April 8, 2013

Weather Channel predicts another
active hurricane season

The Weather Channel has released its first 2013 Atlantic hurricane season outlook, calling for another active season.

The forecast calls for a total of 16 named storms, nine of which are expected to become hurricanes, including five major hurricanes (Category 3 or higher on the Saffir-Simpson Hurricane Wind Scale).

These forecast numbers are above the long-term average from 1950-2012 (12 named storms, seven hurricanes, three major hurricanes) and slightly above the averages for the current active era from 1995-2012 (15 named storms, eight hurricanes, four major hurricanes).

Three straight Atlantic hurricane seasons have had 19 storms.  Only seven Atlantic seasons have had more hurricanes than last season's 10 hurricanes.  Among the four U.S. landfalls were the most intense tropical cyclone to make a U.S. landfall prior to June 1 (Tropical Storm Beryl), a soaking Tropical Storm Debby, a painfully slow Hurricane Isaac, and one of the most destructive storms in U.S. history, Superstorm Sandy. (Sandy became a "post-tropical" system shortly before landfall.)

One particular meteorological field has long-range forecasters concerned about 2013.

"One of the side effects of the anomalous weather pattern during March was a sharp increase in sea surface temperatures in the tropical North Atlantic," said Dr. Todd Crawford, Chief Meteorologist for Weather Services International (WSI), a part of The Weather Company.

"While it is still three months before hurricane season officially begins, this early warming of the tropical waters is an indication that an active season is in store, and our statistical forecast models confirm this hypothesis," said Crawford.  "Our current forecast...may be a bit conservative if the warm tropical ocean temperatures persist heading into the season."

With that said, there may be another factor that may oppose the effect of warmer-than-average ocean temperatures.

"The one potential fly in the ointment is the possible emergence of an El Nino event this summer," said Crawford.  

Stronger wind shear, a nemesis to tropical cyclone development, tends to appear in parts of the Atlantic Basin in a season in which El Nino has developed.  

"At this point, climate and statistical model solutions suggest that this outcome (El Nino) is not particularly likely, however," said Crawford.

"Through scientists at WSI, The Weather Channel has been producing hurricane seasonal forecasts for the Atlantic Ocean since 2006," says Dr. Peter Neilley, vice president, Global Forecasting Services.  

"The forecasts are based on state-of-the-science techniques and inputs such as patterns of ocean temperatures in both the Atlantic and Pacific oceans.  The Weather Channel forecasts have proven quite accurate and generally predict the number of storms within two each year.

"However, it is important to note that our forecasts are for the total number of storms that may occur anywhere within the Atlantic Ocean, and do not attempt to predict the number of storms that will make landfall in the U.S.," says Neilley.

Senior Meteorologist Stu Ostro points out, "Some businesses such as those who are clients of Weather Services International (WSI) find value in hurricane season forecasts. The total number of storms is of interest to me because it matters for how busy I am during the season; for example, there wasn’t a U.S. hurricane landfall in either 2009 or 2010, but the former had nine storms and the latter 19.

"Nevertheless, as I am on record many times as saying, and as is The Weather Channel’s philosophy, these forecasts absolutely cannot accurately predict critical details such as where or how many landfalls will occur and people in hurricane-prone areas should be equally prepared every year regardless of seasonal outlooks."

Ostro adds, "In 1983 there were only four named storms, but one of them was Alicia, a Category 3 which hit the Houston-Galveston area and caused almost as many direct fatalities there as Andrew did in South Florida."

The 1992 season included four hurricanes and one U.S. landfall, Category 5 Hurricane Andrew.

"While the saying might appear trite, Andrew and Alicia exemplify that truly all it takes is one."

On the opposite side of the spectrum from those two relatively inactive hurricane seasons that each had a single devastating landfall was the 2010 season.

That year we saw a total of 12 hurricanes in the Atlantic Basin. In all, there were 19 named storms, which tied 1995 for the third most on record during a season.






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