Hottest Year Possible For 2017 - Part 2

Paul Iñiguez, Science & Operations Officer, NOAA/NWS Phoenix, AZ -- Published 22 December 2017

It is increasingly likely 2017 will become the new hottest year on record for Phoenix, Arizona.

Fig. 1. Running annual average temperature for 2014 and 2017 in Phoenix, AZ.
Values for 2017 are based on observations for Jan 1 through Dec 21
and projected values for Dec 22 through Dec 31.

In a previous post, we looked at the probability of 2017 ending up as the hottest year on record. The current hottest year is 2014 with an average temperature of 77.1 °F. At that time (end of November), the chance of 2017 besting 2014 was 47% and we anticipated 2017's average temperature to land in the 77.1-77.3 °F range. Since then, the first 21 days of December were the 5th warmest on record (60.5 °F) for that period, though that pace was slightly behind 2014's at 61.0 °F. So it will really come down to the final 10 days of the year.

Fig. 2. December max and min temperatures from 2014 and 2017. Values for
December 2017 beyond the 21st are based on current forecast/projections.

The current forecast (as of this writing) calls for high pressure to sit along the West Coast for the remainder of 2017. This would favor warm and dry conditions for the Southwest. There is always a chance that a weak weather system moves into the area, but for now the chances for any significant storms or push of more cold air seem low. With this in mind, it appears December 2017 will likely edge out December 2014 (which continued to cool at the end of the month), thus pushing 2017 as a whole into the number one spot. Current projections end 2017 with an average temperature of 77.3 °F, eclipsing 2014's 77.1 °F. Of the ten hottest years on record, this would 

Top 10 Hottest Years
 1. 2017 -- 77.3*
 2. 2014 -- 77.1 
 3. 1989 -- 76.9 
 4. 2016 -- 76.7 
    2015 -- 76.7 
    2012 -- 76.7 
 7. 2007 -- 76.4 
 8. 2003 -- 76.3 
    2009 -- 76.0 
    2002 -- 76.0 
    1981 -- 76.0 
* Projected