Spring 2007 climate much as usual

Weather log spring 2007

The daily weather log

As sometimes happens, temperatures did not rise in September until late in the month. They then rose to several degrees above normal and stayed there until the end of October. Early November was very cool, and mid-November warm. The daily temperature range increased in dry periods and decreased in rainy periods.
There were two late frosts below 2.2° in September.

Only 2.2 mm of rain fell in September. Much more fell later, in short wet spells around October 12th and 26th, and November 7th and 24th. The two best daily falls were 17 mm each. Total spring rainfall was 122 mm, falling on 23 rain days.

Very cloudy or overcast skies became common in November.

Comparing spring seasons

Although each month this spring had unusual temperatures, the three months taken together did not. Daily maximum, minimum and mean temperatures for the spring, as well as the daily temperature range (16.0°), were all normal. In the extreme drought of spring 2002, the values had been two degrees higher, and the daily temperature range 17.1°. The spring of 2001 had the lowest temperatures in this record.

Two frosts this spring compare with three on the average. Spring 2004 had 10 frosts, including one in mid-October, and one on 3rd November!

Spring rainfall in 2007 (122 mm) fell 44 mm short of the long-term average (166 mm), due to September being 39 mm down. October was only 6 mm down, and November 2 mm up. Spring rainfall averaged over the last nine years is above the long-term average, because the droughty spring of 2002 is more than balanced by the very wet springs of 1999, 2000, and 2005. These were in the ninth decile for spring rainfall.

Climate spring 2007

Data. Rainfall data is from Manilla Post Office, courtesy of Phil Pinch. Dew Point values before August 2005 are from Tamworth Airport 6 am data supplied by the Bureau of Meteorology. Temperatures, including subsoil at 750 mm, and other data are from 3 Monash Street, Manilla.

Cold days in 2007 winter

Weather log winter 2007

The daily weather log

The temperature trends this winter look like a roller-coaster.
June had daily maximum temperatures about four degrees below normal. Two miserable days had maxima eight degrees below. Meanwhile, minimum temperatures were normal.
Maxima returned to normal in early July but, by that time, nightly minimum temperatures were well above normal. All temperatures then plummeted, losing 8°: by mid-July both maxima and minima were about 5° below normal.
By the end of July and early August maxima and minima had shot up again to well above normal. Next, maxima went up while minima went down, making the daily temperature range very large. This temperature range then collapsed to become very small. The winter ended with temperatures near normal.
The high ground in Manilla had 38 frosts* in June, July, and August. The nine-year average is 45. Seventeen nights went below zero and two nights below -4°.
There was quite a lot of rain, but not much fell in July. The amounts were 65 mm in June, 9 in July, and 81 in August. June was above average, July in the second decile, and August in the ninth decile.
There were ten rain days in June, seven in July, and five in August. One event was remarkable: rain fell continuously for more than 36 hours from the morning of 19th August, to a total of 55 mm.
Skies were overcast (8/8) around the periods of rain. In contrast, there were long sunny spells (0/8 or 1/8) in mid-July and the first half of August.

Comparing winter seasons

The average daily maximum temperature was the coldest in the last nine winters. At 16.6°, it was 1.6° below average.
Although the nights of 2005 were warmer, this winter also had warm nights. At 3.4°, they raised the daily mean temperature up to 10.0°, close to normal.
The daily temperature range in winter in Manilla is usually 15.4°. This winter’s cool days and warm nights made its daily range the lowest in these years. It was only 13.2°, typical of places nearer to the coast, such as Singleton.
The winter that stands out is 2002. With the warmest daily maxima (19.2°) and the coldest daily minima (1.7°) it had the remarkably high daily range of 17.5°. Such a range is found mainly in desert areas – which Manilla was at the time!.

Winter is the driest season in Manilla. The average winter rainfall, 125 mm, is just over half the average summer rainfall (227 mm).
This year’s winter rainfall (155 mm) was above average, and near that of 2005 (157 mm). None of the winters on the graph is far from the average except 2002.
The very dry winter of 2002, at 44 mm, was the ninth driest on the 124-year record. It was the driest since 1982 and 1972 (both 32 mm).
The graph just misses the very wet winter of 1998, nine years ago. Split Rock Dam suddenly filled up for the first time. At 304 mm, that was the second wettest winter on record. Only the winter of 1920 was wetter, with 318 mm.
The graph shows the peracentage of mornings with more than four octas of cloud. The winter average is 31%.
This winter, and winter 2000 were the cloudiest. The insulating blanket of cloud stopped the days from getting warm, and the nights from getting cold.
The winter of 2002 had the fewest cloudy days, another sign of how like a desert it was then.

Climate winter 2007

*Frost: A frost occurs when the temperature on the grass is below zero, causing water to freeze in the leaves. Not many stations measure grass temperature. My rule-of-thumb is to declare a frost if the temperature in the thermometer screen (at 1.5 metres) is below +2.2°.

Data. Rainfall data is from Manilla Post Office, courtesy of Phil Pinch. Dew Point values before August 2005 are from Tamworth Airport 6 am data supplied by the Bureau of Meteorology. Temperatures, including subsoil at 750 mm, and other data are from 3 Monash Street, Manilla.