Waning La Nina conditions and a continued warm water cycle in the Atlantic Basin increase the chance that storms will hit the United States during the upcoming Atlantic hurricane season, chief long-range forecaster Joe Bastardi and his AccuWeather.com team said Friday. Bastardi and Andover, MA-based WSI Corp., which issued a separate tropical storm forecast last week, each said those same trends will bring an above average hurricane season.

Bastardi said he and his AccuWeather.com meteorologists try to understand each year where the spread of storm tracks will center. Storms can bunch within a spread, creating discrete areas of increased risk, as they did last year when one such bunch tracked across the northern Caribbean.

“This year early indications show that the spread will move north and east with a target closer to the Southeast U.S.,” Bastardi said.

“The warming [water cycle] is not uniform across the entire Atlantic. In some areas where hurricanes normally form — the central and eastern tropical Atlantic — ocean water temperatures are near or below normal,” he added. “This should limit the number of storms, so we do not expect a near record high number like in the 2005 season. However, considering other factors, the number of storms should be slightly higher than historical averages. The warmest waters relative to normal will be in the northern areas of the Atlantic, especially toward the North American continent. This could potentially increase the threat of major landfalls to the U.S. coast.”

Bastardi and the AccuWeather.com Hurricane Center are looking at 1955, 1996 and 1999 as a few of the years showing similar weather characteristics to the current large-scale patterns. In 1955 Hurricane King made landfall on Florida’s southeast coast; in 1996 Hurricanes Connie and Diane hit North Carolina; and during the 1999 hurricane season Floyd and Dennis made landfall on the North Carolina coast.

Bastardi said he will provide more details and insight on his 2008 Atlantic hurricane season predictions at the AccuWeather.com Hurricane Summit on May 12 in Houston.

In an update of its tropical forecast, WSI forecasters said an active hurricane season will arise from the continuation of warmer-than-normal Atlantic Ocean temperature anomalies into the summer and fall and the likelihood of a favorable or neutral wind shear environment on the heels of the La Nina event.

“Since 1995, most tropical seasons have been more active than the long-term averages due to warmer Atlantic Ocean temperatures. We do not see any reason why this active regime will not continue in 2008,” Crawford said. “The current La Nina event, which is decaying somewhat this spring, should leave behind a wind shear environment that is favorable for the development of tropical systems in the summer and fall of 2008. We have increased our forecast slightly based on continued Atlantic warming in recent months, along with the persistence, albeit a bit weaker, of the La Nina event.”

WSI’s newest forecast numbers are significantly higher than the 1950-2007 averages of 9.7 named storms, 5.9 hurricanes, and 2.3 intense hurricanes. Last year 15 named storms, six hurricanes and two intense hurricanes, Dean and Felix, were created during the Atlantic hurricane season.

In its preliminary tropical storm forecast issued in January, WSI predicted 14 named storms and seven hurricanes, including three intense hurricanes (see NGI, Jan. 7).

The WSI hurricane forecast is in line with that of the MDA EarthSat forecasters, who said the 2008 Atlantic hurricane season will likely be busier than average but quieter than last year. MDA EarthSat said 13 named storms, six hurricanes and three intense or major hurricanes are likely to form during the coming Atlantic hurricane season.

Weather forecasters at Colorado State University (CSU) recently said the U.S. Atlantic basin will likely experience a well above-average hurricane season this year and odds are nearly even that a major hurricane will make landfall on the Gulf Coast (see NGI, April 14). The CSU team’s forecast called for 15 named storms forming in the Atlantic basin, with eight of the storms predicted to become hurricanes, four of them intense or major hurricanes.

Scientists at the National Oceanic and Atmospheric Administration (NOAA) have bucked the trend, saying warmer ocean waters could mean fewer Atlantic hurricanes striking the United States this year (see NGI, Jan. 28).

In its Energycast Outlook issued last week, WSI said cooler-than-normal temperatures will dominate the Southeast and Pacific Coast states in May, June and July, while warmer-than-normal air will settle over much of the rest of the country, especially in the Southwest.

“The impacts of the ongoing La Nina event, combined with the relatively high soil moisture levels, will likely result in a cool May in much of the eastern half of the U.S., followed by a warm June, especially in the Northeast,” said WSI seasonal forecaster Todd Crawford. “The remainder of the summer appears relatively mild in the East, with below-normal temperatures most prevalent in the Southeast. The most significant heat in July and August will emerge from the Rockies across to the Great Lakes.”

WSI forecast cooler-than-normal temperatures across the Northwest, Northeast and Southeast (except Florida), with warmer-than-normal temperatures expected in the Southwest (except California), and Central (except Minnesota and North Dakota) regions.

Energy Security Analysis Inc. (ESAI) said the warmer temperatures in early May, when there is still some lingering generator maintenance, should keep natural gas demand firm at Henry Hub. Cooler-than-normal temperatures in the Ohio River Valley and the East will extend heating degree days into May and will also provide a firm price environment for natural gas. Electrical loads in the Northeast will likely be softer than normal and provide for some power price and implied market heat-rate stability in the region, ESAI said.

The WSI forecast for June calls for cooler-than-normal temperatures to remain in place in the Northwest and move into the Central region (except Texas), while warmer-than-normal temperatures will dominate in the East (except Alabama and Mississippi) and Southwest (except California).

That forecast presents a mixed picture for natural gas demand as the higher-than-normal cooling demand from the Southeast and eastern seaboard will be offset by the lower-than-normal demand expected throughout the central region and along the West Coast, ESAI said. Power prices, implied market heat rates and congestion pricing are expected to be firm in New York and New England due to the higher-than-normal cooling demand and electrical loads. Softer-than-normal loads in California will combine with a normal Northwest hydro season to pressure the California Independent System Operator power prices and implied market heat rates, ESAI said.

WSI looks for warmer-than-normal temperatures throughout the West (except the coastal areas of California, Washington and Oregon) and Central region in July, with cooler-than-normal air moving into the East. With such a large portion of the country covered in warmer-than-normal weather, gas in storage beginning the injection season at a 360 Bcf deficit to last year and liquefied natural gas expected to only trickle in, ESAI said spot natural gas prices will likely be firm in July. But implied market heat rates and congestion power pricing in New York, New England, the Mid-Atlantic and California are likely to be softer and more stable than otherwise.

The WSI forecast follows MDA EarthSat’s prediction earlier this month of June, July and August being 8% cooler nationally than last year and the coolest summer months since 2004 (see NGI, April 21).

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

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