September 2007 Cooler, Wetter

Tawa’s climate during September 2007 was cooler and wetter than the previous two Septembers. Low cloud and fog were recorded on more days last year but otherwise, apart from September 2003 which was particularly wet, September 2007 was typical for the time of year.

September 2003 started with steady rain, culminating in a torrential downpour on the 3rd. Northerly and southerly conditions alternated until the 14th. A thunderstorm woke anyone who had slept in on the 16th, and peak-hour evening commuters were treated to a thorough soaking with a sudden downpour just before 6 p.m. A very low pressure system (964 hPa) off Southland and a high pressure system lurking off North Cape caused severe gale winds on the evening of Thursday 18th. Another 5 minute thunderstorm on the evening of the 20th was followed by a frost on the morning of the 22nd, strong northerlies on the 26th and 27th and a 10 minute hailstorm on the evening of the 29th.

September 2004 was more benign. Workers were greeted with a frost on the morning of the 7th, and conditions were unremarkable until steady rain set in on the 12th, punctuated by intermittent downpours on the 13th. Rain then ceased until steady rain set in for most of the 16th. Dry conditions then prevailed, apart from drizzle on the 19th, 23rd and 25th. A ground frost was noted on the 26th, steady rain commenced on the 28th and a strong southerly arose later in the day. Calmer conditions returned with sunny skies the next day and the month ended with a gusty northerly and misty rain on the 30th.

September 2005 started quietly with generally calm conditions until the middle of the month, apart from a gusty northerly on the 2nd. Gusty northerlies on the 16th increased in strength and brought steady rain the following day until the wind changed to a gale force southerly late on the 18th. Temperatures dropped rapidly and the steady rain on the evening of the 19th was punctuated by hail. Conditions eased and a frost greeted early risers on the 21st. The remainder of the month was unremarkable, apart from a gusty nor’wester on the 25th and steady rain with low cloud and a northerly on the 27th.

September 2006 was a gloomy month with low cloud or fog on eight days. Strong winds from northerly quarters dominated the first 4 days of the month with hazy conditions and low cloud on the 3rd and 4th. Alternating periods of drizzle and showers culminated in a foggy morning on the 7th. Light winds prevailed until a gusty northerly arrived on the 15th.

The wind alternated between north and northwest for several days until changing to the northeast briefly on the 19th. Later in the day, it changed back to the north and increased in strength bringing showers, low cloud and mist. The wind eased slightly until the 22nd when it gained strength and brought low cloud again. The 25th was especially gloomy with fog and drizzle which closed Wellington International Airport. Sunny conditions returned on the 28th, seeing off the drizzle and misty conditions of the previous 2 days.

September 2007 brought welcome relief from cool winter temperatures, with a five day run of bright, warm days from the 19th to the 23rd, when daily maximums got to high teens or early twenties. Nevertheless, the maximum of 21.5 °C on the 20th was lower than 2005’s warmest of 22.1 °C (September 13th), while beating September maximums for 2003, 2004 and 2006.

The average temperature for the month was lower than that calculated for the previous two Septembers, and rainfall was higher. Light snow was recorded on the Rimutaka Hill on the afternoon of the 5th and snizzle (snowy drizzle) was seen to fall in Tawa. Otherwise it was a typical September with short runs of still days punctuated by strong northerlies and chill southerlies.

Automatic and manual readings taken at Tawa since 2003 can be summarised as follows:

The lowest September temperatures were 1 °C (2003), 0 °C (2004), 1.2 °C (2005), 1.6 °C (2006), 0.0 °C (2007).
The average daily low temperatures were 8 °C (2003), 7 °C (2004), 8 °C (2005), 9 °C (2006), 8 °C (2007).
The highest September temperatures were 21 °C (2003), 17 °C (2004), 22.1 °C (2005), 18.7 °C (2006), 21.5 °C (2007).
The average daily high temperatures were 15 °C (2003), 14 °C (2004), 16 °C (2005), 15 °C (2006), 15 °C (2007).

Average temperature: 12.1°C (2005), 12.2°C (2006), 11.3 °C (2007).
Average humidity: 83% (2005), 85% (2006), 82% (2007).

Days with frost: 1 (2003), 2 (2004), 1 (2005) none (2006), 1 (2007).
Days with rain: 23 (2003), 11 (2004), 9 (2005), 10 (2006), 11 (2007).
Days with thunderstorms: 2 (2003), none (2004), none (2005), none (2006), none (2007).
Days with hail: none (2003), none (2004), 1 (2005), none (2006), none (2007).
Days with strong winds: 9 (2003), 3 (2004), 4 (2005), 8 (2006), 6 (2007).
Low cloud or fog days: 2 (2005), 8 (2006), 3 (2007).
Rainfall: 29 mm (2005), 26 mm (2006), 45 mm (2007).

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