An emerging El Nino event -- the warming of water temperatures in the central and equatorial Pacific Ocean -- will bring warmer-than-normal temperatures to the eastern United States in September and October and could keep much of the West cooler than normal, according to forecasters at Andover, MA-based Weather Services International (WSI).

"The recent weather pattern that has resulted in more persistent below-normal temperatures in much of the eastern two-thirds of the U.S. will likely not last into September, as all of the objective seasonal/subseasonal evidence suggests a return to warmth across much of the East," said WSI Chief Meteorologist Todd Crawford. "By October, when the first heating demand starts to kick in, we expect a continuation of mild temperatures across most of the East driven by a very cold Pacific Ocean.

"As we head deeper into the fall, the climate models are becoming more aggressive in spreading very cold early-season air across much of southern Canada and into parts of the northern U.S."

Cooler-than-normal temperatures are expected to dominate the West in September, while temperatures will average warmer than normal across all the rest of the country except Florida and parts of Minnesota and the Dakotas, WSI said.

"Extended warm weather in Texas and the lower Midwest could combine with the start of the generator maintenance season to boost power prices and implied market heat rates in these areas," said Paul Flemming, Energy Security Analysis Inc. (ESAI) director of power and gas. "In the Northeast, generation maintenance is lighter in September; so the slightly warmer-than-normal temperature outlook is not particularly bullish for power prices in PJM, New York or New England. Gas prices should remain soft during the month as inventories approach last year's record level (3,854 Bcf) and begin to approach 4,000 Bcf through September and into October."

As of Aug. 10 working gas in storage stood at 3,261 Bcf, according to Energy Information Administration (EIA) estimates (see Daily GPI, Aug. 17). Despite a reduction in the current surplus over both last year's inventory and the five-year average inventory, stocks are still 442 Bcf higher than last year at this time and 363 Bcf above the five-year average of 2,898 Bcf, EIA said.

WSI's temperature forecast map remains mostly unchanged for October, with warmer-than-normal temperatures expected to remain firmly in place across the central and eastern United States (except Florida).

"Power prices in October generally will be impacted more by generator maintenance schedules than by changes in the lower shoulder-season loads due to weather. However, implied market heat rates will likely be relatively firm in most regions, as generator maintenance season is in full swing during this period and gas prices remain very low. Significantly warmer-than-normal weather in the North Central region will dampen any early-season heating demand from that region," Flemming said.

The WSI forecast team expects the Northeast to experience cooler-than-normal temperatures in November, with warmer-than-normal temperatures sliding into the Northwest. The Central region will remain warmer than normal, WSI said, except northern North Dakota, Minnesota and Wisconsin, and southern and central Texas.

"Cooler-than-normal temperatures in the Northeast and upper Midwest in November will provide a boost to early-season heating demand for natural gas from those key regions," Flemming said. "November power prices will still be supported by strong generator maintenance outages for most of the month, particularly in the Northeast. Although loads are lower in the shoulder period, gas demand from the power sector typically increases during the maintenance season as gas plants make up for lower operations at nuclear and coal plants."

Looking further ahead, Crawford said the emerging El Nino could drive above-normal temperatures across much of the northwestern United States and southwestern Canada this winter, but "it is still too early to call the fate of winter temperatures across the Northeast U.S."

Forecasters at recently said El Nino could herald a strong southern branch of the jet stream across the United States and bring above-normal snowfall to the portions of the East during the 2012-2013 winter season (see Daily GPI, Aug. 17).

July was the hottest month ever for the Lower 48 states, which have also experienced a record-hot first seven months of the year and the warmest 12-month period since recordkeeping began in 1895, according to the National Oceanic and Atmospheric Administration's (NOAA) National Climatic Data Center (see Daily GPI, Aug. 9). As of August 4 there had been 982 cooling degree days in the United States, according to NOAA data.

WSI is scheduled to issue its next seasonal outlook on Sept. 25.

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