Various meteorological or academic entities are joining the bandwagon in calling for an extremely active 2010 Atlantic Basin hurricane season, some even more active than predicted by Colorado State University scientists less than three weeks ago.

The forecast of North Carolina State University professors Lian Xie and Montserrat Fuentes, along with graduate student Danny Modlin, calls for 15 to 18 named storms and eight to 11 hurricanes. That forecast was issued Monday.

Last week, Weather Services International issued a forecast calling for 16 named storms, nine hurricanes and three major hurricanes of Category 3 or above.

On 9 April, Tropical Storm Risk issued a forecast calling for 16.3 names storms, plus or minus 4.1 storms; 8.5 hurricanes, plus or minus 2.8; and four major hurricanes, plus or minus 1.7.

On 7 April, Colorado State University scientist Phil Klotzbach and William Gray released a forecast calling for 15 named storms, eight hurricanes and four major hurricanes.

Several key climatology factors are driving the active season forecasts, led by the fact that the El Niño event in the tropical Pacific Ocean is dissipating and is predicted to shift to either a neutral condition or to a La Niña before August, in time for the peak part of the Atlantic hurricane season.

El Niño causes increased upper level wind shear in the Atlantic, hindering tropical cyclone formation and strengthening.  That wind shear dies down during El Niño neutral and La Niña periods.

In addition, the temperatures in the main tropical cyclone development zone in the tropical Atlantic have been at record highs since February.

Weather Services International Chief Meteorologist Todd Crawford said the sea surface temperatures in the eastern and central tropical Atlantic are warmer now than they were in April of the “freakishly active season of 2005”.

“Our forecast numbers are more likely to rise than fall in future forecast updates heading into the season.”

In addition to the El Niño condition and the high tropical Atlantic sea surface temperatures, trade winds in the Atlantic are expected to remain light during the hurricane season, allowing ocean temperatures to remain high, promoting tropical cyclone development.

One important undetermined variable is the amount of West African summer rainfall. More rainfall in West Africa acts to reduce the amount of Saharan dust that enters the atmosphere over the tropical Atlantic. More dust acts to shield the ocean from sunlight, promoting a cooling trend of the sea surface temperatures. As a result, more West African rainfall promotes a more active Atlantic hurricane season.

Despite the predominance of forecasts predicting a highly active hurricane season, not everyone is on board with that prediction.  The Southern California Weather Authority issued its Hurricane and Monsoon Forecast for 2010 two weeks ago and called for a below to average Atlantic Basin hurricane season.  It predicted a large, elongated ridge to form in the Atlantic increasing wind shear. However, it noted that some storms will escape the shear by rounding the base of the ridge and moving into the Gulf of Mexico.

“These storms will likely be the few that cause major damage, possibly near the 1915 New Orleans hurricane scale,” the SCWXA said.

The North Carolina professors also see an active season in the Gulf of Mexico, with five to seven named storms and two to four hurricanes affecting the area.  They predict three to six of those named storms will make landfall along the Gulf Coast, with an 80 per cent chance one will be a hurricane and a 55 per cent change that one will be a major hurricane.

Weather Services International forecasts an increased risk of a hurricane landfall for the Northeast US this year.

“Our statistical landfall forecast model, which takes into account northern hemispheric ocean temperatures and current atmospheric patterns, is suggesting that the coastline from the Outer Banks to Maine is under a significantly increased threat of a hurricane this season, relative to the normal rates, which are admittedly quite small,” said Mr. Crawford. “Our model suggests that the threat to the Northeast coast this season is on par with that in Florida and the Gulf coastal states."