El Niño Zone Breaks Monthly Water Temperature Record in November

The current El Niño set a monthly record in November, and may eventually become the strongest El Niño on record this winter, according to data just released from NOAA.

Water temperatures near the ocean surface reached their highest positive anomalies on record in the zone of the equatorial Pacific Ocean defining either El Niño or its opposite, La Niña, in November. This means the sea-surface water temperature was farther above average for the time of year than any previous month in reliable records dating to 1950.

Specifically, the water temperature in this region was about 2.35 degrees Celsius above average in November 2015, topping the previous record monthly anomaly from November 1997 by 0.02 degrees Celsius, in reliable records dating to 1950.

El Niño is an anomalous, yet periodic, warming of the central and eastern equatorial Pacific Ocean. For reasons still not well understood, every two to seven years, this patch of ocean warms for six to 18 months, then cools.

This warming of equatorial Pacific water influences the atmospheric pattern from the western Pacific Ocean, including Australia and Indonesia, to North and South America, the Atlantic Ocean, even parts of Europe and Africa.

Pacing this record monthly anomaly was a first-on-record monthly sea-surface temperature of 30 degrees Celsius (86 degrees Fahrenheit) in the equatorial central Pacific well south and southwest of Hawaii, according to Colorado State University tropical meteorologist, Dr. Phil Klotzbach.

Record Strongest El Niño?

The seemingly straight-forward question of whether this El Niño is the strongest on record is, well, complicated.

"It depends on the measure," said The Weather Channel's senior director of weather communications, Stu Ostro. "There's ERSST.v4 versus OISST.v2 (two different sea-surface temperature datasets), and weekly, monthly and three-month sea-surface temperature data."

For historical purposes, the most accepted method of categorizing the intensity of El Niños and their opposite La Niñas utilize the NOAA Climate Prediction Center's three-month running mean SST anomaly, known as the Oceanic Niño Index (ONI), instead of looking at one week or even one month's worth of data.

Based on the latest three-month (September-November) ONI available at the time of this column, the 2015 El Niño is pacing ahead of the 1982-1983 event, but still behind the pace of the strongest El Niño of record in 1997-1998.

Year	Sep-Nov ONI (degrees C)
1) 1997	+2.18
2) 2015	+2.04
3) 1982	+1.86

El Niños typically peak in the winter months, so it is still possible the current El Niño may continue to strengthen a bit over the next month or so. When comparing the current ONI value with the peak values reached in the two strongest El Niños, 2015 (soon 2016) still ranks third. 

Year	Peak ONI (degrees C)
1) 1997-1998	+2.26 (Oct-Dec)
2) 1982-1983	+2.12 (Nov-Jan)
3) 2015-2016	+2.04 (Sep-Nov)

Another variable used to examine not just the sea-surface temperature anomalies, but also the atmosphere's response, known at the multivariate ENSO index (MEI) also places 2015 behind 1997 and 1982 in October and November data, according to Klotzbach.

http://www.wunderground.com/news/strong-el-nino-december-2015