Average sea surface temperature departure from the 1981-2010 average over the four weeks ending on 7 November 2015. Data are from NCEP-NCAR reanalysis. Graphic: climate.gov

By Rong-Gong Lin II and Rosanna Xia
17 November 2015 (Los Angeles Times) – Temperatures in a key location of the Pacific Ocean are now hotter than they ever were in the record 1997 El Niño. Some scientists say the readings show that this year’s El Niño could be among the most powerful on record — and even topple the 1997 El Niño from its pedestal. “This thing is still growing and it’s definitely warmer than it was in 1997,” said Bill Patzert, climatologist with NASA’s Jet Propulsion Laboratory in La Cañada Flintridge. As far as the temperature readings go, “it’s now bypassed the previous champ of the modern satellite era — the 1997 El Niño has just been toppled by 2015.” Daniel Swain, a climate scientist at Stanford University, called the temperature reading significant. It is the highest such weekly temperature above the average in 25 years of modern record keeping in this key region of the Pacific Ocean west of Peru. “This is a very impressive number,” Swain said, adding that data suggest that this El Niño is still warming up. “It does look like it’s possible that there’s still additional warming” to come. “We’re definitely in the top tier of El Niño events,” Swain said. Temperatures in this key area of the Pacific Ocean rose to 5.4 degrees Fahrenheit above average for the week of Nov. 11. That exceeds the highest comparable reading for the most powerful El Niño on record, when temperatures rose 5 degrees Fahrenheit above the average the week of Thanksgiving in 1997. The 5.4 degree Fahrenheit recording above the average temperature is the highest such number since 1990 in this area of the Pacific Ocean, according to the National Weather Service. […] The 1997 El Niño has been considered the strongest such event since the 1950s. The modern era of El Niño tracking came after the 1982-83 event, which came as a surprise and is considered the second strongest on record. The 1997 El Niño was considered so strong and that scientists have been impressed that this El Niño could top that event. […] “It’s not as if we’re waiting for El Niño to actually manifest itself — it has in many ways already,” Patzert said. “There is no doubt: It’s coming.” [more]

El Niño could be the most powerful on record, scientists say Monthly precipitation departure from the long-term average in Africa during October 2015. Data are from the CPC ARC2. Graphic: climate.gov

By Emily Becker
12 November 2015 (climate.gov) – The peak of our current El Niño is expected to occur in the next month or so … but what does that mean? We measure El Niño events by how much warmer the surface waters in a specific region of the equatorial Pacific are, compared to their long-term average. The difference from average is known as the “anomaly,” and we use the average anomaly in the Niño3.4 region as our primary index for El Niño. When the index in this region is at its highest, we have our peak El Niño. However, El Niño-related impacts have been occurring around the globe for months already, and will continue for several months after the warmest temperatures occur in the tropical Pacific Ocean. For example, during the 1997-98 El Niño, the Niño3.4 Index peaked at 2.33°C in November (using ERSSTv4 data, the official dataset for measuring El Niño), and the most substantial U.S. effects occurred through the early spring of 1998. A bit later in this post, we’ll take a look at what’s been going on so far this year. The atmospheric response to the warmer waters is going strong. The Walker Circulation (tropical near-surface winds blowing from east to west, and upper-level winds blowing from west to east) is substantially weakened, as we expect during a strong El Niño. In case you’re unimpressed by a 2°C (3.6°F) change, let’s do a little math. The area covered by the Niño3.4 region is a little more than 6 million square kilometers (2.4 million square miles). One cubic meter of water weighs 1,000 kg. So the top two meters (6.6 feet) of the Niño3.4 region contains about 12 quadrillion kilograms (about 13.6 trillion tons) of water. The energy required to raise one kilogram of water one degree Celsius (the “specific heat”) is 4.19 kilojoules. A 2°C increase in just the top two meters of the Niño3.4 region adds up to an extra 100 quadrillion kilojoules (95 quadrillion BTUs), about equal to the annual energy consumption of the U.S.!

Who’s feeling the effects?

In the U.S., the season of strongest El Niño impacts is December through March. While we’re waiting to see what the strong 2015-16 El Niño brings us, we’ll look around a few other corners of the world to see what’s happened so far. El Niño has substantial impacts in two regions of Africa. I checked in with the Climate Prediction Center’s International Desk to see what’s been going on. In East Africa, including Ethiopia, Somalia, Kenya, Tanzania, Uganda, Burundi, and Rwanda, the primary impact season is October–December, when El Niño tends to enhance the ”short rains” rainy season (the “long rains” season, which is much less ENSO-sensitive, is March-May), leading to wetter conditions. Over the last month, rain has begun to increase across much of the area, and some flooding has been seen in Somalia. Short-term forecasts suggest the wetter conditions should continue through the next few weeks, at least. Southern Africa, including Zimbabwe, Botswana, Namibia, Angola, South Africa, Lesotho, Swaziland, and the southern half of Mozambique, tends to see a drier December–February during an El Niño. Areas of this region, especially South Africa, are very dry right now, after a failed monsoon last year. Another dry year would place more stress on water availability. You can check out recent rainfall conditions in Africa here, and see climate model forecasts for the continent here. In a couple of short sentences, here are some huge impacts: El Niño-related dry conditions in Indonesia have set the stage for devastating fires, and the region is experiencing the greatest number of forest fires since 1997. Also, all the extra warm waters associated with this El Niño are placing heat stress on sea life, and an intense coral bleaching event is underway. El Niños tend to enhance the hurricane season in the Pacific, and depress the Atlantic hurricane season. Phil Klotzbach of Colorado State University had this to say about the wild Pacific hurricane season: “So far this year, there have been a total of 21 Category 4 and 5 storms in the North Pacific, shattering the old record of 17, set in 1997.  The North Central Pacific region (140-180W) has shattered records for most named storms, hurricanes, and major hurricanes tracking through the 140-180W region.” According to Lindsey Long of the Climate Prediction Center, the Atlantic season has been fairly quiet, although the number of named storms has been close to average, at 11 storms so far (including Kate, which formed on Monday). The average is about 12 … but the overall activity of this storm season (the combined strength and duration of all storms, measured as the Accumulated Cyclone Energy (ACE) has been less than 60% of average, and we’ve had 3 hurricanes, half the average number of 6. We won’t know until next spring what exact impact this El Niño will have on the U.S., but it is already making its presence felt around the world. (1) Note that CPC subtracts past 30-year “normals” from the current sea surface value to obtain the Nino-3.4 anomaly values, and the “normals” are updated every five years. Therefore, the long-term trends are removed.  These monthly values are averaged together to obtain our Oceanic Niño Index [ONI].

November El Niño update: It’s a small world