Warm, Dry February 2019

Photo of bushfire smoke at 40 km.

Bushfire at Warrabah

The month began warm, with weekly temperature three degrees above normal, but it ended slightly cool. Day and night temperatures remained near normal. The highest maximum was just under 40°.
The morning of the 13th had very dry air, with a dew point of only 1.7°. (Serious bushfires were burning that day.)
There were only 2 rain days (usually 7). Neither recorded as much as 7 mm.

Graphical log for Feb 2019

Comparing February months

After the extreme heat of January, February was only 1° warmer than normal, by day and by night.
Two indicators of moisture, cloudiness and daily temperature range, were normal. However, the mean early morning dew point, 9.2°, showed the lowest February humidity this century.
The monthly rainfall of 10.6 mm was at the 9th percentile, far below the average (67 mm). This was the 12th driest February, but it had more rain than either February 2017 (6th driest) or February 2015 (ninth driest).
I have reported the on-going drought in another post.

The last 7 February months


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.  Since no 9 am readings have been recorded since August, I have substituted my non-standard gauge readings for all days.
All other data, including subsoil at 750 mm, are from 3 Monash Street, Manilla.

3-year trends to February 2019

February arid

3-year trends to February 2019

February raw anomaly data (orange)

By February 2019, temperatures had returned from very high to normal. Rainfall remained very low, and dew point also became very low.

 Fully smoothed data (red)

Fully smoothed data to August 2018 showed that several trends for the spring were typical of drought:

Maximum temperature anomaly was steadily falling from the record high in March.
Minimum temperature anomaly was a little high and steady.
Subsoil temperature anomaly was falling towards normal from a low peak in June.
Rainfall anomaly was near the record low (smoothed) and steady.
Cloudiness anomaly was near zero.
Dew point anomaly was near the record low (smoothed) and steady.
Temperature range anomaly peaked rather high in July, then fell.

More recent data, only partially smoothed, suggest that temperatures and rainfall have since returned towards drought.


Notes:

January data points are marked by squares.

Smoothing

Smoothing uses Gaussian functions.
For fully smoothed data the function has a Standard Deviation of 2.5 months, it spans 13 monthly data points, and has a half-width of 6 months, which suppresses cycles shorter than 12 months. For partly smoothed data, the span of the function is reduced to 11 months, 9 months and so on.

Fully smoothed data points are plotted in red, partly smoothed data uncoloured, and raw data for the last data point in orange.

Limiting values

Blue diamonds and the dashed blue rectangle show the extreme values in the fully smoothed data record since September 1999.

Normal values

Normal values are based on averages for the decade from March 1999.* They appear on these graphs as a turquoise (turquoise) circle at the origin (0,0). A range of anomalies called “normal” is shown by a dashed rectangle in aqua (aqua). For values in degrees, the assigned normal range is +/-0.7°; for cloudiness, +/-7%; for monthly rainfall, +/-14 mm.

 * Normal values for rainfall are based on averages for the 125 years beginning 1883.

February 2018 had heavy rain at last

Wave cloud photo

Lenticular over Warrabah

Although there were eleven hot days over 35° this month, no days went over 40°. On the average, the second week was just 3.4° above normal, but the first week had been 3.5° below. Through most of the month, the weather was sunny with little rain, making the soil extremely dry. A drought seemed likely.
A violent front on the 25th brought an estimated 54 mm of rain: the heaviest fall in years. There is no official record of this rain event. Nor is there an official record of the only recent events of such a large amount: 47.0 mm on 4 February 2016, and 54.5 mm on 17 June 2015. The latest official readings that were higher were more than five years ago. They were in the record-breaking month of November 2011: 60.8 mm on the 14th, and 62.9 mm on the 27th.

[See note below on “Very wet days at Manilla”.]

Weather log for February 2018

Comparing February months

Compared to last February, this one was not nearly so hot and not so dry. Nights were near normal and days, at 33.9°, only one degree above normal (32.9°). Despite other signs of high moisture, the early morning dew point of 9.9° was very low.
Thanks to the one day of heavy rain, the estimated monthly rainfall total (71 mm) was above the average (67 mm) and at the 65th percentile. Among totals for more than one month, there is just one serious shortage. The 72-month (6-yr) total of 3400 mm is at the 8th percentile (450 mm low).

Climate in February months

Note.
Very wet days at Manilla

Log of decade totals of rainfall excess, Manilla, NSWDaily rainfall amounts of over 50 mm (“flooding rains”) are extreme events that feature in several posts on this blog. A graph in the first post on the topic is a log of every very wet day in the 130-year record. In a second post, I graph the pattern of how the total rainfall in very wet days changes decade by decade (Graph copied here.). Very wet days have a curious relation to drought that is analysed in “More Droughts After Heavier Rains”, Parts I, II, and III.


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, but it is not.  The gauge last reported on 24 September 2017.

All data, including subsoil at 750 mm, are from 3 Monash Street, Manilla.

3-year trends to February 2018

Warm

3-year trends to February 2018

February raw anomaly data (orange)

February 2018, unlike January, had days that were not very hot and nights with normal temperature. Rainfall rose to a normal value. Continuing low moisture was shown only by a very low dew point and a wide daily temperature range.

 Fully smoothed data (red)

Data for winter (JJA) 2017

These latest of the fully-smoothed data points showed that last winter was near-normal and changing little in most respects. Both dew point and temperature range were moving up their graphs towards aridity. Daily minimum temperature and subsoil temperature were cooling.

Main patterns of fully-smoothed data

In this period, the only major departure from normal climate was the cool moist winter (JJA) of 2016. Loops in the top four graphs show that more moisture preceded lower temperature. Minima in daily minimum temperature and in subsoil temperature came several months later, at the end of spring.


Note:

Fully smoothed data – Gaussian smoothing with half-width 6 months – are plotted in red, partly smoothed data uncoloured, and raw data for the last data point in orange. January data points are marked by squares.
Blue diamonds and the dashed blue rectangle show the extreme values in the fully smoothed data record since September 1999.

Normal values are based on averages for the decade from March 1999.* They appear on these graphs as a turquoise (turquoise) circle at the origin (0,0). A range of anomalies called “normal” is shown by a dashed rectangle in aqua (aqua). For values in degrees, the assigned normal range is +/-0.7°; for cloudiness, +/-7%; for monthly rainfall, +/-14 mm.

 * Normal values for rainfall are based on averages for the 125 years beginning 1883.

February 2017 had the hottest day

February 2017 was a month of extreme heat and hardly any rain.

Rainbow

No-rain Rainbow

The temperature rose to 44.9° on the 11th, the highest reading in this record from 1999. The next day, at 43.8°, was the next highest, beating readings of 43.7° on 3/01/2014 and 43.2° on 12/01/2013. These extremely hot days were part of a long heat-wave. Every day reached above 30° for 64 days up to the 19th, and the average weekly temperature was above 30° (4° above normal) from the 1st to the 15th.
Nights also remained warmer than normal until, abruptly, the temperature fell to 9.5° on the 20th: the 4th coldest February night! After that, day and night temperatures were normal.
Rain showers were seen frequently, but the only daily readings (unofficial) were 1.1 mm on the 20th and 3.0 mm on the 27th.

Weather log February 2017

Comparing February months

This was by far the hottest February of the new century, with highest values of all three temperatures: mean maximum temperature (36.8°), mean average temperature (28.4°) and mean minimum temperature (20.0°). Subsoil temperature was normal.
While cloudiness was normal, a rather low dew point and rather wide daily temperature range reflect low moisture, while the rainfall was very low indeed.
The estimated monthly rainfall total of 4.1 mm exceeds that of just a very few February months: 1901 (2 mm), 1932 (3 mm), and perhaps 1923 and 1938 (both 4 mm), but no others. However, this extremely low rainfall for the month has not brought any serious rainfall shortages for totals of more than one month. The four-month total of 123 mm is at the 17th percentile, which is not even as bad as the five-year total (2844 mm) which is at the 14th percentile.

Climate for February 2017.


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 four 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.

3-year trends to February 2017

Parametric plots of smoothed climate variables at Manilla
“Extreme heat with little rain”

3-year trends to February 2017.

February raw anomaly data (orange)

In February 2017 days became extremely hot and rainfall very low. The subsoil temperature rose from low to normal.

 Fully smoothed data (red)

Fully-smoothed values are now available for the winter months (June, July, and August) of 2016. That winter, as daily maximum temperature fell through normal values, a maximum in moisture was shown by maxima in rainfall, cloudiness, and dew point, and a minimum in daily temperature range. None of the smoothed values was extreme; in fact, the dew point remained on the dry side of normal.
Not only daily maximum temperature anomaly fell during the summer. Both the daily minimum temperature anomaly and the subsoil temperature anomaly also fell. The smoothed daily minimum temperature anomaly had just reached a record high value in May, and was still above normal as the summer ended.


Note:

Fully smoothed data – Gaussian smoothing with half-width 6 months – are plotted in red, partly smoothed data uncoloured, and raw data for the last data point in orange. January data points are marked by squares.
Blue diamonds and the dashed blue rectangle show the extreme values in the fully smoothed data record since September 1999.

Normal values are based on averages for the decade from March 1999.* They appear on these graphs as a turquoise (turquoise) circle at the origin (0,0). A range of anomalies called “normal” is shown by a dashed rectangle in aqua (aqua). For values in degrees, the assigned normal range is +/-0.7°; for cloudiness, +/-7%; for monthly rainfall, +/-14 mm.

 * Normal values for rainfall are based on averages for the 125 years beginning 1883.

February 2016: hot, dry days

Photo of cooba blossom

Cooba in February

Weekly average temperatures began 2 or 3 degrees low, but ended with a long warm spell 3 degrees high, that extended into March. Days were especially hot, with the 26th reaching 41.5°, the equal second hottest February day. Nights were seldom very warm, and the early morning of the 26th was 25° cooler than the afternoon.
Few days were cloudy, none of them late in the month
Rain fell only on the 3rd, as three heavy showers of 7mm, 27mm and 13mm. The second shower, at 5pm, had the most intense rain of the new century: 27 mm in less than 27 minutes. Bureau of Meteorology data show that such a half-hour storm, yielding 1 mm of rain per minute, has only a 10% chance of happening here in any year. It is a “one in 10 year event”.

Weather log February 2016

Comparing February months

While the average temperature for the month (25.8°) was normal, the mean daily maximum, at 34.7°, was the hottest for February. A rather low mean daily minimum, (16.8°) made the daily temperature range a desert-like 17.9°. This is the widest February value, 3.5° wider than normal.
Other signs of dryness were the low early morning dew point (10.8°) and very few cloudy mornings (17%).
The total rainfall of 47mm was below the average of 67 mm, but right on the median 50th percentile: just half of all February months have been wetter. Again, there are no serious rainfall shortages for totals for any number of months.

Climate for February 2016


Data. 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.