Temperatures across the eastern third of the country will average cooler than normal over the next three months, while above-average temperatures will dominate much of the West, according to a seasonal forecast from WSI Corp. of Andover, MA, which also reiterated its forecast of a relatively calm Atlantic hurricane season.

The Southeast carries the highest probability for cooler-than-normal weather through September, according to WSI seasonal forecaster Todd Crawford.

“We expect the upcoming transition to warmer temperatures in the western U.S. and cooler temperatures in the Southeast to be the prevailing pattern for the rest of the summer,” Crawford said. “In the Northeast, the cool start will likely be representative of the pattern for the remainder of the summer, although occasional bursts of heat coming from the North Central U.S. will likely impact the area from time to time.”

In its Energycast Outlook for July WSI forecast cooler-than-normal temperatures across all of the East and coastal California, with warmer-than-normal temperatures dominating the rest of the country.

“The eastern states and California represent a large portion of U.S. demand, and cooler temperatures will mean lower loads, moderate power prices and lower natural gas demand from the power sector,” said Paul Fleming, Energy Security Analysis Inc. director of power and gas, in a statement issued in conjunction with WSI’s outlook. “Warmer temperatures in the rest of the country, particularly Texas, will offset lower power sector gas demand from the east.”

WSI said cooler-than-normal temperatures will continue to dominate the East and coastal California in August, and will also move into the South Central region (except West Texas). Much cooler weather is expected in all of the country’s major load centers during the month.

“In the absence of significant hurricane activity, cooler-than-normal temperatures across much of the country will result in lower power sector gas demand, increasing inventory build rates and downward pressure on prices,” Fleming said. “Lower power demand due to moderate temperatures and the economic climate will result in moderate power prices in the major markets. The cooler outlook reduces the likelihood of major heat events in the Northeast.”

By September only the Southeast will continue to see cooler-than-normal temperatures, according to WSI. The Northeast (except Pennsylvania and New Jersey) and coastal California will be dominated by warmer-than-normal temperatures and Texas can expect much-warmer-than-normal weather, the forecaster said.

“Natural gas demand from the power sector is likely to be above average in September, but will not likely offset the trend towards very high inventories in early November,” Fleming said. “Power prices in Texas could be volatile with higher probabilities of late summer heat events.”

The WSI seasonal outlooks reference a standard 30-year norm (1971-2000). The next forecast, for August-November, is scheduled to be issued July 22.

A new El Nino event — warming of surface temperatures in the eastern equatorial Pacific ocean — combined with cooler Atlantic ocean temperatures is likely to make the 2009 Atlantic hurricane season “relatively quiet,” according to the forecaster. WSI, which previously called for a total of 11 named storms, including six hurricanes, with two of them intense (Category Three or greater) forming by Nov. 30 (see NGI, June 1), said it is sticking to that forecast.

“Ocean temperatures in the tropical Atlantic are cooler, relative to normal, than at any time since 1994,” Crawford said. “Further, the new El Nino event continues to strengthen, and the recent patterns of tropical Pacific thunderstorm development have already responded to El Nino. This has resulted in an unfavorable wind shear environment across the tropical Pacific. This early emergence of this enhanced wind shear along with the relatively cool tropical Atlantic temperatures will almost certainly result in a less-active season then last year, and could potentially result in an unusually quiet season.”

The number of tropical storms forecast by WSI would be fewer than occurred during the 2008 season, when a total of 16 named storms, including eight hurricanes, five of them intense, formed in the Atlantic. But it would be about the same as an average hurricane season, which has 11 named storms, including two major hurricanes, according to the National Oceanic and Atmospheric Administration (NOAA).

In its initial hurricane forecast for the 2009 season WSI had predicted 13 named storms, three of them intense (see NGI, Jan. 5). But a continuation of relatively cool tropical Atlantic Ocean temperatures, combined with the waning of a recent La Nina event — unusually cold temperatures in the eastern equatorial Pacific — and normal to above-normal wind shear in the tropical Atlantic, prompted the forecaster to reduce those numbers in April (see NGI, April 27).

Other forecasters calling for a relatively mild hurricane season include Colorado State University (see NGI, June 8), NOAA (see NGI, May 25) and AccuWeather.com Chief Long Range Forecaster Joe Bastardi (see NGI, May 18).

The UK-based Meteorological Office recently said it expects only six tropical storms to occur in the North Atlantic between July and November, well below the long-term average of 12.4 (see NGI, June 22). There were 15 North Atlantic storms during the 2008 hurricane season.

Taking into account its own forecast of mild summer weather, Barclays Capital recently said it expects just a 0.1 Bcf/d uptick in natural gas demand for power generation during May-September compared with the same period last year.

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