Weather patterns may conspire to produce only the fourth Atlantic hurricane season since 1995 with below normal activity according to two forecasting groups.
Phil Klotzbach and Bill Gray of Colorado State University are predicting 10 named storms, 4 hurricanes and 2 major hurricanes (category 3 or higher) in the tropical Atlantic. A second group, WeatherBell is predicting 9-12 named storms, 4-6 hurricanes, and 2-3 major hurricanes.
The 1981-2010 30-year hurricane season (April 1 to November 30) average is 12.1 named storms, 6.4 hurricanes, and 2.7 major hurricanes. Since 1995, the U.S. has been in an active stretch, with average to above average activity in 13 of those 17 years.
Klotzbach and Gray, who have issued April forecasts since 1995, offered the following reasoning for their forecast of somewhat suppressed activity:
The tropical Atlantic has anomalously cooled over the past several months, and it appears that the chances of an El Niño event this summer and fall are relatively high.
Cool ocean temperatures offer less fuel for developing tropical storms and El Nino events often generate hostile winds which shred them apart.
The combination of a weak el Nino that should develop with higher than normal pressures over the eastern and central Atlantic can create strong low level easterlies and enhance shear. Additionally, a less active African tropical wave train is possible as a result of the disruption of the Asian subcontinent monsoon. These are all factors that contribute to the idea of decreased tropical activity for 2012.
Although Bastardi expects less overall activity compared to recent years, he believes storms that develop are likely to be in close proximity to the U.S. coast.
“I don’t anticipate many long tracked storms originating off the African coast. Storms are more likely to form close to the US coast, something I like to call home brew,” Bastardi said.
Whether these storms make landfall pose a “tougher forecast” Bastardi said.
Klotzbach and Gray indicate a lower than average U.S. landfall risk for named storms, hurricanes, and major hurricanes. Here are the landfall probabilities for major hurricanes taken from their report:
1) Entire U.S. coastline - 42% (average for last century is 52%)
2) U.S. East Coast Including Peninsula Florida - 24% (average for last century is 31%)
3) Gulf Coast from the Florida Panhandle westward to Brownsville - 24% (average for last century is 30%)
An interactive website created by Klotzbach and Gray allows you to explore landfall probabilities by region.
Irrespective of forecasts for below average activity for the upcoming season, it should be stressed that it only takes one storm to cause severe damage, loss of life, and suffering. This season marks the 20-year anniversary of Hurricane Andrew - one of the most destructive storms on record - which occurred during an otherwise quiet year.