14. The most important reason for this rapid demise is the fact that the storms source of warm, moist air is cut off. When an adequate supply of water vapor does not exist, condensation and the release of latent heat must diminish. In addition, because the land is usually cooler than the ocean, the low-level air is chilled rather than warmed. Moreover, the increased surface roughness over land results in a rapid reduction in surface wind speeds. This factor causes the winds to move more directly into the center of the low, thus helping to eliminate the large pressure differences.