Composite Map II (Upper Air)
Reference: Graphical Guidance (1994) pp. 18-33, 80-81, 151-152

The Composite Map II (4 panels)

Some Uses of this Map (Images to be completed soon)

  • The 1000-500 millibar Thickness chart, coupled with thee 850 winds, allows one to look at the both the air mass and the low level winds at the same time. You might even notice a strong low level jet just out ahead of a cold front which might mean severe. One might notice a strong low level jet over a warm front which might indicate strong warm advection and a strong rain potential. This image shows an 850 jet off the Atlantic that is likely advecting moisture into the cooler air. This allows rain to wrap around the system..backlash rains.

  • The "540 line" In the cold months (not so much in fall and spring), the 5400 meter thickness line can often serve as a good, general, first guess as to where the rain/snow line might set up. Again, this is just a general idea of where it might be, not an exact placement of the rain/snow line.

  • boundary layer conditions and wind shear
    • ...

  • lapse rates

  • mixing ratio/low level moisture Mixing Ratio, measured in grams of watervapor per kilograms of dry air (g/kg), is a more exact measure of moisture than dewpoint b/c it does not take into account pressure. A Dewpoint of 55 F in Amarillo is not the same as a dewpoint of 55F in Des Moines becuase of the elevation and pressure difference. However, a 9 g/kg Mix ratio means the samething in Des Moines as it does anywhere else. The image shows the mositure axis, and in this case there are two of them. One axis extends from the southwest to the due east through Florida and another extends northwest into Arkansas. These are the areas of most abundant low level moisture

  • 850 millibars baroclinicity. The red dots in this picture show areas of warm advection (where air flows from warmer air into colder air thus advecting warmer air into a region) at 850 usually mean clouds. The blue dots represent cold advection and will usually translate to colder surface temperatures. Often, it is important to note whre the zero degree line is on an 850 chart in forecasting for frozen precipitation.

  • good instablility w/ all 4 pans

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