Gulf and Auckland between 7:30am and 9am on Saturday morning. Favourable conditions for tornado development were present with high dew points, -20c degrees at 500 hPa, converging surface and upper atmospheric winds enabling a vortex to gather strength through strong convergence and divergence.
Radar image showing the line of storms on the frontal boundary
Surprisingly, with conditions ideal for tornadogenesis, MetService did not have a severe thunderstorm watch or warning in place for any part of Auckland. On Friday evening we posted an update on our Facebook page for storms and rain to be in this area around sunrise. As per the NZ severe weather code of conduct, only MetService can issue severe weather watches and warning as per the Meteorological Services Act 1990.
Video shows a non supercell cone tornado moving through Papatoetoe around 8.30am.
The trail of destruction left by the tornado ranged from roofs torn off frame houses, cars overturned, large trees snapped or uprooted, light-object missiles generated, cars and a truck lifted off the ground. This type of damage shows that the tornado was likely to be a EF2 on the enhanced Fujita scale. It's likely that the wind gusts were between 178–217 km/h. Sadly one person died and another was injured when the tornado ripped through a Ports of Auckland shipping container yard in South Auckland.
Thanks to Extreme Pursuit Media for video content of tornado and the aftermath.