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Australia SOI Tilts Toward El Nino

Bryce Anderson
By  Bryce Anderson , Ag Meteorologist Emeritus
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The barometric pressure component of the El Nino-Southern Oscillation (ENSO) feature in the equatorial Pacific Ocean, the Southern Oscillation Index (SOI) has been a reluctant participant in El Nino formation so far this year. This part of the puzzle has emained in a neutral category despite the ocean temperatures reaching above-normal levels from South America all the way west to the International Date Line.

However, that aspect may be changing. The SOI calculation done by the Australia Bureau of Meteorology (BOM) Monday May 11, 2015 showed a 30-day average of -8.87, which placed the 30-day average into El Nino territory at -8 or below. The 90-day SOI average Monday May 11 was -6.55--still in a neutral position but just 1.5 index points away from the -8 figure. The BOM daily SOI calculation Monday May 11 was a robust -40.43. This strongly-negative daily index is part of a string of such sharply-negative totals. In the past five days, we have seen these daily index values: Thursday May 7 -17.80; Friday May 8 -32.30; Saturday May 9 -46.90; Sunday May 10 -44.10; and then the Monday -40.43 daily index.

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This trend--and particularly the trend to not just El Nino-type values but strong El Nino-type values--makes a broad suggestion that El Nino is indeed setting in in the Pacific. We are seeing more weather features pointing to this development as well. Rain has developed in the southern Plains this season, with the heaviest totals in five years in some locales. The Midwest is getting periodic doses of storms and precipitation. And, upper air forecast maps for next week show a strong southern-branch jet stream with the potential for more precipitation. Weather features plus ocean indicators, again, strongly hint that El Nino is around.

The Far West drought may get some easing as well with this trend. The six to ten-day forecast through late next week, Thursday May 21, has above-normal precipitation for all areas of California except for the Desert Southwest. Other dry areas such as the Great Basin and interior Pacific Northwest may also take in this type of moisture.

Back to the subject at hand--the Pacific SOI is showing strong El Nino tendencies. And that generally bodes well for U.S. crop production.

Bryce

Twitter @BAndersonDTN

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