
As America is battered by storms, the effects of El Niño are clearly being felt.

And there could be more to come, say forecasters, who admit we are now in uncharted territory with the phenomenon.

'If past events help predict future ones, then we have probably reached the peak of the 2015–2016 El Niño,' the space agency said.

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The data maps compare sea surface heights in the Pacific Ocean as measured by NASA on January 17, 2015, before the event began, and on January 18, 2016. Note that the January 2015 map shows remnants of a weak 2014 El Niño event that kick-started the intense 2015–2016 event.

WHAT IS EL NIÑO? El Niño is caused by a shift in the distribution of warm water in the Pacific Ocean around the equator. Usually the wind blows strongly from east to west, due to the rotation of the Earth, causing water to pile up in the western part of the Pacific. This pulls up colder water from the deep ocean in the eastern Pacific. However, in an El Niño, the winds pushing the water get weaker and cause the warmer water to shift back towards the east. This causes the eastern Pacific to get warmer. But as the ocean temperature is linked to the wind currents, this causes the winds to grow weaker still and so the ocean grows warmer, meaning the El Niño grows. This change in air and ocean currents around the equator can have a major impact on the weather patterns around the globe by creating pressure anomalies in the atmosphere Advertisement

'Warmer-than-average waters in the eastern tropical Pacific Ocean should start to cool off and shift westward.

'By summer, the tropical Pacific might be back in a neutral state or La Niña cooling could kick in, as it did after major El Niños of the past.

'But will the ocean respond in 2016 the way it did in 1998 and 1983? Given that the planet is hotter than at any time in the past 135 years, there are no guarantees.'

According to researchers from the National Oceanic and Atmospheric Administration, water temperatures in the Niño3.4 region of the tropical Pacific—an area that is usually the focal point of such events—broke a record in December 2015.

Sea surface temperatures averaged 2.38° Celsius above the norm, surpassing December 1997, which was 2.24°C above normal.

For October through December 2015, the three-month temperature average for the Niño3.4 region was equal to the record high from the same months in 1997.

The measurements come from the altimeter on the Jason-2 satellite and show averaged sea surface height anomalies.

Shades of red indicate where the ocean stood higher than the normal sea level; warmer water expands to fill more volume.

Shades of blue show where sea level and temperatures were lower than average (water contraction).

Normal sea-level conditions appear in white.

In its January 14 update, NOAA's Climate Prediction Service stated: 'A strong El Niño continued during December, with well above-average sea surface temperatures across the central and eastern equatorial Pacific Ocean...El Niño has already produced significant global impacts and is expected to affect temperature and precipitation patterns across the United States during the upcoming months...Most models indicate that a strong El Niño will weaken with a transition to ENSO-neutral during the late spring or early summer.'

Tony Busalacchi, an oceanographer at the University of Maryland, said that precipitation has so far 'followed the classic El Niño patterns' observed in the 1997–98 and 1982–83 events.

For instance, in the southern United States, the winter has been cooler than normal and quite wet.

The Pacific Northwest has also been soaked by rain and snow storms.

Across the Pacific, Indonesia and other areas have been dry.

'It has been another 'event of the century' much like the one we just had in 97–98.

The question is: will this event bring California and other western areas out of drought? And how quickly will we flip into La Niña?'

Bill Patzert, a climatologist at NASA's Jet Propulsion Laboratory, sees the potential for a second peak for this El Niño.

How el Nino developed: The maps show conditions in the middle of each of the past 13 months as El Niño has developed.

He points to a recent relaxation in the trade winds and a west wind burst that could refuel the warming trend in the eastern Pacific.

Weaker trade winds in the eastern Pacific allow west wind bursts to push warm waters toward the Americas. (Click here to watch Kelvin waves propagating across the ocean.)

Patzert suspects February and March 2016 could still be very active months for El Niño-driven weather along the western coasts of the Americas.

Forecasters have previously revealed the catastrophic effects this year's record breaking El Niño has had on weather around the world.

They say that even though they expect the sea surface temperature anomalies in the tropical Pacific to decrease gradually over the next several months, 'there is still a lot going on'.

For America, they warn the effect is 'just beginning'.

'El Niño put up some pretty impressive numbers in December, and we're favouring a transition to neutral conditions by the late spring or early summer.' Emily Becker of the NOAA said.

The Niño3.4 index, which compares ocean surface temperatures in the east-central Pacific to the long-term average, broke the record in December, coming in at 2.38°C above average, surpassing December 1997's 2.24°C.

'The main season for El Niño impacts in the U.S. (January–March) is just beginning in the U.S., but it's winding down in other areas of the world,' Becker said.

El Niño around the world: During an episode, areas in green or yellow are likely to become wetter or dryer than normal during the indicated months.

Australia's typical El Niño impact is dry conditions over most of the continent from about July through December, but through this period there hasn't been a very clear deficit except in portions of eastern Australia.

It's possible that a record warm Indian Ocean had a strong effect on the climate in Australia this year, a reminder that the climate system has a lot of moving parts, and impacts from El Niño are expected, but not guaranteed.

That said, in other areas of the world, El Niño impacts were clearer. Much more rain than normal fell in eastern Africa, as their 'short rains' rainy season (October–December) was enhanced by El Niño, while southern Africa has had continued dry conditions. Uruguay, southern Brazil, and Paraguay also experienced a lot of rain, and northern South America has been dry, as often happens in September–December during El Niño.

Forecasters expect the sea surface temperature anomalies in the tropical Pacific to decrease gradually over the next several months, and we're favouring a transition to neutral conditions by the late spring or early summer.

Meteorologists say the current El Nino has stormed its way into the record books, tying 1997-1998 as the strongest recorded.

Mike Halpert, deputy director of the federal Climate Prediction Center, said initial figures for October-November-December match the same time period in 1997 for the strongest El Nino.

Meteorologists measure El Nino based on how warm parts of the central Pacific for three consecutive months.

Records go back to 1950.

El Nino is the natural warming of the central Pacific that changes weather worldwide, including bringing more rain to California.

Halpert said what really matters is what El Nino does during January, when its impact peaks.

Weather Underground meteorology director Jeff Masters said 'Darth Nino may finally have California in its sights,' as a series of storms may dent record drought.

This Jason-2 image shows that the amount of extra-warm surface water from the current El Niño (depicted in red and white shades) has continuously increased, especially in the eastern Pacific within 10 degrees latitude north and south of the equator. In the western Pacific, the area of low sea level (blue and purple) has decreased somewhat from late October. The white and red areas indicate unusual patterns of heat storage. In the white areas, the sea surface is between 6 and 10 inches (15 to 25 centimeters) above normal, while in the red areas, it is about 4 inches (10 centimeters) above normal. The green areas indicate normal conditions. The height of the ocean water relates, in part, to its temperature, and is an indicator of the amount of heat stored in the ocean below.

The current strong El Niño brewing in the Pacific Ocean shows no signs of waning, new Nasa images have revealed.

'El Niño 2015 has already created weather chaos around the world,' Nasa said.

'Over the next few months, forecasters expect the United States to feel its impacts as well.'

The latest Jason-2 image bears a striking resemblance to one from December 1997, by Jason-2's predecessor, the Nasa /Centre National d'Etudes Spatiales (CNES) Topex/Poseidon mission, during the last large El Niño event.

The images show nearly identical, unusually high sea surface heights along the equator in the central and eastern Pacific: the signature of a big and powerful El Niño.

Higher-than-normal sea surface heights are an indication that a thick layer of warm water is present.

El Niños are triggered when the steady, westward-blowing trade winds in the Pacific weaken or even reverse direction, triggering a dramatic warming of the upper ocean in the central and eastern tropical Pacific.

Clouds and storms follow the warm water, pumping heat and moisture high into the overlying atmosphere.

These changes alter jet stream paths and affect storm tracks all over the world.

El Ninio in the ocean: Blue shading shows areas where more clouds than average were present, indicated by greater-than-average absorption of surface OLR (less OLR exiting the top of the atmosphere). Climate.gov figure from CPC data.

This year's El Niño has caused the warm water layer that is normally piled up around Australia and Indonesia to thin dramatically, while in the eastern tropical Pacific, the normally cool surface waters are blanketed with a thick layer of warm water.

This massive redistribution of heat causes ocean temperatures to rise from the central Pacific to the Americas.

It has sapped Southeast Asia's rain in the process, reducing rainfall over Indonesia and contributing to the growth of massive wildfires that have blanketed the region in choking smoke.

El Niño is also implicated in Indian heat waves caused by delayed monsoon rains, as well as Pacific island sea level drops, widespread coral bleaching that is damaging coral reefs, droughts in South Africa, flooding in South America and a record-breaking hurricane season in the eastern tropical Pacific.

THE 2008 El NINO: A 'WILD RIDE' While scientists still do not know precisely how the current El Niño will affect the United States, the last large El Niño in 1997-98 was a wild ride for most of the nation. The 'Great Ice Storm' of January 1998 crippled northern New England and southeastern Canada, but overall, the northern tier of the United States experienced long periods of mild weather and meager snowfall. Meanwhile, across the southern United States, a steady convoy of storms slammed most of California, moved east into the Southwest, drenched Texas and -- pumped up by the warm waters of the Gulf of Mexico - wreaked havoc along the Gulf Coast, particularly in Florida. Advertisement

Around the world, production of rice, wheat, coffee and other crops has been hit hard by droughts and floods, leading to higher prices.

In the United States, many of El Niño's biggest impacts are expected in early 2016.

Forecasters at the National Oceanic and Atmospheric Administration favor an El Niño-induced shift in weather patterns to begin in the near future, ushering in several months of relatively cool and wet conditions across the southern United States, and relatively warm and dry conditions over the northern United States.

'In 2014, the current El Niño teased us -- wavering off and on,' said Josh Willis, project scientist for the Jason missions at JPL.

'But in early 2015, atmospheric conditions changed, and El Niño steadily expanded in the central and eastern Pacific.

'Although the sea surface height signal in 1997 was more intense and peaked in November of that year, in 2015, the area of high sea levels is larger.

'This could mean we have not yet seen the peak of this El Niño.'

During normal, non-El Niño conditions, the amount of warm water in the western equatorial Pacific is so large that sea levels are about 20 inches (50 centimeters) higher in the western Pacific than in the eastern Pacific. 'You can see it in the latest Jason-2 image of the Pacific,' said Willis.

'The 8-inch [20-centimeter] drop in the west, coupled with the 10-inch [25-centimeter] rise in the east, has completely wiped out the tilt in sea level we usually have along the equator.'

The new Jason-2 image shows that the amount of extra-warm surface water from the current El Niño (depicted in red and white shades) has continuously increased, especially in the eastern Pacific within 10 degrees latitude north and south of the equator.

In the western Pacific, the area of low sea level (blue and purple) has decreased somewhat from late October.

The white and red areas indicate unusual patterns of heat storage.

In the white areas, the sea surface is between 6 and 10 inches (15 to 25 centimeters) above normal, while in the red areas, it is about 4 inches (10 centimeters) above normal.

The green areas indicate normal conditions. The height of the ocean water relates, in part, to its temperature, and is an indicator of the amount of heat stored in the ocean below.

Within this area, surface temperatures are greater than 86 degrees Fahrenheit (30 degrees Celsius) in the central equatorial Pacific and near 70 degrees Fahrenheit (21 degrees Celsius) off the coast of the Americas.

This El Niño signal encompasses a surface area of 6 million square miles (16 million square kilometers) - more than twice as big as the continental United States.

While no one can predict the exact timing or intensity of U.S. El Niño impacts, for drought-stricken California and the U.S. West, it's expected to bring some relief.

'The water story for much of the American West over most of the past decade has been dominated by punishing drought,' said JPL climatologist Bill Patzert.

'Reservoir levels have fallen to record or near-record lows, while groundwater tables have dropped dangerously in many areas.

'Now we're preparing to see the flip side of nature's water cycle -- the arrival of steady, heavy rains and snowfall.'

In 1982-83 and 1997-98, large El Niños delivered about twice the average amount of rainfall to Southern California, along with mudslides, floods, high winds, lightning strikes and high surf. But Patzert cautioned that El Niño events are not drought busters.

'Over the long haul, big El Niños are infrequent and supply only seven percent of California's water,' he said.

'Looking ahead to summer, we might not be celebrating the demise of this El Niño,' cautioned Patzert.

'It could be followed by a La Niña, which could bring roughly opposite effects to the world's weather.'

La Niñas are essentially the opposite of El Niño conditions. During a La Niña episode, trade winds are stronger than normal, and the cold water that normally exists along the coast of South America extends to the central equatorial Pacific.

La Niña episodes change global weather patterns and are associated with less moisture in the air over cooler ocean waters.

This results in less rain along the coasts of North and South America and along the central and eastern equatorial Pacific, and more rain in the far Western Pacific.

El Niño events are part of the long-term, evolving state of global climate, for which measurements of sea surface height are a key indicator.

Global temperatures have already smashed records this year, and now meteorologists are warning 2016 will be even hotter.

The annual global temperature forecast from the Met Office suggests 2016 will be between 0.72°C and 0.95°C above the long-term average of 14°C.

Man-made global warming, along with a smaller effect from the natural El Niño phenomenon in the Pacific, are expected to push temperatures towards record levels next year.

Professor Chris Folland, Met Office research fellow, said: '2015 is on track to be the warmest year on record, and this forecast suggests 2016 is likely to be as warm, if not warmer.'

The forecast for 2016 is higher than the predictions for 2015 made a year ago, which suggested temperatures would be 0.52°C to 0.76°C above the 1961 to 1990 long-term average.

The latest data for 2015 suggests it is 0.72°C above the average, making it the hottest year on record.

With 2014 also one of the hottest on record, Professor Adam Scaife, head of long range prediction at the Met Office, said: 'This forecast suggests that by the end of 2016 we will have seen three record, or near-record, years in a row for global temperatures.'

The Met Office said it does not expect the record-breaking run to continue indefinitely, but it shows how global warming can combine with smaller, natural fluctuations such as El Nino to push the climate to unprecedented levels of warmth.

Experts previously warned global average surface temperatures in 2015 are likely to reach what they call the 'symbolic and significant milestone' of 1°C (33°F) above the pre-industrial era.