August natural gas futures hovered near unchanged Tuesday as forecasts for expanding heat supported cooling demand, but gains remained limited as traders weighed cooler weather across the East and the potential for Tropical Storm Bertha to disrupt Gulf Coast LNG operations. A Tropical Storm Warning remained in effect from the Alabama-Florida border westward to southeastern Louisiana, with storm surge watches extending along much of the northern Gulf Coast. That strength could come under pressure later this week if Bertha disrupts Gulf Coast export operations. NGI sees 39 Bcf buildStorage deficit narrowsThe next major catalyst for natural gas prices could come Thursday, when the US Energy Information Administration releases weekly storage data. The estimate compares with a 27 Bcf injection during the same week last year and the 30 Bcf five-year average.