Colorado State University (CSU) forecasters maintained their earlier forecast, which called for a well above-average hurricane season this year with 15 named storms forming in the Atlantic Basin by Nov. 30. Eight of the storms are likely to become hurricanes and four of those hurricanes are expected to develop into intense or major hurricanes (Category 3 or greater) with sustained winds of 111 mph or greater, the CSU forecasters said last Tuesday.

“Conditions in the tropical Atlantic look quite favorable for an active hurricane season,” said CSU forecaster Phil Klotzbach. “Sea surface temperatures are anomalously warm, while sea level pressures and levels of vertical wind shear are quite low. Our primary concern is the warming waters in the equatorial Pacific. At this point, we do not believe that an El Nino will develop by late this summer; however, this is a possibility that must be monitored closely.”

Long-term averages are 9.6 named storms, 5.9 hurricanes and 2.3 intense hurricanes per year, the forecasters said.

Formation and dissipation of the first tropical storm of the 2008 Atlantic hurricane season came and went over the course of last weekend with no threat to Gulf of Mexico oil and gas interests. Tropical Storm Arthur developed Saturday in the western Caribbean Sea and wasted little time in moving ashore over Mexico’s Yucatan Peninsula, where it was downgraded to a tropical depression Sunday.

Tropical Storm Arthur was included in the CSU hurricane forecast, meaning that the forecasters expect 14 more named storms to form this year.

The CSU forecasters also said there is a 69% chance that at least one major hurricane will make landfall on the U.S. coastline this year and a 44% chance that a major hurricane will make landfall on the Gulf Coast from the Florida Panhandle west to Brownsville, TX.

Since 1995 the Atlantic basin has averaged 3.8 major hurricanes a year, up from 1.5 major hurricanes a year between 1970-1994. The increase “is primarily a result of the multi-decadal increase in the Atlantic Ocean thermohaline circulation that is not directly related to global temperature increase,” said CSU forecaster William Gray. “Changes in ocean salinity are believed to be the driving mechanism.”

The predictions reiterated the CSU team’s April tropical storm forecast (see NGI, April 14). The team’s preliminary forecast, released in December, had predicted a somewhat above-average 2008 hurricane season, with 13 named storms and seven hurricanes, including three major hurricanes (see NGI, Dec. 10, 2007). The CSU team is scheduled to issue a seasonal update of its 2008 Atlantic basin hurricane activity forecast on Aug. 5.

Most of the top hurricane forecasters are looking for active storm development. The National Oceanic and Atmospheric Administration (NOAA) last month said projected climate conditions point to a near-normal or above-normal hurricane season in the Atlantic Basin this year (see NGI, May 26). The outlook indicates a 60-70% chance of 12 to 16 named storms, including six to nine hurricanes and two to five major hurricanes, NOAA said.

WSI Corp., which had already forecast an active 2008 Atlantic hurricane season, upped the ante slightly in an April update of its tropical forecast, calling for 14 named storms and eight hurricanes, including four intense hurricanes (see NGI, April 28). 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.

MDA EarthSat forecasters also said the 2008 Atlantic hurricane season will likely be busier than average but quieter than last year (see NGI, April 21). MDA EarthSat forecasters said 13 named storms, six hurricanes and three intense or major hurricanes are likely to form during the coming Atlantic hurricane season. meteorologist Joe Bastardi said the East Coast will be at greater risk this coming hurricane season even though the number of named storms is expected to be about average, and Gulf of Mexico interests can expect seven to 10 days with at least the threat of weather disruptions (see NGI, May 19).

Using NOAA data and its own storm tracking tool, forecasting network WeatherBug said it expects 10-12 named storms and an above-average Atlantic hurricane season (see NGI, June 2).

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