A total of 11 named storms, including two hurricanes, have formed in the Atlantic Basin this year, but it took an unnamed trough of low pressure in the central Gulf of Mexico (GOM) to force the first weather-related shut-ins and evacuations of energy interests offshore.

Tropical Disturbance 35 on Thursday was producing a large area of cloudiness, thunderstorms and gusty winds over the eastern and central GOM, according to the National Hurricane Center (NHC), which gave the system an 80% change of becoming a tropical cyclone by Saturday. The system was expected to move slowly to the northwest and “interests along the entire northern Gulf of Mexico coast” should monitor its progress, NHC said.

BP plc was shutting in production and evacuating all personnel from its operated assets in the GOM, spokesman Tom Mueller told NGI Thursday afternoon.

“BP-operated assets included in this evacuation include Mad Dog, Holstein, Atlantis, Nakika, Pampano, Horn Mountain, Marlin and Thunder Horse,” Mueller said.

Shell Oil Co. on Thursday said it was “moving forward with a plan to reduce the number of employees” at most of its GOM operations and had begun to take some actions to shut in production.

“Those actions are focused on some of our subsea fields that require specific treatments to ensure the production can be restored after the storm passes. The impacts are minimal at this point and we are monitoring Shell non-operated downstream infrastructure for further impacts to our production that may occur,” Shell said. Weather conditions were impairing staff movement, “but we are using all available resources to safely evacuate employees,” the company said.

Chevron Corp. on Thursday said it was evacuating nonessential personnel in the GOM but “no production has been affected.”

Transcontinental Gas Pipe Line (Transco) said that approximately 200 MMcf/d of gas scheduled to flow to through its pipeline had been shut in. Based on the projected storm track and intensity, Transco on Thursday said it did not anticipate any supply allocation would be required as a result of supply interruptions from the storm.

Tropical Disturbance 35 is expected to grow in intensity and could become “the next billion-dollar disaster for the U.S., by way of flooding,” according to AccuWeather.com’s Justin Roberti. Meteorologists think the system will grow into a tropical storm or hurricane, he said.

“The consensus among nearly 100 meteorologists at AccuWeather is that this will be an extensive, slow-moving system, capable of affecting the same areas for days with downpours, stormy seas and rough surf conditions. Rough seas alone have potential to shut down rigs in the Gulf for an extended period…Considering potential for damage, impact to the petroleum industry and commerce in the Gulf Coast region, the system, as of yet to gather a name, could be the next billion-dollar disaster in a mountainous year of costly storms for the U.S.”

Ironically, while Tropical Disturbance 35 threatened the GOM, the system that had been the season’s second hurricane was downgraded Thursday afternoon. Tropical Storm Katia was located about 930 miles east of the Northern Leeward Islands with maximum sustained winds of 70 mph and did not appear to represent as much of a threat to GOM energy interests as did the less powerful low pressure system. Katia was expected to restrengthen somewhat, according to NHC, but most projections had the storm moving toward the northwest — and away from the GOM — by early next week.

NHC on Thursday was also tracking a non tropical low pressure system about 360 miles north of Bermuda. That low was given a 50% change of becoming a tropical cyclone and was expected to move to the northeast.

Hurricane Irene steered clear of the GOM but turned out the lights on millions of East Coast residents and in doing so cut demand for natural gas by about 2.8 Bcf (see Daily GPI, Aug. 30).

AccuWeather.com forecasters last month predicted a ramping up of tropical activity (see Daily GPI, Aug. 12) and WeatherBELL Analytics chief meteorologist Joe Bastardi has said he expects tropical storm activity in the Atlantic Basin to increase, with multiple hurricanes forming by mid-September (see Daily GPI, Aug. 17). WSI Corp. last week increased its 2011 Atlantic hurricane forecast, saying it now expects a total of 15-18 named storms, including eight hurricanes, four of them Category Three or greater, to form this year (see Daily GPI, Aug. 25), and a series of tropical forecasters, including the National Oceanic and Atmospheric Association (see Daily GPI, Aug. 5), Colorado State University (see Daily GPI, June 2) and MDA EarthSat (see Daily GPI, May 18) have predicted above-average tropical storm activity in the Atlantic Basin.

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