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Expert: - 5/7/2007


Question
Hey! Learning met at a basic level, this confuses me:
Cold front passes. Cold air replaces warm air. Cold air sinks down towards the surface, giving high pressure. High pressure means warmer conditions, so why are cold fronts associated with cold temperatures? Likewise for warm fronts, I'm veyr confused!

Answer
Daniel,

This is a basic density issue. Cold air is more dense than warm air. That means that cold air is heavier than warm air, it weighs more, and thus the pressure it exerts is higher. Warm air is lighter and less dense, and so the pressure that it exerts is less...thus the lower pressures.
That is why the air pressure generally drops somewhat during the day as it heats up, even when there is no change in air mass and everything is basically stagnant.
High pressure systems themselves can change character, depending on where they originated, and where they eventually migrate to. A large high coming down out of central Canada can first bring in an impressive shot of bitterly cold, arctic air. However, that same high can turn into a heat pump high as it moves to a position off of the Southeast coast...if you are referring to the Northeast.
I hope this helped.

Sincerely,

Dave Dombek
Expert Senior Meteorologist
AccuWeather.com

Accuweather

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Dave Dombek

Expertise

A weather enthusiast from an early age, Dave Dombek is now an AccuWeather meteorology expert.

Experience

Dave received his B.S. degree in meteorology from the Pennsylvania State University in May of 1980. Dave joined AccuWeather in July of 1980, beginning in the Snow Warning Service late that fall after his few month period of training. Within a short period of time, Dave got involved in radio broadcasting. He spent over 25 years broadcasting forecasts on radio stations throughout the Mid-Atlantic and Northeast states, and has also done newspaper forecasts and television briefings. Currently, Dave is the lead television briefer for all of AccuWeather's television clients in the northeatern quarter of the nation. In his daily forecasting routine, Dave helps coordinate the forecasts in the northeastern part of the country. He is also the Director of Forecaster Hiring and is in charge of hiring new meteorologists. Finally, Dave is the supervisor of the climatology department at AccuWeather. An avid outdoorsman, Dave enjoys hunting and trout fishing. He also enjoys watching football and is a student of history and current events. If Dave doesn't already have enough on his plate, he is married with two teenage daughters. He also leads a small Messianic congregation in the State College, Pa. area.

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