3-year trends to September 2018

Equable, less sunny

3-year trends to September 2018

September raw anomaly data (orange)

Like last month, climate anomalies were in retreat from drought. All moisture measures, except rainfall, moved lower on the graphs. Both the daily temperature range and the percent of cloudy mornings recovered from extreme values.

 Fully smoothed data (red)

Fully smoothed data for March 2018 broke the previous month’s record for daily maximum temperature anomaly (x-axis), advancing from +1.58 to +1.63 degrees. The March smoothed rainfall anomaly of −27.1 mm (top left graph) equaled the 20th-century record minus value set in July 2002. Both these records may be broken by fully-smoothed figures for April 2018.
By March 2018, the trend for decreasing rainfall with increasing daily maximum temperature (top left graph) had lasted eight months. Other variables had different patterns. Most were just beginning to move towards drought after several months with little change.
Daily minimum temperature, after six months of sustained rise, then began to fall. Subsoil temperature anomaly was rising, lagging daily maximum temperature anomaly by five months.


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.

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