Deteriorating technical factors contributed to pressure on cotton futures last week as index funds began rolling longs forward, trend-following funds did some month-end repositioning and U.S. harvesting gained momentum.

Spot December lost 252 points during the week ended Thursday to close at 70.21 cents. It fell to a double low around 69.80 cents, the lowest intraday print since July 26, and bounced both times to close above the psychologically important 70 cents. March shed 147 points to 71.50 cents.

December finished a turbulent October with a modest loss for the month of 58 points or 0.82 percent to 70.07 cents. This masked a wild 936-point rollercoaster ride to a five-month high at 79.19 cents on Oct. 18 and a plunge to a 14-week low to 69.83 cents on Oct. 31.

The spot delivery staged a bearish outside-range reversal on Tuesday, nudging above the prior-session high and its 100-day moving average (72.91) and then falling heavily to finish the day below recent lows. Follow-through selling then pounded December to new lows for the move.

Traders initially covered some shorts as Hurricane Sandy approached the Eastern Seaboard and then when it didnΆt inflict as much crop damage as originally feared in the Carolinas and Virginia pondered the effects the historic storm might have on the economy and thus on cotton demand.

With funds rolling longs from December by selling it and buying March and other forward contracts, open interest fell 10,081 lots to 100,840 in the spot delivery and increased 9,948 lots to 79,598 in March. Certified stocks grew 3,155 bales to 11,603. Awaiting review were 5,139 bales.

The market braced for updated USDA supply-demand reports next Friday after a series of bearish estimates featuring all-time high world stocks.

In cash trading, grower-to-business sales increased to 15,817 bales from 10,356 bales the previous week. Prices fell to an average of 65.95 cents from 68.43 cents, reflecting a decline to 13.18 cents from 14.96 cents in premiums over loan repayment rates. Daily price averages ranged from 65.29 to 67.41 cents.

The U.S. cotton harvest advanced 12 percentage points during the week ended Oct. 28 to 50 percent complete, six points behind a year ago but three points ahead of the five-year average, USDA reported.

Conditions improved, with good up a point from a week ago to 32 percent and poor down a point to 12 percent. The other ratings were unchanged at 11 percent excellent, 27 percent fair and 18 percent poor.

Ratings improved in Alabama, Georgia, North Carolina and Virginia; declined in California, Kansas Oklahoma and South Carolina; and held steady elsewhere. The report didnΆt fully reflect the effects of Sandy in North Carolina and Virginia.

Growers had harvested 34 percent of an estimated 1.1-million bale crop in North Carolina and 45 percent of a projected 170,000 bales in Virginia. Those percentages were down from averages of 52 percent in North Carolina and 61 percent in Virginia.

Based on crop estimates around Oct. 1, the two states were expected to account for 7.6 percent of the U.S. upland output. SandyΆs main effects on cotton were expected on quality rather than yields.

In the two largest cotton states, harvesting reached 42 percent done in Texas, down from 44 percent a year ago but up from 32 percent on average, and 37 percent complete in Georgia, against 47 percent and 38 percent, respectively.

Cotton beltwide was 96 percent open, a point behind last year but a point ahead of the 2007-2011 average.

With picking nearing completion in the Delta, harvesting and ginning continued to accelerate rapidly on the Texas High Plains, where sample receipts at Lubbock jumped to just over 40,000 a day last week from 35,700 the prior week 18,500 the week before that.

Daily receipts are expected to peak soon in the mid-40,000s, up from the mid-30,000s last season but down from around 55,000 in 2010. Classing for the season was on track to cross the half-million bale mark on Thursday, compared with 469,871 a year ago.

Quality has continued to improve and now is “looking much more like a normal crop” after a rather rough start attributed mainly to some cloudy, damp days, said Kenny Day, head of the USDA Lubbock facility.

Color grades have shown marked improvement, reflecting a period of sunny days, in the 162,000 bales classed during the week ended Oct. 25, up from 60,300 the previous week.

White cotton accounted for 81.1 percent for that latest week for which statistics currently are available, up from 60.1 percent the prior week. Color 31 (middling) and better totaled 80.9 percent. The predominant color was 21 (strict middling) at 50.6 percent.

Leaf grades were mostly 2s and 3s and averaged 2.56, while staple lengths averaged 34.98 with 82.8 percent stapling 34 and longer and 63.9 percent pulling 35 and more. Micronaire readings averaged 4.09 with 83.8 percent in the base range of 3.5-4.9.

Strength averaged 29.7 and uniformity averaged 79.74. Extraneous matter remained higher than desirable with total bark at 23.2 percent, though down from the previous weekΆs 24.3 percent.

Meanwhile, trend-following funds bought 18,484 lots — they covered 18,466 shorts and added only 18 longs — to more than quadruple their net longs in futures with options during the week ended Oct. 23. This raised their net longs to 23,792 lots, largest since Sept. 20, 2011.

Index funds bought 1,719 lots to boost their net longs to 66,061, while small traders bought 6,393 lots to raise theirs to 9,327.

Commercials sold a net 26,597 lots to expand their net short position to 99,182 lots, largest since Feb. 8, 2011. They added 33,650 shorts and 7,055 longs.

This latest Commodity Futures Trading Commission report covers the period in which prices hit the October high. When the fund-spec short-covering and new buying slowed, prices fell.