SOFTS-Cocoa falls to multi-month lows, arabica coffee tumbles

* Harmattan winds not expected to impact cocoa supply

* Arabica falls despite expectation for index fund buying

* Raw sugar expected to test 18 cents -Sucden

(New throughout, updates prices; adds trade comment, second byline/dateline)

NEW YORK/LONDON, Jan 8 (Reuters) - Cocoa futures inched down to the lowest level in several months on Tuesday as dealers eyed weather conditions in top growing region West Africa, while arabica coffee prices dropped more than 3 percent, giving back the previous day's gains.

Robusta coffee and sugar futures also fell, with the discount of the spot ICE raw sugar contract widening to the biggest in more than three months.

Cocoa futures on both Liffe and ICE Futures U.S. fell along with the Thomson Reuters-Jefferies CRB index, a global benchmark for commodities, as the U.S. dollar climbed and as dealers kept a close eye on the seasonal dry Harmattan winds in West Africa. The winds were not expected to impact supply there.

The intensity of the dusty Harmattan, which blows southward from the Sahara Desert from December to March, could determine the size and the quality of the Ivorian 2012/13 crop as it enters the last stage of the main harvest, farmers said.

"If it stays dry for much longer, then of course that will start to be a concern," a London-based broker said.

Liffe May cocoa futures settled down 21 pounds, or 1.5 percent, at 1,430 pounds after dipping to 1,425 pounds, the lowest level for the second month since mid-April 2012.

On ICE, March cocoa futures finished down $52, or 2.3 percent, at $2,215 per tonne, the spot contract's weakest settlement since July 25, 2012.

Cocoa arrivals at ports in top grower Ivory Coast reached around 696,000 tonnes by Jan. 6 since the start of the season in October, exporters estimated, down nearly 6 percent from a year ago.

"The early delays have now been caught up," a broker said, referring to a slow start to the 2012/13 season due to sector-wide reforms including a fixed farmgate price.

Dealers monitored expectations for Europe's fourth-quarter cocoa grindings, due to be published on Jan. 15, with forecasts for a fall of around 6 percent. North American grind data is scheduled for release Jan. 17.

Arabica coffee futures were also lower, with March down 2.45 cents, or 1.6 percent, at $1.4795 per lb by 12:43 p.m. EST (1743 GMT), after dropping 3.2 percent to $1.4565.

Index rebalancing was expected to support the market, which had spurred buying in the previous session, but what appeared to be speculative selling pushed the market lower, dealers said.

"Most people were expecting the market to go up because index funds have announced very publicly that they have to be buyers over this week and coffee's one of the commodities that they have to buy the most," said one U.S. dealer.

The market dropped about 3 cents, or 2 percent, within 10 minutes earlier in the session, in what dealers believed was speculative short selling.

"My guess is that they're trying to spook the longs and to spook anybody at origin who's waiting to take advantage of index buying and try to convince them to panic and sell the market lower, to negate the positive impact of the index buying this week," the U.S. dealer said, referring to index funds.

Index reweighting is expected to be done in both ICE coffee and sugar futures after their weak performances in 2012.

"The problem is always that the market pre-empts it, so I don't think it's a major issue," a London-based broker said, noting there was speculator buying on Monday ahead of expected index buying.

March robusta coffee futures closed down $48, or 2.5 percent, at $1,915 a tonne.

Dealers said Vietnam was behind in its sales compared with previous years as sellers hoped for higher prices.

"There has been a view that the market has been undervalued, so they've held back a little bit," the broker said.

SUGAR EASES AS RAW SPREAD WIDENS

Raw sugar futures turned lower, reaching the weakest level in more than three weeks, with dealers noting the market was vulnerable to breaking below the recent range.

March raw sugar futures on ICE were down 0.12 cent, or 0.6 percent, at 18.74 cents a lb, remaining above its more than two-year low hit in December of 18.31 cents.

Its discount to the May contract grew to 0.24 cent, the biggest for the spot contract since the end of September.

"We continue to expect the market to gravitate to support levels rather than resistance and in the medium term a test of the support around 18 cents," said Thomas Kujawa, at brokerage Sucden Financial.

Deutsche Bank said that as the market had breached 19 cents, it was possible prices could slide towards 16 cents, although producers' reluctance to sell could stem losses.

"With producer selling likely to dry up as prices head lower, in our view it is unlikely for prices to approach this level," the bank said in a commodities note.

March white sugar on Liffe fell $2.80, or 0.6 percent, to $508.00 per tonne.

($1 = 0.6218 British pounds)

(Editing by Keiron Henderson, Jane Baird and Phil Berlowitz)