Dry Air in Winter 2017

Photo of red Eucalyptus flowers

Eucalyptus leucoxylon in winter

This winter had remarkably dry air. The lowest early morning dew point was -10.0°, and the winter mean was -0.5°. Both were record low values. Through the season, the dew point got further and further below the early morning temperature, ending five degrees lower.

Daily maximum and minimum temperatures were near normal. However, they were more than a degree cooler than in the recent winters of 2009 and 2013.

Graphical log for winter 2017

With dry air came a wide daily temperature range of 16.3°, second only to 17.5° in the winter of 2002. It also brought sunny weather, with only 32% cloudy mornings. While that was near the average for my “normal” decade 1999-2008, it was lower than in any recent winter. The winters of the last decade, 2007-2016, were much more cloudy, averaging 45% cloudy mornings. Winter 2016 had 53%!

There were four brief spells of rain this winter, none with heavy rain. They were spaced about seventeen days apart. That sequence had begun in autumn, with heavier falls then. After the 4th of August there was no rain at all.

The total rainfall of 89.8 mm was at the 27th percentile, well below the winter average of 125 mm. Five recent winters had similar amounts of rain: 2000 (98 mm), 2001 (107 mm), 2003 (102 mm), 2004 (97 mm) and 2006 (104 mm). Two were much drier: 2002 (44 mm) and 2011 (55 mm).

Climate for winter 2017


Data. A Bureau of Meteorology automatic rain gauge operates in the museum yard. From 17 March 2017, 9 am daily readings are published as Manilla Museum, Station 55312.  These reports use that rainfall data when it is available. All other data, including subsoil at 750 mm, are from 3 Monash Street, Manilla.

Advertisements

Wet Autumn 2017

Sunset photo.

Manilla Sunset

Autumn this year had normal temperatures, in stark contrast to very high temperatures both in the summer and in the autumn of last year. The decline to winter was not smooth, however, but went by steps. For three weeks in each month there was no cooling then, after some rain, there was a sudden cooling through three, four, or five degrees.
Rain fell frequently except for two gaps of a fortnight each, the first coming in mid-April. The second ended with 32.8 mm of rain registered on May the 20th. There were 26 rain days, which is twice usual number, and more than in any autumn in the new century.

Graphical log for autumn 2017

There was plenty of moisture. Only the early morning dew point (8.1°) was low, by half a degree. The daily temperature range was a narrow 14.5°, and the cloudiness a high 41%.
The total rainfall of 192.8 mm was at the 80th percentile, far above the autumn average of 134 mm. There has not been a wetter autumn since 1990 (203 mm). A little earlier there was a cluster of wetter autumns: 1977 (307 mm), 1979 (203 mm), 1982 (238 mm), 1983 (314 mm: 4th wettest), and 1988 (231 mm). Autumn 1894 was the very wettest, with 388 mm.

Climate for autumn 2017


Data. A Bureau of Meteorology automatic rain gauge operates in the museum yard. From 17 March 2017, 9 am daily readings are published as Manilla Museum, Station 55312.  These reports use that rainfall data when it is available. All other data, including subsoil at 750 mm, are from 3 Monash Street, Manilla.

Summer 2016-17 the hottest

Young bearded dragon

Tiny Dragon

This summer, like summer 2013-14, was marked by repeated heat waves. The first, early in December, was brief. Another, in mid-January, led into one that was hotter, and persisted through the first half of February. On a weekly basis, temperatures did not fall below normal at any time in the season. Mid-February had the two hottest days of the new century, at 44.9° and 43.8°.
Although there were as many rain days as usual (22), only two days had rainfall exceeding 15 mm, and there was almost no rain in February.

Graphical log for summer 2016-17.

Comparing summer seasons

Mean temperatures set new records for the summer season: daily maximum 35.6°, average 27.6°, and daily minimum 19.7°. Each of these was more than a degree higher than the old record. Nearly all such figures for the months December, January, and February had also been records. However, the subsoil temperature for the summer (24.7°) was low.
Two indicators of moisture were a little low: mean early morning dew point (13.4°) was down 0.7°, and mean daily temperature range (15.9°) was 0.8° wider than usual.
The percentage of cloudy mornings (38%) was almost the same as in the last four summers, and lower than in the previous two. However, 38% is much more cloudy than the “normal” figure of 31% cloudy mornings that was set in the decade 1999-2008. Summers were more sunny then.
This summer’s rainfall was very low. The unofficial total of 101.4 mm would place it as the seventh driest on record. As shown on the graph, summer 2013-14 was drier (85 mm). Otherwise,  there has not been a drier summer in the half-century since 1964-65 (70 mm).

Climate for summer 2016-17


Data. Rainfall figures are usually from the automatic rain gauge at Manilla, published on the internet by the Bureau of Meteorology as Station 55031. However, the gauge ceased recording five months ago (8/10/16), and this month’s readings are from my non-standard gauge. All data, including subsoil at 750 mm, are from 3 Monash Street, Manilla.

Cool spring 2016

Photo of a wildflower

Nodding Chocolate Lilies

Through September, days were very cool, making for a narrow daily temperature range. Then, through October, both days and nights were very cool. In November, days and nights were nearer to normal but, in contrast to September, the daily temperature range was wide. The dew point failed to rise during the season, making the air very dry in November.
Rain fell frequently up to the middle of November, then ceased. There were 24 rain days, when there are normally 19 in spring. The highest reading was 28.8 mm on the 14th of September. The season total of 216.4 mm was rather high, in the 77th percentile.

Graphical log for spring 2016
All temperature measures were below normal by 1.5° to 2.0°. Only spring of 2001 had low values like that but in 2010 the mean daily maximum (only) was 2.5° below normal.
Measures of moisture were near normal, with cloud, rainfall, and daily temperature range on the moist side, and dew point on the dry side.

Climate for spring 2016


Data. Rainfall figures for this season began from the automatic rain gauge at Manilla, published on the internet by the Bureau of Meteorology as Station 55031. That gauge ceased reporting on the 8th of October, and later readings are from my non-standard gauge. All other data, including subsoil at 750 mm, are from 3 Monash Street, Manilla.

Extremely wet winter 2016

Water flowing over a weir

Manilla Weir Fish Ladder

This winter, with 227.4 mm of rain, was the fifth wettest in the record from 1883. In order of rainfall, wetter winters were: 1920 (318 mm), 1998 (304 mm), 1950 (261 mm) and 1952 (233 mm). This winter’s total was more than 100 mm over the average (125 mm). The heaviest daily fall, 37 mm, was on 5 June, and there were four other falls of more than 15 mm; two in June and two in August.
There were big week-long swings in temperature through June and July. On four occasions nights were more than four degrees warmer than normal and on one occasion days were four degrees cooler than normal. No such swings occurred from late July to mid-August, then days became five degrees cooler than normal. In this winter, there were few spells of either hot days or cold nights. The number of frosts (42) was near the usual number (44).

Graphical log for winter 2016
While the mean temperature of the season was normal, most other measures of climate were not.
The winter seasons of 2016 and 2010 were both extremely moist. Winter 2016 had more rain (227 mm versus 160 mm) and more cloudy days (53% versus 49%). In other respects 2010 was more moist: the dew point was higher (3.7° versus 2.5°), and the days had a narrower temperature range (12.5° versus 12.8°). The daily temperature range for winter is usually much wider: 15.3°. It was 17.5° in winter 2002!

Climate for winter 2016


Rainfall figures for this month are from the automatic rain gauge at Manilla, published on the internet by the Bureau of Meteorology as Station 55031. All other data, including subsoil at 750 mm, are from 3 Monash Street, Manilla.

Autumn 2016 had many warm spells

Photo of a garden in Manilla NSW

Autumn Garden

The season was marked by a series of warm spells. The three warmest, coming early in each month, reached 3° to 4° above normal. In the first two, days and nights were equally warm; in the third, nights were much higher above normal than days, making the daily temperature range narrower than normal by 4°. The only cool spells having temperatures below normal were in the third week of March and the last week of May. All three frosts of this season came in the final week .
Rain came in five episodes, spaced a week or two apart. There were 12 rain days, which is the usual number, but the highest reading was only 20.8 mm.

Weather log for autumn 2016
This was the warmest autumn in this short record. Daily maximum, mean, and minimum temperatures were all more than 1.5° above the average for the decade beginning March 1999. The subsoil temperature at 750 mm was also rather high.
The composite Moisture Index was normal, rainfall being a little low and cloudiness rather high (36%, when the autumn “normal” is 25%).
The total rainfall of 88.3 mm was below the autumn average of 134 mm, and in the 35th percentile.

Climate for autumn 2016.


All data, including subsoil at 750 mm, are from 3 Monash Street, Manilla. Rainfall data up to 26/3/15 is from Manilla Post Office, Station 055031.

Summer 2015-16 cool then warm

Photo of San Pedro cactus blooming

San Pedro cactus blooms

Taken as a whole, this summer was nearer to normal than last summer. Several numbers were close to average: daily maximum temperature, daily mean temperature, daily minimum temperature, and daily temperature range. The mean early morning dew point was rather low, while the cloudiness and total rainfall were a little high.
There were two very hot days over 40° (the usual number) and 29 hot days over 35° (just 6 more than usual).

Weather log for summer 2015-16A very cool spell came in early December, between other cool spells in late November and late December. Then, from mid-February through to early autumn, the weather was very warm. With this warmth came dry air, a wide daily temperature range, and sunny skies.
The total rainfall of 253.6 mm was above the summer average of 227 mm. After 20 rain days (the usual number), rainfall ceased on the 4th of February. Had it continued, the total might have reached a very wet 350 mm.

Climate log for summer 2015-16.


All data, including subsoil at 750 mm, are from 3 Monash Street, Manilla. Rainfall data up to 26/3/15 is from Manilla Post Office, Station 055031.