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Last night a friend and I were standing in a field, watching the landing patterns into Grand Rapids Michigan. There was no wind, and the temperature was dropping rather quickly after sunset. A strange, 5 foot high fog developed across the field, rolled out of the line of trees, through the open area, and over to a small, slow moving stream. Shortly after, it reversed direction, and crossed back over the field, to the line of trees, where it again changed direction. As there was no wind, what caused it to change direction? We could actually feel it slide across us, and it never got any taller. Any ideas? Kris and Chris

...................................................................... Hello Kris and Chris. This ghostly movement of ground fog is a fairly common event in terrain such as you describe. The line of trees along side the airport radiate heat quickly in the early evening, and of course, the trees and vegetation add water vapor to the air. When the air becomes 100 percent saturated, either fog or dew will form. Fog formation depends upon a 3-5 knot wind. If there is no wind...dew will form. A higher wind speed will begin to disperse the fog. You may not have felt it, but a slight breeze moved the fog across the field. It may have even been caused by the extremely local breeze caused by the airplanes taking off or landing. This thin layer of ground fog can be extremely hazardous. When we are on final approach, we are able to see down thru the thin layer of fog which is hardly noticeable. Just as we flare out for the landing, we enter the fog, and horizontal visibility is zero. What a surprise! This rapidly changing fog condition is also very common near bodies of water like ponds, swamps, ocean, lakes near airports. Mystery writers often speak of the "cold cloak of fog" wrapping around the soon-to-be murder victim. It is an eerie feeling, as you experienced...you said you could "feel it" slide across you. Learn from the experience, and keep it in mind when landing in near-clam conditions just after sunset. Happy Landings! JOE     [Topics]

Hi, Is the phrase "lake effect snow" a reference to the snow forming off of one of the Great Lakes or can it refer to any lake? I'd appreciate clarification. Armando

...................................................................... Hello Armando. Lake Effect Snow is usually used (in the U.S.) in regards to a weather phenomenon most commonly found on the leeward side of the Great Lakes in the late fall and early winter, hence the name. It can happen along the lee shores of any large body of water including the ocean.. (but curiously it is still most often called "lake effect" instead of "Ocean effect." Before the body of water freezes over, a cold dry wind blows across the expansive stretch of water, picking up moisture by evaporation. The air becomes increasingly moist until it is near saturation. The water is warmer than the air, so slight lifting is taking place, although cloud tops will usually be only 3-4,000 feet. When the air moves over the shoreline, the land mass is colder than the water (land radiates heat faster than the water) causing the air to settle and the lifting stops. The moisture, in the form of snow "dumps" onto the land within a mile to five miles from the shoreline. Sometimes, this snow can accumulate to many feet deep!. It is usually very light and fluffy in nature. It is possible to have the water vapor "sublimate" into visible moisture, without going thru the cloud formation stage. That is, snow will form and drop to earth with no cloud in the sky! I used to fly often into Muskegon, Michigan which is right on the shores of Lake Michigan. One time at 11:00 P.M. while on ILS approach we went from clear sky, NO clouds, into blinding snow at 700 feet. An actual blizzard was occurring on the surface...all due to lake effect. They get it many times each year...sometimes it snows every day for more than a week. Since the snow is fluffy, it gets about three feet deep, but from that point on it begins to compact, so it never seems to get deeper. We used to kid around by saying "it snows all day, and goes back up at night!" Happy Landings! JOE     [Topics]

I am researching the Internet for a teacher who has approximately 100 students. She would like as many links to weathermen across the US. Her main objective is to compare how weather is forecast all over the states by students being able to e-mail different meteroligists and asking how they forecast weather. The internet is great for weather links, do you have any ideas for me? D

...................................................................... Hi D. I would suggest contacting the Weather Chanel in Atlanta Georgia. They have a web site, and will be helpful in advising you how to contact other weather people. Happy Landings! JOE     [Topics]

I'm intereested in finding good images of actual wether satellites. I'm working on a project for the military that involves their system for mobile weather forecasting. If you know of a place or way I can obtain images of the satellites, please let me know. Thank you, Kristi

...................................................................... Hello Kristi, I would think NASA (they are on the web) and the U.S. weather Bureau (also on the web) would have good images for your use. Happy Landings! JOE

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