Manilla’s Frosts to 2014

Graphical log of frosts

This post updates a similar one by including three more years to make a total of sixteen.

The Number of Frosts in Each Year

The first graph is a log of the number of frosts in each year. The pattern is different when counting all frosts or only severe frosts.
The log for all frosts had two periods of stable, medium numbers of frosts: from 1999 to 2003, and from 2008 to 2011. Three years had many frosts: 2004 (68), 2006 (70), and 2012 (69). The year 2007 had the fewest frosts (43) until beaten by 2013 (34).
In the logs for severe frosts below minus 2° or minus 4° in the thermometer screen, the drought year 2002 stands out as the most frosty by far. It had the coldest mornings: -5.1° on both the 2nd and 11th of July.

The Last Three Years

Monthly frosts in 2012, 2013, and 2014.

The second graph compares the mean seasonal pattern of frosts with the patterns for the three latest years: 2012, 2013, and 2014.
The frost season of 2012, which almost matched the record 70 frosts of 2006, began early and ended late. May had 13 frosts (like the 14 of 2006) and September had 10 (like the 8 of 2003).
The curve for the season of 2013 ( the new record fewest) was like that of a normal frost season, but lower.
The year 2014 was not very frosty, because the season began late, with no frosts in May and only nine in June.

Monthly frosts each year

Graphs showing the seasonal frost patterns for earlier years are copied here.







There is 2013 reserch on frost in NSW titled “Understanding frost risk in a variable and changing climate” reported here.
It is in GRDC Update Papers (Grains Research and development Corporation). The research is done by Steven Crimp and co-workers at CSIRO Climate Adaption Flagship.
Referring to the period 1960 to 2010,
“Over many parts of NSW the frost season length has broadened by as much as 40 days and the mean number of consecutive frost days has increased to 5 days.”

Frosty Dry September 2012

The daily weather logWeather log September 2012.

The severe frost of -2.7° on the 2nd was the coldest September night on this 14-year record. Having ten frosts in the month had not happened before, either. Most were “black frosts” because there was no dew to freeze. The extremely low Dew Point of minus 7.4° on the 2nd has been exceeded only once: minus 9.3 on 17/5/11.
With such dry air, two of the sunniest days had maximum temperatures more than 25° above the night-time minima.
Rain showers occurred on 5 days (normal), but the total was only 20.4 mm.

 Comparing September monthsClimate September 2012.

Days (24.0°) were 0.2° warmer than average, and nights (5.8°) were 1.2° colder than average.
The mean Dew Point of 0.8° is a new record low-humidity value for September, beating last year’s value of 1.7°. Low humidity brought less September cloud than in the last four years.
The low rainfall of 20.4 mm is in the 29th percentile for September. While the 12-month rainfall total to date is still extremely high (over 900 mm), the 2-month total (31 mm) is now a serious rainfall shortage, in the 9th percentile of 2-month totals.

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.


Manilla’s Frosts

I have a 13 year record that shows how frosty Manilla is, and how some years are frostier than others. My thermometer is on high ground, so people living where cold air collects will have had more frosts. However, my readings show changes from one time to another. As I do not have a thermometer in the grass, I have recorded a frost when my screen reading is below +2.2°.

There is a matching post for Manilla’s hot days.

Total frosts

The first graph shows the number of frosty mornings in each year. The most frosts were in the years 2004 (68) and 2006 (70); the fewest were in the years 2007 (43) and 2010 (44). The 13-year average is 54.
The graph also shows the number of mornings colder than zero, minus two, and minus four degrees. On the average, these occurred on 26, 7, and 1 mornings per year. For those colder than zero degrees, 2006 was again the frostiest, but 2002 was also very frosty. Counting only the most severe frosts (below minus two or minus four degrees) 2002 was the frostiest year. It had the coldest mornings: -5.1° on both the 2nd and 11th of July.Frosts each year, and seasonal distribution.

Frosty months

The second graph shows how most frosts come in the winter months, especially July, with some frosts in autumn, but few in spring and none in summer. Few come before Anzac Day (25th April) or after Labour Day (first Monday in October in NSW).

The graphs below show that each year was different. The drought year 2002 had the highest number of frosts in a single month: 27 in July – half of all frosts in that year. By contrast, the 70 frosts of 2006 were spread through the months of winter and autumn: there were more frosts in June and August than in July. Continue reading

August 2008 very cold and cloudy

The daily weather log

Weather log August 2008

The second week of August was the coldest week of the year. Temperatures by day and night were six degrees below normal. In the whole month few temperatures were above normal. Only six days got above 20°, compared to the usual twelve. The very last night soared to nine degrees above normal.
However, no days or nights were particularly cold. Although the 13th was the coldest morning of the winter at -2.8°, it was only a little lower than -2.7° on the 11th and 20th (and also on the 12th of July).
Most days had very dry air, with morning dew points below zero. Despite that, there was a lot of cloud. The number of mornings free of cloud was only five, the fewest in ten Augusts.
There were nine rain days spaced through the month, totalling 31.6 mm.

 Comparing August months

Climate August 2008

All the mean temperatures (daily maximum, daily mean, and daily minimum) were the lowest for August in a decade. The mean was over two degrees below normal.

It was a frosty month. In ten Augusts, none had as many minima below -2° (6) or below zero (14) as this one, but August 2005 had more total frosts (21 versus 18) counting minima below +2.2° in the screen.
Mean humidity (morning dew point) was extremely low. At -0.4°, it was over two degrees below normal. In the decade, only July 2002 had drier air, with a mean morning dew point of -3.1°.
There were more cloudy mornings (55%) than in any August of the decade. Five of the seven cloudiest months of the decade have come within the last ten months: Nov ’07, Dec ’07, Feb ‘08, Jul ’08, and Aug ’08. All had 50% or more cloudy mornings, almost twice the decade median of 27%.
The rainfall total, 31.6 mm, is on the 46th percentile for August, and below the average (40 mm). Totals for several months together are much the same as a month ago, but the serious shortage has moved back to the six-month total. The total for 2 months (July and August) is in the 28th percentile, 3 months in the 41st, 4 months in the 25th, 5 months in the 17th, and 6 months in the 7th percentile . Rainfall totals for longer periods are normal.

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. Temperature and other data are from 3 Monash Street, Manilla.


Fine cold days in July 2007

The daily weather logWeather log July 2007

Most days in July were cooler than normal. The first chart shows cold days persisted for more than a fortnight. The coldest, on the 16th, reached only 10.5°, which is 5° below normal. However, the weather was mainly pleasant, with more fine days and fewer cloudy days than usual.

There were warm nights at each end of the month, including one 7° above normal. In the middle, there were thirteen frosty nights in a row (below +2.2 degrees in the thermometer screen). The lowest temperature for the month was minus 4.4°. There were 17 frosts in total; far fewer than the 28 frosts of July 2002. (Note added in 2014: Up to, and including 2011, minima have been below minus 4° only sixteen times:  June 2000 (5), June 2002 (1), July 2002 (6), July 2003 (2) and July 2007 (2).)

With both days and nights being so cold, the weekly average temperature went as low as 4.7° below normal on the 17th.

There were seven rain days, which is normal, but the highest reading (on the 1st) was only 4.2 mm.

 Comparing July monthsClimate July 2007

This July had colder daytime maximum temperatures than any July in the last seven. Night-time minimum temperatures were also a bit on the low side. July 2002 stands out from the others. It had by far the lowest night-time temperatures in these years: three degrees below the average. Cloudiness was low in both 2002 and 2007.

The month’s rainfall of 9.0 mm is quite low, in the 12th percentile for July. However, there have been few dry months recently, so no totals for more than one month are as low as the 20th percentile.

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. Temperature and other data are from 3 Monash Street, Manilla.