Convective Condensation Level (CCL) is the height at which a parcel of air, when heated sufficiently from below, rises and becomes saturated. It is where newly forming convective clouds should form bases. There are two methods used to find CCL. One method uses the surface dew point to find CCL. This is known as the parcel method because it evaluates a parcel of air near the surface. It is commonly designated CCL_P The second method evaluates CCL using the moist layer near the surface and is known as the moist-layer method, designated CCL_ME The parcel method works well when predicting the bases of ordinary cumulus clouds, while the moist-layer method is preferred when predicting thunderstorms and associated phenomena. Both should be evaluated when analyzing the Skew T.

To determine CCL_P draw a line upwards from the surface dew point parallel to the nearest saturation mixing ratio line until your line

Figure 6-2-6.-Determination of the lifting condensation level. 

intersects the plotted temperature curve. This is CCL_P See figure 6-2-7. 

Now that we have determined CCL_P we can very quickly calculate the temperature the surface must reach if clouds are to form at CCL_P. This is the Convective Temperature (parcel method) CT_P Once a parcel of air near the surface has heated to this temperature, it will rise to its condensation level without ever being colder than the surrounding air. The CT is found by proceeding from CCL dry adiabatically to the surface, See figure 6-2-7.

Finding CCL_ML  is a little more complex. Draw a light line parallel to the temperature curve 6C cooler than the temperatures on the lowest 150 millibars of your sounding. Your line represents a dew point depression roughly equivalent to 65 percent relative humidity. The area where the dew point curve is to the right of your line is considered a moist layer. Now, bisect the dew point curve in the moist layer, or the dew point curve in the lower 150 millibars if the moist layer exceeds the must reach if clouds are to form at This lower 150 millibars, with a mixing ratio line. The level where this mixing ratio line crosses the temperature curve is CCL_ML See figure 6-2-8 for an example of CCL_ML  Note that in figure 6-2-7 insufficient moisture is present to find CCL_ML  When insufficient moisture is present, it should be noted in the analysis block of the Skew T. Although cumulus clouds may form during the day if the temperature increases sufficiently, there is not enough moisture present to, form cumulonimbus clouds.

Following the dry adiabat to the surface from CCL_ML and reading the temperature will give us the Convective Temperature (inked layer method) We have discussed where clouds may form due to mechanical lift or heating. Now we will look at a situation where clouds may form even if we do not have a large amount of heating or some mechanical lift. and reading the temperature will give us

Figure 6-2-7.-Convective condensation level and convective temperature by the parcel method. 

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