Seven days into the 2000 hurricane season, Colorado State University's hurricane forecast team, led by William Gray, is now predicting 12 named storms, eight hurricanes and four major hurricanes.
Gray, a professor of atmospheric science, had originally predicted 11 named storms, seven hurricanes and three major hurricanes in his initial December 1999 forecast and in the first update, issued on April 7.
On Wednesday, however, Gray said a series of changes in atmospheric and oceanic conditions, so-called "climate signals," led the team to project the higher numbers.
The new forecast suggests an above-average hurricane season roughly similar to or slightly weaker than those in 1995, 1996, 1998 and 1999.
Gray noted that the prediction of an above-average season follows a trend begun in 1995, when changes in global circulation systems led to the five most intensive consecutive storm seasons on record. The years 1995-99 saw 65 named storms, 41 hurricanes and 20 major hurricanes.
Another factor leading to the increase in predicted numbers, according to Gray: "The Quasi-Biennial Oscillation is not coming down from an easterly direction as fast as we thought." The oscillation is a roughly two-year pattern of stratospheric winds that blow from the east, then from the west, and then from the east again. Winds from the east tend to inhibit hurricane formation.
In the Atlantic, relatively warm sea-surface temperatures at both high and low latitudes are a favorable indicator of storm formation and are expected to be present later in the 2000 season, which runs through the end of November.
Also in the Atlantic, lower than normal atmospheric pressures, which enhance hurricane development, are expected to be present during the height of the hurricane season.
In the Pacific Ocean, sea-surface temperature patterns associated with higher Atlantic Ocean hurricane activity are present. Easterly upper-level equatorial winds over the Atlantic and South America are favorable for enhanced Atlantic hurricane activity.
Gray said the Caribbean basin faces a possibility of landfall by one or more major hurricanes — about 15 percent above the past century's average.
Although the forecasters originally saw the 2000 hurricane season as only moderately above average, the indications of increased activity did not surprise them, according to Gray. He has theorized that an oceanic circulation system commonly referred to as the "Atlantic conveyor belt" affects the number of major hurricanes that make landfall along the East Coast. While it does not influence the number of weaker cyclone systems very much, the number of major hurricanes forming and making landfall is increased.
Major hurricanes, when normalized by coastal population, inflation and wealth per capita, generated about 85 percent of the hurricane-spawned destruction.
Gray and his colleagues at Colorado State University predict the number of named storms, hurricanes, and major hurricanes, along with measures of duration such as named storm days, and give overall estimates of annual hurricane activity and destructive potential. They do not predict when or where a storm will occur, what category it will achieve or what specific track it will take.
More on the latest report from the hurricane research team at CSU is available at clicking here.
