Crozet Weather Almanac: July 2015


Is a Super El Niño Developing?

By Heidi Sonen & Roscoe Shaw

El Niño conditions have developed and there is good reason to believe that we will soon have a “Super el Niño.”  Even though this is a perfectly natural and often beneficial occurrence, it will no doubt lead to a year of sensational headlines and hype about the horrible destruction wrought by El Niño.

So what exactly is El Niño?  The phenomenon was first noticed by fishermen off the coast of Peru.  In a typical year, southeast winds push ocean surface water away from the coast and it is replaced by upwelling from below.  This brings nutrients and a fabulous fish harvest.  But some years, the winds switch and the upwelling stops and the fishing is terrible.  Peruvians dubbed this “el Niño” referring to the Christ child since the switch usually happened around Christmas.

From the 1920s to the 1960s, meteorologists gradually began to realize that El Niño was an oscillation that is global in scope and repeats itself from time to time.  The opposite condition, La Nina, was also identified.  El Niño is characterized by a huge warming of sea surface temperatures in the eastern Pacific off the coast of South America.  El Niño’s fingerprints can be found in tree rings and ice cores back for thousands of years.  Why this happens is unknown but there are many other climate oscillations that have been identified recently such as the AMO and PDO which can operate over differing time scales, often measured in decades.

So what does El Niño mean for our weather?  Not much.  Our weather is almost completely the same in El Niño versus La Nina years.  But that is not the case in other places.  The best news is that El Niños tend to be quite wet in California.  California has been in a historic drought and most of their rain falls in winter so the potential Super El Niño could be great news.  Wetter and cooler than normal weather is also likely over much of the southern USA with warm and dry conditions likely across the northern USA.

El Niño also raises global temperatures temporarily.  The Super El Niño of 1997-98 produced the warmest global temperatures on record.  Those records are in jeopardy for 2015 and 2016 before some cooling kicks in with the next La Niña.

July Recap

July was very “normal.”   Temperatures were a touch below normal which is always nice in July and the hottest was just 92.  Rain was also a touch below normal but it rained frequently and the timing was good so plants didn’t get too thirsty.

Rainfall Totals:

  • Mint Springs  3.80”
  • Batesville   4.40”
  • White Hall   2.02”
  • CHO Airport  1.16”
  • Waynesboro 4.18”
  • Nellysford  3.49”
  • Univ of VA  4.22”
Chart courtesy Heidi Sonen & Roscoe Shaw
Chart courtesy Heidi Sonen & Roscoe Shaw


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