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-   -   How come wind direction does not match storm direction? (http://www.bikeforums.net/general-cycling-discussion/548336-how-come-wind-direction-does-not-match-storm-direction.html)

duke_of_hazard 06-03-09 08:22 PM

How come wind direction does not match storm direction?
 
In a rainstorm, I often notice the Doppler radar shows the storm moving in one direction but the wind direction is different. How can that be? Shouldn't the wind direction always be the same as the overall direction the storm is heading?

nahh 06-03-09 08:27 PM

There's always a headwind, weather is irrelevant.

norwood 06-03-09 08:33 PM

I'm not a meteorologist nor did I stay in a Holiday Inn Express last night, but I believe it has something to do with storm cells being typically low pressure areas. That is they tend to pull air currents (wind) into them. I could be wrong however.

surfrider 06-03-09 09:09 PM

A little amatuer meteorology:

Storms (low pressure cells) generally travel from west to east across the USA/North America. However, the storm cell itself tends to spin internally, with the low pressure ones spinning counterclockwise (?) and the high pressure (clear days) cells spinning clockwise. Which way the wind is blowing depends on what part of the storm is passing over you. Example is a hurricane, which is a severe low pressure storm. If you are going to get directly hit by it,you'll experience high winds blowing in one direction, then calm (the 'eye') then high winds blowing in the opposite direction. it you're at its edge, you'll only get wind in one direction.

BTW: The high and low pressure 'cells' spin in the opposite direction in the Southern Hemisphere.

Cyclaholic 06-04-09 08:34 AM

"if everything appears to be going OK then you've overlooked the one thing that is going wrong" It's a corollary of Murphy's law.

It means that you can either enjoy the tailwind and ride into a rainstorm or you can ride away from the rain and into a tailwind. Simultaneously riding with a tailwind and away from a storm would contravene the fundamental laws of nature and cause the end of the universe.

ghettocruiser 06-04-09 01:13 PM

As mentioned, most storms are convective, meaning air rises within them. In order the replace this rising air, wind blows in towards the storm at ground level from all directions.

The actual path of the storm is determined by high-level winds, which are often different from those felt at ground level.

BarracksSi 06-04-09 01:53 PM

Quote:

Originally Posted by norwood (Post 9037962)
I'm not a meteorologist nor did I stay in a Holiday Inn Express last night, but I believe it has something to do with storm cells being typically low pressure areas. That is they tend to pull air currents (wind) into them. I could be wrong however.

Quote:

Originally Posted by ghettocruiser (Post 9042227)
As mentioned, most storms are convective, meaning air rises within them. In order the replace this rising air, wind blows in towards the storm at ground level from all directions.

The actual path of the storm is determined by high-level winds, which are often different from those felt at ground level.

Yup, yup. A good storm can be drawing ground-level air into its base from quite a ways outside its cloud boundaries, especially while it's in its forming stages.

Most, if not all, visible clouds are from warmer, more moist air being pushed or lifted into cooler, drier upper air layers. Storms are just big, fast versions, and they're taking in a lot of low-lying air to build up like they do.

StephenH 06-04-09 03:18 PM

You tend to think of storms as big balloon-like objects that float along with the breeze. But they're not. They're caused by the interactions of different air currents, and that air can be moving while the storm is stopped. So two big air masses can move into each other, and the storm is the collision, which can stay in one place, even though the air masses are moving.

An analogy: You can have a waterfall in a river. The waterfall stays in one place, even though the the water is moving right along.

BarracksSi 06-04-09 03:33 PM

Quote:

Originally Posted by StephenH (Post 9043165)
An analogy: You can have a waterfall in a river. The waterfall stays in one place, even though the the water is moving right along.

Interesting analogy. To apply it to a building thunderstorm, reverse it -- imagine the waterfall "falling upwards", which means that it'll have to suck water from the river beneath it. Near the "waterfall" (which might be called a waterspout at this point ;)), the flow of water is towards the "storm".

spinnaker 06-04-09 06:29 PM

Ground level winds will often change direction right before a storm. If it is windy and the wind suddenly drops, then picks up 180 degrees from where it was, it is time to run for cover.

spinnaker 06-04-09 06:30 PM

Quote:

Originally Posted by BarracksSi (Post 9043246)
Near the "waterfall" (which might be called a waterspout at this point ;)), the flow of water is towards the "storm".

Waterspouts are a really cool phenomena, I have had the pleasure of several in my life at a very save distance. :)

Doug5150 06-04-09 07:08 PM

In addition to the different wind directions at different altitudes, storms can push "waves" ahead of themselves, and the wind direction changes as these waves pass--the wind is forward (same direction the wave is moving in) in front of the wave, and reverses when the wave passes over and you're behind it.

http://science.nasa.gov/headlines/y2...ndularbore.htm
~

StanSeven 06-04-09 07:23 PM

The short answer is highs and lows involve rotating movements from different directions. When they pass through an area, visualize what a counter-wise circular motion does.

BarracksSi 06-04-09 08:13 PM

Quote:

Originally Posted by spinnaker (Post 9044085)
Ground level winds will often change direction right before a storm. If it is windy and the wind suddenly drops, then picks up 180 degrees from where it was, it is time to run for cover.

It's even cooler when your ears pop. :thumb:

You'd think that my growing up on the Plains would expose me to more tornadoes, though. However, we knew that when the sirens sounded, it's time not to go looking for danger, but to the basement instead. I did catch one on video with a meteorologist-to-be college friend on a storm chase -- followed it 'till it roped out, too.

StephenH 06-04-09 08:30 PM

Here's my graphical explanation. Warm moving one way, cold air the other, the storm is where they're colliding, and in this case is getting moved north like a zipper. Of course, real life is more complicated.
http://i192.photobucket.com/albums/z...eous/Storm.jpg


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