The Colorado State University hurricane forecast team continues to predict an above-average 2013 Atlantic basin hurricane season due primarily to unusually warm water in the tropical Atlantic Ocean and an expected lack of an El Niño event. The team calls for 18 named storms during the hurricane season, between June 1 and Nov. 30. Nine of those are expected to become hurricanes and four of those are expected to become major hurricanes (Saffir/Simpson category 3-4-5) with sustained winds of 111 mph or greater.
“The tropical Atlantic remains anomalously warm, and it appears that the chances of an El Niño event this summer and fall are unlikely,” said Phil Klotzbach, of the CSU Tropical Meteorology Project. “Typically, El Niño is associated with stronger vertical shear across the tropical Atlantic, creating conditions less conducive for storm formation.”
CSU is in its 30th year of issuing Atlantic basin seasonal hurricane forecasts.
The team’s annual predictions are intended to provide a best estimate of hurricane activity during the upcoming season, not an exact measure. The forecasts are based on the premise that global oceanic and atmospheric conditions, such as El Niño, Atlantic basin sea-surface temperatures and sea- level pressures that preceded past active or inactive hurricane seasons, provide meaningful information about similar conditions that will likely occur in the current year.
“All vulnerable coastal residents should make the same hurricane preparations every year, regardless of how active or inactive the seasonal forecast is,” said William Gray, founder of the Tropical Meteorology Project and co-author of the forecast. “It takes only one landfall event near you to make this an active season.”
The Atlantic basin has been in an active hurricane period since 1995, due to a change in large-scale atmospheric and oceanic conditions. These active periods typically last about 25 to 35 years, based upon historical records since the mid-19th century.
Other than the two very active landfall years of 2004 and 2005, the United States has not experienced as many major hurricanes as would be expected given this active cycle.
“The United States has been especially fortunate in experiencing no major hurricane landfalls since 2005,” Gray said. “Prior to the past seven years, there had not been a seven-year period on record since 1851 with no major hurricane landfalls in the United States. These conditions should not be expected to continue.”
175 percent of average this season
The team predicts that tropical cyclone activity in 2013 will be about 175 percent of the average season. By comparison, 2012 witnessed tropical cyclone activity that was 131 percent of the average season.
The hurricane forecast team’s probabilities for a major hurricane making landfall on U.S. soil in 2013 are:
• Entire U.S. coastline – 72 percent (average for last century is 52 percent)
• U.S. East Coast including Florida Peninsula – 48 percent (average for last century is 31 percent)
• Gulf Coast from the Florida Panhandle westward to Brownsville, Texas – 47 percent (average for last century is 30 percent)
• Caribbean – 61 percent (average for last century is 42 percent)
Probabilities of tropical storm-force, hurricane-force and major hurricane-force winds occurring at specific locations along the U.S. East and Gulf Coasts are listed on the forecast team’s Landfall Probability website at www.e-transit.org/hurricane. The site provides probabilities for all coastal states as well as 11 regions and 205 individual counties from Brownsville, Texas, to Eastport, Maine. Klotzbach and Gray update the site regularly with assistance from the GeoGraphics Laboratory at Bridgewater State University in Massachusetts.
The full forecast report is available at http://typhoon.atmos.colostate.edu/.
The team will issue a forecast update on Aug. 2.