March 1, 2004
A: FROM MENTOR JOAN LUSK IN RI
The gulf stream is actually an ocean current - water rather than wind. You may be thinking of the jet stream, the high-level, fast winds that blow from west to east and affect jet planes' ground speed. This site has a lot about the gulf stream:
http://k12science.ati.stevens-tech.edu/curriculum/gulfstream/

The gulf stream is warm; sailors going to Bermuda can tell with at thermometer when they are in it and know that they are being swept to the northeast by it.
This link shows real-time water temperatures in the Atlantic, and the warm gulf stream is pretty obvious.
http://www7320.nrlssc.navy.mil/altimetry/images/modas_images/today/gst_sst.gif drifting buoys could measure the speed of the flow, but evidently the modern way is with altimeters - I dont' know how that works, but the pictures are cool even though the water is warm! http://www.deos.tudelft.nl/altim/gulfstream/

The basics about the jet stream (and a great deal of info on weather in general) are at
http://www.usatoday.com/weather/tg/wjstream/wjstream.htm A more technical site http://squall.sfsu.edu/crws/jetstream.html lets you see animations of the jet stream behavior over the past few days. Airlines of course make use of this information - you may have heard a pilot say that he's varied the route to take advantage of the jet stream. It seems that weather balloons are the main way to get instruments aloft http://www.usatoday.com/weather/tg/wballoon/wballoon.htm

Anticipating a wind shift is a vital skill for sailboat racers. I confess that I wasn't very good at it when I was racing... you look at patterns of wind on the water, on any flags that may be flying on shore, and most importantly on how other boats are responding to the wind where they are. If you are downwind of the shift it will probably come to you soon. Typically the wind oscillates about an average direction with a fairly regular frequency; if you've been sailing in a lift for that length of time you can expect a header soon.

I don't know if pilots can tell - perhaps from cloud formations - that the wind is different or the temperature is different some miles away... I think they rely more on professional forecasts and measurements being relayed to them. But local activity like thunderstorms and tornados would be visible, too, and pilots do take evasive action.