# 9th-12th July - Damaging winds and flooding in north of North Island

 

This storm, affecting areas still recovering from a similar storm back in March, caused much damage due to a combination of torrential rain and severe gales.

 

On the 9th, a deepening depression, which had formed off the NSW coast the day before, moved eastwards towards the far north of the North Island, increasing an east to northeast flow over Northland. At the same time, an intense high to the south of the Tasman Sea pushed a strong ridge into seas just east of the South Island. This situation stayed the same for the next few days, though the low had moved to the north of the North Island on the 10th.

 

Rain became increasingly heavy in Northland as the flow strengthened on the 9th and had become torrential in exposed areas by the next day, with major falls also affecting the Coromandel Peninsula, and by late in the day, the east coast north from Gisborne. Totals over these two days included 272mm in Kaeo, 194mm at Whangarei Airport, 153mm in Kaikohe, and 121mm at Castle Rock. (Coromandel) Severe easterly gales also lashed the upper North Island on the 10th and 11th.

 

Much disruption was caused by both the wind and the rain, including slips, power cuts, fallen trees, and flooded streams and rivers. The town of Kaeo was worst affected. A state of emergency was also declared in the Thames district due to flooding and wind damage, while parts of Auckland were adversely affected too. In total, about 130,000 homes lost power during this storm - some weren't reconnected until over a week later.

 

While northern areas were being blasted by the storm, the South Island was shivering as icy air from high latitudes was trapped over the island thanks to the ridge. Inland areas experienced severe frosts (eg -9C minimum in Twizel on 9th) as well as some freezing fogs which suppressed daytime highs. (only 1C maximums in Alexandra on 10th and 11th) Eastern coasts as far north as the Wairarapa were plagued by drizzly showers, light snow on the hills and chilly daytime temperatures. Blenheim recorded an unusually low 5C maximum on the 9th.

 

Mean sea-level analyses for midday NZST 9th July to midday NZST 12th July in 12 hours steps are shown here.

 

 

 

 

 

# 27th-31st  July - Heavy rain causes flooding in lower South Island

 

During this period heavy rain resulted in flooding on Stewart Island and later in eastern parts of Otago and South Canterbury.

 

On the 27th and 28th, and mild northwesterly flow covered NZ (20C maximum in Napier on 27th), while a stationary front lay to the south. This front resulted in heavy rain falling over Stewart Island and Fiordland.

 

Meanwhile, a low developed in the North Tasman Sea during this period. During the 29th, this low deepened rapidly and moved south, becoming slow moving to the west of central NZ by the next day. This resulted in a period of heavy rain in the north of the North Island, but not enough to cause much disruption this time. However, the large low pressure system also set up a moist easterly flow over southern NZ. In Mid and North Canterbury, heavy rain fell overnight on the 30th, but wasn't prolonged enough to cause anything more than a little surface flooding.

 

By contrast, the rain was much more persistent in South Canterbury and eastern parts of Otago. Flooding was widespread and severe enough to force evacuation of houses in some places, eg in Milton and Palmerston. One positive aspect of this storm was a good dumping of snow on southern ski-fields which had previously hadn't a decent enough cover, due to prolonged dry (albeit often very cold) weather.

 

Even further south, the stationary front mentioned earlier persisted near Stewart Island, but was now incorporated into the moist easterly flow. Heavy rain continued over the island, resulting in severe slips and washouts in the small settled part of the island. (some homes were cut off)

 

On the 31st, the low pressure system moved over the country and weakened, eventually stopping the rain in the south. Unsettled weather in the North Island resulted in yet another tornado in Taranaki, this time tipping a truck over near Waitara.

 

Mean sea-level analyses for midday NZST 27th July to midday NZST 31st July in 12 hours steps are shown here.

 

 

 

CHRISTCHURCH WEATHER - WINTER 2007

 

JUNE

To cap off an unseasonably warm May, June began with a balmy 20C maximum, 6C warmer than the first day of summer in December 2006! However, this warmth wasn't to continue. A trough and cool southerly change brought the first significant rain for a month overnight 2nd/3rd, as well as fresh snow to the previously bare ski-fields. From then on it became colder in the city with south or southwest flows, though these generally brought little rain. The coldest outbreaks were from the 7-9th and 21st-26th - significant snow fell to low levels in the south and about the main divide, but only some lighter falls dusted Banks Peninsula to quite low levels early on the 8th and again on the 25th, plus scattered sleet in and near the city and a dusting on the higher Port Hills on the latter occasion. While most of the month was dry, rainfall totals reached near normal after a wet day on the 29th. Thanks to an active low pressure system in the Tasman Sea and very moist northeasterlies ahead of it, quite heavy falls resulted in some surface flooding in Christchurch.

 

JULY

High pressure to the south and east led to this month being generally cold and cloudy, apart from a mild spell towards the end. A spell of very cold southeasterlies from the 5th-7th brought snow to low levels in many parts of Canterbury, but only brief light flurries of snow and sleet were reported in and around Christchurch. After the weather cleared, there was a heavy frost on the morning of the 8th. Onshore flows, often with drizzly showers, were frequent for the next few weeks. There was another cold southerly outbreak on 21st/22nd bringing some hail and sleet, plus a light dusting of snow on the higher Port Hills.

By contrast, after a heavy frost on the morning of the 23rd, the week from 23rd-28th, was much milder with westerly and northwesterly flows. Then a deep low pressure system crossed over during the last three days of the month. Christchurch and environs received a period of heavy rain overnight 29th/30th, but this eased on the 30th. (through persisting further south, with widespread flooding in South Canterbury and eastern Otago)

 

AUGUST

A variety of weather systems crossed over this month, but these generally didn't bring much precipitation to Christchurch. Very cold southerlies brought snow to low levels in parts of Canterbury on the 13th/14th, including rural areas just to the west of the city early on the 14th. After the weather cleared, there was a heavy frost on the morning of the 15th. By contrast, there were some spells of warmer weather when airflows tended west or northwest.

 

Ben Tichborne