Storm Impacting the Northwest U.S.; Fire Weather Conditions in Southern California; Severe Weather in the South

A Pacific storm is bringing areas of low elevation rain, moderate to heavy mountain snow, and high winds to the Northwest. Strong Santa Ana winds and very dry conditions are producing elevated to critical fire weather conditions in southern California. Isolated strong to severe thunderstorms are possible through early Wednesday morning across parts of northeast Texas into western Tennessee. Read More >

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Upper Air

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NOAA
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Upper Air

The NWS Tampa Bay office is one of 92 sites across North America and the Pacific Islands plus 10 locations in the Caribbean that launch weather balloons each day. Balloons are launched twice per day at each location at the same time: midnight and noon Greenwich Mean Time.

The balloon preparation usually starts about an hour before launch time. Balloons are inflated in a building separate from the main office, called the inflation shelter. Hydrogen, a gas which is lighter than air, is used to fill the balloons. A bright orange parachute is tied to the bottom of the balloon and then the weather instrument, called a radiosonde, is tied to the bottom of the parachute. The radiosonde is a lightweight instrument that measures temperature, relative humidity, and wind data. Special software, including GPS, is used to track the radiosonde as it goes up into the atmosphere. The software also transmits real-time data to a computer located in the NWS office so that it can be monitored and quality controlled.

As the balloon goes up into the atmosphere, it encounters decreasing air pressure, which in turn causes the balloon to expand. By the time it pops roughly 100,000 feet in the air, it is the size of a small building. The parachute helps slow the falling instrument to prevent injury or damage to people or things on the ground. Because Florida is surrounded by so much water, most of the instruments are lost into the ocean. However, some fall on land and are recovered. Averaged over all the sites in the U.S., about 20% of the instruments are found and returned. These can be placed in a special bag enclosed with the radiosonde and mailed back so that they can be refurbished and used again.

The entire flight, from the time that the balloon is released, to the time that it pops, usually takes about 1 hour and 45 minutes. Once the flight is nearly completed, forecasters get a graphical picture of the state of the atmosphere, called a Skew-T diagram. Forecasters use these diagrams to infer how stable or unstable the atmosphere is and from there they can assess the threat for severe weather, which includes tornadoes, hail, and strong winds. The data from each weather balloon and radiosonde launched around North America are ingested into computer models that are used by meteorologists to aid in the forecasting process.

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Storm Impacting the Northwest U.S.; Fire Weather Conditions in Southern California; Severe Weather in the South

Tampa Bay Office Tour Upper Air