Airborne Vertical Atmospheric Profiling System The AVAPS uses dropsondes, also known as dropwindsondes, coupled with Global Positioning System (GPS) receivers to measure the state of the atmosphere during their descent. The devices can measure vertical profiles of pressure, temperature, humidity, and wind during their descent through the atmosphere. More accurate wind profiles are now available because of a unique square-cone parachute that reduces the initial shock load and stabilizes the dropsonde as it falls. To learn more, please see AVAPS at the Global Hydrology Resource Center (GHRC) website. Alpha Pattern The Alpha Pattern resembles an "X". It begins 100 miles from the storm center. The aircraft descends to 10,000 or lower for weaker systems. The pilot proceeds along the initial path through the storm center and outward 100 miles. At the end of the first leg, turn left 45 degrees and fly a 200-mile leg. Once again turn left 45 degrees, then fly 200 miles taking the aircraft through the eye for the second time. The pilot can choose to repeat the pattern if fuel allows, or head for home To learn more, please see Alpha Pattern at the Hurricane Hunters website. 3D-Modeling Doppler Radar The suite is made up of three radars, including a horizontally scanning X-band radar mounted in the lower fuselage and a vertically scanning X-band radar mounted in the tail. The two X-band (3.2 cm) Doppler radars can scan continuously and provide a horizontal resolution of about 150 meters. When used in unison, the radars can create 3-D images which even tighter resolution. Dropsondes Also known as dropwindsondes, these packages carry instruments to measure pressure, temperature, humidity and exact location/altitude via a sophisticated GPS receiver. They are deployed from flight level and descend to the surface. A unique square-cone parachute reduces the initial shock load at deployment and stabilizes the dropsonde as it descends. To learn more, please see Dropsonde at the Surface and Sounding Systems Facility (SSSF) website. Frontal Boundary The transition zones between two separate air masses, called frontal or baroclinic zones, are divided into fronts. Fronts are as large as real weather systems, and can be several thousand kilometers long and wide. By definition, a frontal system includes its own low, bringing foul weather: low cloud, precipitation, icing, turbulence, storms and tornadoes. These are the colored lines seen on television weather forecasts. There are blue colored Cold Fronts, red Warm Fronts, lavender Occluded Fronts, Stationary Fronts and so on. To learn more, please see Frontal Systems at the Sky Watchers website. Gamma Ray Spectrometer Package The Airborne Gamma Radiation Snow Survey Program uses aircraft to make airborne Snow Water Equivalent measurements. These measurements are used by forecasters issuing river and flood forecasts, water supply forecasts, and spring flood outlooks. The GRSP acquires data to assess: (1) Above-ground moisture held in the snowpack in the form of snow, ice lenses, ground ice, and standing water. (2) Above-ground moisture plus some measure of the soil moisture above field-holding capacity. (3) The aggregate change in both the above-ground moisture and the total soil moisture from some previously established measurements. Data runs are typically 10 miles long and 1,000 feet wide covering an area of 2 to 3 square miles. On each flight, the pilot will make 5-10 data runs over the specified area. To learn more, please see Airborne Gamma Survey Program at the National Operational Hydrologic Remote Sensing Center (National Weather Service, NOAA) website. GPS Dropsondes (See Dropsondes). Icing Study Package The Icing Study Package is mounted to the belly of specially modified WHI aircraft. These aircraft have state of the art deicing equipment to protect the crew and aircraft. The study package contains a variety of sensors that can be synchronized with ground-based platforms to study the accretion of ice on aircraft surfaces. To learn more, please see Aircraft Icing at the FAA William J. Hughes Technical Center website. Laser/Photographic Sensor Package This package combines the high resolution of CCD imaging systems with the capability of the latest airborne LIDAR system. The CCD imaging system is used to make high-resolution images of at wavelengths ranging from infrared to ultraviolet. The LIDAR system is an airborne, pulsed, scanning, coherent Doppler laser radar that remotely senses the distribution of wind velocity and aerosol backscatter to produce 3-D radar images of the troposphere and lower stratosphere. To learn more, please see MACAWS at the Multi-Center Airborne Coherent Atmospheric Wind Sensor website. Low Center This is the point with the lowest barometric pressure in a cyclonic weather system. In the study of tropical systems and winter storms, this is the primary starting point. There can be surface, mid-level and upper-level centers within the same weather system. These may or may not be aligned. To learn more, please see Low Pressure Centers at the Department of Atmospheric Sciences (DAS), University of Illinois at Urbana-Champaign website. Modified Alpha Pattern This is a scaled down version of the Alpha Pattern used to study major tropical systems. It resembles an "X" with the point where the lines cross as close to the center of the tropical system as possible. It begins 50 miles from the center of the system. The pilot descends the aircraft as required and proceeds along this initial path through the center and outward 50 miles on the opposite side of the system. At the end of the first leg, turn left 45 degrees and fly 100 miles. Turn left 45 degrees once again flying 100 miles through the storm for the second time. The pilot can choose to repeat the pattern if fuel allows, or head for home. It may be necessary to alter the mid-point of the pattern when investigating weaker, or rapidly developing, tropical systems. To learn more, please see Alpha Pattern at the Hurricane Hunters website. NOAA Buoy Package Upon request, WHI can load up to four 700-pound drifter in the cargo bay of our WC-130. These are then deployed out of the rear door of the aircraft at designated points in the projected path of the tropical system. These buoys transmit valuable information to WHI Meteorological staff in San Juan. The information may be analyzed on site or sent on to the client. To learn more, please see Drifting Buoy Data at the Drifting Buoy Data Assembly Center, NOAA website. Operations Center WHI personnel are stationed around the world in seven Basin Operation Centers. The chief operations facility is in a former military bunker complex carved out of a mountain about 20 miles southeast of San Juan, Puerto Rico. The other six operations centers are based in locations proximate to the major tropical weather basins, but outside the main threat areas where possible. If this is not possible, hardened facilities are used. Jump to the Atlantic Basin Operations Center (San Juan, Puerto Rico) or any of the other Basin Operations Centers for maps and further information. Optimum Routing WHI pilots are responsible for knowing the operating parameters of any aircraft under his command. This information is used to plan the most efficient route and cruise settings for the journey to the mission area. Crew safety, maximum efficiency, and minimizing enroute flight time to increase the data collection period must all be weighed in route planning. Mobile Staging Area From the seven operations centers, WHI often moves aircraft and personnel to temporary locations for logistical purposes. These Mobile Staging Areas (MSAs) are set up as needed to handle the various weather theaters. Unlike the operation centers, MSAs are located close to the action to decrease flight time. WHI Logistics Division personnel can pull up stakes and move an entire MSA out of harms way within 24 hours. Jump to the Atlantic Basin Operations Center - MSAs (5 MSAs) or any of the others Basin Operations Centers - MSAs for maps and further information. Severe Thunderstorms A thunderstorm containing at least one of the following: 3/4 inch hail, wind gusts in excess of 58 mph, or a tornado. A severe thunderstorm may contain any combination of these elements, as well as torrential rains. For more information on the study of severe, potentially tornadic, thunderstorms check the link below. To learn more, please see VORTEX-95 Operations Plan at the National Severe Storms Laboratory, NOAA website. Stepped Frequency Microwave Radiometer Calibration The Stepped Frequency Microwave Radiometer (SFMR) is used to measure, process and transmit surface wind and rainfall rate information to WHI headquarters. There the observations are used to determine actual surface sustained gale force, storm force and hurricane force wind radii as well as surface peak sustained wind and radius of maximum surface wind. Rainfall rate data is used in projecting the amount of rainfall landfall areas can expect from the system. To learn more, please see WP-3D Remote Sensors at the Hurricane Research Division, NOAA website.

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