The following content was provided by meteorologist Gail Martell of MartellCropProjections.com:
El Nino Chatter
Several stories of a potential El Nino have emerged in recent weeks, as there are some expecting an El Nino beginning in the Southern Hemisphere winter (June-August 2014_. Australia's Bureau of Meteorology predicts the El Nino-Southern Oscillation would remain in a neutral state, neither El Nino nor La Nina, through the Southern Hemisphere autumn (March-May). The door may be open to the development of a El Nino thereafter. In their bimonthly report, the Bureau claimed "while most ENSO indicators are neutral, strong westerly winds have developed in the far western tropical Pacific that "may lead to some warming of the western tropical Pacific Ocean in the coming weeks."
If the El Nino developed, it would be detrimental for Australia wheat production. There is a strong correlation between the El Nino and in drought in eastern Australia. New South Wales is particularly sensitive to the ENSO signal, Australia's second top wheat state accounting for 37%-40% of the national production.
La Nina Signal Strengthens
Talk of a potential El Nino comes at a time when the La Nina "signal" has strengthened. Sea surface temperatures last week fell .65 C below normal in the sensitive Nino 3.4 region where ENSO conditions are closely monitored. For a full-fledged La Nina to occur, sea surface temperatures must maintain below the -.50 C threshold temperature for many weeks and months.
The La Nina has dominated in the Pacific equatorial sea in recent years occurring twice, June 2010-May 2011 and August 2011-April 2012. Not since mid 2009-April 2010 has a full blown El Nino developed. In the historical records going back to 2000, there have been only 4 El Ninos and 6 La Ninas, based on Climate Prediction Center records.
The question is if the La Nina signal has strengthened, why has eastern Australia been so dry? Both the January rainfall map and also the November-January map show widespread drought in New South Wales.
A full fledged La Nina may be required the expected wet conditions to develop While sea surface temperatures have steadily declined in recent weeks, only recently have sea-surface temperatures fallen below the threshold value (-0.50 C) in the Nino 3.4 region. The Climate Prediction Center has strict definitions for the La Nina. Sea surface temperatures must remain below the threshold for many consecutive weeks, even months, before a full-fledged La Nina is declared.
This is a climate fluctuation, not related to week-to-week changes in weather patterns. In a full-fledged La Nina, specific weather patterns develop that promotes very heavy rainfall in Eastern Australia and throughout the Indonesian Basin. At the same time Argentina typically is dry.
Interestingly, the Eastern Australia forecast has suddenly become wet, consistent with a strengthening La Nina signal. In the United States the La Nina effect causes extreme cold in winter, also consistent with the current weather conditions.