The GULFSTREAM- IV: NOAA’S High-Flying Meteorological Platform NOAA’s Gulfstream-IV jet is the agency’s newest high-flying, high-tech platform in its hurricane forecasting arsenal. The jet flies around developing hurricanes to create a detailed picture of the surrounding upper atmosphere; the data it collects enable forecasters to improve hurricane track and landfall predictions by up to 20 percent. This capability helps save lives, property and evacuation costs by more accurately identifying where a hurricane will make landfall. The G-IV is a sophisticated twin-engine jet whose primary mission is to fly hurricane surveillance missions in support of forecasters at NOAA’s National Hurricane Center. With a range of nearly 4,000 nautical miles, the G-IV’s cruising altitude of 45,000 feet provides observational coverage at levels critical for defining weather systems in the upper atmosphere. Since the beginning of the 1997 hurricane season, the G-IV has flown missions around every Atlantic-based hurricane that has posed a potential threat to the United States. Missions cover thousands of square miles surrounding the hurricane, gathering vital data with GPS (Global Positioning System) dropwindsondes. The GPS dropwindsonde is a small, lightweight, selfcontained and expendable device that measures and transmits vertical profiles of barometric pressure, ambient air temperature, relative humidity, and GPS Doppler shifts, which are used to compute wind speed and direction. Data from the dropwindsondes are transmitted back to the G-IV. Through rigorous quality control measures on board the aircraft, the information is prepared for transmission to the National Hurricane Center in Miami, Fla., and the National Centers for Environmental Prediction in Camp Springs, Md. There the data are available for many numerical forecast models, providing important information about regions—mostly over oceans—in which there are no other sources of weather data. Computer modeling is the foundation of all NOAA weather and flood forecasts. Weather models solve a series of complex equations that simulate the present and future states of the atmosphere. The numerical models that utilize G-IV data fulfill two important purposes: to help forecasters make accurate predictions of how intense a hurricane will be and when and where it will make landfall; and to help hurricane researchers achieve a better understanding of storm processes, thereby improving their forecast models. Hurricane Missions The G-IV may fly hurricane surveillance missions in tandem with NOAA’s WP-3 Orion hurricane research aircraft, which fly at much lower altitudes and collect data that complement the G-IV data. Together, these aircraft provide the most comprehensive data coverage collected in the environment of hurricanes. The missions not only provide hurricane forecasters with critical data via the numerical model forecasts, but also give real-time indicators of the overall weather conditions working together that influence the tracks of hurricanes. These data also enable researchers to investigate the factors related to hurricane track forecasts and gain further knowledge in this scientific field of study. Winter Storm Missions During the winter months, NOAA’s interest in severe weather becomes focused on the winter storms affecting the western, central and northeastern United States. These storms are continually being monitored and studied to advance our understanding of them and improve winter storm forecasts. The G-IV’s first operational mission was a research project called the Fronts and Atlantic Storm Tracks Experiment, or FASTEX, a cooperative program developed by NOAA and the European meteorological community. Both the G-IV and a P-3 participated in this field experiment to collect research data on the severe winter storms that move eastward across the Atlantic Ocean and affect western Europe. Ultimately, the findings should lead to better forecasts for the west coasts of both Europe and North America, as well as a better understanding of how oceanic winter storms affect world climate. In 1998 and 2001 the G-IV participated in datacollection experiments designed to help scientists learn more about Pacific- driven storms and improve the forecasts for these events. The weather over the Pacific often has a major and immediate influence on the weather on the U.S. West Coast, and affects weather two to three days later over the eastern United States. Data collected and understanding of storm processes gained during 1998 proved to be especially valuable with the forecasting of El Niño, which dominated U.S. weather patterns during much of that year. Aircraft Operations Center The G-IV is maintained and operated by NOAA’s Aircraft Operations Center located at MacDill Air Force Base in Tampa, Fla., AOC is charged with the management of NOAA aircraft, personnel, budget and facilities in support of the assigned fixed-winged and rotorwinged aircraft. AOC is part of the Office of Marine and Aviation Operations, which includes civilians as well as officers of the NOAA Corps, the nation’s smallest uniformed service. NOAA Corps pilots and civilian flight engineers, meteorologists and electronic engineers are highly trained to operate NOAA’s hurricane aircraft during the severest weather conditions. Much of the scientific instrumentation flown aboard NOAA aircraft is designed, built, assembled and calibrated by AOC’s Science and Engineering Division. During non-hurricane season months, the G-IV and P3s are tailored by AOC engineers for use in other severe weather and atmospheric research programs and flown by NOAA Corps pilots worldwide in a variety of weather conditions. For more information contact Jeanne Kouhestani, NOAA Marine and Aviation Operations public affairs, at (301) 713- 3431, ext. 220. NOAA Public Affairs | Reporter Resources | NOAA Backgrounders Updated March 2003