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Opposing Winds

Thought I posted this last Tuesday or so!

Ann and I were talking last Friday, and she mentioned that once she looked up and saw two sets of clouds going in directly opposide directions. Isn’t that amazing?

Let’s think about how this could happen. Remember that our weather generally comes from the west. But storms — not just hurricanes, but ordinary thunderstorms — are spirals of wind, spiraling counter-clockwise around a low-pressure center. Now, if that spiral were all the wind there were, then the storm would never go away. Why does the storm go along to the east? Because there are other winds, and those winds take it. Unless a storm is very high indeed, the prevailing winds continue right above it, so all you have to do is superimpose a west wind on a spiral and you have a whole series of possibilities:

crossed winds

Now you can see that on the east side of the storm (on the right) the winds of the storm and the winds above the storm are at right angles. These crossed winds — winds at right angles — tell you that you are directly in the path of a storm.

On the south side of the storm, upper and lower winds would both be from the west; in that case, you are not in the center of the storm’s path and will not get its worst fury, whatever that is. If you are in a plane, you want to go round a thunderstorm on this side.

On the north side, the storm winds would be from the east and the prevailing winds from the west. Again, you are not really in the path of the worst of the storm, see? You might not even get wet; depends on the storm. In an airplane, however, you will get buffeted coming from the west; an eastbound plant wants to pass this storm on the south side. But on the ground, it’s just a neat show, and that’s where Ann was the day she saw opposing winds. In fact, all of us have been there many times.

Finally, look at the¬†west side of the storm. Here the winds are crossed at right angles again — north and west — but the storm is leaving. So crossed winds come every time a storm passes right over you, first when it comes and then when it goes. You can figure out for yourself whether a storm is coming or going, right?

So if it’s so common, how come Ann thought it so unusual?

Well, number one, people don’t look up. ‘Specially when a storm is coming and there’s so much to pick up and put away before the rain. But I’m pretty sure Austin told me he had seen it too. How about the rest of you?

Number two, sometimes there are so many low clouds that you don’t see the upper ones. In the thick of a storm, you only see the lower clouds. But there’s often a time before a storm when blue skies mix with two levels of clouds. Watch for this.

The bottom line is that it’s not really all that uncommon to have crossed or opposing winds. What’s uncommon is looking up enough to notice. Thanks Ann.

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