Despite relative calm during the first two months of the 2010 hurricane season, the final four months of the 2010 Atlantic hurricane season are likely to pack a punch for the Gulf of Mexico and the U.S. coastline, according to forecasters at the National Oceanic and Atmospheric Association (NOAA) and Colorado State University (CSU).

“Everything is in place for a very active year,” said Gerry Bell, lead seasonal hurricane forecaster at the NOAA Climate Prediction Center, which last week released an updated forecast calling for a 90% chance of an above normal season.

The 2010 hurricane season, which runs until Nov. 30, has gotten off to a quiet start. The first two named storms of the season, Hurricane Alex and Tropical Storm Bonnie, created little threat to GOM oil and natural gas production. A third named storm, Tropical Storm Colin, formed last week and was expected to pass just west of Bermuda Saturday or Saturday night before heading almost directly north with little or no effect on the United States mainland, the National Weather Service (NWS) said Friday. Showers and thunderstorms associated with an area of low pressure located about 650 miles west of the Cape Verde Islands had a medium chance (40%) of becoming a tropical cyclone over the weekend, according to NWS.

Despite the slow start to what most forecasters say could be an above-average hurricane season, “the key message is that significant activity is still predicted for the remainder of the season,” Bell said. Two months of relative calm in the Gulf of Mexico at the beginning of the season shouldn’t lull anyone to sleep, he said.

“Historically for above-normal seasons we tend to see three to four named storms in the Gulf of Mexico. For the August to November period, which is what we’re coming into now, historically these above-normal seasons have three named storms getting into the Gulf. So there’s certainly a threat of storms getting into the Gulf of Mexico.”

A recently formed La Nina event — an unusual cooling of ocean surface temperatures off the western coast of South America — the tropical multi-decadal signal and warmer-than-average water in the tropical Atlantic and Caribbean all favor the formation of an unusually high number of tropical storms, according to NOAA forecasters.

“All indications are for considerable activity during the next several months,” Bell said. “As we’ve seen in past years, storms can come on quickly during the peak months of the season. There remains a high likelihood that the season could be very active, with the potential of being one of the more active on record.”

NOAA’s updated outlook calls for a 70% probability of a total of 14-20 named storms (including Alex, Bonnie and Colin), including eight to 12 hurricanes, four to six of them intense (Category Three or greater). The upper bounds of those ranges have been lowered since NOAA’s initial 2010 outlook (see NGI, May 31), which reflected the possibility of even more early season activity, Bell said.

NOAA’s updated forecast numbers are well above the 1950-2009 average of 10 named storms, six hurricanes and three intense hurricanes and slightly above the more recent 1995-2009 average of 14 named storms, eight hurricanes and four intense hurricanes. Nine named storms formed during 2009, including three hurricanes, two of them intense.

CSU forecasters last week said they expect the remaining months of the 2010 season to produce as many as 18 named storms, including 10 hurricanes, five of them intense. The CSU team said it anticipates a “well above-average probability” of a major hurricane making landfall in the United States and the Caribbean.

The CSU team said it is maintaining its previous forecast for a “very active” Atlantic hurricane season (see NGI, June 7) and anticipates a “well above-average probability” of a major hurricane making landfall in the United States and the Caribbean. The forecast, which is based on a model that utilizes 60 years of past data, “is predicting a very active season for the Caribbean,” it said.

The probability of a major hurricane making landfall along the U.S. coastline this year is 75% compared with the last-century average of 52%, according to the CSU forecast. There is a 64% probability of at least one major hurricane tracking into the Caribbean this year, and a 49% probability of at least one major hurricane making landfall on the Gulf Coast between the Florida Panhandle and Brownsville, TX.

AccuWeather.com Chief Long Range Forecaster Joe Bastardi has said 2010 could be one of the most active seasons on record (see NGI, May 24) and WSI Corp., which had increased its Atlantic hurricane forecast three times this year, last month lowered its expectations from 20 named storms to 19, while keeping its prediction that there will be 11 hurricanes and five intense hurricanes (see NGI, July 26).

NOAA has said the maturing La Nina could also bring with it above-normal temperatures for the southern and eastern United States, and an increased chance of precipitation for the Gulf Coast and Southeast (see NGI, July 19).

Bastardi last week said that the weakening of El Nino — the warming of surface temperatures in the central and eastern equatorial Pacific Ocean — and the current La Nina event will influence weather across the United States through this winter.

Chicago, Milwaukee and Minneapolis could be in the heaviest snow zone and other cities in the nation’s northern tier, including Detroit, Seattle and Portland, could receive above-normal snowfall, Bastardi said. At the same time, Washington, DC, and New York City will probably experience normal amounts of snowfall. And while the East is likely to see winter get off to a fast start, with temperatures tumbling in November and December, much of the country could enjoy a major thaw in January, he said.

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