Despite the presence in the central Atlantic of the year’s fourth named storm and a high probability that an area of low pressure off the coast of Africa could form into another tropical cyclone, Andover, MA-based WSI Corp. has for the second time this summer lowered the number of hurricanes in its 2010 Atlantic hurricane forecast.

WSI said it expects 18 named storms, including 10 hurricanes, five of them intense (Category 3 or stronger), to form before the season ends Nov. 30. In its previous tropical storm forecast WSI had called for 20 named storms, including 11 hurricanes and five intense hurricanes (see Daily GPI, July 21). WSI warned that the new 2010 forecast numbers are still well above the long-term (1950-2009) averages of 10 named storms, six hurricanes, and two intense hurricanes and slightly above the averages from the more active recent 15-year period (1995-2009) of 14/eight/four.

“Although the season hasn’t had a record-breaking start, historically warm tropical Atlantic ocean temperatures and an enabling wind shear environment should mean that the upcoming three months will be very active,” said WSI Chief Meteorologist Todd Crawford. A La Nina event — an unusual cooling of ocean surface temperatures off the western coast of South America — is still expected to create tropical storms in the Atlantic, he said.

“Slow starts during emerging La Nina events are par for the course,” Crawford said. “Over the last seven tropical seasons where a transition to La Nina occurred, 85% of all named storms occurred after Aug. 16. This means we are still very, very early in the season.

“More importantly, however, eastern and central tropical Atlantic sea surface temperatures remain at record warm levels, even warmer than the freakishly active season of 2005. While the early part of the season has been hampered by small destructive pockets of wind shear and widespread dry air, likely parting gifts from the recent strong El Nino event, the atmosphere is now quickly becoming more favorable for tropical development. We have reduced our numbers a bit to account for the lagged start, but are still just as bullish as ever on the remainder of the season.”

The East Coast from North Carolina’s Outer Banks to Maine has “an enhanced risk of hurricane landfall this season,” according to WSI.

“Our model suggests that the threat to the Northeast coast this season is on par with that in Florida and the Gulf coastal states,” Crawford said.

The 2010 hurricane season has gotten off to a quiet start. The first three named storms of the season, Hurricane Alex and tropical storms Bonnie and Colin, created little threat to GOM oil and natural gas production. On Tuesday Danielle, which had been a hurricane, weakened to a tropical storm with maximum sustained winds of 70 mph. Danielle was moving west-northwest at 18 mph about 895 miles east of the Lesser Antilles, according to the National Weather Service (NWS). Danielle was expected to turn to the north over the next few days and pass to the east of Bermuda on Sunday, NWS said. A large area of showers and thunderstorms located about 150 miles south-southwest of the Cape Verde Islands appeared to be forming into a tropical depression and had a 90% chance of becoming a tropical cyclone, NWS said.

Forecasters at the National Oceanic and Atmospheric Association have said they also expect the La Nina event to bring “significant” hurricane activity this year, despite the hurricane season’s slow start (see Daily GPI, Aug. 6). Colorado State University forecasters have predicted an active hurricane season and said they see a “well above-average probability” of a major hurricane making landfall in the United States and the Caribbean (see Daily GPI, Aug. 5). Chief Long Range Forecaster Joe Bastardi has said 2010 could be one of the most active seasons on record (see Daily GPI, May 20).

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