Tuesday, 1 October 2002
Record strong westerlies for September In many eastern areas: sunny and unusually warm with below average rainfall In the west: high rainfall, cloudy, wet and unsettled
Very strong west to north westerlies during September resulted in dry, sunny, windy, and unusually warm conditions, with 75 percent (three quarters) or less of normal rainfall, in many eastern areas of both islands. In contrast, wet, cloudy and unsettled conditions occurred on the West Coast, including coastal Southland, Southern Lakes and alpine areas, as well as Taranaki and King Country. Significant soil moisture deficits are now apparent in central Marlborough and soil moisture levels are lower than normal in other parts of the east of the South Island, particularly in South Canterbury, and northern and Central Otago.
The national average mean temperature of 11.1°C was 0.7°C above normal. However, mean temperatures were about 2.0°C above normal in areas between Kaikoura and mid Canterbury, and near average in Westland. Record high mean daily maxima (3°C above normal) occurred throughout Canterbury, equivalent to late October conditions. Sunshine totals were at least 110 percent of average in many eastern regions from Gisborne to Southland. Lower than normal sunshine hours were recorded in many western regions from Taranaki to Fiordland.
September’s climate pattern was dominated by well below average pressures over the Southern Ocean, with more frequent anticyclones northeast of New Zealand. West to northwest airflow prevailed over New Zealand with its highest frequency for any month since October 1988, and the highest for any September since measurements began in 1948, producing the marked west–east climate contrasts.
Unusually warm in the East
Mean temperatures were at least 1.0°C above normal in many eastern areas from Gisborne to Otago, being about 2.0°C above normal in some areas between Kaikoura and south Canterbury. Temperatures ranged from 0.5 to 0.9°C above normal in eastern Northland, Waikato, and the western North Island from south Taranaki to Wellington, and were slightly above average in most other regions. They were near average in Westland.
Near or record high mean September temperatures were recorded at:
| Location | Mean temperature | Departure (°C) | Records began | Comments |
|---|---|---|---|---|
| Napier Airport | 12.8 | +1.4 | 1974 | 2nd highest |
| Napier, Nelson Park | 13.9 | +1.9 | 1870 | Well above normal |
| Whakatu | 12.5 | +1.5 | 1983 | Equal highest |
| Blenheim Research | 12.2 | +1.5 | 1932 | 3rd highest |
| Kaikoura | 12.1 | +2.0 | 1964 | Equal highest |
| Christchurch Gardens | 12.0 | +2.0 | 1864 | Equal highest |
| Lincoln | 11.2 | +2.0 | 1881 | Well above normal |
| Dunedin Airport | 10.0 | +1.4 | 1963 | 3rd equal highest |
| Dunedin, Musselburgh | 11.1 | +1.8 | 1947 | Highest |
Daytime maxima were between 2.0 and 3.0°C above normal in many eastern locations from Hawke’s Bay to Otago.
Near or record high September mean daily maximum temperatures were recorded at:
| Location | Mean temperature | Departure (°C) | Records began | Comments |
|---|---|---|---|---|
| Napier, Nelson Park | 19.5 | +2.8 | 1870 | Highest |
| Hanmer Forest | 17.0 | +2.9 | 1906 | 3rd highest |
| Kaikoura | 16.3 | +2.8 | 1964 | Highest |
| Christchurch Gardens | 18.1 | +3.2 | 1864 | Highest |
| Winchmore | 16.7 | +2.7 | 1950 | Equal highest |
| Timaru Airport | 17.1 | +2.9 | 1962 | Highest |
| Dunedin, Musselburgh | 15.9 | +3.0 | 1947 | Highest |
Below average rainfall in many eastern regions, wet in the West
Rainfall was below average for the third consecutive month from Marlborough to north Canterbury, September totals being 75 percent or less of average in many eastern areas from Gisborne to Otago, and isolated areas of inland Southland. Rainfall was also 75 percent or less than average in eastern Northland, Waikato and western Bay of Plenty. The month was unsettled, with rainfall totals at least 125 percent of average in all South Island Alpine regions, Fiordland, coastal Southland, Southern Lakes and parts of Buller and Westland, as well as Taranaki and King Country.
Near or record September rainfall was recorded at:
| Location | September rainfall (mm) | Percentage of normal | Year records began | Comments |
|---|---|---|---|---|
| Middlemarch | 10 | 35 | 1931 | 2nd lowest |
| Milford Sound | 1139 | 206 | 1930 | 2nd highest |
| Queenstown Airport | 140 | 229 | 1968 | 2nd highest |
| Queenstown | 223 | 290 | 1871 | 2nd highest |
| Manapouri Airport | 202 | 174 | 1992 | Highest |
Sunny in the East, cloudy in the West
Sunshine and solar radiation totals were at least 110 percent of average in many eastern regions from Gisborne to Southland. However, totals were less than 90 percent of average in many western regions from Taranaki to Fiordland.
Highlights
Extreme temperatures
- The highest air temperature for the month was 24.7°C, recorded at both Darfield and Waimate on the 16th. The highest September air temperatures on record at these locations are 27.8°C and 30.0°C respectively.
- The lowest air temperature for the month was –5.9°C, recorded at Ranfurly on the 14th. The lowest September air temperature on record there is –6.9°C.
Significant Hail-storm
- Heavy hail fell in central Takaka just before noon on the 12th, with hailstones reported as “pea to moth-ball size”, lying 10cm deep in places.
- A localised, but rather heavy hail-storm occurred over Wellington’s eastern suburbs (of Mirimar, Kilbirnie and Lyall Bay) at about 7 am on 12 September, resulting in the temporary closure of the airport, due to icy conditions on the runway. Pea-size hail-stones lay a few centimetres deep in areas, some still present after 2 hours.
Intense rainfall
- Heavy rainfall at Milford Sound totalled 459 mm for the 48 hours to 9am on the 19th, of which 315 mm occurred in 24 hours.
Severe gales
- Severe northwest gales buffeted parts of Canterbury on the 22nd, resulting in damage to a number of properties. Wind gusts to 117 km/h were recorded at Rangiora and 115 km/h at Darfield.
Damaging frost
- Frost-fighting equipment, such as water sprinklers, windmills and up to 40 helicopters, was used to counter potentially damaging frost in vineyards in parts of Hawke’s Bay during the night of 25/26 September. Some areas reported damage to 10–50 percent of Chardonnay, Pinot Noir and Merlot vines. Whakatu recorded a grass minimum of –7.3°C, the lowest there in September since records began in 1983, with a screen minimum of –2.0°C the second lowest on record.
For further information, please contact:
Dr Jim Salinger – Principal Scientist, Climate NIWA National Climate Centre – Auckland Phone +64 9 375 2053 [email protected]
Stuart Burgess – Climatologist NIWA National Climate Centre – Wellington Phone +64 4 386 0569 [email protected]
Geoff Baird – Communications Manager Phone +64 4 386 0543 [email protected]
Acknowledgement of NIWA as the source is required.