seasonal forecast

Everyone Agrees: 2004 to be Active Season
Continuing the above-average trend, this season could see eight hurricanes heading our way.

The nation’s top two hurricane research and forecasting organizations warn that the 2004 hurricane season will continue the current trend of above-average activity with up to eight hurricanes expected and a 70 percent probability of at least one intense hurricane making landfall.

Both the National Oceanic and Atmospheric Administration (NOAA) and the Colorado State University cyclone research center issued their last pre-season forecasts in May. Both see the 2004 hurricane season, running through the end of November, having at least 14 tropical storms with six to eight developing into hurricanes and at least two of them becoming intense storms.

50/50 PROBABILITY
Colorado State University tropical cyclone researcher William Gray and his hurricane forecast team maintain their predictions for above average Atlantic basin hurricane activity in 2004. Gray and his colleagues at Fort Collins, CO, call for a total of 14 named storms to form in the Atlantic basin this year. Of these, eight are predicted to become hurricanes and three are anticipated to evolve into intense hurricanes (Saffir/Simpson Category 3, 4, 5) with sustained winds of 111 mph or greater. The long-term average is 9.6 named storms, 5.9 hurricanes and 2.3 intense hurricanes per year.

These forecast numbers are exactly the same as the team’s April 2 forecast (see HP, Spring 2004, page 6). The team’s early December extended range forecast called for 13 named storms, seven hurricanes and three intense hurricanes.

“Global predictors obtained and analyzed through this point . . . consistently point to the 2004 Atlantic basin hurricane season being an active one,” Gray said. “We expect tropical cyclone activity to be well above average with about 145 percent of the average seasonal activity.”

NOAA forecasters also are predicting an above-normal Atlantic hurricane season. NOAA’s outlook is for 12 to 15 tropical storms, with six to eight systems becoming hurricanes, and two to four of those major hurricanes.

Homeland Security’s Federal Emergency Management Agency (FEMA) officials joined NOAA in urging Gulf and Atlantic Coast states to be prepared for an active season, which runs through November 30.

“The forecast is the result of thousands of hours of work by NOAA and its partners,” said retired Navy Vice Adm. Conrad C. Lautenbacher, Ph.D., undersecretary of commerce for oceans and atmosphere and NOAA administrator. “NOAA investments in high-speed computers, improved weather modeling and extensive Earth observation systems enable our scientists and forecasters to gather and synthesize information and begin the process of preparing the public to take action.”

“NOAA’s 2004 Atlantic hurricane season outlook indicates a 50 percent probability of an above-normal season, a 40 percent probability of a near-normal season and only a 10 percent chance of a below-normal season,” said retired Air Force Brig. Gen. David L. Johnson, director of the NOAA National Weather Service. Similar seasons averaged two to three landfalling hurricanes in the continental United States, and one to two hurricanes in the region around the Caribbean Sea.

MAKING LANDFALL
The Colorado State forecast team also continues to warn of the considerably higher than average probability of at least one intense (or major) hurricane making landfall in the United States this year. According to the forecast, there is a 71 percent chance of an intense hurricane hitting somewhere along the U.S. coastline in 2004 (long-term average is 52 percent).

For the U.S. East Coast, including the Florida Peninsula, the probability of an intense hurricane making landfall is 52 percent (long-term average is 31 percent). For the Gulf Coast from the Florida Panhandle westward to Brownsville, TX, the probability is 40 percent (the long-term average is 30 percent). The team also calls for above-average major hurricane landfall risk in the Caribbean.

ACTIVE TREND
NOAA’s Atlantic hurricane outlook reflects a likely continuation of above-normal activity that began in 1995. Since then all but two Atlantic hurricane seasons (the El Niño years of 1997 and 2002) have been above normal.

NOAA scientists are predicting ENSO neutral conditions (neither El Niño nor La Niña) through July. There is a likelihood these conditions will continue through the peak August to October months of the hurricane season. The main factors in the above-normal outlook are the active phase of the Atlantic multi-decadal signal and a continuation of warmer-than-normal ocean temperatures across the tropical Atlantic. These conditions are associated with circulation patterns that favor an above-normal hurricane season.

Gray believes the United States has been fortunate over the past few decades in experiencing only a few major hurricanes making landfall in Florida and along the East Coast. The last nine years have witnessed 122 named storms, 69 hurricanes and 32 major hurricanes in the Atlantic basin. During that period, only three of the 32 major hurricanes—Opal, Bret and Fran—crossed the U.S. coastline. Based on historical averages, about one in three major hurricanes comes ashore in the United States.

“We cannot say exactly when or where it will happen, but climatology will eventually right itself, and we must expect a great increase in landfalling major hurricanes,” Gray said. “As a result, and with the large coastal population growth in recent decades, it is inevitable that we will see hurricane-spawned destruction in coming years on a scale many times greater than what we have seen in the past.”

The Colorado State team believes the United States is in a new multi-decadal era for increased storm activity, and that 2004 will follow this active trend.

“The past nine years constitute the most active consecutive years on record for Atlantic basin tropical cyclone activity, and we believe that the United States has entered a new era of enhanced major hurricane activity,” said atmospheric research scientist and forecast team member Philip Klotzbach. “Particularly along the East Coast, citizens should be prepared for two or three decades of increased major hurricane activity, which also means increased probability of landfalling hurricanes.”

The forecast team does not anticipate El Niño conditions in 2004. The Colorado State forecast team also does not attribute changes in recent and projected Atlantic basin hurricane activity to human-induced global warming.

UNDERSTANDING VARIABILITY
Gray and his team continuously work to improve their forecast methodologies based on a variety of climate-related global and regional predictors (see HP, Winter 2004, page 12).

“We are continually making progress in improving statistical hurricane forecasting techniques and in better understanding why there is such variability in month-to-month and year-to-year Atlantic basin hurricane activity,” Gray said. “Our ongoing forecast research is allowing us to continually improve hurricane prediction skill.”

NOAA’s 2004 Atlantic hurricane outlook is a joint product of scientists at the NOAA Climate Prediction Center, the Hurricane Research Division and the National Hurricane Center. NOAA meteorologists use a suite of sophisticated numerical models and high-tech tools to forecast tropical storms and hurricanes. Scientists rely on information gathered by NOAA and the U.S. Air Force Reserve personnel who fly directly into the storms in hurricane hunter aircraft; NOAA, NASA and the U.S. Department of Defense satellites; NEXRAD WSR-88D radars and partners among the international meteorological services.