RESEARCHERS STUDY FORMATION OF HURRICANES

August 28, 2006 — Reasons how and why some easterly African waves develop into hurricanes and some do not is still largely unknown. This earliest stage of intensity change is just one aspect that hurricane researchers with the NOAA Atlantic Oceanographic and Meteorological Laboratory in Miami, Fla., are studying this summer as a part of the Intensity Forecast Experiment, or IFEX. (Click NOAA satellite image for larger view of Saharan Air Layer or SAL. Click here for high resolution version, which is a large file. Please credit “NOAA.”)

"Intensity change is NOAA's top tropical cyclone research priority as it is the most difficult component to forecast and can significantly alter how a community prepares for a landfalling storm," said Frank Marks, director of the NOAA Hurricane Research Division.

These investigations continued as NOAA hurricane researchers were in the sky to observe what was then Tropical Storm Debby over the open eastern Atlantic Ocean and learn more about the role that dry, dusty air that originates off of Africa may have on the early intensification of such storms as they develop.

As part of NOAA's hurricane intensity research efforts, the NOAA Gulfstream-IV jet aircraft observed Tropical Storm Debby as it moved towards the central Atlantic Ocean and gradually showed signs of organization. Tropical Storm Debby, like Tropical Storm Chris, is one of the first few easterly waves of the 2006 hurricane season to originate off the African coast and travel across the Atlantic while forecasters wait and watch for signs of development. These waves in the atmospheric flow, named for the geographic location where they are born, are known as Cape Verde storms and are the seedlings for more than half of the systems that eventually earn a name from the NOAA National Hurricane Center. (Click NOAA image for larger view of crew taken in Barbados following the completion of the first-ever NOAA Gulfstream-IV SALEX mission into Tropical Storm Irene taken Aug. 7, 2005. Click here for high resolution version. Please credit “NOAA.”)

Tropical Storm Debby is of particular interest to NOAA researchers because of its association with a large mass of dry dusty air that originated over the African continent and traveled westward over the Atlantic called the Saharan Air Layer, or SAL. NOAA hurricane researchers and their colleagues are studying the interactions of this regularly occurring SAL phenomena and its apparent ability to temporarily suppress hurricane development and intensification. Hurricanes thrive in environments of moist warm ocean air and appear to struggle to intensify when they are surrounded by these large SAL outbreaks and the associated very dry air.

"The SAL may be yet another piece of the puzzle in advancing our understanding of tropical cyclone genesis and intensity change in the North Atlantic and Caribbean Sea," said Jason Dunion, a meteorologist at the NOAA Atlantic Oceanographic and Meteorological Laboratory and NOAA's hurricane field program director.

During the two planned research flights around Tropical Storm Debby, NOAA scientists deployed numerous miniature weather stations called GPS dropwindsondes into the region surrounding the convection, sampling the wind speed, pressure, temperature and moisture. Scientists are looking to describe this environment and compare it to satellite estimates of the SAL as well as the storm's correlated intensity. Information gathered during these flights was sent to the NOAA National Hurricane Center, NOAA's National Centers for Environmental Prediction and other locations where models are able to incorporate and interpret this new data set.

The 2006 international African Monsoon Multidisciplinary Analysis, or AMMA, is a concurrent research effort that compliments NOAA's IFEX goal to observe and describe intensity change in storms developing off the African coast. Much of NOAA's research in AMMA is being directed at the Saharan Air Layer and how it interacts with developing hurricanes.

In 2007 NOAA, an agency of the U.S. Commerce Department, celebrates 200 years of science and service to the nation. Starting with the establishment of the U.S. Coast and Geodetic Survey in 1807 by Thomas Jefferson much of America's scientific heritage is rooted in NOAA. The agency is dedicated to enhancing economic security and national safety through the prediction and research of weather and climate-related events and information service delivery for transportation, and by providing environmental stewardship of the nation's coastal and marine resources. Through the emerging Global Earth Observation System of Systems (GEOSS), NOAA is working with its federal partners, more than 60 countries and the European Commission to develop a global monitoring network that is as integrated as the planet it observes, predicts and protects.

Relevant Web Sites
NOAA Saharan Air Layer Research

NOAA Hurricane Field Program

NOAA Intensity Forecast Experiment, or IFEX

NOAA Hurricane Research Division

NOAA Atlantic Oceanographic and Meteorological Laboratory

Media Contact:
Jana Goldman, NOAA Research, (301) 713-2483 ext. 181 or Erica Rule, NOAA Hurricane Research Division, (305) 361-4541