July 2019 Weather Report

Essentially a very dry month, possibly foreshadowing a very dry year. While humidity was not far off normal it didn't develop into rain.  Temperatures were a little above normal, as would be expected from the proven global warming trend.   The most notable feature of wind was the pronounced bias towards the South-West to North section of the wind rise.

Rainfall

What is this thing called rain?  My weather station recorded 24 mm during the month with the heaviest fall being 9 mm on the 15th.  The BoM managed slightly better with 26.6 - in a couple of cases showers seem not to have made it far past the coast.  This is very much below average and below the miserable total for 2018.

 The number of days with more than 0.2mm was also down on last year and the average.

 Looking at the value generated by pro-rata estimation of the total year to date is not a happy picture.

This projects the total for 2019 as 594 mm, which if it happens would be the lowest, by ~60 mm, since the series started in 1975.  

Temperatures

Overall a slightly warmer than usual month, with the temperature anomaly (current month average - long term month average) calculated on BoM data for their site near the airport, coming in at +0.35^oC.  The progression of the anomaly on a "month-to-date" basis shows a cold start to the month followed by a warm patch and ending with a slow decline to the final figure.

At Angophora Drive the daily maxima and minima are shown below.  Both occupy a reasonably narrow band.

 Maximum temperatures

Overall the average maximum was slightly warmer than last year and the average.

Looking at daily extremes the highest maximum (21.1^oC on the 12^th) was the 10^th highest July maximum.  The lowest maximum (11.1^oC on the 30^th) was the 11^th lowest July maximum.

Minimum temperatures

The average minimum was slightly above the long term average and somewhat more above the 2018 value.

Looking at daily extremes the lowest minimum (3.6^oC on the 1^st) was the 121^st lowest July maximum.  Simply put, not very low at all!  The highest minimum (12.1^oC on the 16^th) was the 6^th highest July maximum and could thus almost be rated 'snuggly'.

Humidity

Following the BoM example I look at the relative humidity at 0900 and 1500 hrs.  In July they followed a similar pattern.

 The 13th is an outlier but the BoM  shows a similar spike in humidity!  I am not sure what is going on but checking the hourly data for my site suggests a front has come through:

Date	Time	Temp Out	Hi Temp	Low Temp	Out Hum	Dew Pt
13/07/2019	1:00:00 PM	12.7	12.7	11.9	55	3.9
13/07/2019	2:00:00 PM	12.3	13	11.9	58	4.2
13/07/2019	3:00:00 PM	8.9	12.4	8.4	82	6
13/07/2019	4:00:00 PM	9.1	9.1	8.6	74	4.7
13/07/2019	5:00:00 PM	8.4	9.1	8.4	72	3.7

Looking at past years the average humidity for 0900 is a little above average, but much higher than 2018.

 For 1500 Hrs the 2019 humidity was below average, but again above the value for 2018.

 Wind

I now use the 1500 windspeed as my basic measure and in the next chart plot the values for home and BoM.  Note that I use different scales as the BoM is, as usual, much breezier than Angophora Drive.  The pattern is quite similar with a correlation coefficient of 0.71.

 Using the average daily wind run as my attribute for long term comparison the long term average  value for the BoM site is well above that for Angophora Drive in July (as expected).  I think the pattern is broadly consistent,

The final characteristic of the wind is the direction.  The pattern this month is more extreme than usual with 88% of readings from SW to North.  (I shall do a little more on assessing the usual direction as my data set increases.)