 It's important to remember that water vapor imagery very rarely gives us insights about surface or near surface moisture. For example, check out this water vapor image of North America and the Western Atlantic Ocean in the image on the left, and focus in on the Caribbean Sea. Note the general dark shading in the region, indicating a relatively warm, effective layer and a dry upper atmosphere. The zoomed in version on the right focusing on Puerto Rico, Hispaniola, and much of the Caribbean Sea gives us a better look at exactly where the dark shading is located. It certainly includes Puerto Rico and Hispaniola. But don't let the dark shading cause you to conclude that the entire air column is dry. Adding surface station models to the water vapor image shows surface dew points of 72 degrees at these stations in the Dominican Republic and Puerto Rico. So concentrations of water vapor near the surface are quite high. The low level air mass is moist, but you would never know it from the appearance of the water vapor image because radiation from the large amounts of water vapor near the surface is absorbed by water vapor higher up in the middle regions of the atmosphere. Furthermore, the station models indicate varying degrees of partly cloudy skies. The clouds that were present were fair weather cumulus clouds, shallow puffy clouds that often dot the tropical sky. They usually have tops that are only several thousand feet above the ground, and radiation from the tops of these clouds was being absorbed by water vapor above, which cloaks these low topped clouds from the satellite radiometer's view. Rare exceptions do occur when water vapor from the lower troposphere does appear on water vapor images. That can sometimes occur when columns of air are extremely dry and there's not enough water vapor in the middle or upper troposphere to absorb emissions from water vapor near the surface or from the tops of the low clouds. But typically, indications of water vapor near the surface or low top clouds do not appear on water vapor images.