Much of the country can expect temperatures to average warmer than normal throughout the summer, with population centers in the Northeast likely to experience increasingly intense and widespread heat into August and September, according to forecasters at Andover, MA-based WSI Corp.

“The heat has built rather quickly this summer across most of the eastern two-thirds of the U.S.,” said WSI Chief Meteorologist Todd Crawford. “The current high-latitude atmospheric blocking has resulted in a break from the heat across the northern tier of the country during the past week, but it appears that this blocking will wane as we head further into summer. As this occurs, the heat will become more favored across the northern U.S.” The Southwest will also be quite hot for the remainder of the summer, Crawford said.

At the same time, low-level tropical easterly winds will become established earlier than normal, helping to bring a cooler, rainier pattern to the Southeast.

“For the July-September period as a whole, we are forecasting 824 population-weighted cooling degree days, higher than the 1971-2000 average of 766, but lower than last year’s extreme value of 937,” Crawford said.

That’s a somewhat warmer outlook than previously forecast by WSI (see NGI, May 30) and significantly different than MDA EarthSat Weather’s forecast of summer temperatures averaging 14.5% cooler than last year (see NGI, May 23). forecasters have said they expect the lingering effects of a recent La Nina event to translate into a “year without a summer” for the nation’s midsection (see NGI, June 6).

WSI’s forecast calls for cooler-than-normal temperatures to be in place in the Southeast, Northwest and coastal California in July, with warmer-than-normal temperatures dominating elsewhere.

“With natural gas inventories running 10.9% below last year’s level to start the summer, the forecast for warmer-than-normal temperatures over most of the country in July will not leave much opportunity for injections to close the year-over-year gap,” Energy Securities Analysis Inc. Senior Analyst Chris Kostas said in a statement issued in conjunction with WSI’s outlook. “Cooler-than-normal temperatures expected along the Pacific Coast and the Southeast should offset some of the bullish underpinnings expected from the rest of the country, but they are unlikely to offset enough to make up the deficit to last year.” Increased gas demand from electricity grid operators should keep gas prices firm despite year-over-year gas production increases, Kostas said.

Warmer-than-normal temperatures will move into the Northwest and coastal California in August, leaving only the Southeast experiencing cooler-than-normal temperatures, WSI said. That should keep gas prices firm through the month, according to Kostas.

“With the Southeast expected to be the only cooler-than-normal region, aggregate natural gas demand should remain firm,” he said. “Implied market heat rates and power prices in ERCOT [the Electric Reliability Council of Texas], PJM-East, New York and New England should run high in August, as increased power demand pushes prices up the supply curve. The large spread between gas and oil could send power prices soaring in load pockets of eastern PJM and New York City, even if oil-fired generation is called on for a limited number of hours during the month. California may experience a marked increase in power prices between July and August as temperatures shift from cooler than normal to warmer than normal and seasonal hydro production tapers off.”

The bake will continue in the Northeast and much of the rest of the country in September, though cooler-than-normal temperatures are expected to return to the Northwest and coastal California, WSI said. Gas demand, implied market heat rates and power prices are likely to remain firm as summer concludes, Kostas said.

“Although we expect inventory levels to make their way toward 3,800 Bcf by the end of the injection season, natural gas prices are unlikely to collapse in September due to the much-warmer-than-normal temperatures that are expected this summer,” he said.

While no named storms have formed since the beginning of the 2011 Atlantic hurricane season on June 1, it is still likely to produce 15 named storms, including eight hurricanes, four of them Category Three or greater — the same as the 1995-2010 average — WSI said. Weather conditions remain in place to create the “active-normal” tropical forecast it first issued in April and reaffirmed last month (see NGI, May 2), according to WSI, which said the Gulf Coast is under “a significant threat for hurricane landfall.”

“While we cannot explicitly state exactly where or when a hurricane might make landfall, our model does have some skill in distinguishing which coastal regions may be more favored than others,” Crawford said. “For the upcoming season, our hurricane landfall prediction model suggests increased chances (relative to normal) of U.S. landfall in 2011, especially in the western Gulf states.”

The consensus forecast this year is for an above-average hurricane season, with the National Oceanic and Atmospheric Administration, and MDA EarthSat all calling for above-average numbers of named storms and hurricanes. Forecasters at Colorado State University have said they expect to see 16 named storms form in the Atlantic Basin by Nov. 30, with nine turning into hurricanes, five of them major hurricanes.

A total of 19 named storms formed in 2010, with 12 of them becoming hurricanes, including five intense hurricanes. The long-term (1950-2009) averages for the Atlantic hurricane season are 10 named storms, six hurricanes and two intense hurricanes; the 1995-2009 averages are 14, eight and four, respectively.

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