December 2013: air still dry

The daily weather logWeather log December 2013.

The month began cool, including two nights at 6.9°, the coldest December nights in this record. Later it became very warm, with one night of 24.0° and one day of 40.2°. Spells of sunny weather were separated by five rainy days.
The relative humidity on the afternoon of the 29th was the record low value of 4%, as on 10/1/13 and 13/8/13. (These values may be wrong. Few hygrometers can be read so low.)

Comparing December monthsClimate December 2013

This December was warm: just slightly cooler than December last year, and very much warmer than those of 2010 and 2011. Extremely dry air brought a new record low December mean morning dew point of 8.8°.
Subsoil temperature (25.7°) remained 1.5° above normal.
The total rainfall of 45.6 mm was in the 28th percentile, well below the average of 74 mm. However, there are still no serious shortages in rainfall totals for more than one month.

The Year 2013

This was one of the warmer years in the new century (but much cooler than 2009). It had the driest air, with a mean early morning dew point of 5.4°, 1.5° below average. The air has become drier each year since 2010.

This year also had the highest subsoil temperature: 22.1°, 1.9° above average.
Extremely high rainfall in June (98mm) was balanced by very low rainfall in August (6.4mm) and October (15mm), for a low annual total of 576 mm, in the 37th percentile.


Data. Rainfall data is from Manilla Post Office, courtesy of Phil Pinch. Temperatures, including subsoil at 750 mm, and other data are from 3 Monash Street, Manilla.

Cloudy December 2010; cloudy year

The daily weather log

Weather log December 2010

December moved further into the cool, cloudy, humid and wet part of the climate cycle that Dorothea Mackellar called “Flooding Rains”. Nearly all days were cooler than normal, the 19th by as much as 12°. Some nights were also cool, the 21st being 10° below normal.
The highest rainfall reading of 26.4 mm came early in the month. The total of 113.8 mm came in 15 rain days. In 126 years, only six months have had more than 15 rain days. No month ever had more than the 18 rain days of June 1950.

Comparing December months

Climate December 2010

Both the mean daily maximum temperature (28.1°) and the mean daily mean temperature (22.2°) were the lowest for December on this 12-year record. The mean daily temperature range (11.7°) was also a record low value. The mean subsoil temperature (22.7°) was the lowest December value since 1999.
There were 58% cloudy mornings, nearly twice the normal percentage..
The rainfall of 113.8 mm is in the 82nd percentile for December, far above the long-term average of 74 mm. Totals for groups of 2-, 3-, and 4-months are now all above the 90th percentile.

The year 2010

The rainfall for the year was 719 mm. This is well above average, in the 64th percentile, but the years 2004, 2007, and 2008 were just as wet. Most remarkable is that the number of rain days in the year, 112, was the highest ever. The average year has 69 rain days, and the year with the fewest rain days (38) was 1898.
The year was by far the cloudiest in 12 years: half the mornings were cloudy, when normally only one-third of them are. Every month was cloudier than usual.
With the cloud came remarkably even temperatures. Taking average values, the daily maximum temperature (24.6°) was a degree cooler than usual, the daily minimum temperature (11.3°) was a degree warmer than usual, and the daily range of temperature (13.3°) was two degrees narrower than usual.


Data. Rainfall data is from Manilla Post Office, courtesy of Phil Pinch. Temperatures, including subsoil at 750 mm, and other data are from 3 Monash Street, Manilla.