Sep Nymex natural gas (NGU24) on Tuesday closed up by +0.068 (+3.50%). Sep nat-gas prices Tuesday posted moderate gains as short-covering emerged after US weather forecasts turned hotter for the middle of this month. On Tuesday, the Commodity Weather Group said that forecasts shifted hotter for the midwestern to eastern parts of the US for Aug 16-20, which should boost nat-gas demand from electricity providers to power increased air conditioning usage. On Monday, nat-gas prices tumbled to a 3-1/2 month nearest futures low on forecasts for cooler US weather amid elevated nat-gas stockpiles. Cur…