* Raw sugar open interest at June 2013 high
* Spot raw sugar spread moves to premium
* Arabica sell-stops seen triggered around $1.41 (Adds details in paragraph 1, updates prices, and adds trade comment; adds second byline, NEW YORK dateline)
By Marcy Nicholson and David Brough
NEW YORK/LONDON, April 8 (Reuters) - Raw sugar futures surged to a three-week peak in heavy volume on ICE on Wednesday on speculation that nearby supplies may be tightening, while heavy spreading lifted the spot contract to a premium for the first time since February.
Arabica coffee tumbled on chart-based and speculative selling, while New York cocoa rose on support from dollar weakness. Both markets dealt in heavy volume buoyed by spread activity.
ICE spot raw sugar futures hit a session high of 13.13 cents a lb, the loftiest since March 13, on concerns about limited supplies before the start of the cane harvest in center-south Brazil this month.
"There is tighter availability for prompt shipment and we're seeing more short-covering," said Tracey Allen, commodity analyst at Rabobank.
May raw sugar futures on ICE settled up 0.20 cent, or 1.6 percent, at 12.97 cents a lb. The May/July spread SB-1=R surged as high as 0.13 cent, the biggest premium on a spot continuation chart since Feb. 27, when the March contract expired.
Raw sugar futures total open interest rose for the ninth straight session to 936,040 lots on Tuesday, the highest since June 2013, exchange data showed.
May white sugar closed down 40 cents, or 0.1 percent, at $366.40 per tonne. The spot white premium over the raws LSU-SB1=R dropped as low as $80.29 per tonne, the lowest since March 13.
"The whites premiums are weakening, possibly because the Indian government is now considering offering incentives for white exports," a London-based broker said.
Arabica futures sank on chart-based selling around $1.41, where sell stops were triggered, traders said.
"The market is not paying attention to the strength of the Brazilian real and the lack of selling from origins, but more focusing on the technical picture," said Rodrigo Costa, director of coffee for Societe Generale in New York.
May arabica finished down 6.25 cents, or 4.4 percent, at $1.357 per lb, its biggest drop since March 3.
Traders said talk that a major trade house raised its crop forecast for Brazil may have added pressure.
London May robusta coffee futures closed down $16, or 0.9 percent, at $1,790 per tonne.
New York May cocoa futures settled up $22, or 0.8 percent, at $2,807 a tonne, while London May cocoa ended up 2 pounds, or 0.1 percent, at 1,944 pounds a tonne. (Editing by Ruth Pitchford, Dale Hudson and Peter Galloway)