Expectations for bumper Brazilian corn and soybean crops, needed to replenish depleted world supplies, took a knock with ideas that the El Nino weather pattern, which typically brings plentiful rain, may prove a mild version.
Official meteorologists in Australia, a country heavily affected by El Nino weather and which closely follows the phenomenon, noted mixed indications of the start of an event.
While Pacific water temperatures, a key signal, and the southern oscillation index, a measure of air pressure differences between Tahiti and northern Australia, "approached or exceeded El Nino values during the past fortnight, indicators such as the trade winds and tropical cloud patterns have yet to show typical El Nino signatures", the Australian Bureau of Meteorology said.
Weather models suggested that Pacific temperatures will, having hit "values close to, or greater than, typical El Nino thresholds" return "to neutral towards the end of 2012 or early 2013".
A weak El Nino would be welcomed by some farmers, such as palm oil producers in Indonesia and Malaysia where El Nino typically bring dry weather and sparse rainfall.
Lim Siew Kim, chairman of palm group Anglo Eastern Plantations, said on Thursday: "It is generally expected that the imminent El Nino weather phenomenon will lead to a weaker palm oil output in South East Asia."
And the weak El Nino would tie in with observations of an improving Indian monsoon. Rains were 6% above average in the latest week, although remain 12% below average so far after a weak start, the country's weather office said on Thursday.
However, for Brazilian farmers, talk of a weaker El Nino "was the last thing they wanted to hear", said Michael Cordonnier, the respected crop scout who has close ties to South America.
"The idea the El Nino may be mild, or not come at all, has got everybody quite concerned. Brazil wanted an El Nino in place by now."
El Nino conditions are linked to unusually wet weather, and higher yields, in much of Brazil, the reverse of the dryness caused by the La Nina pattern which kicked in last year, fuelling a 10m-tonne drop to 65.5m tonnes in 2011-12 soybean output.
Forecasts for Brazil's 2012-13 soybean production
Agroconsult:83.1m tonnesSafras: 82.3m tonnesAgRural: 82m tonnesSoybean and Corn Advisor: 82m tonnesAbiove: 81m tonnesUS Department of Agriculture: 81m tonnes
Dr Cordonnier, who himself has factored in an 82m-tonne crop, said it was too early yet to think of downgrading the forecast, "before a bean has even been planted".
"We are not talking about a disaster if the El Nino is weak, or does not come at all. But it does make things more worrisome for Brazil."
Concerns have been exacerbated by a dearth of rain in Mato Grosso, the top soybean producing state, where temperatures are expected to hit 100 degrees Fahrenheit this weekend, and with the opening of the sowings window only two weeks away.
"There have not been any rains in Mato Grosso since the end of June and there is no significant rain in the near-term forecast," he said.
While there is plenty of time left for sowings without suffering a yield penalty, plantings delays would nonetheless have a significant market impacts.
Besides pushing back the harvest, and leaving consumers to rely longer on drought-depleted US soybean supplies, delays would defer sowings of the follow-on safrinha corn crop too, which in 2011-12 represented nearly one half of the total Brazilian harvest.
Long-range weather forecasts the rainy season ending early, perhaps in February, add a further threat to safrinha corn hopes, in threatening that crops will have little soil moisture to draw on during the grain-filling period.
"If corn planting is late, and rains end early, then we are in trouble," Dr Cordonnier told Agrimoney.com.
Producers who would be helped by the absence of El Nino also include cocoa farmers in West Africa, where the weather pattern typically brings unfavourably dry conditions.
Eastern Australian grain growers, often presented with a moisture deficit by the weather pattern, look set for dry conditions even without it, the Australian Bureau of Meteorology said.
"Regardless of the [El Nino] state, the tropical Pacific remains warmer than average.
"This, combined with other influences on Australian climate such as cooler than normal waters to the north of the continent and the patterns of cloud and ocean temperatures in the Indian Ocean, tends to favour below-average rainfall over eastern Australia."