The Aviation Weather Center (AWC) in Kansas City, MO is a central aviation
support facility of the National Weather Service. It issues two primary products:
• AIRMET (Airmen’s Meteorological Information): Information on icing,
turbulence, mountain obscuration, low-level wind shear, instrument meteorological conditions, and strong surface winds.
• SIGMET (Significant Meteorological Information): Issued for significant
weather that may affect an airport or flight path in a given area. There are
two types:
• Convective: Issued for an area of thunderstorms affecting an area of
7,800 km
2
(3,000 mi
2
) or greater, a line of thunderstorms at least 110 km
(60 nmi) long, or severe or embedded thunderstorms in any area that are
expected to last 30 minutes or longer.
• Non-convective: Issued for severe turbulence over an area of 7,800 km
2
(3,000 mi
2
), severe icing over that area, or instrument meteorological
conditions over that area resulting from dust, sand, or volcanic ash.
Upper air weather data is essential for weather forecasting and research, and for
operating stratospheric balloons. The NWS operates 92 radiosonde locations in
North America and ten sites in the Caribbean. A small, expendable instrument
package is suspended below a 2 m (6.6 ft) wide balloon filled with hydrogen or
helium, then released daily at or shortly after 1100 and 2300 UTC, respectively.
Data obtained during the flights is coded and disseminated, at which point it can
be plotted for analysis. In recent years, the NWS has started to incorporate data
from commercial aircraft into its numerical models. Balloon teams make use of all
the data available in making a launch decision.
Operationally, the OCC and the ROCC are required to do the following:
• Coordinate with the FAA (or equivalent foreign agency) to ensure that
NOTAMs based on the predicted flight path are issued 24 hours prior to
launch.
• Obtain a launch clearance window from the FAA (or equivalent foreign
agency).
• Calculate a predicted trajectory based on the pre-launch profile of winds. The
predicted trajectory and the associated impact predictions must also be
included. Vehicles that have achieved at least 3 flights with no vehicle failures
and/or anomalies that have impact to public safety are deemed to be proven.
• Calculate a recovery point and time that satisfies the risk criteria. The time
and location of the recovery point shall be coordinated with (and clearance
to terminate be obtained from) the FAA or equivalent foreign agency.
Launching a balloon requires the conjunction of light low-level winds (in order to
comply with the limitations of the CSBF dynamic launch technique) and suitable
upper-level winds (so that the balloon remains within telemetry range of a ground
74 Mission Drivers and Operations
support facility of the National Weather Service. It issues two primary products:
• AIRMET (Airmen’s Meteorological Information): Information on icing,
turbulence, mountain obscuration, low-level wind shear, instrument meteorological conditions, and strong surface winds.
• SIGMET (Significant Meteorological Information): Issued for significant
weather that may affect an airport or flight path in a given area. There are
two types:
• Convective: Issued for an area of thunderstorms affecting an area of
7,800 km
2
(3,000 mi
2
) or greater, a line of thunderstorms at least 110 km
(60 nmi) long, or severe or embedded thunderstorms in any area that are
expected to last 30 minutes or longer.
• Non-convective: Issued for severe turbulence over an area of 7,800 km
2
(3,000 mi
2
), severe icing over that area, or instrument meteorological
conditions over that area resulting from dust, sand, or volcanic ash.
Upper air weather data is essential for weather forecasting and research, and for
operating stratospheric balloons. The NWS operates 92 radiosonde locations in
North America and ten sites in the Caribbean. A small, expendable instrument
package is suspended below a 2 m (6.6 ft) wide balloon filled with hydrogen or
helium, then released daily at or shortly after 1100 and 2300 UTC, respectively.
Data obtained during the flights is coded and disseminated, at which point it can
be plotted for analysis. In recent years, the NWS has started to incorporate data
from commercial aircraft into its numerical models. Balloon teams make use of all
the data available in making a launch decision.
Operationally, the OCC and the ROCC are required to do the following:
• Coordinate with the FAA (or equivalent foreign agency) to ensure that
NOTAMs based on the predicted flight path are issued 24 hours prior to
launch.
• Obtain a launch clearance window from the FAA (or equivalent foreign
agency).
• Calculate a predicted trajectory based on the pre-launch profile of winds. The
predicted trajectory and the associated impact predictions must also be
included. Vehicles that have achieved at least 3 flights with no vehicle failures
and/or anomalies that have impact to public safety are deemed to be proven.
• Calculate a recovery point and time that satisfies the risk criteria. The time
and location of the recovery point shall be coordinated with (and clearance
to terminate be obtained from) the FAA or equivalent foreign agency.
Launching a balloon requires the conjunction of light low-level winds (in order to
comply with the limitations of the CSBF dynamic launch technique) and suitable
upper-level winds (so that the balloon remains within telemetry range of a ground
74 Mission Drivers and Operations