In weather forecasting, the only certainty is uncertainty. The data from Isha's weather balloon ends up at the National Center for Environmental Prediction in College Park, Maryland, the starting point for nearly all weather forecasts in the United States. Her information becomes one drop in a very large bucket of data taken in each day. Temperature, pressure, wind speed and direction in the atmosphere, tens and thousands of point observations are used every hour of everyday, as kind of a starting point. That's where we begin the simulation, from those observations. Thanks to the power of today's computers, forecasters can run their weather simulations not once, but several times. For each run, they slightly alter the initial conditions to reflect the inherent error built into the measurements and the uncertainty in the model itself. The process is called ensemble forecasting and the results are called spaghetti plots. >> We're looking at about 100 different forecasts here for the jet stream at

about six days ago. We have the actual jet stream drawn as the white line on here today. And you can see how most of these forecasts six days ago were well north of where we actually find the jet stream this morning. And then we'll go to a 5 day forecast, and a 4 day forecast, and a 3 day forecast. And then down to 2 days, and the day of the event. And you can see how the model forecasts all converge on that solution which is what you would expect them to do. But when you go back to the 6 day forecast, you can see the large spread in the ensemble solutions for this particular pattern. 1.) Why do we trust a 1 day forecast more than a 6 day forecast?