El Nino And Summer Rains In Southeast Arizona

The NWS Office at Tucson put up information on its web site regarding summer rainfall (June through September) during El Nino events. See:  http://www.wrh.noaa.gov/twc/climate/ElNi%C3%B1o_Monsoon_rainfall_seaz.php

The Albuquerque also put up a fairly comprehensive and more technical report on their web page. See:
http://www.srh.noaa.gov/images/abq/Briefings/2014%20North%20American%20Monsoon%20%28NAM%29%20Outlook.pdf

I have looked at the NWS charts for the southeast Arizona stations and will summarize them from a slightly different perspective than the Tucson Office did. First, I considered "near normal" summer rain to be plus/minus 15 percent of the long-term summer normal (for period 1981-2010). Then I considered the stations in eastern Pima and Santa Cruz Counties (only 5 sites shown by the NWS) separately from the stations in Cochise County. I also looked only at the most recent 10 El Ninos, beginning with that of 1969 (I have more confidence and the observational data are more complete for these events). The chart data for Bisbee are incomplete and I did not consider them.

For the five stations in eastern Pima and Santa Cruz Counties: There were 27 events that had drier than normal summers; 7 that had wetter than normal summers; and 16 El Nino summers were near normal. (The numbers for Tucson were 4 dry, 2 wet, and 4 near normal.) Clearly the chances favor drier than normal or near normal conditions for the coming summer.

For the seven stations in Cochise County the breakout goes: 34 dry, 8 wet and 28 near normal, so again the chances favor drier or near normal conditions.

For all El Nino summers and all stations I considered there were 51 percent dry and 37 percent near normal, so dry still predominates, but one can hope for near normal also. But if one considers only the last 5 El Nino summers for all stations then 73% were dry and only 22 percent were near normal, so the data from 1991 on really favor dry conditions during recent El Nino summers.

Finally, I examined all 10 El Nino summers as a function of station elevations. Three stations are at elevations higher than 5,000 ft MSL (Chiricahua NM, Coronado NM, and Kitt Peak) and their summers yield 14 dry, 14 near normal and only 2 wet. For the stations below 4,000 ft MSL (Arivaca, Benson, Nogales, and Tucson)  their summers yield 19 dry, 13 near normal, and 8 wet. But 15 of the dry summers were after 1991 and the only 1 was wet.

Bottom line is that if I had to bet on this summer, I'd go for dry here in metro Tucson.