Thursday, 18 January 2018

Looking at heatwaves in January

This January is being disgusting for heat.  However, is it being more disgusting than usual?  Theer are many ways of looking at this and I have tried to set out some of them blow.

I'll begin with a chart plotting days with a maximum over 30oC for the last 4 years.  I have chosen that period as it comes from my Weather Station so change of site isn't an issue.
Last year was very hot (or bad, if you prefer). The spell of 12 days then was not as bad as the 17 consecutive days over 30oC recorded by Lynton in January - February 2011!

I have compiled a profile of maxima for January 2018 using my data to the 17th and the rest of the month from various forecast.  The next chart compares the result of that with the actual data for 2017.
I think that shows that last year was worse!

In terms of heat wave days (ie number of days in periods of 3 days or more of >30oC and minima >10oC), it looks as though this January will rack up 19 days (if the forecasts are correct).  Last year was 22. 

The average number of January Heat Wave Days since 2010 is 16.75 and since 1993 is 14.2 (which includes a period in the noughties where I think the recording device was biased upwards).  So this year is overachieving but not dramatically so. 

I charted the number of Heat wave days since the year ended 30 April 1994.  (I apologise for the unnecessary orange shadow, but it does look pretty!)

Although the value of r2 for the polynomial trend line is not great the pattern suggests that what we are experiencing now could be not a long way off what will become normal in the future.

Just for comparison in January the maximum temperature for Dubai in years since 2012 ranges between 27oC) and 30oC).  The average daily maximum over the month is between 20oC) and 24oC).  I wish I was there.



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