Forecasting high above San Diego - CBS News 8 - San Diego, CA News Station - KFMB Channel 8

Forecasting high above San Diego

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SAN DIEGO (CBS 8) - Although we may be strangers to hurricanes and tornadoes, every rise and drop in the mercury, change in wind direction, and fraction of rainfall matters to us here in San Diego. In this Earth 8, we go behind the scenes of forecasting, all the way up to the stratosphere.

Weather forecasting begins with one high-altitude balloon full of hydrogen and a battery-operated data collector known as a radiosonde.

"The radiosonde gives us the best vertical resolution of any instrumentation for measuring the atmosphere. Unfortunately money dictates how many you can have spatially on the ground," meteorologist Tina Stall said.

If there's one thing a meteorologist wants more of, it's a detailed observation of the atmosphere. That's what this technology does best. It measures temperature, wind speed, direction, pressure and humidity -- all the things necessary to make the most accurate forecast.

"The West Coast is sort of your first line of defense as far as upper air observations go that can help the rest of the country see what's going on," Stall said.

The weather balloon is about five feet in diameter at the start. As soon as we release from Miramar and it gets up to 100,000 feet, it grows up five times its size. At that point it will tear, fall under a parachute and return all the valuable weather data back to Earth.

During the flight, the radiosonde, which dangles 100 feet below the balloon, is exposed to temperatures as cold as 130 degrees below zero and air pressure less than one percent of what's found on earth's surface. That far up in the stratosphere, you and I couldn't survive without wearing a pressure suit.

Now it's time to examine the data fed real time from the transmitter.

"You're pretty much getting an observation every 16 feet," Stall said.

The balloon is climbing 16 feet a second, that's about 10 miles per hour.

The National Weather Service operates from 92 stations across the U.S., launching twice a day, 12 miles apart.

San Diego weather may be sunny and 70 more often that not, but that doesn't make forecasting easier. Being a West Coast city, there is a huge void in weather data coming from the west with 2,500 miles of ocean between us and Hawaii. If we could get consistent weather balloon launches offshore, it would greatly improve our ability to time the arrival of storms or predict rainfall totals.

"We have to, in the end, use best judgment, see where our consensus lies and go with your gut," Stall said.

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