Storm-watchers this week were tracking a disturbance just off the coast of Africa that looks like it has the potential to develop into a tropical storm in the next few days. Dr. Jeff Masters' Wunderblog has the story here. The possible/maybe/someday storm isn't news, however. What is news is that so far, there's no news in the 2009 hurricane season. A full month into the official season, no named storm has appeared in the Atlantic region. Asks a story by Willie Drye in National Geographic magazine, "Hurricane Season 2009: Where Are All the Storms?" As the National Geographic story mentions, there seem to be some objective forces at work that would tend to limit the incidence of tropical storm formation. An "El Nino" condition in the southern Pacific ocean in particular has pulled the Northern Hemisphere's jet stream south over the Atlantic basin. There, the jet stream sets up "wind shear" conditions in the upper atmosphere that can clip the tops off of circulating wind patterns, preventing the convective currents that engender strong storms. But a quiet June and July don't necessarily portend a quiet fall. The National Hurricane Center graphic below shows the historic pattern of storm incidence through the entire storm season. As the graph indicates, most storms occur between August and October, with the peak occurring during mid-September.
The Miami Herald cites the example of 2004, when the first named storm didn't crank up until the last day of July — but Florida ended up getting pounded by Hurricanes Charlie, Frances, Ivan, and Jeanne (" Hurricane season's been a breeze, but don't breathe easy yet," by Curtis Morgan). Jeff Masters notes, "The first named storm of the year didn't occur until August in ten of the past fifty years (20%). Only two of these ten seasons ended up with more hurricanes than average (seven or greater)." Then, he points out, there's 1992 — a year that had one, un-named subtropical storm, followed finally by the first named storm of the year — Hurricane Andrew, which shattered the previous record for hurricane dollar damage. In view of current conditions and the quiet early summer, government officials have scaled back their predictions for the season. The National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center (CPC) now gives 70% odds that the Atlantic will see 7 to 11 named storms, with 3 to 6 of those being hurricanes and 1 or 2 being major hurricanes. That's down from a May forecast of 9 to 14 named storms, 4 to 7 hurricanes, and 1 to 3 major hurricanes. But as NOAA forecaster Gerry Bell said, "It only takes one strike to make it a bad year."