·                     Soil moisture: Significant deficits in western areas of the North Island

·                     Temperature: Above average in the north and west, below average in Otago

·                     Sunshine: Well above normal in west and south of the South Island

Low rainfall occurred in the alpine areas and west of the South Island, with one of the driest autumn’s on record. It was very dry and sunny in the west and south of the South Island and Manawatu. Mean autumn air temperatures were above average in the north and west of both islands, but below average in Otago. The national average temperature of 13.3 °C was exactly average for autumn. But in the South Island unusual in March, and May brought extended periods of frost. It was extremely sunny in the west and south of the South Island.

Rainfall was about 50 percent (half) of normal in alpine areas and in South Westland, Fiordland, and less than a quarter of normal in Timaru. Unusually, significant soil moisture deficits (at least 110 mm) persisted until the end of March in many western North Island areas, dramatically affecting dairy production. Seven people drowned in a river flood in April, whilst May was unusually windless and extremely dry in many South Island places. The overall autumn climate pattern was dominated by more anticyclones to the south and southeast of the South Island, and depressions northwest of the North Island, producing more easterlies and northeasterlies.

·                     The highest temperature during autumn 2008 was 34.8 ºC recorded at both Timaru Airport, and 35°C (rounded to the nearest degree) at Culverden and Woodbury on March 19th. This was 1°C less than the highest ever New Zealand March temperature of 36°C recorded at Ashburton in 1956. Heatwave conditions occurred from 18-21 March in inland and eastern South Island areas, with temperatures of 30°C or more, and many locations recording their highest March temperatures on record.

·                     The lowest air temperature during the month was -7.7ºC recorded at Albert Burn in Central Otago on May 5^th under clear skies. It was much frostier than normal in May, with ground frosts of 5°C or more occurring on 24 days in some inland areas.

·                     April produced several high rainfall/flood-producing events – the worst being that of 14-16 April with 132 mm in 24 hours in Takaka on 14 April, 126 mm at Matamata, 108 mm at Rotorua and 101 mm at Taupo on the 15^th – the deluge caused flooding of homes in Rotorua, and a river flood on the Mangetopopo drowning seven people, and earlier in the day a man was struck by lightning and killed near Dargaville. On 29 and 30 April 40 mm at Paraparaumu, 95 mm at North Egmont, and 94 mm in Wellington caused flooding in the Okato, the Kapiti Coast and Wellington.

·                     By 29^th March severe and significant soil moisture deficits (more than 130 and 110 mm) were present in throughout the west of the North Island from Auckland to the Manawatu, east of North Island, and the east of the South Island. The combination of the hot and dry conditions meant that dairy farmers continued drying off dairy stock, with sheep farmers selling stock early. April rainfall ended the severe and significant soil moisture deficits.

·                     Of the five main centres, Auckland was easily the warmest, Wellington by far the wettest, Hamilton the sunniest and Christchurch the driest. Autumn temperatures were above average in Hamilton and Wellington, and below average in Christchurch. Rainfall was well above normal in Wellington, near normal in Auckland, and below normal in the three other centres. Autumn sunshine was near normal in Auckland and Christchurch, and above normal in Hamilton, Wellington and Dunedin.

Rainfall

Autumn rainfall was about 50 percent (half) of normal in alpine areas and south Westland, Fiordland, and less than a quarter of normal around Timaru. Cape Reinga record almost 200 percent (double) normal rainfall, and 150 percent (one and a half times) normal rainfall occurred in eastern Bay of Plenty, parts of the east of the North Island and Wellington.

Temperature

Seasonal mean temperatures were about 0.5 °C above average throughout the north and west of both islands. They were closer to average in other North Island areas, and below average but about 0.5°C in Marlborough, Canterbury and Central Otago.

Sunshine

Autumn sunshine hours and/or solar radiation were at least 110 percent of normal in the southwest of the North Island, the west, south and alpine areas of the South Island. Southern and alpine areas received totals in excess of 120 percent of normal. Only in Gisborne were totals less, being 90 percent of normal.

Dr Jim Salinger – Principal Scientist, Climate

NIWA National Climate Centre – Auckland Phone +64 9 375 2053

j.salinger@...

Geoff Baird Communications Manager Phone +64 4 386 0543

g.baird@...

Acknowledgement of NIWA as the source is required.

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NOTABLE WEATHER IN NZ  - AUTUMN 2008

MARCH

* 1st - Heavy rain about and west of the Southern Alps and later in Southland.

* 2nd - Heavy rain easing on South Island West Coast and Southland, but a period of heavy rain in eastern Otago. Colder southerlies spreading up South Island, with only 11C maximums in Invercargill and Dunedin.

* 3rd - Rather cold southeasterlies in east from Wairarapa to Southern Hawkes Bay. Fresh snow on Canterbury mountains, including 15cm on Mt Hutt. Only 13C maximums in Oamaru and Ashburton.

* 4th - Heavy rain in ranges of Gisborne and northern Hawkes Bay.

* 5th - A brief period of rain in Wanganui area in morning.

* 7th - Some heavy afternoon showers around Auckland due to sea-breeze convergence.

* 9th - Cold front crosses South Island, preceded by early morning north westerly gales in Southland, and followed by a brief period of southerly gales in coastal Canterbury and Kaikoura. (some damage to trees in Christchurch)

* 13th - Some heavy falls of rain in Gisborne ranges.

* 14th - Some thunderstorms in a line from Northland to Waikato.

* 15th - 31C maximums in Alexandra and Timaru.

* 18th - Near record 32C maximum at Dunedin Airport, though only 22C maximum in the city. 31C maximum in Alexandra and 30C in Tokoroa.

* 19th - Very warm day in Canterbury and Otago, due to northwesterly flow. Record 35C maximum in Timaru, plus 31C in Alexandra and 30C in Queenstown.

* 22nd - Only 14-15C maximums in east and south of South Island in wake of cool southerly flow.

* 23rd - Light frosts in many sheltered parts of Otago.

* 26th - Warm 27C maximum in Wanganui.

* 27th-28th - 26-28C maximums in southwest of North Island, thanks to sunny skies and a light northeasterly flow. Also, a warm 29C maximum in Amberley on 27th, as warm northerlies affect Canterbury.

* 29th - Some heavy rain on South Island West Coast.

* 30th31st/ - Heavy rain about central NZ, especially the Tararuas. (81mm at Angle Knob on 30th; 219mm at North Egmont both days; 81mm in Kelburn)

APRIL

* 1st - Squally southerly change sweeping up South Island in afternoon, with thunderstorms and hail in Canterbury later afternoon and evening. Some surface flooding reported in places, including Ashburton and Christchurch.

* 2nd - 0C minimum in Queenstown. Only 10C maximum in Invercargill, thanks to cloud cover and an onshore flow.

* 3rd - 1C minimums in Lumsden and Timaru.

* 4th - Heavy rain in Fiordland and about the Westland ranges. Warm 25C maximums in Wanganui and Palmerston North.

* 6th - Some heavy rain in the far north. Afternoon thunderstorms in some central and southern parts of the North Island.

* 7th - Rather cold 13C maximums in Oamaru, Timaru, Ashburton, and Christchurch under a cool southerly flow.

* 8th - Heavy rain about the Gisborne and Hawkes Bay, especially in the ranges. 110mm at Te Puia Springs; 109mm at Pukeoranga. (Hawkes Bay)

* 11th - 0C minimum in Waiouru.

* 13th - 1C minimum in Alexandra, but rising to a 23C maximum under clear skies.

* 14th-19th   - Unsettled period, including deadly storms in North Island, followed by cold snap. (see details below)

* 21st - -1C minimum in Twizel; 1C minimums in Timaru and Masterton. 17C maximum in Invercargill drops to 8C in the afternoon, as gale west to southwest winds hit the far south following a cold front.

* 22nd - Severe southwesterly gales in coastal parts of Otago and Southland.

* 23rd - 0C minimum in Ashburton. More southwesterly gales in coastal Otago and Southland.

* 24th - 0C minimums in Timaru and Manapouri.

* 27th - Only 8C maximum in Alexandra, as fog persists there into the afternoon.

* 28th - 24-25C maximums in many eastern places.

* 29th April-5th May - Unsettled period, including heavy rain and snow. (see details below)

Another stormy period lashed many areas during this period, with more heavy thundery downpours in the North Island, followed by a wintry southerly blast, and then yet more heavy falls of rain in the north of the North Island.

On the 29th April, a deep low pressure system and associated trough approached NZ from the west. A warm front (closely followed by a cold front) moved onto the far north in the evening, while a larger cold front moved in from the west overnight. The combination of these system resulted in thunderstorms in the north of the North Island, with some heavy downpours. These fronts moved away to the east on the 30th April, but the main low and more cold fronts crossed the South Island during the day the North Island at night. More thunderstorms resulted in many places, including a heavy downpour which caused flooding in Wellington overnight the 1st May. Rotorua and Taranaki also suffered from significant flooding during this period, with 131mm recorded at Dawson Falls. Other high totals included 178mm at Ngunguru (Northland) and 159mm at Haparapa. A tornado caused some damage at Tarawera on the Napier-Taupo Highway on the 29th.

Behind this, there was a colder southerly change, with some snow on the southern hills by the 1st. Another cold front moved onto the South Island late in the day. As this front moved north, a low formed on it and had moved to the east of the South Island by late on the 2nd. This resulted in very cold southerlies spreading over most of the island, with some hail, thunderstorms and snow to fairly low levels. Conditions became particularly wintry about coastal Canterbury in the evening, with unseasonably heavy snow on the Port Hills above Christchurch, while the city was lashed by hail and sleet.

During the 3rd May, the low moved gradually away to the east, maintaining very cold showery southerlies over southern and central NZ, with snow showers continuing on Canterbury hills and now also on the central and southern North  Island high country, including both the Desert and Rimutaka Hill roads. (though both stayed open)

By the 4th May, a much weaker southerly flow affected the east of the country. However, during the day, a large low pressure system in the northeastern Tasman Sea pushed a warm front down over the northern and central North Island during the day with rain, heavy in some places. (83mm recorded in Tauranga, with flooding there in parts of Auckland) In the central high country, the existing airmass was still cold, and the rain fell as snow overnight during the 4th/5th above about 700 metres. Both the Napier-Taupo and Desert Roads were affected - they stayed open, but the Napier-Taihape route was closed for a time.

On the 5th, the low system gradually moved east over the North Island, but conditions remained unsettled over much of the island, with some heavy falls of rain in the north. Snow levels gradually rose in the central high country, but temperatures remained cold in the southern and central North Island, with New Plymouth recording a chilly 9C maximum.

Overnight 5th/6th, the system moved off to the east, taking all the stormy weather with it.

MAY

* 6th - Icy -6C minimums in Alexandra and Lumsden.

* 8th - A chilly start to the day around Auckland, with 3C minimums in many places away from the sea. By contrast, a warm afternoon in many parts of NZ, as a northerly flow develops. 21C maximum in Culverden; 20C maximum in Tokoroa. Heavy rain on South Island West Coast and northwest Nelson, eg 140mm at Cropp.

* 9th - Heavy rain in central North Island and Hawkes Bay/East Coast Ranges, eg 100mm at Tarawera. (on Napier-Taupo Highway) Flooding Te Puia. Balmy 20C maximum in Kapiti, under a fohn northeasterly flow. However, cold in the  southern half of the South Island, with snow above about 800 metres on the ranges.

* 10th - 20C maximums in Northland.

* 11th - Some hail showers in Canterbury, as a cold southerly freshens.

* 12th - Frosty -3C minimum in Timaru; -2C minimums in Twizel and Wanaka.

* 13th - Frosty dawn in many areas, eg -3C minimums in Taumaranui, Waiouru, and Christchurch Airport.

* 15th-17th - Foggy in many areas under a large anticyclone. Disruptions to Auckland and Hamilton Airports. Black ice on Desert Road overnight 16th.

* 19th/20th - Mild 19C maximums in Wanganui on both days under a fohn northeasterly flow.

* 22nd - Cold southeasterly flow spreading over much of the South Island, with some snow on the southern high country. Only 6C maximum in Queenstown.

* 23rd - Cold southeasterly flow over the South Island with snow on the high country, especially in Central Otago. 25cm accumulates at Coronet Peak, while Crown Range Road has to cleared by graders. Snow level down to about 400-500 metres. Only 5C maximums in Queenstown and Alexandra. Some heavy, thundery rain in the far north.

* 24th - Light snow continuing on inland South Island high country, with another 5C maximum in Queenstown. Heavy rain in Gisborne and Hawkes Bay, with some slips and flooding around Hastings.

* 26th - Areas of fog in inland and southern South Island. Only 5C maximum in Gore. Some thunderstorms in Northland and Coromandel. Slips from recent rain close State Highway 38 between Wairoa and Wakaremoana.

* 27th - Frosty morning many areas, eg -3C minimums in Taumaranui and Lumsden. Areas of fog in Central Otago, resulting in Alexandra only reaching 6C. Heavy overnight rain in Northland.

* 28th - -5C minimum in Fairlie. More areas of fog in inland South Island. All day fog keeps Wanaka from rising above 3C, while Alexandra only has a 4C maximum.

* 29th - -6C minimum in Fairlie.

* 31st - Only 6C maximum in Alexandra.

* 14th-19th   - Unsettled period, including deadly storms in North Island, followed by cold snap.

This period saw a trough cross NZ bring very stormy weather to many parts of the North island, were thunderstorms and downpours resulted in tragic consequences. It was followed by the first major wintry blast of the year, bringing snow to low levels in parts of the South Island.

A band of thunderstorms crossed the north of the North Island on the 15th, bringing heavy downpours to many areas. 94mm fell in Opononi, Northland, in only three hours. A group of horse riders were struck by lightning near Dargaville, killing one man. However, an even bigger tragedy occurred in Tongariro National Park, when a flash flood caused by a downpour washed away seven kayakers from a school trip to their deaths.

On the 16th, a shallow, but complex area of low pressure lay over NZ, with a low centre moving onto the northern North Island later in the day. The frontal system which delivered the previous day's thundery downpours remained over the northeastern North island, with further heavy rain and thunderstorms in the ranges of Eastern Bay of Plenty/Gisborne/East Cape, and northern Hawkes Bay until the morning of the 17th, when the northern low moved away to the southeast. Totals included 360mm at Haparapa (Bay of Plenty) and 201mm at Waikura. (Gisborne)

A cold front moved onto the far south during the evening of the 17th, and crossed the rest of the country the next day, followed by a colder southwesterly flow. Conditions became very cold in the southern South island during the day and into the 19th, with snow showers to low levels in inland Southland and South Otago (about 2-4cm settling above about 250 metres), plus also Dunedin's hill suburbs and higher parts of Central Otago. The south was also lashed by hail and thunderstorms.

On the 19th, the flow tended more southerly, allowing the wintry conditions to spread north. Snow fell to about 250 metres in parts of North Canterbury early in the day (lightly dusting Oxford) and later gave dustings to Mt Ruapehu and Taranaki.

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MONTHLY WEATHER NOTES FOR CHRISTCHURCH - AUTUMN 2008

MARCH

Most of this month was settled for Christchurch and Canterbury, with below normal rainfall. The only unsettled period was during the first three days, when a complex trough crossed the country with rain at times in Canterbury. Cold southerlies from late on the 2nd through the morning of the next day brought fresh snow to the Alps, including 15cm reported at Mt Hutt. The only other weather of note was a brief period of southerly gales on the afternoon of the 9th, which caused some damage in parts of the city. There were some warm summery days during the month, especially on the 19th, when record maximums were recorded in many places in mid and South Canterbury.

APRIL

Apart from a thunderstorm with heavy hail (thanks to a cold front and strong southerly) on the evening of the 1st, the first half of the month was relatively settled, with only a few weak fronts crossing over. From the 15th-17th, a complex low pressure system crossed NZ, with some light rain at times in Christchurch. This was followed by a cold disturbed south to southwest flow; only a few brief showers affected the city on the 18th, but by early the next morning, the showers were more frequent with some thunder and hail. Snow fell on higher Banks Peninsula hills, but was reported as low as about 250 metres in the Oxford Area and near Amberley.

Settled weather returned from the 19th, but an active trough moved the South Island from the Tasman Sea by the end of the month. The 28th and 29th were marked by warm temperatures in Christchurch as a north to northwest flow prevailed. However, temperatures fell on the 30th as a colder southerly flow developed, with rain by evening.

MAY

The month kicked off with an unusually early wintry outbreak, and the rest of the month continued colder than normal. A low moved to the east of Canterbury on the 2nd, strengthening a southerly flow over the South Island. In Christchurch, this brought rain, hail and sleet (initially some thunderstorms nearby) to the city that night, with heavy snow on the Port Hills above about 200 metres. Rain and hail showers continued until the following afternoon.

For the remainder of the month, a predominance of onshore airflows (often southerly) resulted in colder than normal temperatures persisting. Precipitation, though, was no more than occasional drizzle. Nights were often frosty during the fine breaks.

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