Click on the following link to view the weather map: https://www.weather.gov/ima

Question

Click on the following link to view the weather map: https://www.weather.gov/images/abr/EventSummaries/Thunderstorms_Tornadoes/20100723/22_mlcp.gif

(NOTE: the contours are MLCAPE and the hatched, shaded area represents MLCIN).

***Use this page (http://www.spc.ncep.noaa.gov/exper/mesoanalysis/new/viewsector.php?sector=19) to find additional information about the products on this map.***

Under the thermodynamics tab, you will see “CAPE - 100mb Mixed Layer” with a “?” next to it. Click on the “?” to find out more about “CAPE - 100mb Mixed Layer.”

1a) How is the MLCAPE determined?

1b) Estimate the MLCAPE value at 22Z in Vivian.

1c) Note the “void” in MLCIN near Vivian. What does this indicate about the atmosphere at that
point?

Explanation / Answer

1a. To determine MLCAPE (Mixed Layer Convective Available Potential Energy) we first calculate the average temperature and moisture variables in lowest 100mb layer and then later lifting that layer. ML CAPE is used to check instability during the daytime as this period of time usually has mixed up atmosphere.

The advantage of using MLCAPE (J/KG) is that it filters out patterns that would show erroneously high SBCAPE.

1b. At 22Z in Vivian region in South Dakota has varying value of ML CAPE . At normal the value remains between the range of 500-1000 Jkg-1.While during thunderstorms there might be alteration in the normal value and sometimes it actually exceeds and goes up by 50%.

Besides that there is also a wide variation to the values of MLCAPE depending on weather conditions and other factors which are calculated with respective sounding. Variations usually takes place with more than 50% chance of increase or decrease to the original value.Here at 22Z it is around 850-1000 Jkg-1.

1c. CIN or Convective Inhibition is about preventing the air parcel from ground surface to reach the level of free convection.Now it is usually covering the ground surface and the air parcel being cooler ( denser) surrounds it and further it accelerates the air parcel downward.

The areas of dominant CIN have more stable conditions , temperature is slightly warmer and has clear weather conditions without a chance of any thunderstorm in those areas. While it is quite opposite in cases where there is less or areas void of CIN - weaher conditions is not so good and it is highly likely that there will be an occurance of hail or thunderstorm in that region .CIN usually gets reduced causing heating and moistening produced as a result of convective weather.

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