NEW YORK — Rabobank’s annual commodities outlook predicted that global agricultural prices are likely to advance during the first half of 2013 on tight supplies but weaken during the second half as increased production creates a world-wide surplus.

Rabobank said grain and oilseed prices are expected to be volatile, with a first-quarter rally fading amid softer prices for the remainder of 2013. Soybean meal was singled out as likely to perform the worst among agricultural commodities while palm oil was viewed as having the greatest upside potential.

“Weak global economic growth and continued macro uncertainty may cause a slight drag on demand for agricultural commodities in 2013,” said Luke Chandler, global head of Rabobank’s Agri Commodity Markets Research department. “A low U.S. dollar will provide support for prices. Speculative money flows will also remain very sensitive to macro uncertainties. Using the S&P Agri Index as a proxy for our commodity forecasts, we expect a decline in agricultural prices of around 10% in 2013.”

The price gains early in 2013 were seen as attracting more production worldwide, although inventories were expected to remain low and to feed market volatility. Rabobank noted that global stocks-to-use of corn, soybeans and wheat likely will rise just 1.9 percentage points to 19.9% and will remain below 2011-12 levels, keeping a floor under prices in the second half of 2012.

“Multi-season surpluses will be required to rebuild inventories and rebalance fundamentals,” the Rabobank commodity outlook said.

Commodity supplies will fluctuate and the global economy will face challenges, but world GDP was forecast to increase 3.75% in 2013, mostly sustaining demand, Rabobank said in its commodity outlook, titled “Outlook 2013—rebalancing on a tightrope”.

Rabobank, one of the world’s largest banks, with nearly $1 trillion in assets and operations in more than 40 countries, made its forecast of 2013 prices and comparisons with 2012 across a wide range of agricultural sectors, including wheat, corn, soybeans, soy oil, soybean meal, palm oil, sugar, coffee, cocoa and cotton.

Rabobank expressed confidence in its most recent commodity outlook, noting that “in the 2012 report, the key themes identified by Rabobank — economic slowdown, speculators and the U.S. dollar, policy risk, and capacity constraints — did in fact contribute to shaping 2012 prices.”