| 1. | Hurricanes are deep low pressure systems that are born over tropical seas.
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| 2. | Positive pressure ventilation systems are now more common than negative pressure systems.
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| 3. | A high-pressure system was keeping Felix from rolling northward up the coast.
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| 4. | Sunday, a powerful low pressure system brought inclement weather to the Northeast.
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| 5. | Elsewhere, a strong Canadian high-pressure system will push eastward across New England.
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| 6. | A slow-moving low pressure system will move through the northern Tennessee Valley.
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| 7. | Gabrielle formed out of a low pressure system that quickly developed.
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| 8. | A pair of low-pressure systems will direct much cooler air into the Northwest.
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| 9. | Elsewhere, a high pressure system brought quiet conditions in the South.
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| 10. | The first low-pressure system hit Thursday, dumping snow throughout northern Arizona.
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