When I need quick information on the weather, there are two Web sites I like to use:
Doppler weather radar and satellite imagery are used for modern weather forecasting. But you don't need sophisticated equipment to do your own short-term weather forecasting. This is what you need:
Barometer
Any device that responds to small changes in atmospheric pressure can be used in weather forecasting; you don't even need "graduations" on the device because it is the direction of change that is important, not the reading on a scale. When air pressure is increasing, this is an indication that the atmosphere is descending in your location; conversely, decreasing pressure indicates that the atmosphere is ascending. Surface air pressure becomes high or low, respectively (compared to average value).
| The most common household barometer, called an aneroid barometer because it doesn't use a liquid, is basically an accordion-like metal chamber with a vacuum inside. As air pressure outside the chamber decreases, the springy metal is able to relax causing the chamber to expand. A pointer mechanism tracks the change in chamber size. | |
Wind Direction
| Weather systems generally move from west to east across the continental United States (view the Radar Loop during a stormy period and see for yourself). Once you find which way is west and face that direction, east will be behind you, north to your right and south to your left. |  |
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The wind's "name" refers to the direction from which the wind is blowing. So if you face west and the wind is blowing from behind, that is considered an east wind. |
The term wind applies only to horizontal surface air motion. There is no wind if you are at the exact locations of atmospheric ascent or descent; but if you are between such locations, you feel the wind because "wind will blow from high to low" as the atmosphere tries to balance out the vertical motions.
As you can see from this diagram, cloud and storm formation is favored in the region where the air is ascending. If the winds around a storm were as simple as this, you would expect a storm to be approaching if the wind were at your back while facing west (air heading west on its way toward surface low pressure).
Coriolis Effect
Because of the Earth's rotation, winds don't blow directly toward surface low pressure. Instead, the winds deflect to the right of the original direction of motion and spiral inward. Viewed from above, the winds from the previous diagram look like this:
So the winds move counterclockwise and inward toward surface low pressure (storms). The wind direction, when facing west toward an approaching storm, is therefore southeast or south. Likewise, after the storm has passed you the wind direction tends to be northwest or north.
Clouds
As you face west toward an approaching surface low (storm), you face toward a region where air is ascending and cloud formation is favored. Depending on moisure content of the air, the clouds may be high and thin (dry air) or low and thick (moist air). It takes some time for the moisture level in the air to increase enough for rain to form; so generally clouds lower and thicken as you go toward an approaching storm or as the storm moves toward you.
Summary
So if you see high, thin clouds to the west only and you feel a south wind and atmospheric pressure is decreasing, there is a pretty good chance that a storm will arrive within 24 hours.
More Information
The previous discussion is oversimplified, in that storms sometimes form along fronts rather than at one spot. For a discussion on storms, wind shifts and fronts, click here.