That low-pressure system will bring "drier, cooler air" to the region, Kallas said. The storms are not expected to be severe in Appleton and Green Bay. A low-pressure system is moving in, bringing some humidity first, the NWS said, and a slight chance of thunderstorms Tuesday night starting from 9 to 10 p.m. The rest of the week, however, is forecast to bring some relief. In addition, the humidity, which came in yesterday, will keep the overall temperatures down today and Wednesday, Kallas said. However, the heat and humidity won't be as "atrocious" as it was 10 days ago, according to Tasos Kallas, a meteorologist with the National Weather Service in Green Bay. On top of that, increasing humidity could drive the heat index up from 90 to 100. Near-record heat is expected again today, with high temperatures possible from 88 to 94 degrees. On Labor Day, Appleton reached a high of 93 and Green Bay, 91, the NWS said. The radiosonde data are transmitted over computer networks to all NWS Weather Forecast Offices and to weather stations across the world.Many Appleton and Green Bay residents will start their school year sweltering.Ī heat dome caused these two cities to break high temperature records on Labor Day - and the heat's unlikely to let up Tuesday, according to the National Weather Service. From the models, weather charts and information are developed from which all forecasts are derived. The data collected by the network of radiosonde stations is also the basic ingredient that goes into computer models, or simulations, of how the atmosphere flows across the Northern Hemisphere. Click here for the latest upper air soundings from the U.S. The upper air "sounding" allows forecasters to evaluate the vertical distribution of temperature, humidity and wind, which is critical to forecasting severe thunderstorms and tornadoes in the summer and winter storms in the winter. Here's an example of how the collected data are displayed for meteorologists (click for larger image). In the pictures on the far right, the radiosonde instrument is visible against the sky as a small white box. The object just below the balloon is the parachute, which allows the instrument to float safely back to earth once the balloon bursts. Some (perhaps 20% nationwide) are found and returned to the NWS for refurbishing so that the instrument can be re-used. Many, though, fall harmlessly into a forest or a large body of water. Summer launch (photos by Linda Skowronski, NWS Green Bay): Winter launch (photos by Peg Zenko, Green Bay): Weather Balloon Launch-In All Kinds of Weather (click on images below for larger view): So, from this simple instrument, the complete temperature, moisture, wind and pressure field in the vicinity of the launch station can be obtained during its two hour journey to nearly 100,000 feet up into the atmosphere. The height of the balloon is also calculated. The winds aloft are computed from the measured elevations and location of the radiosonde at a given pressure (recall pressure decreases with elevation). The radiosonde consists of a radio transmitter, GPS, temperature sensor (called a thermistor), humidity sensor (called a hygristor), and pressure sensor. The NWS Green Bay office is the only one in Wisconsin to launch the radiosondes (launched locally shortly after 5 AM / 5 PM CST and 6 AM / 6 PM CDT). (Click here for a map of stations in the U.S.) Under the helium or hydrogen-filled balloon a small instrument, called a radiosonde, dangles on a string broadcasting continuous weather data back to the launch site. Twice a day, seven days a week, nearly 900 stations around the world (including at the NWS Weather Forecast Office in Green Bay) release weather balloons into the atmosphere to obtain upper air weather information.
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