Is it the Cold Front or the Cold Air that Gives More of an Impact?

Weather Talk

POSTED: Tuesday, February 25, 2014 - 10:52am

UPDATED: Wednesday, February 26, 2014 - 12:58pm

Many people say the term "cold front" when they are really talking about the cold air mass following behind it.

I was doing my forecast, while eating my breakfast this morning, and I was focusing on two cold fronts tracking into the Borderland. One cold front is due early Wednesday and another, stronger one on late Saturday into Sunday. Many times the air modifies or warms as the air mass pushes in and I refer to them as just “cool fronts”. I thought about how much as meteorologists and weather forecasters will emphasize the “cold Front”. Now a cold front does produce gusty winds, sometimes rain or snow on its leading edge and it ushers in colder air. The colder air mass behind the front is what keeps the area cold and has a longer lasting impact. In today’s “Weather Talk” I will define cold and warm fronts, their differences and about the weather produce.

In weather, all fronts are boundaries between masses of air with different densities, usually caused by temperature differences.

A cold front is a warm-cold air boundary with the colder air replacing the warmer. Cold weather fronts usually move from northwest to southeast. The air behind a cold front is colder and drier than the air in front. When a cold front passes through, temperatures can drop more than 15 degrees within an hour. While a winter cold front can bring frigid air, summer cold fronts often can more accurately be called "dry" fronts because they are most often associated with much drier air.

On a weather forecast map, a cold front is represented by a solid line with blue triangles along the front pointing and towards the warmer air.

There is usually an obvious temperature change from one side of a cold front to the other. An abrupt or dramatic temperature change over a short distance is a good indicator that a front is located somewhere in between.

As a cold front moves into an area, the heavier, cool air pushes under the lighter, warm air it's replacing. The warm air cools as it rises. If the rising air is humid enough, water vapor in it will condense into clouds and maybe precipitation.
In the summer, an arriving cold front can trigger thunderstorms, sometimes severe thunderstorms with large hail, dangerous winds and even tornadoes. As a cold front arrives in a particular place, the barometric pressure will fall and then rise. Winds ahead of a cold front tend to be from a southerly direction while those behind the front, in the cooler air, tend to be northerly. In fact, weather stations use the shift from a southerly to a northerly wind direction as the indication that a cold front has passed through.

A warm front is defined as the changeover region where a warm air mass is replacing a cold air mass. Warm fronts usually move from southwest to northeast and the air behind a warm front is warmer and moister than the air ahead of it. When a warm front passes, the air becomes noticeably warmer and more humid than it was before.
On a weather forecast map, a warm front is represented by a solid line with red semicircles pointing towards the colder air and in the direction of movement.Again, there is typically a noticeable temperature change from one side of the warm front to the other, much the same as a cold front. If colder air is replacing warmer air, it is a cold front, if warmer air is replacing cold air, then it is a warm front. Warm fronts do cause air to rise and if there is enough moisture they do produce showers and thunderstorms as they are moving through an area.

Because cold fronts move along the ground where they encounter friction, they move slower at ground level than they do further up in the atmosphere. For this reason, cold fronts tend to be more sloped than warm fronts.

Typically cold fronts move faster than warm fronts. The combination of higher speed and slope push warm air masses upward very quickly. This quick upward air movement causes the warm air being displaced to cool quickly, becoming turbulent. This turbulence often can be the cause of extremely violent weather.

Because cold fronts move quickly, the weather associated with them typically also moves quickly and passes over a particular location in a short period of time. The turbulent weather generally stays right in line with the front.

A cold front is where a cold air mass is pushing into a warmer air mass. Cold fronts can produce dramatic changes in the weather. They move fast, up to twice as fast as a warm front. Cold air is dense so it is able to quickly plow a warm air mass ahead of it.

Commonly, when the cold front is passing, winds become gusty; there is a sudden drop in temperature, and heavy rain, sometimes with hail, thunder, and lightning. Lifted warm air ahead of the front produces cumulus or cumulonimbus clouds and thunderstorms. Atmospheric pressure changes from falling to rising at the front. After a cold front moves through your area you may notice that the temperature is cooler, the rain has stopped, and the cumulus clouds are replaced by Stratus and stratocumulus clouds or clear skies.

The first cold front this week, on Wednesday, will just drop the temperatures 6 to 8 degrees. I wish we had some enough moisture to produce some long over showers or thunderstorms. The second cold front, on Sunday, looks to be stronger, colder and may even produce some area mountain snow. We know that cold fronts replace warmer air masses and warm fronts replace colder air. Both cold and warm fronts can and often do produce rain, storms and cold fronts snow and wintry variety of a rain/snow mix. The fronts get noticed because they are the edge of the air masses that bring about sometimes dramatic change. But the longer lasting impact is made by the colder or warmer air mass that has move in.

Chuck DeBroder, Chief Meteorologist
KTSM, NewsChannel 9, NBC, El Paso, TX
cdebroder@ktsm.com
www.facebook.com/Charles-DeBroder
www.twitter.com/ Chuck DeBroder NC9 @wxchuckNC9

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