The Lake Charles National Weather Service Office is one of over 100 sites in the United States that regularly conduct upper air observations. Data from these observations consist of pressure, temperature, dew point temperature, wind direction and speed. This data is used locally and is also transmitted to NCEP (National Centers for Environmental Prediction) for use in development of all short and long range forecast models. This data is the heart of most guidance that meteorologists use.

When the data is used locally, it can tell the meteorologists whether conditions are favorable or unfavorable for cloud or thunderstorm development, and if so, whether the thunderstorms will be severe. High temperatures and wind direction and speed for the day can also be computed with this data. There are many other uses for this data locally. An example of the most current observation or sounding using the Skew-T log P Thermodynamic diagram for Lake Charles can be seen by clicking here.

Model data generated by NCEP starts with plots of the standard pressure levels of the atmosphere. They are at 850 hPa, 700 hPa, 500 hPa, 300 hPa and 250 hPa. These plots consist of the height of that particular standard pressure level as well as the temperature, dew point, wind direction and speed. This data, in conjunction with satellite and current conditions, enables the meteorologist to determine which of the numerous forecast models will be used for the forecast.

The upper air or radiosonde observation is conducted twice daily at 12Z and 00Z UTC at all upper air observing sites worldwide. There are instances where special observation are taken due to severe weather or various research projects.

1. At Lake Charles, the tracking system used is called ART (Automatic Radiotheodolite). It basically consists of a tracking dish, located in a dome above our inflation building, lots of cable, and the control units, one in the dome and one in the main office.

2. The balloon, when filled with hydrogen, measures about 6 feet in diameter. As the balloon rises, the atmospheric pressure decreases allowing the hydrogen to expand. When the balloon gets to a burst height, which normally exceeds 100,000 feet, its diameter will be greater than 30 feet.

3. Attached to the balloon is the train which consists of 70 to 120 feet of cotton string and a parachute.

4. At the end of the train is the instrument package or radiosonde.

5. Data is funneled through the dish and control units to a small PC which runs the MicroART (Microcomputer Automatic RadioTheodolite) software package. This allows the incoming data to be processed immediately and the operator to quality control data through the use of alphanumerics and graphics .

To see the sequence of events of a balloon release, click here.

A new Radiosonde Replacement System is being developed. Information on the system is available from NWS Headquarters.

The Future of the Upper Air Program:

There are numerous systems being used to supplement the current upper air program. The most important one is satellite. The new GOES satellite has the capability to determine temperatures and pressures at the various levels using its atmospheric sounder. This data is vital to the models in data sparse areas, especially oceans. Images of sounder data can be seen by clicking here.

Another method has been the development of wind profilers. This data, much like satellite, is near real-time. There is one profiler in Louisiana at Winnfield and one in East Texas at Palestine.

With the onset of Doppler radar and its ability to detect wind fields, an algorithm was produced to create a vertical wind profile of the atmosphere. The absence of clouds, bugs, or dust in the upper atmosphere to reflect energy back to the radar is the only set back to this method of getting wind data. Click here for data from various sites.

With all the new technology coming on-line, the old method of launching balloons will become a thing of the past, probably within the next decade or two.