plot of streamlines and isotherms at 850 and 500 hPa

Question

In practice, many forecasters estimate the total advective change of stability on a given sounding by estimating the temperature advection at several levels in the troposphere using the actual winds and isotherms from upper air analyses. This procedure takes into account the combined lapse rate advection and shear effects, if both are present.

These plots show streamlines and isotherms at 850 and 500 hPa. Based strictly on advection, will the stability increase or decrease in the 850-500 hPa layer at St. Cloud, MN (circled)?

Increase
Decrease

The correct answer is INCREASE.
In the 850-hPa analysis, there is clearly cold temperature advection taking place at St. Cloud, while at 500 hPa, there is neutral or even slightly warm temperature advection taking place. Cooling the lower portion of the layer, coupled with no change or slight warming near the top results in a net increase in the stability of the 850-500 hPa layer.


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