Upper-air analysis questions

[dmckemy]

I have some questions regarding upper-air charts....I recently purchased Tim's forecasting simulator, but don't really know a lot about upper wind charts and what to look for....I sorta have an idea for what forecasters look for when using these charts, but my depth of knowledge of these things is pretty limited.

For the 250mb winds, I believe that this is where you can look to find the jet stream. I know that localized wind maximums are jet streaks, and that the right entrance and the left exit are areas are conducive for cyclogenesis at the surface. Can the 250mb winds also be evaluated for find other weather features?

For the 500mb winds, well, I'm not exactly sure what forecasters can use those for....in Tim's forecast simulator, there are areas where there's these contours (that go up by two...ex: 8,10,12,14) within the 500mb heights, and some have an 'x' in the middle while some have an 'n' in the middle...are those vorticity values?

As for 850mb winds, I believe that forecasters can find LLJ's in the atmosphere, and this can become really important in severe weather cases.

Also, just a random question, but on the surface analysis maps on Tim's forecast simulator, some of the station plots are blue, some are red, and some are black...what do the colors represent? I think I've noticed that the stations change colors, so I wasn't too sure if it was important....

I have had several meteorology courses up to this point, but none of the courses have concentrated in forecasting...Any help/feedback is greatly appreciated!

 

[Greg Blumberg]

You're right about all that so far.

The 'x' and the 'n' stand for the "max" and "min" of the vorticity values. Something also to take into account with the 250 mb chart and jet streams. Consider the seasons. When it's wintertime, the atmosphere compresses more than in the summertime. Thus jet stream's height change. Be sure to also check the 300 mb map.

500 mb winds are the best to look at. I find that's where you'll find most of the information of the going ons in the atmosphere, i.e. shortwaves, a general idea of where the trough is, upper level lows. It's a good mid-range level to look at to get an idea of what's going on in the atmosphere overall. I also pay attention to the temperatures, as the temperatures in the mid-atmosphere are important to figure out instability and how intense convection may be. Figuring out the location of the 0 degree and -20 degree isotherm is also important in hail. Whenever I start forecasting or seeing what the weather looks like, I start with the water vapor imagery and the 500 mb map. The 500 mb map is very, very important.

I have not used the forecast simulator, so I can't say much about what you mean by the colors of the station plots...but I can maybe relate it to the surface plots that are shown on the NCAR RAP weather site. The colors for the plots on that site relate to flight instrumentation rules. You can learn more here:

http://www.rap.ucar.edu/weather/info/index.php?referrer=surface