I notice that on some mornings that there is dew all over my boat and on other mornings it is bone dry. Can you tell what causes this? Is it any indication of that day's weather?
Hey Steve...sorry for the delay in answering...but a very good question. I will answer your second question first. Although there is never a 100% accurate indication of the entire day's weather...morning dew usually occurs during pleasant weather when skies are clear. Two things cause dew (or frost for that manner when temps get below freezing). Dew forms when the air very close to the surface becomes saturated and condensation of the water vapor occurs. To get saturated air...you need high amounts of water vapor AND you need cooler temperatures. It is the cooler temperature that portends pleasant weather. At night during cloudless skies...there is a lot of "radiational cooling"...or heat escaping into the upper atmosphere. When there are clouds...the clouds act as a "thermal blanket" trapping the heat.  Next time you notice dew...try to think if there were cloudless skies...I bet there were. Lastly...I will mention that the temperatures at the surface are not always uniform and depend highly on the type of material. For instance...dew is often associated with grass because grass will cool faster than concrete. Notice next time what has dew on it and what doesn't. Pavement almost never has dew because it retains the heat from the day before...your boat is made of fiberglass probably which cools much faster. Hope this helps! doug
Joined: 2007-11-22