June, July and August will be 8% cooler nationally than last year and the coolest summer months since 2004, according to forecasters at MDA EarthSat in Rockville, MD.

In a Summer Outlook released last Tuesday, the forecasters said the summer months, while cooler than in recent years, will still be 4% warmer than the 30-year norm measured from 1971 to 2000. Temperatures will be hottest in the interior West and coolest in the Northeast, Mid-Atlantic and Midwest, with an 8% drop in summer population-weighted cooling degree days nationally compared to last year, they said.

“The bottom line here is a cooler look to this upcoming summer compared to especially the last three summers,” said Matt Rogers, MDA EarthSat director of weather. “The U.S. has recently been tracking cooler than the 10-year running mean and warmer than the 30-year fixed mean. These themes look to continue through the summer months.”

Emerging dryness in parts of southern to western Texas could promote early strong heat, especially during May and June, while dryness in the Southeast is expected to decrease in the coming months, creating less of a concern for major summer heat there, the forecasters said.

MDA EarthSat forecasters said 13 named storms, six hurricanes and three intense or major hurricanes (Category 3 or greater) are likely to form during the coming Atlantic hurricane season. Last year 15 named storms, six hurricanes and two intense hurricanes, Dean and Felix, were created during the Atlantic hurricane season; long-term averages are 9.6 named storms, 5.9 hurricanes and 2.3 intense hurricanes per year. Cooler Atlantic water temperatures may act to offset the enhancing impact of the La Nina effect, they said.

The MDA EarthSat hurricane forecast was in line with findings by climate scientists at the National Oceanic and Atmospheric Administration (NOAA), who have said warmer ocean waters could mean fewer Atlantic hurricanes striking the United States this year (see NGI, Jan. 28). In a report published in Geophysical Research Letters, the NOAA scientists said warming of global sea surface temperatures is associated with a sustained long-term increase of vertical wind shear in the main development region for Atlantic hurricanes.

But other forecasters say the 2008 Atlantic hurricane season will be an active one. The forecasting team 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 between June 1 and Nov. 30, with eight of the storms predicted to become hurricanes, four of them intense or major hurricanes.

In January WSI Corp. forecasters said a 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 will bring an active 2008 Atlantic hurricane season (see NGI, Jan. 7). WSI’s forecast called for 14 named storms and seven hurricanes, including three intense hurricanes, during the coming Atlantic hurricane season.

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