El Niño

What is El Niño

Today, the term El Niño refers to the warming of the ocean surface or above-average sea surface temperatures in the central and eastern tropical Pacific Ocean. This warming causes a shift in the atmospheric circulation with rainfall becoming reduced over Indonesia and Australia, while rainfall and tropical cyclone formation increases over the tropical Pacific Ocean. The low-level surface trade winds either weaken or start blowing from the other direction, i.e. from west to east along the equator.

El Niño events are thought to have been occurring for thousands of years. Modern day research techniques have managed to find at least 30 El Niño events since 1900, strongest being ones in 1982-1983, 1997-1998 and 2014-2016. Each country has a different threshold for what is classified as an El Niño event.

There is no consensus on if climate change will have any effect on the occurrance, strength and duration of El Niño events. The anomaly usually happens at irregular intervals of two to seven years, and lasts nine months to two years. Average period length is five years. Every El Niño is different in terms of its magnitude and duration.

El Niño results from interaction between the surface layers of the ocean and the overlying atmosphere in the tropical Pacific. This is a very complicated process and involves unstable air-sea interaction and planetary-scale oceanic waves.

El Niño is detected using several methods, which include in-situ observing systems (buoys) and distance monitoring by satellites. Very complex computer models of the global ocean and atmosphere then use this data to predict El Niño.

  • El Niño conditions - warming occurs seven to nine months
  • El Niño episode - warming occurs more than nine months

Normal Conditions

  • trade winds blow from east to west along the equator, from south america to asia, in the tropical pacific ocean
  • sea surface temperature is approximately 8°c (14°f) warmer off the coast of asia than in the eastern pacific
  • clouds and rainfall are found in rising air over the warmest water near asia
  • east pacific is relatively dry

El Niño Conditions

  • trade winds relax in the central and western pacific, i.e. weakening of easterly trade winds
  • rainfall follows the warm water eastward, with associated flooding in peru, increased rainfall across the southern tier of the us, drought in indonesia and devastating fires in australia
  • large changes in the global atmospheric circulation

Effects of El Niño

  • Africa - east africa experiences wetter-than-normal conditions from march to may and drier conditions than normal from december to february in south-central africa
  • Asia - extensive drought in the western pacific and rainfall in the normally dry eastern pacific
  • Europe - effects are controversial, complex and difficult to analyze
  • North America - effects most pronounced from October to March. Majority of Canada has a milder winter and spring (except eastern Canada, where there is no significant impact). In the US, wetter conditions are observed along the Gulf Coast between Texas and Florida, drier conditions are observed in Hawaii, the Ohio Valley, Pacific Northwest and the Rocky Mountains. Wetter weather in California and South-West depends on the strength of that particulat El Niño.
  • South America - increased rainfall across the east-central and eastern Pacific Ocean, including parts of South American west coast. Effects are stronger than in the North America and include warm and very wet weather between April and October along the coasts of northern Peru and Ecuador (usually resulting in major flooding). Also, reduction in upwelling of cold, nutrient-rich water leads to fish kills off the shore of Peru and the local fishing industry can suffer severely. Southern Brazil and northern Argentina also experience wetter conditions, usually during the spring and early summer. Central Chile receives a mild winter with lot of rainfall. Drier and hotter weather occurs in parts of the Amazon River Basin, Colombia and Central America.

Current State

El Niño has transitioned to ENSO-neutral, which is most likely to continue through Northern Hemisphere winter 2019-20 (50-55% chance).

Historical Data

Warm (red) and cold (blue) periods based on a threshold of +/- 0.5oC for the Oceanic Niño Index (ONI) [3 month running mean of ERSST.v4 SST anomalies in the Niño 3.4 region (5oN-5oS, 120o-170oW)], based on centered 30-year base periods updated every 5 years.

Year

DJF

JFM

FMA

MAM

AMJ

MJJ

JJA

JAS

ASO

SON

OND

NDJ

1950-1.5-1.3-1.2-1.2-1.1-0.9-0.5-0.4-0.4-0.4-0.6-0.8
1951-0.8-0.5-0.20.20.40.60.70.91.01.21.00.8
19520.50.40.30.30.20.0-0.10.00.20.10.00.1
19530.40.60.60.70.80.80.70.70.80.80.80.8
19540.80.50.0-0.4-0.5-0.5-0.6-0.8-0.9-0.8-0.7-0.7
1955-0.7-0.6-0.7-0.8-0.8-0.7-0.7-0.7-1.1-1.4-1.7-1.5
1956-1.1-0.8-0.6-0.5-0.5-0.5-0.6-0.6-0.5-0.4-0.4-0.4
1957-0.20.10.40.70.91.11.31.31.31.41.51.7
19581.81.71.30.90.70.60.60.40.40.40.50.6
19590.60.60.50.30.2-0.1-0.2-0.3-0.10.00.00.0

Year

DJF

JFM

FMA

MAM

AMJ

MJJ

JJA

JAS

ASO

SON

OND

NDJ

1960-0.1-0.1-0.10.00.00.00.10.20.30.20.10.1
19610.00.00.00.10.20.30.1-0.1-0.3-0.3-0.2-0.2
1962-0.2-0.2-0.2-0.3-0.3-0.20.0-0.1-0.1-0.2-0.3-0.4
1963-0.4-0.20.20.30.30.50.91.11.21.31.41.3
19641.10.60.1-0.3-0.6-0.6-0.6-0.7-0.8-0.8-0.8-0.8
1965-0.6-0.3-0.10.20.50.81.21.51.92.02.01.7
19661.41.21.00.70.40.20.20.1-0.1-0.1-0.2-0.3
1967-0.4-0.5-0.5-0.4-0.20.00.0-0.2-0.3-0.4-0.3-0.4
1968-0.6-0.7-0.6-0.40.00.30.60.50.40.50.71.0
19691.11.10.90.80.60.40.40.50.80.90.80.6

Year

DJF

JFM

FMA

MAM

AMJ

MJJ

JJA

JAS

ASO

SON

OND

NDJ

19700.50.30.30.20.0-0.3-0.6-0.8-0.8-0.7-0.9-1.1
1971-1.4-1.4-1.1-0.8-0.7-0.7-0.8-0.8-0.8-0.9-1.0-0.9
1972-0.7-0.40.10.40.70.91.11.41.61.82.12.1
19731.81.20.5-0.1-0.5-0.9-1.1-1.3-1.5-1.7-1.9-2.0
1974-1.8-1.6-1.2-1.0-0.9-0.8-0.5-0.4-0.4-0.6-0.8-0.6
1975-0.5-0.6-0.7-0.7-0.8-1.0-1.1-1.2-1.4-1.4-1.6-1.7
1976-1.6-1.2-0.7-0.5-0.30.00.20.40.60.80.90.8
19770.70.60.30.20.20.30.40.40.60.70.80.8
19780.70.40.1-0.2-0.3-0.3-0.4-0.4-0.4-0.3-0.10.0
19790.00.10.20.30.20.00.00.20.30.50.50.6

Year

DJF

JFM

FMA

MAM

AMJ

MJJ

JJA

JAS

ASO

SON

OND

NDJ

19800.60.50.30.40.50.50.30.0-0.10.00.10.0
1981-0.3-0.5-0.5-0.4-0.3-0.3-0.3-0.2-0.2-0.1-0.2-0.1
19820.00.10.20.50.70.70.81.11.62.02.22.2
19832.21.91.51.31.10.70.3-0.1-0.5-0.8-1.0-0.9
1984-0.6-0.4-0.3-0.4-0.5-0.4-0.3-0.2-0.2-0.6-0.9-1.1
1985-1.0-0.8-0.8-0.8-0.8-0.6-0.5-0.5-0.4-0.3-0.3-0.4
1986-0.5-0.5-0.3-0.2-0.10.00.20.40.70.91.11.2
19871.21.21.10.91.01.21.51.71.61.51.31.1
19880.80.50.1-0.3-0.9-1.3-1.3-1.1-1.2-1.5-1.8-1.8
1989-1.7-1.4-1.1-0.8-0.6-0.4-0.3-0.3-0.2-0.2-0.2-0.1

Year

DJF

JFM

FMA

MAM

AMJ

MJJ

JJA

JAS

ASO

SON

OND

NDJ

19900.10.20.30.30.30.30.30.40.40.30.40.4
19910.40.30.20.30.50.60.70.60.60.81.21.5
19921.71.61.51.31.10.70.40.1-0.1-0.2-0.3-0.1
19930.10.30.50.70.70.60.30.30.20.10.00.1
19940.10.10.20.30.40.40.40.40.60.71.01.1
19951.00.70.50.30.10.0-0.2-0.5-0.8-1.0-1.0-1.0
1996-0.9-0.8-0.6-0.4-0.3-0.3-0.3-0.3-0.4-0.4-0.4-0.5
1997-0.5-0.4-0.10.30.81.21.61.92.12.32.42.4
19982.21.91.41.00.5-0.1-0.8-1.1-1.3-1.4-1.5-1.6
1999-1.5-1.3-1.1-1.0-1.0-1.0-1.1-1.1-1.2-1.3-1.5-1.7

Year

DJF

JFM

FMA

MAM

AMJ

MJJ

JJA

JAS

ASO

SON

OND

NDJ

2000-1.7-1.4-1.1-0.8-0.7-0.6-0.6-0.5-0.5-0.6-0.7-0.7
2001-0.7-0.5-0.4-0.3-0.3-0.1-0.1-0.1-0.2-0.3-0.3-0.3
2002-0.10.00.10.20.40.70.80.91.01.21.31.1
20030.90.60.40.0-0.3-0.20.10.20.30.30.40.4
20040.40.30.20.20.20.30.50.60.70.70.70.7
20050.60.60.40.40.30.1-0.1-0.1-0.1-0.3-0.6-0.8
2006-0.8-0.7-0.5-0.30.00.00.10.30.50.70.90.9
20070.70.30.0-0.2-0.3-0.4-0.5-0.8-1.1-1.4-1.5-1.6
2008-1.6-1.4-1.2-0.9-0.8-0.5-0.4-0.3-0.3-0.4-0.6-0.7
2009-0.8-0.7-0.5-0.20.10.40.50.50.71.01.31.6

Year

DJF

JFM

FMA

MAM

AMJ

MJJ

JJA

JAS

ASO

SON

OND

NDJ

20101.51.30.90.4-0.1-0.6-1.0-1.4-1.6-1.7-1.7-1.6
2011-1.4-1.1-0.8-0.6-0.5-0.4-0.5-0.7-0.9-1.1-1.1-1.0
2012-0.8-0.6-0.5-0.4-0.20.10.30.30.30.20.0-0.2
2013-0.4-0.3-0.2-0.2-0.3-0.3-0.4-0.4-0.3-0.2-0.2-0.3
2014-0.4-0.4-0.20.10.30.20.10.00.20.40.60.7
20150.60.60.60.81.01.21.51.82.12.42.52.6
20162.52.21.71.00.50.0-0.3-0.6-0.7-0.7-0.7-0.6
2017-0.3-0.10.10.30.40.40.2-0.1-0.4-0.7-0.9-1.0
2018-0.9-0.8-0.6-0.4-0.10.10.10.20.40.70.90.8
20190.80.80.80.80.60.5

Source: NOAA, Wikipedia, livescience.com


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This wiki might help to use the full potential of Groenkloof weather website. The info section explains the hard and software and connections used.(In the menu bar under the sub menus Weather station and Groenkloof Weather) Weather data updates every minute.(for both the mobile and desktop sites) There is a mobile page with current conditions, forecast, forecast map, station history (with drop down menu for today, yesterday, month, year etc. showing all parameters) and lastly a graph with drop down menu for time period and parameter. (Very useful for quick references ) One can switch to the desktop page using the link in bottom right hand corner and vice versa. The desktop version is where very detailed weather info is available. ( Useful for more in depth detail ) It is divided in “blocks” The sunrise/sunset times and day length is shown. Moon with dates of full moon, new moon etc. The current block shows weather values in easy to read numerical format and updates every minute. “Live gauges” updates every minute and when the curser is hovered over a parameter it will show the min and max values and the time when this occurred. In the forecast maps one can use the menu bar top left of block to choose from windy or dark sky maps. Within the map one can choose from different parameters like wind, temperature, rain, thunder, clouds, pressure etc. Then station data is shown with now, max, min values and drop down menu for different time periods. There is also a history block where one can choose different parameters and a trends block with 1,3,6,12,24 hrs etc trends. Next is a forecast meteogram which is dynamic and moving the cursor over it will show all weather parameters at that point. Then easy to read forecast with dropdown the default using the Norwegian institute of meteorology values.(seems to be most accurate) Next is rainfall for today, this month, this year (from January) Drop down gives more options like seasonal(from September) etc. Rain balance is the stations values measured against 100 year rain data for Pretoria obtained from SA weather services. Next is graph with several drop down options and a day pie graph where one can pick dates and parameters. In extremes one can pick a parameter like absolute temperature, precipitation etc. to see max/min value dates and times. There is a air quality block click within block for more info. Map to show location of station. Webcam with view from Herbert Baker Street updates every 5 minutes. For aviation enthusiasts Cloud height time to sunset and density altitude. Then SA weather warnings from SA weather services, lightning detection and fire danger index. Followed by calendar, earthquakes and astronomical events. World weather...shows current conditions in few world cities. Database: data is stored every 5 mins and available data runs from January 2014. The menu at the top is really self explanotory and here there are countless information, statistics etc. Enjoy!! Leon :leonrossouw@me.com

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