MetService February 2023 Brief Summary – An extreme month, dominated by Cyclone Gabrielle
In a summer that never really got going for the North Island, February brought more of the same - extreme weather related to Cyclone Gabrielle 12-15 February, followed by several downpour events. In contrast, the lower South Island experienced an extremely hot, sunny and rather dry February, until a rain maker brought some drought relief on the 21st/22nd, followed by an unseasonably cold change that resulted in summer-time snow falling on the southern ski fields.
Cyclone Gabrielle (12 – 15 February) will go down as one of New Zealand’s worst storms in recent memory, and the most severe since Cyclone Bola in 1988. On the back of a record-breaking wet January, impacts were widespread and devastating across the northern and eastern North Island.
To give insight into the extreme intensity of Cyclone Gabrielle, a MetService weather station at Great Mercury Island recorded air pressure of 966.7hPa on the 14th. This ranks in the lowest 10 air pressures ever recorded in the North Island (the record is 962.9hPa at Cape Reinga in 1851).
A nationwide State of Emergency was declared on 14 February, as Cyclone Gabrielle lashed the North Island – only the third time such a declaration has been made in New Zealand’s history. The declaration was issued to support six regions that had already declared a Local State of Emergency: Northland, Auckland, Tairāwhiti, Bay of Plenty, Waikato, and Hawkes Bay.
(For a regional summary, see https://blog.metservice.com/TropicalCyc ... lleSummary).
Gabrielle wasn’t the only high intensity rain event for the North Island - downpours affected the upper North Island on multiple occasions in February. The New Zealand low-elevation 1 hour rainfall record was under threat several times; a particularly active thunderstorm day on 24 February saw 79mm fall in 1 hour in north Auckland producing further flooding. Another thunderstorm also brought a tornado to Waihi on the morning of the 25th.
(The 1 hour low-elevation rainfall record is 109 mm, recorded at Leigh, 20 May 2001)
Preliminary stats for the main centres:
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Feb 2023 Average Temps, Rainfall, Sunshine and departures from 1991-2020 normals ℅ NIWA
Site T-max °C T-min °C T-mean °C Rain mm Sun hrs
Auckland, Mangere 23.6 -0.4 16.5 +0.1 20.1 -0.1 190 337% 188 93%
Tauranga Aero 23.4 -1.0 16.7 +0.9 20.0 -0.1 231 278%
Hamilton Aero * 23.9 -1.1 14.5 +1.4 19.2 +0.1 127 176% 177 96%
Wellington, Kelburn 20.9 +0.3 15.1 +1.2 18.0 +0.7 198 356% 170 80%
Christchurch Aero 23.6 +1.4 13.0 +1.5 18.3 +1.4 94 235% 216 111%
Dunedin, Musselburgh 21.4 +2.7 13.6 +2.1 17.5 +2.4 34 48% 243 145%
Greymouth Aero 23.4 +3.6 14.6 +1.9 19.0 +2.7 114 72% 234 121%
* Sunshine from Ruakura