Weather 101: Clearing up confusion

By: James Hopkins Email
By: James Hopkins Email

Ever wonder what goes into putting together a weather forecast?

It takes time and consideration. As a meteorologist I take quite a few calls and e–mails from confused viewers. The majority of which are confused by the same few weather terms over and over again.

"The terms are a little confusing, I don't always know what they mean," says Shea Roberts, freshman at Mesa State College.

Another MSC freshman, Megan Velarde, says, "Sometimes I think they forget that they are talking to average people who have never taken a climate or weather class."

Weather forecasts are meant to be informative and help you plan your day. Researchers at the University of Washington tested more than 450 college students and found that many are confused when it comes to what meteorologists are saying. Like when we can expect rain.

"I understand 50 percent but when it's 20 I really don't know," says Velarde. The two most common misconceptions about the chance of rain is that the percentage means coverage area or time of day, they are both wrong.

Let's break it down. Let's says a forecast calls for a 20 percent chance of rain. That means in 100 days with similar weather conditions, rain has fallen on only 20 of those days. That's for the entire forecast area at any time of the day.

Another area that has folks scratching their heads is the description of sky conditions. "I really don't know what their definition of partly cloudy means," says Velarde. The truth is "officially" there's no difference between partly cloudy and partly sunny. But this is how it breaks down officially: The scale goes from zero to 100 in percentages and the partly sunny and partly cloudy classification fall within the same percentage range right smack in the middle.

% Of Sky Cover Term
0-12--------------------------------Sunny/Clear
13-37------------------------------Mostly Sunny/Mostly Clear
38-74------------------------------Partly Sunny/Partly Cloudy
75-87------------------------------Mostly Cloudy
88-100----------------------------Cloudy/Overcast

"When they say partly cloudy you think more clouds and partly sunny is more sun," says Roberts. Usually it depends on the forecaster's preference on which term to use. The only real determining factor is the time of day. One thing all forecasters can agree on is that partly sunny is not appropriate for a nighttime forecast.

The last and sometimes the most confusing is pressure systems. "I don't ever really know what high and low pressure means, they try to point it out but it never really makes that much sense,"says Velarde. High pressure, which is designated on the map by a blue H, means that the air is descending which causes it to expand and dry out causing clearing conditions and usually nice weather. Low pressure, designated on the map by the red L, means the air is rising. Rising air condenses and cools causing clouds to develop and generally means stormy weather. One example of extreme stormy weather is a hurricane, which is the strongest of all low pressure systems.

"Before I took an Earth Science class in college that was taught by a meteorologist, I thought high pressure meant higher temperatures and low pressure meant cooler weather was coming," says Amanda Condrey, a University of North Carolina Graduate.

Fronts, especially cold fronts, symbolized on the map by the blue lines, typically bring a change in temperature and moisture. Often times rain or snow storms will develop along these approaching fronts.

If you're still unclear, send me an email at james.hopkins@nbc11news.com.


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