Published Tuesday, February 25, 2003 in the San Jose Mercury News

What's the weather like in Baghdad in February? Or March?

People who have never thought about the climate along the Persian Gulf are now mulling over those questions. A major concern about a possible conflict in Iraq is the weather and how it might affect military operations.

The first consideration is seasonal, as the climate of Baghdad falls somewhere between Phoenix and Death Valley. In the winter and spring, conditions are relatively moderate except in the northern mountains that border Turkey, where heavy snow can fall.

In May, the temperatures start to reach triple digits, with the average highs peaking at 110 degrees in July and 108 in August.

A challenge in such harsh conditions is to monitor and forecast the weather. At the recent 83rd annual meeting of the American Meteorological Society in Long Beach, vendors displayed a variety of new technologies to bring up-to-the-minute weather data to the field.

Integral Systems of Lanham, Md., has recently debuted Skylight, a satellite distribution system for getting near-real-time imagery and forecasts to forward operating areas. The system can deliver imagery from military and civilian satellites as well as forecast data within two hours. Previous field systems often had data that was more than six hours old.

The brains behind the forecast models used by operational meteorologists include supercomputers, and the Navy's Fleet Numerical and Oceanography Center in Monterey just had a transplant. Their suite of aging computers has been replaced by the latest supercomputers from Silicon Graphics of Mountain View. The SGI computers will give the Navy the ability to keep up with the latest computer models of the atmosphere and ocean.

Another key company in delivery of meteorological information is IPS Meteostar, based in San Carlos.

IPS is partnered with Integral Systems and SGI in a variety of projects, using their LEADS meteorological software to display weather data and produce forecasts for a number of countries. They also have plans for a low-cost Emergency Response Vehicle that can monitor the weather and biohazards in real time, and relay its data via satellite to any location in the world.

Q If the atmosphere is polluted with stuff causing acid rain, smog and very bad smells, why is snow always white? Shouldn't it be discolored by impurities in the air? Terrie Meyer - Rohnert Park

A Snow can indeed be polluted, but in California most of our snow is at high elevations above the places where many pollutants are produced, and is generally far from the highest concentrations. This is not the case in some of the industrialized cities in the East and in parts of Europe and Asia.

Q I was wondering, what exactly is happening on cold days and nights when you can see your breath? Shaun Moran - Santa Rosa

A What we are seeing is water vapor in our breath condensing into tiny liquid water droplets, technically known as steam or evaporation fog. This happens when the air is cold and close to saturation. The addition of moisture from a person's exhalation is enough to induce saturation, and then condensation occurs. However, the tiny little cloud that is produced dissipates rapidly as it mixes with surrounding drier air.

Q What is the ``storm track,'' and how does it funnel storms into the Bay Area? Also, how is the track related to the jet stream? Curtis Panasuk - San Carlos

A The general usage of the term ``storm track'' is to make it synonymous with ``jet stream.'' While this is not always the case, the region where the jet stream is the strongest is usually an area where storms are the most intense. Meteorologists also look at the trajectory of the jet stream across the Pacific as a predictor of where these storms will go. To monitor the jet stream, see this excellent Web site from San Francisco State University: http://virga.sfsu.edu/crws/jetstream.html

Jan Null, founder of Golden Gate Weather Services, is a retired lead forecaster with the National Weather Service. Send questions to him c/o Weather Corner, 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 them to weathercorner@ggweather.com or fill out a form online at http://ggweather.com/questions.htm