By Timothy Puko NEW YORK–Natural-gas prices closed lower Tuesday with traders unconvinced that a warming forecast would translate into a significant increase in demand. The front-month September contract settled down 2.6 cents, or 0.7%, to $3.911 a million British thermal units on the New York Mercantile Exchange. The more actively traded October contract settled down 3 cents, or 0.8%, to $3.949/mmBtu. September options expired at close and the contract expires Wednesday. Both contracts flip-flopped around unchanged on a lot of mixed signals, primarily from the weather, analysts said. Though most forecasts showed another spurt of summer heat coming in early September, that wasn’t a unanimous prediction. The warmer forecasts also included signs that cooler fronts could break up or limit the heat likely to hit the south and east. “Without the forecast (for heat) being extended into the first three weeks of September, we don’t really have enough momentum…to […]