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Forecasting Questions Answered

If you didn't have any weather instruments, how could you tell if storms are coming?

Fortunately we have many high-tech tools to help us try to predict the weather. However, if we didnt have the technology there are still other "signals" to look at from Mother Nature.

Many weather systems have a certain cloud pattern. Watching how the clouds build into the area can be a good indicator of future weather.

Wind direction is also a good indication for impending weather. Most of us already know the differences in conditions if were feeling a south wind compared to a northwest breeze. In Rochester, our weather generally comes from the west.

In the early days of weather prediction, meteorologists communicated with a western city as a way of foreseeing the local weather. The most successful meteorologists will use both high-tech and low-tech means for a successful forecast.

What is the early history of forecasting tornados?

With the amount of devastation a tornado can cause, it is hard to believe there was a time when meteorologists were not allowed to mention them in their forecasts. 

Before 1938, there was a ban on using the word tornado in forecasts, fearing it would panic the public. Even after this ban was lifted, very few forecasters would even mention them because little was known about tornadoes and how they formed. 

Then, in 1948 a significant step was made in tornado forecasting. Two Air Force weather officers, E.J. Fawbush and C. Miller, successfully predicted a tornado at Tinker A.F.B. This led the U.S. Weather Bureau to begin training forecasters on tornado prediction. 

Finally, in 1952 the first public tornado forecast was issued. This group of forecasters became known as the Severe Weather Unit. Now, severe weather outlooks are given by the Storm Prediction Center.

How do you forecast lake effect snow?

When arctic air moves into Western New York, 13WHAM meteorologists will be looking for certain criteria for lake snows to develop.

First, the surface temperature must be cold enough for the snow not to melt. Secondly, temperatures at approximately 5000 ft in altitude must be about 15 degrees Celsius colder than the lake water temperature. The lake water warms the cold air at the surface and it begins to rise. This creates what we call lake induced instability. We also need winds to be blowing at the nearly same direction through this layer. If they are not, the intensity of the snowfall can be drastically reduced.

If all these are present, we most likely include lake snow in our forecasts. The real forecast difficulty lies in determining exactly where and to some extent and how much snow will fall.

What is the significance of weather satellites?

When forecasting weather, satellites are one of the most important tools that meteorologists have at their disposal. There are three types of satellite imagery that we can utilize. The first is infrared imagery.

This is important because it measures the temperature of the cloud tops. When we see very cold cloud top temperatures, especially in the summer, this can alert us to developing severe weather.

The second kind is water vapor imagery. This affords us the opportunity to see circulations, such as a developing storm system, in the atmosphere. We look for a swirl, or comma shape to indicate them. These images, while very useful, offer less resolution. However, with visible satellite imagery, the resolution can be astounding. Such things as jet contrails and even cracks in Great Lakes ice cover are visible on a clear day.

How many steps are here to get the forecast to my television?

Getting the weather forecast to your television actually takes many more steps than you might think.

First, two of our meteorologists each make a forecast. Then we discuss and compare the two forecasts, and agree on a final forecast. Once the forecast is finalized, the on-air meteorologist prepares the presentation that appears on television.

He or she creates each individual graphic that you see during the weather segment. Each graphic is updated and recreated based on the new forecast. This usually takes several hours.

Aside from what you see on TV, both the on-air meteorologist and off-air meteorologist have other duties. These duties include forecasting for local radio stations, the weather-line telephone recording,, private clients, and the Democrat and Chronicle.

How is a weather map constructed?

While making a weather forecast, the present weather conditions across the area must be observed. These observations can come from many sources, and allow a weather forecaster to predict future state of the atmosphere. 

Meteorological data comes from a network of observation stations throughout the world. There are over 10,000 land-based stations constantly gathering data. Even ships navigating the ocean provide weather information four times a day. Typically, land observations are reported hourly from airports. Upper atmospheric data comes from aircraft and instrument packs attached to weather balloons know as radiosondes. Upper air data is typically reported twice daily, but can be obtained more frequently if severe weather is imminent in a particular location. 

After the data is recorded, it is sent to the National Center for Environmental Prediction where it is analyzed and constructed into charts and maps for weather prediction.

When you forecast a 30% chance of rain does that mean that 30% of the area will get rain or that the area will get rain for 30% of the day?

A forecast that calls for a 30% chance of rain or snow means that 30% of the forecast viewing area will see precipitation (for a given time period).

WHAM-TV Meteorologists dont use probability of precipitation (POP) forecasts often, but the NWS uses this type of forecast frequently. The method increases or decreasing the possibility of precipitation over certain areas. Normally isolated rain or snow would affect less than 30% of the area. Scattered rain, snow, or thunder could affect 30-70% of the area. Rain (likely) means that over 70% of the area could see rain.

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