Issued at 01:59pm 31-Jul-2006
Wet Winter Weather Explained
MetService Meteorologists say that the weather which brought the wettest July on record to parts of the Wairarapa and
Wanganui is due to an unusual cluster of weather patterns.
"These areas were hit by three rain-making low pressure systems during the first three weeks of July," explained
MetService Weather Ambassador, Bob McDavitt. "These three wet events, from 4th to 7th, 12th to 16th and 19th to 22nd
July brought three MetService rain-measuring stations their wettest July on record. Up until noon on Monday, Masterton
has had 256 millimetres
(mm) of rain this month, compared with its past wettest July of 176mm in 1996. In the same period Ngawi, near the
southeast tip of the North Island, recorded 354mm, well exceeding its previous wettest July of 205mm in 1994. And
Wanganui's 176mm also set a new record, beating the previous high of 173mm for July 1998."
McDavitt links these wet episodes to a blocking anticyclone centred well east of New Zealand. "In itself a blocking
anticyclone is not unusual, but what was distinctive about these episodes was the repeated sogginess of the low-pressure
systems."
McDavitt continued to say that the Pacific Ocean as a whole is showing no real trend towards either a La Nina or an El
Nino. "We have no reason to expect any particular weather pattern to dominate over the next few weeks.
Another low-pressure system is getting ready to cross central New Zealand later this week, and it may bring some heavy
rain to eastern Bay of Plenty on Wednesday, but is not expected to be as wet as the three we had in the first half of
July."
ENDS