WEATHER MACHINES NEED HUMAN TOUCH

While forecasting the weather is a pretty sophisticated business, with advanced radar and satellite scans, determining existing conditions remains as easy as it always has been.

Look out a window.

If you see snow, you can safely conclude that it's snowing. If you see rain, it's fair to deduce that it's raining.

As Bob Dylan put it: "You don't need a weatherman to tell which way the wind blows."

At Cape Girardeau Regional Airport, however, it's not that simple.

For several years, the airport has been equipped with the Automated Surface Observing System (ASOS). The system is intended to establish weather conditions for pilots flying in or out of the airport.

As far as the National Weather Service and the Federal Aviation Administration are concerned, ASOS readings are the "official" weather.

Problem is, the system isn't always accurate.

ASOS consists of two sensors placed 18 inches apart that shoot up into the sky to gather readings.

"Unfortunately, the weather in that particular spot isn't necessarily the weather at the entire airport," said Larry Davis, the airport's chief air traffic controller.

For example, if the sky is totally clear except for one small cloud immediately over the sensors, the system could determine that visibility at the airport is poor.

"The biggest problem situation is where you have guys up above and they can see the runway, but the system shows zero visibility," said airport manager Bruce Loy.

Davis said it's common for the system to determine that visibility is only a half-mile or less, when controllers in the tower can see clearly for four or five miles.

"A pilot getting a briefing might think the weather in Cape Girardeau is pretty bad when, in fact, it's not that bad," Davis said.

The airport would like permission to augment the system by hooking up a computer to ASOS that would allow controllers to input correct information when faulty readings occur. That way, the "official" weather would reflect the "actual" weather.

This could be easily done -- if only the National Weather Service would agree to it.

Back when the airport's tower was federally controlled -- because of cutbacks, the city took it over several years ago -- the FAA paid the weather service to install ASOS.

For a time, a human observer monitored the system and compensated for errors. Since the system was officially certified as accurate -- about three years ago, according to Davis -- there has been no observer.

While the regional weather service office in Paducah, Ky., favors augmenting the system, Davis said permission at the national level hasn't been forthcoming.

"On the local level they support us," Davis said. "On the national level, they want us to pay them to make it work."

Davis said the weather service wants the airport to pay it $3,000 annually to fix the system.

"Why should we pay them to make sure their equipment is accurate?" Davis asked.

And why would it cost $3,000 a year for controllers to look out of the tower window to see what the weather is?

"To be honest, I don't understand that myself," Davis said.

Both Davis and Loy said the inaccuracies don't hamper flight safety. In fact, the system is more likely to say the weather is poor when it is good rather than the other way around.

When controllers issue the "official" weather at the airport, Davis said they add, unofficially of course, what the "actual" conditions are.

However, he fears that when controllers do that, the airport and the city could be assuming some liability.

"On one hand, I believe that if you know it's not right, you should say something," Davis said. "But from a legal standpoint, ASOS is the 'official' weather."