Question: Which phenomenon that is associated with a band of warm ocean water that develops in the central and east-central equatorial Pacific, was cited as the cause for the 2016 Vietnam floods?

Context paragraphs:
Ocean color: The "color" of the ocean is determined by the interactions of incident light with substances or particles present in the water.  White light from the sun is made up of a combination of colors, which are broken apart by water droplets in a ‘rainbow’ spectrum.  Large quantities of water, even in a swimming pool, would appear blue as well.  When light hits the water surface, the different colors are absorbed, transmitted, scattered, or reflected in differing intensities by water molecules and other so-called optically-active constituents in suspension in the upper layer of the ocean.  The reason open ocean waters often appear blue is due to the absorption and scattering of light.  The blue wavelengths of light are scattered, similar to the scattering of blue light in the sky but absorption is a much larger factor than scattering for the clear ocean water.  In water, absorption is strong in the red and weak in the blue, thus red light is absorbed quickly in the ocean leaving blue.  Almost all sunlight that enters the ocean is absorbed, except very close to the coast.  The red, yellow, and green wavelengths of sunlight are absorbed by water molecules in the ocean.  When sunlight hits the ocean, some of the light is reflected back directly but most of it penetrates the ocean surface and interacts with the water molecules that it encounters.  The red, orange, yellow, and green wavelengths of light are absorbed so that the remaining light we see is composed of the shorter wavelength blues and violets.

Deep ocean water: Deep ocean water (DOW) is the name for cold, salty water found deep below the surface of Earth's oceans.  Ocean water differs in temperature and salinity.  Warm surface water is generally saltier than the cooler deep or polar waters; in polar regions, the upper layers of ocean water are cold and fresh.  Deep ocean water makes up about 90% of the volume of the oceans.  Deep ocean water has a very uniform temperature, around 0-3 °C, and a salinity of about 3.5% or as oceanographers state as 35 ppt (parts per thousand).

High-Nutrient, low-chlorophyll: High-nutrient, low chlorophyll (HNLC) is a term used in marine ecology to describe areas of the ocean where the number of phytoplankton (standing stock) are low and fairly constant in spite of high macro-nutrient concentrations (nitrate, phosphate, silicic acid).  In general, some essential inorganic substances like nitrate may be present in oceanic waters in concentrations low enough to be limiting to plant production, but in HNLC regions the level of nitrate is never significantly depleted.  Instead, these regions are limited by low concentrations of metabolizable iron.  There are two popular explanations for the existence of HNLC regions: the iron hypothesis and the ‘grazing control hypothesis'.  HNLC regions cover 20% of the world’s oceans in three major areas: equatorial Pacific Ocean, subarctic Pacific Ocean and the Southern Ocean.

2008 Vietnam floods: The 2008 Vietnam floods affected north and central Vietnam, as well as southern parts of the People's Republic of China after three days of heavy raining.  The rainfall, which began October 30, is the heaviest in 24 years, a state meteorological official told the Vietnam News Agency, and were the worst floods in Hanoi since 1984.  At least 66 in Vietnam and 34 in China have been killed because of the flooding.  Overall, 15,000 families evacuated their homes, and almost 100 schools, 100,000 houses, 241,000 hectares of crops, and 25,400 hectares of fish farms were submerged or damaged in the floodwaters.

Tropical Warm Pool: The Tropical Warm Pool (TWP) or Indo-Pacific Warm Pool is a mass of ocean water located in the western Pacific Ocean and eastern Indian Ocean which Consistently exhibits the highest water temperatures over the largest expanse of the Earth's surface.  Its intensity and extent appear to oscillate over a time period measured in decades.

El Niño: El Niño (] ) is the warm phase of the El Niño Southern Oscillation (commonly called ENSO) and is associated with a band of warm ocean water that develops in the central and east-central equatorial Pacific (between approximately the International Date Line and 120°W), including off the Pacific coast of South America.  El Niño Southern Oscillation refers to the cycle of warm and cold temperatures, as measured by sea surface temperature, SST, of the tropical central and eastern Pacific Ocean.  El Niño is accompanied by high air pressure in the western Pacific and low air pressure in the eastern Pacific.  The cool phase of ENSO is called "La Niña" with SST in the eastern Pacific below average and air pressures high in the eastern and low in western Pacific.  The ENSO cycle, both El Niño and La Niña, cause global changes of both temperatures and rainfall.

2016 Vietnam floods: The 2016 Vietnam floods affected central Vietnam, resulting in estimated 27.000 thousands of homes entirely submerged by rising water.  Meteorologists cited the 2016 Asian monsoon, among the strongest in years, and the El Niño as the cause.  The last time the area was heavily flooded was during the 2008 Vietnam floods.

2014–16 El Niño event: The 2014–16 El Niño was a warming of the eastern equatorial Pacific Ocean that resulted in unusually warm waters developing between the coast of South America and the International Date Line.  These unusually warm waters influenced the world's weather in a number of ways, which in turn significantly affected various parts of the world.  These included drought conditions in Venezuela, Australia and a number of Pacific islands while significant flooding was also recorded.  During the event more tropical cyclones than normal occurred within the Pacific Ocean, while fewer than normal occurred in the Atlantic Ocean.

Westerly wind burst: A westerly wind burst is a phenomenon commonly associated with El Niño events whereby the typical east-to-west trade winds across the equatorial Pacific shift to west-to-east.  A westerly wind burst is defined by Harrison and Vecchi (1997) as sustained winds of 25 km/h over a period of 5–20 days.  However, no concrete definition has been determined, with Tziperman and Yu (2007) defining them as having winds of 14 km/h and lasting "at least a few days".  On average, three of these events take place each year, but are significantly more common during El Niño years.  They have been linked to various mesoscale phenomena, including tropical cyclones, mid-latitude cold surges, and the Madden–Julian oscillation.  Their connection with Kelvin waves also indicate a connection with the onset of El Niño events, with every major occurrence since the 1950s featuring a westerly wind burst upon their onset.

Caribbean Current: The Caribbean Current is a warm ocean current that transports significant amounts of water and flows northwestward through the Caribbean from the east along the coast of South America and into the Gulf of Mexico.  The current results from the flow of the Atlantic South Equatorial Current as it flows north along the coast of Brazil.  As the current turns north through the Yucatán Channel, it is renamed the Yucatán Current.  The Caribbean Current water comes from the Atlantic Ocean via the North Equatorial, North Brazil, and Guiana Currents.  The circulation of the Columbia-Panama Gyre flows counter-clockwise to the Caribbean Current.

Supporting paragraphs: 2016 Vietnam floods El Niño
Answer: El Niño