12:20 PM | An update on El Nino - it continues to strengthen and could end up rivaling some of the strongest events in recent history

Overview

El Nino conditions developed last year in the equatorial part of the Pacific Ocean and they have intensified significantly in the past few months. In fact, it appears that this El Nino may end up rivaling in strength the strongest such events in recent history which took place in 1972-1973, 1982-1983 and 1997-1998. This type of natural phenomenon features warmer-than-normal sea surface temperatures in the tropical Pacific Ocean while its counterpart called La Nina is correlated with colder-than-normal waters. Given the fact that the Pacific Ocean is by far the world’s largest, an El Nino can have significant ramifications on weather and climate in many parts of the world; especially, one that is strengthening into a such a strong event.

In the past 60 days, warmer-than-normal sea surface temperature anomalies (orange area) have spread westward from the west coast of South America into the central equatorial Pacific Ocean. Computer forecast models are in general agreement that this strengthening trend in the El Nino will continue for the next few months perhaps then followed by some weakening at the end of the year or early in 2016. Meanwhile, as El Nino intensifies in the equatorial Pacific Ocean, colder-than-normal sea surface temperatures have expanded significantly in the northwestern part of the Pacific Ocean as well as across the northern Atlantic Ocean (not shown) and this, in many ways, is equally as impressive as to what is occurring in the tropics.

Ramifications of a strong El Nino

The tropical region of the Pacific Ocean is perhaps the most important section of any ocean across the world in terms of weather and climate and strong El Nino conditions can have the following ramifications around the globe:

1) An El Nino in the summertime typically results in below-normal activity in the tropical Atlantic Ocean as it tends to generate stronger-than-normal upper level winds which act to suppress "African-wave" storm development. So far, the Atlantic tropical season has underperformed and that overall trend should continue.

2) An El Nino in the summertime typically results in normal-to-cooler-than normal temperatures across the Midwest and Northeast US. In fact, temperatures through the halfway point of summer have been relatively close-to-normal in the Mid-Atlantic’s I-95 corridor and longer term forecasts suggests a continuation of relatively moderate conditions well into the month of August.

[Note – both items 1 and 2 are described in detail in Vencore Weather’s 2015 Tropical Outlook: http://vencoreweather.com/2015/05/05/1000-am-2015-tropical-and-mid-atlantic-summertime-outlooks/]

3) An El Nino is likely to result in more rainfall compared to normal in the Southwest US which should alleviate drought conditions in California during the next 6-12 months or so. In fact, a significant rain event pounded southern California last weekend as the remains of a Pacific Ocean tropical system – aided by El Nino conditions - pushed into that region of the country.

[Oceanic Nino Index (ONI) values since 2000 (red=El Nino, blue=La Nina, black=neutral); courtesy NOAA]

4) An El Nino is likely to cause a spike in global temperatures. The table (above) lists the monthly “Oceanic Nino Index” since the year 2000 with El Nino events in red and La Nina conditions in blue. The last two El Nino events were rather moderate by comparison to the current one and both resulted in a short-term spike in global temperatures.

In the plot below, global temperature anomalies shown back to the year 2005 are in a jagged, but generally downward trend (data courtesy Ryan Maue, WeatherBell Analytics, Inc.). The circled areas (below) show the global temperature spikes associated with the most recent two El Nino events that occurred in 2006-2007 and 2009-2010. An important finding also revealed by this plot is that each of these two "El-Nino-induced" spikes was followed quickly by a sharp drop in global temperatures once the El Nino conditions subsided - and it is quite likely that the same thing will occur following this current El Nino.

[Global temperature anomalies from 2005 through today using NOAA's CFSR/CVSv2 data; data courtesy Ryan Maue at WeatherBell Analytics, weatherbell.com]