This post updates a similar one by including three more years to make a total of sixteen. It is in the same format as a recent post on Manilla’s frosts. Because the summer, which has the most hot days, crosses from one calendar year to the next, I have begun each year at July. I have called days warmer than 35° “hot days”, and days warmer than 40° “very hot days”.
I have analysed the pattern of hot days in more detail in a later post “Hot days and ENSO”. By finding the relative frequency of hot days in all of the hotter months, I show that there is a cyclic variation related to ENSO. The cycle period is near 1.5 years, not 3 years as the log of annual frequency of hot days (above) suggests.
Graphical log of hot and very hot days
The first graph is a log of the number of hot and very hot days in each year. The three years with the most hot days had almost the same number: the year ’02-’03 had 41, the year ’09-’10 had 44, and the year ’13-’14 had 43. The two years with the fewest were ’07-’08 which had 5, and ’11-’12, which had only 4. The 13-year average is 26. Counting only the very hot days, ’03-’04 had the most (6), and four years had none at all. On the average, two days exceeded 40° in a year. (These are thirteen-year averages, not updated.) The number of hot days per year seems to have a cyclic pattern, with a period that increases from two years to four years during this short record. This is just a curiosity. The pattern of hot days has a lot in common with the pattern of smoothed monthly temperature anomalies for all months. These are plotted here, on a graph that relates them to ENSO. The relation of Manilla daily maximum temperature to ENSO was quite close from 1999 to 2011, but failed almost completely since mid-2011. In the earlier post on frosts, no cyclic pattern can be seen, nor any relation to ENSO.
New Record hottest days
In the sixteen years, there have now been 37 days hotter than 40 degrees: that is, 2.4 days per year. It remains true that December has fewer very hot days than November or February. A new record was set on 12/1/2013 by a daily maximum temperature of 43.2 degrees, beating the 42.6 degrees of 20/11/2009. This record was broken again on 3/1/2014, with 43.7 degrees. In the latest year, the hottest day (41.1 degrees) ranked only 12th, and it was not in summer, but in November.
Three new annual graphs
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
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.
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.”
I have used my 13-year weather record to find the number of hot days in each year and in each month. Earlier I did the same for frosty mornings. Because the summer, which has the most hot days, crosses from one calendar year to the next, I have begun each year at July.
I have called days warmer than 35° “hot days”, and days warmer than 40° “very hot days”.
Total hot days
The first graph shows the number of hot and very hot days in each year. The most hot days were in the year ’09-’10, which had 44; the fewest were in the year ’11-’12, which had only 4. The 13-year average is 26, but the number of hot days is quite different from year to year.
Counting only the very hot days, ’03-’04 had the most (6), and four years had none at all. On the average, two days exceeded 40° in a year.
Months with hot days
The second graph shows how the number of hot and very hot days peaks strongly in January, with very few earlier than November or later than March. On average, Manilla’s summer has about 22 days warmer than 35°, while spring has 3, and autumn only 1.
The other graphs show how each year had a different pattern of hot days. The highest monthly peaks, each 19 hot days, came in January 2003 (following drought) and January 2007. Annual peaks also came in January in 2008 and 2012, but these peaks were extremely low: only 4 and 3 hot days. Continue reading
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.
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.
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