Published Tuesday, December 2, 2003 in the San Jose Mercury News

Weather Corner

Gift-giving ideas, from high-tech to quaint, for weather fans

Looking for that perfect holiday gift for the weather enthusiast in your life? Here are a number of items for those who want to learn more about meteorology.

Every other month, I look forward to receiving my favorite weather magazine, Weatherwise. It is full of well-written weather-related articles appealing to both the casual reader or dedicated weather junkie. It has a great mix of information on current weather topics, weather history, weather education and weather folklore. To see a preview or order the magazine, check

Recently I visited the Northeast, and I was fascinated by the abundance and variety of weather vanes on the roofs of homes and businesses. I also discovered the home of Vermont Weatherworks, where they hand-paint some truly gorgeous wooden vanes with a whole menagerie of animals. They have vanes topped by whales, fish, birds and other wildlife plus about a dozen breeds of dogs available. One caveat -- these are so beautiful you may want to make room for them inside of your house as a decoration. They can be viewed online at For a beautiful metal weather vane, check out Weathervanes of Maine at

A really nice weekly engagement calendar focused on weather issues recently landed on my desk. ``Weather, A Collection of Photography, Facts and Stories'' is beautifully illustrated, with daily weather facts. Did you know that on Dec. 2, 1970, ``Spectators were treated to an unusual sight in Utah when a snow tornado crossed the Timpanogas Divide, spewing snow 1,000 feet into the air''? On the facing page for each week there are interesting articles and color photos on a variety of weather topics. In the back of the book is a fold-out map of worldwide weather extremes and a chart where you can graph your own weather for a year. This can be viewed at

For the ultimate gift to give the on-the-go techno weather lover, see the Storm Hawk. Utilizing the color iPaq PDA from Compaq, it combines a GPS unit with live radar to tell you not only where you are going but what the weather is along the way. Proprietary software, called Storm Vision, will also give the location of storm cells 30 minutes into the future. Storm Hawk also receives the latest weather advisories and warnings, along with the locations of lightning, via a built-in cellular connection. See

Q.  Sometimes after a cold night, when the morning sun first hits cold roofs or fences, a steam-like vapor swirls into the air. Is there a name for this phenomenon? It always makes me realize that our little planet is just the right distance from the sun to warm up again after the night. Suzanne Schettler - Ben Lomond

A.  The Earth's energy balance is indeed remarkable. The vapor you refer to it is called ``evaporation fog'' or ``steam fog.'' As the sun's energy strikes water droplets that are on the roof, some evaporate into water vapor just above the surface of the roof. However, if the air is cold enough, they will almost instantaneously condense into tiny cloud droplets, and this is what you are seeing.

Q.  If there is no wind, how fast does a typical raindrop fall? Same for a typical snowflake?  Daryl Adams - San Jose

The terminal velocity of a falling raindrop through still air depends on its size. An average raindrop is about 2 millimeters in diameter and has a maximum fall rate of about 14.5 miles per hour or 21 feet per second. A large raindrop, 5 mm in diameter, falls at 20 mph (29 feet/second), but drops of this size tend to fall apart into smaller drops. Drizzle, which has a diameter of 0.5 mm, has a fall rate of 4.5 mph (7 feet/second).

Snowfall rates are just a variable. Heavy wet snow can ``zip'' down at as much as 9 mph (13 feet/second), while a small light flake will seemingly float down at 1.5 mph or just over 2 feet per second.

Q.  I am wondering if a tornado would show up on GOES (a weather satellite). If so, what would it look like? Alissa Hicks - Novato

A.  There are a number of limitations that prevent tornadoes from being visible from space. First, the best resolution of the GOES (Geostationary Operational Environmental Satellite) is just slightly more than a half-mile, while the diameter of a tornado averages about 100 yards. Tornadoes also occur under massive cloud shields that would prevent seeing them from space, even with higher resolution imagery.

Jan Null, founder of Golden Gate Weather Services, is a retired lead forecaster with the National Weather Service. Send questions to him c/o WeatherCorner, San Jose Mercury News, 750 Ridder Park Drive, San Jose, Calif. 95190. You also can telephone questions at (510) 657-2246, fax them to (510) 315-3015 or e-mail, or fill out a form online at Please indicate in your e-mail what city you live in.