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The South American Monsoon System Summary September 2015-May 2016

The South American Monsoon System Summary September 2015-May 2016. Prepared by Vernon E. Kousky Climate Prediction Center / NCEP June 2016. For more information, visit: http://www.cpc.ncep.noaa.gov/products/Global_Monsoons/American_Monsoons. Summary : Onset Phase.

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The South American Monsoon System Summary September 2015-May 2016

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  1. The South American Monsoon System SummarySeptember 2015-May 2016 Prepared by Vernon E. Kousky Climate Prediction Center / NCEP June 2016 For more information, visit:http://www.cpc.ncep.noaa.gov/products/Global_Monsoons/American_Monsoons

  2. Summary : Onset Phase • The rainy season onset phase (SON) featured: • Below-average rainfall over most of northern South America, the Amazon Basin, central and southeastern Brazil, with rainfall deficits exceeding 300 mm in many areas. • Above-average rainfall over central Colombia, most of southern Brazil and Paraguay, and portions of Uruguay and northeastern Argentina. • Strong El Niño conditions were present in the tropical Pacific.

  3. Summary : Mature Phase • The rainy season mature phase (DJF) featured: • Below-average rainfall over the Amazon Basin, most of central Brazil and portions of Southeast Brazil, with rainfall deficits greater than 400 mm in several areas. • Above-average rainfall over portions of Peru, Northeast Brazil, most of Paraguay, Uruguay, southern Brazil and northern and central Argentina. • Strong El Niño conditions were present in the tropical Pacific.

  4. Summary : Decay Phase • The rainy season decay phase (MAM) featured: • Below-average rainfall over central, Southeast and Northeast Brazil, southern Chile and southern Argentina, with deficits greater than 300 mm observed over portions of northern northeastern Brazil, and the Amazon Basin. • Above-average rainfall over portions of northern South America, Ecuador, extreme northern Peru, extreme southern Brazil, and Uruguay. • Weakening El Niño conditions were present in the tropical Pacific.

  5. General Summary • In general, below-average rainfall was observed over the Amazon Basin, and most of central and Northeast Brazil during September 2015-May 2016, with less than 50% of average precipitation in several areas. Above average rainfall occurred over Ecuador, Paraguay, Southern Brazil, Uruguay, and portions of central and northern Argentina. • Northern Northeast Brazil experienced its fifth consecutive year of drought conditions. • Southeast Brazil experienced below-average rainfall, but the deficit was much less than that observed during the 2014-2015 wet season, which was the driest September-May rainy season since the mid-1950s.

  6. Outline • Onset phase • Mature phase • Decay phase • Seasonal Departures from Average • Northeast Brazil drought • Southeast Brazil drought • Summary

  7. SAMS Core Region SAMS core region (Central Brazil – CBR)

  8. Precipitation Climatology ONSET DATES

  9. Precipitation Departures: Onset Phase (Sep-Nov 2015) During September-November 2015 rainfall was below average over most of northern South America, the Amazon Basin, central and southeastern Brazil, with rainfall deficits exceeding 300 mm in many areas. Above-average rainfall was observed over central Colombia, most of southern Brazil and Paraguay, and portions of Uruguay and northeastern Argentina.

  10. SON Historical Time Series for CBR Region 1981-2010 mean 2015

  11. SON Historical Time Series for CBR Region • 12 of the last 14 years have featured below-average precipitation over the CBR region during the onset phase of the SAMS wet season. • During SON 2015 total rainfall, as indicated in the CPC gridded analysis, was the lowest during the period of record (1979-2015). Rainfall during SON 2015 was about 60% of average (deficit ~150 mm).

  12. Tropical Pacific and Atlantic SST Anomalies (Sep-Nov 2015) During September–November 2015, SSTs were above average throughout the equatorial Pacific Ocean (180°W-80°W) (strong El Niño conditions). In the tropical Atlantic, SSTs were above average north of the equator and near average along and south of the Equator.

  13. Precipitation Departures: Mature Phase (Dec 2015-Feb 2016) During December 2015-February 2016 rainfall was below average over the Amazon Basin, most of central Brazil and portions of Southeast Brazil, with rainfall deficits greater than 400 mm in several areas. Above-average rainfall was observed over portions of Peru, Northeast Brazil, most of Paraguay, Uruguay, southern Brazil and northern and central Argentina.

  14. DJF Historical Time Series for CBR Region 1981-2010 mean

  15. DJF Historical Time Series for CBR Region • The last 12 years have featured near- or below-average precipitation over the CBR region during the mature phase of the SAMS wet season. • The lowest total in the period of record occurred in DJF 2014/15. Rainfall was about 65% of average (deficit ~290 mm). Rainfall during the DJF 2015/16 season was the second lowest total on record (deficit ~200 mm).

  16. Tropical Pacific and Atlantic SST Anomalies (Dec 2015-Feb 2016) During December 2015–February 2016, positive SST anomalies were observed throughout the equatorial Pacific (strong El Niño conditions). Over the Atlantic, equatorial SSTs were near or slightly above average.

  17. Precipitation Climatology END DATES

  18. Precipitation Departures: Decay Phase (Mar-May 2016) During March-May 2016 rainfall was below average over central, Southeast and Northeast Brazil, southern Chile and southern Argentina, with deficits greater than 300 mm observed over portions of northern northeastern Brazil, and the Amazon Basin. Above-average rainfall was observed over portions of northern South America, Ecuador, extreme northern Peru, extreme southern Brazil, and Uruguay.

  19. MAM Historical Time Series for CBR Region 1981-2010 mean

  20. MAM Historical Time Series for CBR Region • During the last 7 years rainfall has been below average over the CBR region during the decay phase of the SAMS wet season. • During MAM 2016, rainfall was less than 60% of average (deficit ~170 mm, the second driest MAM period on record).

  21. Tropical Pacific and Atlantic SST Anomalies (Mar-May 2016) During March-May 2016, equatorial SSTs were above average in the Pacific Ocean (weakening El Niño conditions). In the tropical Atlantic, SSTs were near or above average.

  22. Precipitation Departures: September 2015- May 2016 During September 2015 - May 2016 rainfall was below average over southern Venezuela, Brazil, north of 22⁰S, and southeastern Bolivia (percent of average less than 50% in several areas). Rainfall was above average over Paraguay, southern Brazil, Uruguay, and portions of central and northern Argentina.

  23. SONDJFMAM Historical Time Series for CBR Region 1981-2010 mean

  24. SONDJFMAM Historical Time Series for CBR Region • There has been a noticeable downward trend in precipitation over the CBR region during the SAMS wet season, especially since 2004. • Beginning in 2005 the gridded precipitation analyses have used only real-time station observations. • The number of real-time stations is considerably less than the number of historical stations available in making the gridded analyses for the period 1979-2005, especially in the CBR region. • Thus, the magnitude of the recent decrease in the CBR region is uncertain.

  25. Northeast Brazil Drought • During February-April 2016 rainfall was about 50% of the average in northern NE Brazil and about 26% of the average in southern Northeast Brazil. • Northern NE Brazil experienced its fifth consecutive drier than average February-May (see next slide).

  26. February-April Historical Time Series 1981-2010 mean 1981-2010 mean In NNE and SNE FMA 2012-2016 (red box) rank as the driest five consecutive FMA periods during 1979-2016.

  27. Southeast Brazil Drought • Rainfall during the peak of the 2015-2016 wet season (DJF) was greater than the previous three wet seasons, but still below the long-term average (see next slide). The region over Southeast Brazil (SEBR) selected for analysis is shown in this figure.

  28. Southeast Brazil Drought (DJF) Rainfall during the last seven DJF seasons has been below average, based on the CPC gridded analyses (1979/80 – present).

  29. Summary : Onset Phase • The rainy season onset phase (SON) featured: • Below average rainfall over most of northern South America, the Amazon Basin, central and southeastern Brazil, with rainfall deficits exceeding 300 mm in many areas. • Above-average rainfall over central Colombia, most of southern Brazil and Paraguay, and portions of Uruguay and northeastern Argentina. • Strong El Niño conditions were present in the tropical Pacific.

  30. Summary : Mature Phase • The rainy season mature phase (DJF) featured: • Below average rainfall over the Amazon Basin, most of central Brazil and portions of Southeast Brazil, with rainfall deficits greater than 400 mm in several areas. • Above-average rainfall over portions of Peru, Northeast Brazil, most of Paraguay, Uruguay, southern Brazil and northern and central Argentina. • Strong El Niño conditions were present in the tropical Pacific.

  31. Summary : Decay Phase • The rainy season decay phase (MAM) featured: • Below-average rainfall over central, Southeast and Northeast Brazil, southern Chile and southern Argentina, with deficits greater than 300 mm observed over portions of northern northeastern Brazil, and the Amazon Basin. • Above-average rainfall over portions of northern South America, Ecuador, extreme northern Peru, extreme southern Brazil, and Uruguay. • Weakening El Niño conditions were present in the tropical Pacific.

  32. General Summary • In general, below-average rainfall was observed over the Amazon Basin, and most of central and Northeast Brazil during September 2015-May 2016, with less than 50% of average precipitation in several areas. Above average rainfall occurred over Ecuador, Paraguay, Southern Brazil, Uruguay, and portions of central and northern Argentina. • Northern Northeast Brazil experienced its fifth consecutive year of drought conditions. • Southeast Brazil experienced below-average rainfall, but the deficit was much less than that observed during the 2014-2015 wet season, which was the driest September-May rainy season since the mid-1950s.

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