Building a Weather-Ready Nation
What does the Riverton forecast office have to do with forecasting hurricanes? Well, more than one would think!
There are about 100 sites in North America, the Pacific Islands, and the Carribean (over 800 sites across the planet) that routinely release weather balloons 2 times per day, at the same time each day at 00 and 12 UTC. NWS Riverton is one of these sites. Attatched to the weather balloon is a parachute and an instrument package called a Radiosonde. The radiosonde package includes instruments that measure pressure, temperature, and relative humidity. A small battery operated transmitter on the radiosonde transmits the data from the instruments as well as the position of the balloon, back to a receiver on the ground where the location data is used to compute the wind speeds aloft. This wind data and the data from the instrument package is then used as input in global forecast models.
The equation for cloud cover used by the GFS (Global Forecast Model) - other equations are used for each weather element at every layer of the atmosphere from the surface to nearly 100,000 ft above the earth's surface. The data from the weather balloons is used to populate these equations, then the computer models turn these equations into graphical representations of the weather up to 14 days in the future. These graphic representations are interpreted by a forecaster and are translated for the general public into a forecast. (Imagine if we had to calculate all of these equations by hand every 6 hours!)
What does that have to do with Riverton? The storm currently bringing snow to our region will end up steering Sandy down the line so forecasters at the National Hurricane Center need to sample the storm as much as possible as it passes across the intermountain west. In addition to our "routine" 00Z and 12Z launches, it has been requested of us that we also provide upper air observations for the "off-hour" runs of the Global Forecast Models, which are run at 18Z and 06Z. Typically the "off-hour runs" of the models use interpolated upper air data from the 00Z and 12Z runs and are often less accurate. So, when high impact systems approach the United States, it is often requested of us that we do 4 launches per day in support of more accurate model runs. It is believed that Hurricane Sandy could hit the eastern seabord with widespread gale to hurricane force winds over densely populated urban areas - the National Weather Service and the Hurricane Center would like to give those who are affected as much warning as possible so that they can plan accordingly or get out of harm's way.
The latest forecast track from the National Hurricane Center, based on global model data.
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