The closing weeks of the 2012 Atlantic hurricane season, which officially runs until Nov. 30, will see what has been a busy tropical season winding down quickly, according to Weather Services International (WSI), which increased its forecast to 17 named storms, including nine hurricanes, two of them major (Category 3 or higher).

There have already been 14 named storms and eight hurricanes since the season began June 1. In its previous update, WSI had said it expected 14 named storms, including seven hurricanes, three of them major (see Daily GPI, Aug. 22). The Atlantic basin this year has "clearly been more active than we expected," said WSI Chief Meteorologist Todd Crawford.

"The tropical Atlantic Ocean temperatures warmed considerably during the summer and the patterns of stronger-than-normal wind shear, typically observed during emerging El Nino events, took longer to arrive than originally thought," Crawford said. "However, the last couple of weeks have been fairly quiet; considering we are at what has historically been the most active time of year. Further, medium-range guidance does not indicate any strong signal for increased activity through the rest of September as an enhanced subtropical jet stream develops.

"Finally, the historical data suggest that tropical seasons often end rather abruptly as El Nino advances. In fact, no more than three named storms have developed after Sept. 20 during the last four appearances of El Nino events. The weight of evidence suggests a slow finish to the season, and we are only expecting three more named storms and one hurricane during the remainder of the season."

The only storm to have caused serious trouble for energy interests in the Gulf of Mexico (GOM) so far this year was Hurricane Isaac, which made landfall Aug. 28 and ultimately disrupted gas processing operations for more than 10 Bcf/d of the 13.5 Bcf/d of total processing capacity in the affected area, according to Energy Information Administration data (see Daily GPI, Sept. 14). The Bureau of Safety and Environmental Enforcement estimated that 75.52% (3.264 Bcf/d) of daily natural gas production and 94.99% (1.311 million b/d) of daily oil output in the GOM was shut in in the immediate aftermath of the storm (see Daily GPI, Aug. 31).

The National Oceanic and Atmospheric Administration last month raised its tropical forecast to a total of 12-17 named storms, including five-eight hurricanes, two-three of them major (see Daily GPI, Aug. 10), and forecasters at Colorado State University have said that they expect a total of 14 named storms in the Atlantic Basin this year, including six hurricanes, two of them major (see Daily GPI, Aug. 7).

On Tuesday the National Hurricane Center (NHC) was monitoring Tropical Storm Nadine, the season's 14th named storm, as it moved slowly to the west-southwest in the Atlantic Ocean about 455 miles south-southwest of the Azores. The storm was expected to remain in the central Atlantic through the weekend, NHC said. Nadine has been an unusually long-lasting storm. It first formed as a tropical depression more than 1,200 miles east of the Lesser Antilles Sept 11; on Sept. 14 it became the eighth hurricane of the Atlantic season about 725 miles east of Bermuda; two days later it was downgraded to tropical storm status and, by Sept. 21, had further weakened to a post-tropical cyclone. It regained tropical storm status on Sept. 23, NHC said.

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