NOTABLE WEATHER IN NEW ZEALAND - SPRING 2007

This season was memorable for some very stormy weather in October, including severe gales and heavy rain in places. September and November were more settled, with lack of rain becoming a concern for some areas by the end of the season.

SEPTEMBER

# 1st - 20C+ maximums in eastern areas. (23C maximum in Kaikoura) Heavy rain in Fiordland. (107mm recorded at Milford Sound) Northwesterly gales about Cook Strait.

# 2nd - 21C maximum in Gisborne, before cooler southerly change in late afternoon.

# 3rd - Heavy rain in Fiordland and Westland, easing early on 4th. 120mm recorded at East Homer; 152mm at Waiho.

# 4th - Northwesterly winds gust up to 135kph at Castlepoint. Very cold southerly over South Island, with snow to low levels in many eastern areas. Several centimetres blanket the Canterbury plains as low as about 100 metres, with 6-8cm recorded in some places. Geraldine and Ashburton are briefly dusted, while snow flurries are reported at Christchurch Airport. Traffic disrupted for a time on Dunedin's northern motorway.

# 5th - Cold southerlies spread over North Island, with some snow showers on the high country, but not enough to disrupt travel. Brief snow at summit of Rimutaka Hill Road about midafternoon.

# 6th - Widespread heavy frosts in wake of cold southerly outbreak. -6C minimum in Fairlie and Hanmer Forest; -8C frost at Dunedin Airport. Only 9C maximum in Taupo.

# 7th - More heavy frosts in parts of South Island, eg -11C grass minimum at Mt Cook Village.

# 9th - Deep low results in heavy rain in northeastern North Island (Northland to East Cape), with severe easterly gales in far north. 56mm recorded at Cape Reinga; 57mm in Whangarei; 43mm in Kaeo.

# 10th - Heavy rain and southerly gales lash Gisborne/East Cape area, as low moves to east.

# 11th - Frosty dawn in some inland parts of South Island, eg another -11C frost at Mt Cook Village.

# 12th - 20C maximum in Alexandra in a northerly flow.

# 13th - Heavy rain about and west of the Southern Alps and in the Tararuas. 73mm recorded at Arthurs Pass; 202mm at Waiho; 120mm at Angle Knob.

# 15th - 22C maximums in Alexandra and Kaitaia; 22C maximum in Gisborne. Some heavy rain in Westland, eg 80mm at Waiho in 9 hours.

# 16th - Warm 20C+ maximums in eastern areas and the far north. 24C maximum in Kaikoura and 23C in Gisborne.

# 17th - Another warm 23C maximum in Gisborne. A sunny 21C maximum in Alexandra, but Invercargill reaches only 10C under a cool southwesterly flow.

# 18th - A warm, humid northerly flow results in 20-22C maximum from Thames and Auckland northwards.

# 19th - Warm day in North Island under a northeasterly flow, with 20C maximums in several places (eg Hamilton, Auckland, New Plymouth, and Palmerston North) This airstream brings heavy rain to Northland, eg 102mm in Kaikohe. Chilly start to the day in many lower South Island areas, eg Dunedin Airport has -2C minimum (-5C frost), though it rises to a mild 17C there in afternoon.

# 20th - Unseasonable 23C maximum in Kapiti; 24C at Wanganui Airport. (September record)  22C maximums in Kaitaia and Alexandra. Dunedin Airport reaches 19C, rising from a -2C minimum. Cave system at Waipu, Northland floods as result of recent heavy rain, resulting in six teenagers having to be rescued.

# 21st - Areas of low cloud and fog about east coast of South Island. (Christchurch Airport operations affected for a time in morning) This keeps Kaikoura from reaching no higher than 11C. By contrast, Blenheim and Kapiti bask in warm 21C maximums.

# 22nd - Some thunderstorms in Northland and northern parts of Auckland region. Warm spell continues in southwest of North Island under fohn northeasterly flow, with 20C maximums in Palmerston North and Kapiti. 21C maximum in Ashburton.

# 23rd - 20-21C maximums in many northern and eastern parts of North Island, but colder southerlies over much of South Island with fresh snow on the mountains. (about 10cm on ski-fields)

# 24th - Scattered afternoon thunder and hail storms in north of North Island (especially in Auckland, Waikato, and Rotorua), resulting from a combination of 18-20C maximums and an unstable airmass. Waterspout reported off the coast near Tauranga. 21C maximum in Gisborne. Contrasts in South Island between east and west, with a drizzly 9C maximum in Ashburton but a sunny 18C in Greymouth.

# 25th - Cold in east of South Island under a southerly flow, with maximums only about 10C in many places. Snow and sleet on Dunedin hills in evening. By contrast, sunny on the West Coast, with maximums in the high teens.

# 26th - Cold southerly flow over NZ with 8-10C maximums in Canterbury and 10C in Masterton. Snow showers on eastern ranges of North Island, and light falls reported to low levels in North Canterbury, eg near Amberley.

# 27th - Frosty morning in many areas, eg -3C minimum in Waiouru and -2C in Blenheim. (frost fighting measures used to protect Malborough orchards)

# 28th - Frosty morning again in many places, eg -4C minimum in Waiouru and -5C frost at Dunedin Airport. However, 21C maximums in Alexandra and Hanmer as northerly flow develops over South Island.

# 29th - Warm 22C maximum in Lyttleton. Heavy rain develops on South Island West Coast.

# 30th - Heavy rain about and west of the Southern Alps. (402mm recorded at Waiho over two day period) Some thundery downpours in Taranaki. 20-22C maximums in east of South Island.

OCTOBER

# 1st - Northwesterly gales for a time in inland Canterbury. Thunderstorms in many northern and western areas (including Auckland, with hail - lightning strikes house in Rodney district); also in parts of Otago (plus brief hail in Canterbury) in afternoon.

# 2nd-4th - Stormy period no.1. (see details below)

# 7th-11th - Stormy period no.2 (see details below)

# 14th-18th - Stormy period no.3 (see details below)

# 19th - Unseasonably heavy morning frosts in many areas in wake of previous day's cold outbreak, eg -7C frost at Christchurch Airport. Some damage to vines in Malborough.

# 20th - More frosts in many parts of North Island, eg -4C minimum in Waiouru. Frost damage to crops in Hawkes Bay.

# 23rd-24th - Stormy period no.4, with damaging gales in places (see details below)

# 25th - Further gales about far southern coasts. (53 knot gust in Invercargill), slowing the recovery efforts from previous day's storms. A frosty dawn in many South Island places, but warming up quickly (eg 24C maximums in Oamaru and Timaru) as a westerly flow redevelops.

# 26th/27th - Cold southerlies move onto far south late on 26th and affect eastern areas the next day. Some hail about Banks Peninsula, and light snow showers about some South Island high country areas.

# 28th - Morning frosts in many areas.

# 30th - Warm in eastern areas in a northwesterly flow, eg 27C maximum in Lyttleton and Timaru Airport, and 26C maximum in Oamaru. Heavy rain in Fiordland, eg 182mm at Milford Sound.

NOVEMBER

# 4th/5th - Heavy rain in parts of central NZ and central North Island exposed to northwest, eg Tararuas. (160mm at Angle Knob)

# 5th - Cold southwesterly flow over South Island, with snow showers reaching fairly low levels in Southland and South Otago. (eg flurries in Clinton)

# 6th - Frosty start to day in parts of South Island in wake of cold southwetserly. -3C at Lauder.

# 10th - About 30mm rain in Opotiki  from an overnight downpour.

# 11th - A few afternoon thunderstorms about inland high country areas of North Island and upper South Island.

#11th/12th - Heavy rain in Fiordland. (75-90mm) Heavy overnight rain on Kermadec Islands. (150mm in six hours at Raoul Island)

# 12th-14th - Cold snap with gales in North Island. (see details below)

# 18th - Warm 29C maximum in Hanmer.

# 20th - Warm day in many inland parts of South Island, eg 31C maximum in Alexandra (highest November maximum since 1986) and 30C maximum in Hanmer.

# 21st - Very warm maximums again in many eastern parts of South Island, eg 32C maximum in Hanmer; 31C in Alexandra (again!); 30C in Ashburton and Blenheim.

# 22nd - 30C maximums in Napier and Hastings.

# 23rd - 29C maximum in Wairoa (2nd highest recorded for November)

# 24th - Summery 27C maximum in Nelson. Heavy rain in the far north closes the road to Cape Reinga for a time.

# 25th - November record 33C maximum in Blenheim. 28C maximum at Tauranga Airport (equal 2nd highest for month since 1913); 32C in Kawerau; 29C in Motueka. Temperatures reach high 20s in Canterbury, but a cool southerly change in afternoon sends thermometers plummeting, eg Christchurch drops 5C in two minutes, then 12C in 50 minutes!

# 26th - November record 27C maximum in Te Puke.

# 27th - Cold southerly spreads over South Island. Some hail in the south (eg Invercargill) and snow showers on the ranges.

# 30th - Some afternoon thunderstorms in central North Island, spreading to coastal Bay of Plenty by evening. (some surface flooding in Tauranga) Only 12C maximum in Timaru, due to cloudy onshore airflow.

MAJOR EVENTS

# 2nd-4th October - Stormy period no.1.

 An active cold front moved onto the South Island on the 2nd, preceded by a northwesterly flow over the country. There had already been several days of unsettled weather to mostly western areas over the previous three days (see notes above), and during this day thunderstorms continued in western areas, while heavy rain fell in Fiordland, eg 60mm at Milford Sound in 12 hours. Cold southerlies spread onto the South Island in the evening, with snow lowering on the high country.

 A cold south to southwest blast swept over the rest of NZ on the 3rd, with 9-10C maximums in many eastern South Island places and 11C maximums in Masterton and Taupo. Snow fell to low levels in Otago and Southland; vehicles were stuck on Lindis Pass in early morning and the Milford Road was closed by snow and avalanche risk. Hail and sleet were reported in Christchurch, while southerly gales lashed the east coast of South Island. Snow showers also affected the central North Island, including the Desert Road, but not enough to cause disruption. Meanwhile, hail showers peppered the north of the North Island.

 The flow died out that night with frosts in some areas (-6C minimum in Waiouru), worrying orchardists. (especially in Hawkes Bay and Malborough) However, a northwesterly flow soon arrived in morning, quickly raising temperatures in eastern areas. (by afternoon many places are as much as 10C warmer than the day before!) However, it remained cold about and west of the South Island main divide, as a new frontal system moved in and brought heavy rain to West Coast. (125mm fell at Waiho) Heavy snow fell about the high country, disrupting travel on southern passes. The Milford Road remained closed due to avalanche danger, while chains were essential on the Haast Pass. Wanaka shivered on only 3C at 1pm. The northwesterlies rose to gale in inland Canterbury and also Wellington and Wairarapa (78 knot gust at Castlepoint; 75 knot on Mt Kaukau), causing some damage.

Mean sea-level analyses for midday NZDT 2nd October to midday NZDT 4th October in 12 hour steps are shown here.

# 7th-11th October - Stormy period no.2

A frontal system approached the South Island from the west in the early hours of the 7th, rapidly increasing the northwesterly flow preceding it. Gales caused some damage in Canterbury (eg a roof blown of at LeBons Bay) overnight and early morning, and further north about Malborough, Wellington, and Wairarapa during the day. However, these warm northwesterlies also pushed the thermometer up to 27C in Hastings and 25C in Napier. Meanwhile, heavy rain about and west of the mountains in the northern South Island and about the Tararuas pushed rivers to flood levels. Waiau township (North Canterbury) had to be temporarily evacuated due to the rising waters of the Waiau River.

 The frontal system became slow moving over the North Island through to the 8th. Heavy rain and thunderstorms continued about central NZ, along with northwesterly gales.

 On the 9th, a low formed in the northern Tasman Sea, pushing moist air back down onto the North Island in a northerly flow. This low then moved to the west of central NZ, where it remained until finally moving away to the southeast of the South Island by the 12th. Heavy rain continued about central areas, with 106mm recorded at Tunakino (Malborough). Many rivers were at high flood levels as a  result of all this persistent rain. Cloud cover and an onshore flow also suppressed maximum temperatures in the northeast of the South Island, with chilly 11C maximums in Blenheim and Kaikoura on the 10th. In Hawkes Bay, hail was reported on the Takapau Plains on the 11th.

Mean sea-level analyses for midnight NZDT 6th October to midday NZDT 11th October in 12 hour steps are shown here.

# 14th-18th October - Stormy period no.3

 A deep low crossed to the southeast of  the South Island on the 14th. Westerly gales lashed many parts of northern and central NZ. (northwesterly about Cook Strait) Gusts to 130kph were recorded in the Ruahine Ranges and 70 knots at Manukau Heads. Trees were felled on the Takapau Plains.  Further south, a period of southerly gales affected coastal Otago.

 Another  trough quickly crossed NZ on the 15th, with yet more westerly gales in the southeast of the North Island.

 On the 16th, the flow tended northwesterly over the country and strengthened. Gales affected some inland South Island areas as well as the south of North Island, eg 76 knot gusts on Mt Kaukau. A motorcyclist was blown off road near Woodville. Heavy rain fell about and west of the Southern Alps and on the Tararuas, eg 180mm at Cropp, 160mm at Arthurs Pass and at Angle Knob. Canterbury's main rivers reached 6 month high flows by next morning.

 During the 17th, an active trough moved onto NZ. Heavy rain continued about central NZ and the central North Island. 72mm was recorded in Ohakune up to 9am next morning; 30mm falling in one hour from 10-11am on 17th) Northwesterly gales in Hawkes Bay resulted in Napier Airport being closed for a time in the morning. Cold southerlies spread over the South Island in afternoon, with snow falling on the southern hills.

 The trough crossed North Island on the 18th, with some thunder and hail, especially in northern areas. A tornado was reported near Reporoa in afternoon. A cold south to southeast flow gradually spread over island, with some snow to the high country by evening, including the Desert Road. (which remained open) Heavy rain from thunderstorms lashed the Gisborne area in late afternoon and evening. In the South Island, the wintry southerly flow gradually died out, after giving early snow to about 300m in Southland, Otago, and inland Canterbury. About 6cm snow coated parts of the Mackenzie Country with a light dusting also in Fairlie.

Mean sea-level analyses for midday NZDT 14th October to midnight NZDT 18th October in 12 hour steps are shown here.

# 23rd-24th October - Stormy period no.4, with damaging gales in places

A deep depression passed to the south of South Island during the 23rd, with a cold front crossing NZ. Combined with high pressure to the north of the North Island, this resulted in tight isobaric gradients over the country. Ahead of the front, northwesterly gales affected eastern areas and central NZ. Southern Hawkes Bay was severely lashed by these winds with much damage, including roofs lifted in Dannevirke and trucks blown over.

After the front had passed, severe west to southwest gales blasted coastal Southland and Otago, with extensive damage there, including power cuts and fallen trees. Gusts up to 76 knots were recorded on Stewart Island, while Gore reached 53 knots and Dunedin Airport 63 knots.

The low had moved well to the east by evening and so the airflow decreased and winds eased. However, more fronts arrived the next day, with west or northwest gales again in eastern areas and southwesterly gales in the far south following the fronts. While generally not as severe as the previous day (though a 66 knot gust was recorded in Invercargill), the winds were still disruptive to clean-up efforts. A 12 year old girl was killed in Christchurch when a westerly gust blew her into the path of an oncoming bus.

To add to the chaos, in Southland the winds were accompanied by squally thunderstorms with hail. These storms also affected Otago and then spread into parts of Canterbury in the afternoon. Christchurch was hit in the early evening, with power cuts in some rural areas near the city.

Mean sea-level analyses for midday NZDT 23rd October to midday NZDT 24th October in 12 hour steps are shown here.

# 12th-14th November - Cold snap with gales in North Island.

The last bout of stormy weather for the season resulted from an active trough crossing NZ, bringing a cold southerly outbreak with high country snow and severe southerly gales to exposed parts of the North Island.

The trough arrived in the South Island late on the 12th, with several fronts approaching from the southwest. During the 13th, as the trough moved northeast, cold southerlies spread over the island. Scattered thunderstorms and hail came with the change, a waterspout sweeping in from the sea near Birdling's Flat (Canterbury) in the afternoon during a particularly heavy thunderstorm. Another big thunderstorm hit Wellington late that evening as the southerly arrived there.

By the next day, a deep low had formed on the trough to the east of central NZ, resulting in a strong cold southerly flow over most of the country. South to southwest gales lashed the North Island, being severe in some exposed places, especially about Wellington and eastern coasts. Gusts of up to 74 knots were recorded on Mt Kaukau and Kelburn gusted to 56 knots. Cook Strait ferries were disrupted by high seas. In Auckland, the Skytower had gusts up to 52 knots. Snow fell on the high country of both islands; in the central North Island it fell as low as Waiouru for a time in early morning and the Desert Road was hazardous for a while. The flow gradually eased during the day, but temperatures remained well below normal, eg reaching only 11C in Ashburton.

Mean sea-level analyses for midday NZDT 12 November to midday NZDT 14th November in 12 hour steps are shown here.