A new La Nina event — the cooling of ocean surface temperatures off the western coast of South America — and other conditions are likely to bring warmer-than-normal temperatures to much of the United States through September, according to the latest seasonal forecast from Andover, MA-based WSI Corp.

Portions of the central and northern Plains will be spared the unusually warm weather, according to WSI seasonal forecaster Todd Crawford, who said the rapidly evolving La Nina indicates more heat across the northern United States as the summer progresses.

“In the Atlantic, record warm ocean temperatures also favor warmer-than-normal temperatures across a majority of the U.S.,” Crawford said. “On the other hand, near-record soil moisture levels across parts of the central and northern Plains, along with a lack of any significant drought conditions in the U.S., will temper the overall magnitude of the heat. By early July, we expect heat to spread across most of the western U.S. and to persist across the Southeast, while relatively cooler temperatures persist across the north-central and northeastern U.S. By August and September, we expect the heat to become more widespread across the northern U.S.

“For the July-September period as a whole, we are forecasting 836 population-weighted cooling degree days, 7-8% more than last year and about 10% more than the 1971-2000 mean.”

The WSI forecast for July calls for cooler-than-normal temperatures in the Northeast and North Central areas, with warmer-than-normal temperatures dominating the rest of the country.

“Gas demand from the power sector for cooling will likely be strong in all regions except for the Northeast and North Central areas,” Energy Security Analysis Inc. (ESAI) Director of Power and Gas Paul Flemming said in a statement issued in conjunction with WSI’s outlook. “Warmer expectations in the Southwest, the Rockies and Texas for July indicates higher probabilities of heat events, which would drive high demand for both gas and power in these regions.”

Warmer-than-normal temperatures will move into the Northeast in August, while the Southeast will become cooler than normal and much of the central United States will experience near-normal temperatures, WSI said.

“Gas demand for cooling should be weaker than normal in the Gulf Coast regions, but could be offset by higher demand in the Northeast,” Flemming said. “We would expect power prices in the Northeast markets to be volatile in August given the warmer-than-normal temperature projections.”

By August, WSI expects warmer-than-normal temperatures to be spread across all of the country except the Southeast, which will see cooler-than-normal temperatures.

“Gas demand for cooling should be strong in the Northeast and Midwest and overall demand should be strong during September relative to normal conditions. Power prices in the Northeast markets could continue to be volatile in September due to the high chance of late summer heat events,” Flemming said.

The WSI forecast was generally in line with one recently issued by AccuWeather.com Chief Long Range Forecaster Joe Bastardi, who said he expects the summer of 2010 to be warmer than normal for much of the country, with average temperatures nationwide “much warmer” than the summer of 2009 (see Daily GPI, May 25).

The WSI seasonal outlooks reference a standard 30-year norm (1971-2000). The next WSI forecast, for the August-October period, is scheduled to be issued July 20.

©Copyright 2010Intelligence Press Inc. All rights reserved. The preceding news reportmay not be republished or redistributed, in whole or in part, in anyform, without prior written consent of Intelligence Press, Inc.