NEW ZEALAND WEATHER. BRIEF REVIEW OF THE WEATHER WINTER 1988 (Fig. 1)

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1 Weather and Climate (1989) 9: NEW ZEALAND WEATHER BRIEF REVIEW OF THE WEATHER WINTER 1988 (Fig. 1) Rainfall for winter was above normal in central highcountry regions of the North Island, Wanganui, Manawatu, along the west coast of the South Island, in Southland, Otago and inland highcountry areas of Canterbury. The wettest regions were Manawatu, South Westland and inland areas of Southland and Otago, where rainfall totals ranged between 150 and 190 percent of normal. It was drier than usual in all regions of New Zealand which were sheltered from the west and south-west. Rainfall was less than 60 percent of normal in much of Canterbury and as low as 50 percent of normal in coastal areas of North Otago. The mean temperature for New Zealand, calculated from 7 indicator stations (one of which goes back to 1853) was 9.1 C. This was 1.0 C above normal and was the third highest recorded. The warmest winter was that of 1984 when 9.4 C was recorded. In some places in central Otago and inland Canterbury mean temperatures were as high as C above normal. One of the major factors which contributed to the warmer weather was that there were fewer periods of very cold southerly condi ,6 1.0 SUNSHINE Pereentege of Normal ( ) WINTER Nme Zei land Meteorological Service Seimrture from M k s, ) WINTER ((IV))TEMPERAXURE Neer Unload Mettorotogmal Service 1 Fig. 1: Winter Rainfall (a) maps based on observations from 46 stations; temperature (b) departure maps based on observations from 43 stations; sunshine (c) based on observations from 33 stations.

2 30 ISO Conditions were generally windier than usual in the south of the North Island, and over much of the South Island, especially in Southland and Otago where windy days (gusts of at least 34 knots) occurred with almost twice the normal frequency. Strong winds (recorded by radar balloon flights) at midday, over Southland occurred on 44 percent of the days. This was the most since 45 percent in MONTHLY SUMMARIES JUNE-AUGUST 1988 RAINFALL of N o m, ( , WINTER 1988 Mow notiond ifetoorolcoficol Service tions than is usual, and these lasted for only brief periods of time. For example, the average number of days in winter ( ) with maximum temperatures of less than 8.0 C recorded at Kelburn is 9. This winter there were only 2. Only one ground frost was recorded at Kelburn (the normal is 2), which was the least since 1971 when there were none. This made the winter the second least frosty at Kelburn since records began in Cloudier than normal conditions were recorded in all western regions of the North Island north of Horowhenua and along the west coast of the South Island. The winter was rather cloudy in Auckland and Waikato. Hours of bright sunshine were only 76 percent of normal at Auckland City, which was the lowest since records began in 1963, and 77 percent of normal at Ruakura which was the lowest since records began in Sunnier than normal conditions prevailed in eastern regions of New Zealand from Hawkes Bay to South Canterbury. Just over 120 percent of normal sunshine was recorded at Christchurch Airport, making it the sunniest since June was warmer than usual. Mean daily temperatures were at least 0.5 C above normal throughout much of New Zealand. They were C higher in places north of Auckland, in western Bay of Plenty, western regions of the North Island from Waikato to Manawatu and in inland Canterbury. A very low air temperature of -8.4'c was recorded at Dunedin Airport on the morning of the 16th, together with a C ground frost. This was the lowest air temperature recorded there in any month since records began in Temperatures as high as 22.5 C were recorded at Christchurch Airport in warm dry northwesterly conditions on the 8th. This was the highest in 33 years of records. A maximum temperature of 24.2 C was recorded at Napier Airport in similar conditions on the 19th, which was the highest measured since records began in Rainfall was only percent of normal in Hawkes Bay and northern parts of the Auckland region. It was also drier than normal in Northland, other parts of Auckland and in eastern regions of New Zealand sheltered from the south-west, where totals ranged from percent of normal. Rainfall was percent of normal in Manawatu, along the West Coast of the South Island and in Central Otago. Totals were almost twice normal in South Westland. Only 378 mm (59% of normal) was recorded at Kelburn in the 6 months ending 30 June. This was the lowest since 287 mm in 1939 and the 9th lowest since recording began in Heavy rain, totalling 153 mm, was recorded at Glenorchy (near Awakino) in the 24 hours to 9am on the 8th. Five houses were evacuated and hundreds of hectares of farmland were flooded due to heavy rain in the same area on the 19th. On

3 the same day heavy rain caused slips and closed the Manawatu Gorge road for a time. Hours of bright sunshine were percent of normal over much of the South Island. In Canterbury and Southland they were as high as 125 percent of normal. Over the North Island it was cloudier than usual (especially in Horowhenua and Manawatu with percent of normal hours). The region from East Cape to Poverty Bay had near normal sunshine. On the whole, July was wndier than average over much of New Zealand, especially in the far south. Strong winds occurred for 37 percent of the time, for the period 1 January to 31 July over the south of the South Island. This was equal to 37 percent in the same period in 1987, and was the highest since records began in Rainfall was above normal in eastern regions of the North Island north of Wairarapa, high country regions, Southland, much of Otago and in most regions exposed to the west or south-west. It was very wet in Auckland City, western Manawatu, Fiordland and Southland, with totals being approximately twice normal (and up to three times normal in Central Otago). A total of 154 mm (214% of normal) recorded at Invercargill Airport was the highest recorded there in July, since records began in Heavy rain was recorded in Auckland on the 17th, where in most places totals for the 24 hours to 9am on the 18th ranged from mm, with some surface flooding. Flooding also occurred in Gisborne when over 100 mm was recorded in the 48 hours to 9am on the 18th. A total of 304 mm was recorded at Coromandel in the 72 hours to 9am on the 18th; 186 mm having been recorded in the 24 hours to 9am on the 17th. A total of 31 mm was recorded at Kelburn, Wellington, in moist north-west conditions, in the hour from just before midnight on the 23rd until just before 1 lam on the 24th. This equalled the all time record for one hour's rain at Kelburn. Heavy rain was recorded again in Northland, Auckland, Bay of Plenty and Manawatu on the 24th. Most totals to 9am, on the 25th ranged from mm. A state of civil emergency was declared in Palmerston North, af- ter many homes were flooded. About 10 houses were seriously damaged by the water and more than 100 were evacuated. The flood was reported as being the worst affecting the region since 1976 and damage was estimated at $2-3 million. Drier than normal conditions were recorded in eastern regions of the South Island from Kaikoura to North Otago. In these regions totals ranged from percent of normal. Only 8 mm was recorded at Oamaru. For the 7 months from 1 January to 31 July, only 200 mm had been recorded at Christchurch Airport. This was the least ever recroded for that period since records began in 1944, being only 50 percent of normal. Temperatures were much warmer than usual over most of New Zealand in July. Mean daily temperatures were C above normal in many regions. They were about 2 C above in Waikato, Manawatu and eastern regions of the South Island (north of Southland and coastal Otago). In some inland areas of Canterbury and Otago they were as much as 3 C above normal. The mean temperature for New Zealand, calculated from 7 indicator stations, was 8.9 C. This was 1.3 C above normal and was the highest on record (equal with 8.9 C in 1985). The mean temperature recorded at Kelburn was 9.7 C (1.3 C above normal), which was the second equal highest since records began in Other Wellington records indicate that, for Kelburn, it was likely to have been the second highest since The highest was 9.8 C in July The mean temperature at Christchurch of 7.1 C (2.0 C above normal) was the highest since records began in Hours of bright sunshine were below normal in most western regions of New Zealand. They were very low in Auckland, Bay of Plenty, Taranaki, and central regions of the North Island, where they ranged from percent of normal. Only 98 hours (74 % of normal) were recorded at New Plymouth Airport, which was the lowest since records began in 1939). It was sunnier in eastern regions, from Hawkes Bay to North Canterbury and in Wellington. Hours of bright sunshine were up to 130 percent of normal in Wairarapa. August was another windier than average 31

4 32 month over much of New Zealand, especially in the far south. Strong winds occurred for 50 percent of the midday readings over the south of the South Island, which was the highest in August since records began in The high frequency of strong winds was due to the lack of anticyclonic conditions; persistent west to south-west airstreams affected t h e region. Strong winds occurred for 39 percent of the midday readings, for the period 1 January to 31 August over the south of the South Island. This was the highest frequency there since records began in Light snow was recorded in eastern regions of the South Island in cold southerly conditions on the 1 lth. Cold south-west winds following the passage of a cold front over New Zealand on the 19th also brought snow to Otago. Another cold southerly airstream moved on to the South Island on the 24th and covered the whole country on the 25th, bringing more hail and sleet to Wellington and also snow, which lay for a time in many eastern regions of the South Island. Similar conditions occurred on the 30th with snow in Southland and Otago, which later spread northward. A light scattering of snow fell on the Rimutaka Range (east of Wellington), and sleet was reported in the Wellington suburbs of Newlands and Karori in the afternoon. Rainfall totals ranged between percent of normal in Auckland, Taupo, central high country regions of the North Island, south Westland, Fiordland and Southland. Totals ranged between percent of normal i n Northland, eastern regions o f the North Island, Wellington, Marlborough, Nelson and coastal areas of Canterbury and Otago. Over much o f New Zealand August was warmer than usual. Mean daily temperatures were 0.5 to 1 C above normal in many regions. They were as high as 1.5 C above normal in some areas of inland Canterbury. Maximum temperatures as high as 22 C were recorded in Hawkes Bay in north-west conditions on the 24th. of normal. I t was especially sunny in Christchurch where a total of 190 hours (134% o f normal) was recorded, which was the second equal sunniest August since records began in SPRING 1988 (Fig. 2) Rainfall f o r Spring was below normal i n East Cape, Gisborne and Marlborough. Particularly dry conditions prevailed in eastern regions of the South Island, as f a r south as Otago, where totals were only percent of normal. Only 55 m m (41% o f normal) was recorded for the season at Christchurch Airport, which was the lowest since 45 mm (34 % of normal) in 1949; records began in The low rainfall in eastern regions was the resut of unusually persistent north-west conditions. North-west winds (recorded by radar balloon flights) over the south of the South Island, at midday, occurred on 58 percent of the days. This was the most, equal with 1978, since records began in These also contributed to above normal rainfall in western regions of R A I N FA L L Poreento.o o f N o r m a l ( ) Hours of bright sunshine ranged from percent of normal in Northland, Auckland and western regions of the South Island. It was sunnier in all eastern regions of New Zealand, and Manawatu, Horowhenua, Wellington and Nelson. In these regions hours of bright sunshine were mostly percent SPRING Now Z e a l a n d l i e t o o r o l o g o c o l S o f n o t Fig 2: Spring 1988 Rainfall (a) departure maps based on observations from 46 stations; temperature (b) departure maps based on observations from 46 stations (c) based on observations from 23 stations.

5 33 The mean temperature f o r New Zealand calculated f r o m 7 indicator stations w a s 13.3 C (1.2 C above normal) and was the highest since 13.2 C recorded in 1893, and also the highest since records began i n Mean temperatures were 1-5 C above normal i n many regions, but they were C above normal in eastern regions of the North Island and i n Marlborough and Canterbury. Mean temperatures in South Westland and Fiordland were about normal Hours of bright sunshine were rather low (only 75-85% of normal) due to the unsettled conditions which affected western regions, Northland a n d Auckland. Elsewhere t h e y were near normal. MONTHLY SUMMARIES SEPTEMBER-NOVEMBER 1988 T E M P E R AT U R E 8., r t u r. K o r m n a l SPRING New Z e a l a n d h d e L o o r o l o p e a l S a r t. X SUNSHINE Peacoats,. o t 0 0 ) SPRING I N A ) ) New Z e a l a n d i d e t e n i a l o g i c I N e, e i n a 1 New Zealand south of about Auckland. Record high spring rainfall (as much as twice normal) was recorded in much of South Westland and Fiordland. September was, i n m a n y places, much cloudier and warmer than normal. A major event in September was that of flooding. Heavy rainfall affected Southern Hawkes Bay and Northern Wairarapa on the 1st and 2nd. In many places totals of mm were recorded in the 48 hours to 9am on the 3rd. These conditions were associated with a strong moist easterly airstream which covered the area, as a slow moving depression crossed the North Island to the north of the regions. Flooding was extensive i n f l a t low lying f a r m l a n d a r e a s i n t h e n o r t h o f Wairarapa. A substantial amount of rain was also recorded in Greymouth, on the 12th and 13th, in moist northwesterly conditions, when a particularly active trough affected the area. Heavy rain, totalling 111 mm at Greymouth and as much as 200 m m in the high country, was recorded in the 24 hours to 9am on the 13th. This caused the Grey River to burst its banks and severe flooding occurred in Greymouth. About 200 houses were flooded and the flood was noted as being the worst ever recorded there. A notable feature o f the month was the absence of cold southerly airstreams. There were few anticyclonic events and westerly airstreams were rather persistent. Combined, these conditions contributed to make September a much warmer month, with very little

6 34 rainfall in eastern regions of the South Island and more wind than usual over much of the country. Strong winds occurred for 38 percent of the midday readings, over the south of the South Island, for the period 1 January to 30 September, which was the highest frequency there since records began in Rather dry conditions prevailed in Canterbury and North Otago, due to persistent westerlies. Only 1 m m was recorded a t both Oamaru Airport and Timaru Harbour. These were the lowest since records began in 1941 and 1943 respectively. Many other places in Canterbury and North Otago recorded less than 10 mm. Only 243 mm was recorded for the year t o 30 September a t Christchurch Airport. This was the second driest for that period; the driest was in 1982, with 237 mm. The six months ending September, at Christchurch Airport, with 164 mm was the driest for that period since records began in Rainfall totals were about twice normal in Hawke's Bay, much o f Manawatu and i n Fiordland. As much as 1085 mm was recorded at Milford Sound. This was the second highest since records began in The total of 148 mm (231% o f normal) recorded a t Napier Airport was the highest since records began in Rainfall totals o f percent o f normal were recorded in southern Wairarapa, Wellington, Westland and Southland. As a whole, New Zealand experienced the warmest September ever recorded. The mean temperature, calculated from 7 indicator stations was 11.9 C which was 1.6 C above the normal. The previous record was 11.6 C i n M e a n d a i l y maximum temperatures were C above n o r m a l i n Gisborne, Hawkes Bay and north Canterbury. At Christchurch Airport they were 3.2 C above (being even higher than the normal for October) and the highest since records began i n Temperataures were near normal in Fiordland and about 1 C above in Westland. In most other places they were C above normal. A grass minimum temperature o f -8.5 C was recorded at Christchurch Airport on the morning of the 9th. This was the lowest since records began in Once again i t was cloudier than normal in Northland a n d Auckland, where i n m o s t places it was the fifth consecutive month with below normal sunshine and the seventh month with less than normal sunshine this year. In all other regions, except those to the east of the ranges (excluding Southland) it was also a rather cloudy month. Record l o w hours o f bright sunshine were recorded not only i n Auckland, but also i n many places further south and west o f the ranges o f the North Island. Only 90 hours (57% o f normal) was recorded at Auckland City and 105 hours (65% of normal) at Kelburn, being the least since records began in 1962 and 1930 respectively. October was, in most places, a rather windy and warmer than normal month. A marked feature of the weather in October, was an almost continuous series of west or north-west airstreams which affected New Zealand. These were due to a steady passage of anticyclones which passed to the north of the country, and also many deep depressions which tracked to the south. The only significant, though brief break in this regime, was on the 21st, when a trough of low pressure, which had moved eastward on to New Zealand, was followed by cooler southerly conditions. The persistent w e s t t o north-west a i r streams associated with the generally large pressure differences from north to south contributed t o making October rather windier than average in many places. There were 29 days with wind gusts of at least 63km/hr (34 knots) recorded a t Kelburn, which was the most for any month, for at least 21 years. A total of 13 days were recorded at Christchurch Airport (the most since an equal number of days in October 1968), and 22 days at Invercargill Airport, which was the most f o r a t least 35 years. North-west winds were recorded for 64 percent of the midday observations at Invercargill, which was the third highest frequency in October in 32 years of record. Mean sea level pressures were excrptionally low over the south of the South Island. The average 9am reading for the month at Invercargill Airport was only hpa, some 15.2 hpa below average, and the lowest for any month since records began in They were also very low over the North Island, where Kelburn the average of hpa (9.2 hpa below a verage) was the lowest recorded in October since Rainfall totals were above normal in most western regions o f New Zealand south o f

7 Auckland, in Nelson and in much of Southland. Rainfall was about twice normal in Buller and Westland, but it wan particularly wet in South Westland and Fiordland, where in some places totals were three to four times normal. Rainfall totalling 1351 (373% of normal) recorded at The Hermitage was the highest in October since records began in A total of 1912 mm (351% o f normal) was recorded at Milford Sound, which was also the highest recorded there i n October since records began in This also appears t o be the highest rainfall total ever recorded in October in New Zealand. A total o f 3709 m m was recorded there in the last three months, which is also another record for this period in New Zealand. Rather dry conditions continued to prevail in drought affected Canterbury and North Otago. Some stations recorded very little rain over the t h e months, August-October. Some of these were 22 mm at Oamarn (township), 25 mm at Timary Gardens and 29 mm at Palmerston North. Only 26 m m was recorded at Oamaru Airport, which was the lowest in 48 years of record. A total of 35 mm at Middlemarch was the lowest since 32 mm in 1929, and 36 m m recorded a t Waimate was the lowest for this period since recorded began in In October, rainfall was, in eastern regions from Gisborne to Otago (including Wellington), only about percent of normal. The 15 mm (22% of normal) recorded at Gisborne Airport was the lowest in 52 years of record. Only 5 mm (8% o f normal) was recorded at Kaikoura, which was the lowest in 40 years of record, 8 m m (16% o f normal) a t Timaru Gardens, 9 m m (21 % o f normal) at Christchurch Airport, and 10 mm (26% of normal) at Oamaru Airport. A total of 23 mm (46% of normal) was recorded a t Dunedin Airport. This was equal to 23 mm in 1963 when records began. Rainfall was about percent of normal in Bay of Plenty and percent of normal in Northland. Only 252 mm were recorded in the year to 31 October at Christchurch Airport, which was the lowest for that period since records began in Once again much of New Zealand experienced another warmer than normal month. The average New Zealand temperature was 13.2 C (1.1 C above normal). This was the fifth warmer than normal month in a row, and the 35 warmest October since 1962, when 13.4 C was recorded. M e a n d a i l y temperatures w e r e about 2-3 C above normal in eastern regions of both islands. They were 3.5 C above a t Napier Airport, 3.2 C above at Kaikoura and 2.9 C above a t Christchurch Airport. Mean daily maximums of 21.7 C (4.9 C above normal) and 22.8 C (4.8 C above normal) were recorded a t Christchurch and Napier Airports respectively. These were equivalent to midsummer mean daily maximum temperatures and were due mainly to the high frequency of north-west days. I t was cooler than usual though i n Westland and Fiordland, where mean temperatures were about C below normal. Temperatures werenear normal i n Southland and central Otago. Elsewhere they wre C above normal. Again, it was cloudier than normal in western regions of New Zealand, south of Auckland. Hours of bright sunshine were less than 70 percent of normal along the West Coast of the South Island. Hours o f bright sunshine were percent of normal in Northland, Auckland, B a y o f Plenty, Gisborne a n d Hawkes B a y. Elsewhere t h e y w e r e n e a r normal. A break in the persistent west to north-west conditions occurred after the f i r s t week o f November. Northeasterlies were more frequent than usual in November over the north of the North Island. Rainfall totals were percent o f normal in much of Bay of Plenty and Nelson. About twice normal rainfall was recorded at Kawerau. It was a little wetter than normal in Taranaki, Wanganui, Wellington and Wairarapa. Totals were less than 70 percent of normal in Auckland, Gisborne, inland areas of Canterbury and in southern Otago. Only 27 mm (36% of normal) was recorded at Lake Coleridge. In other areas o f Canterbury and Otago they ranged from percent of normal, which helped a l i t t l e t o relieve t h e prevailing drought conditions. A t the end of November only 291 m m (49% o f normal rainfall) had been recorded at Christchurch Airport, which was the lowest since records began in Temperatures were again much warmer than normal over New Zealand. The average New Zealand temperature was 15.2 C (1.4 C above normal), being equal to November The only other warmer November was that of

8 , with 15.3 C. Mean daily temperatures were 1 C above normal in most places, 2 C above in western regions of the North Island, in Canberbury and Otago and 3 C above normal at The Hermitage (Mt Cook). A maximum of 31.3 C was recorded at Napier Airport, in fine northwesterly conditions, on the 4th. Rather cloudy conditions prevailed in Northland and Auckland (where totals were only 70% of normal). It was also cloudier in Waikato, Bay of Plenty and Gisborne, where totals ranged from percent of normal. It was sunnier in the Central Otago, Mackenzie Basin area, where totals ranged from percent of normal. Elsewhere they were near normal. Many thanks are due to the New Zealand Meteorological Service for providing the climatological data from which this summary was compiled. S. Burgess