mucapes?

[senorpepr]

I was reading the latest SPC bulletin and they mentioned mucapes.

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PARCEL TRAJECTORIES SUGGEST THAT MUCAPES WILL GENERALLY BE LESS THAN 500 J/KG.

Does anybody has any information on these, how they are figured, and what the resulting number relates to (ie. X j/kg = severe thunderstorms, etc.)

Thanks

[Guest]

Mike, I found the following at SPC's website:

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MUCAPE (Most Unstable Convective Available Potential Energy) is a measure of instability in the troposphere. This value represents the total amount of potential energy available to the most unstable parcel of air found within the lowest 300-mb of the atmosphere while being lifted to its level of free convection (LFC). No parcel entrainment is considered. The CAPE calculation uses virtual temperatures, but the CIN value does not. SPC forecasters have noted that non-virtual CIN calculations tend to define areas of weak cap more accurately than if the virtual temperature was considered.

[senorpepr]

hmmm... thanks for the info Brian

[Guest]

At your service.

[senorpepr]

The weather in the local area looks a bit interesting this week. NWS has a chance of tstms everyday this week with the possibility of severe tstms on Thursday and Friday -- large hail being the factor.

[Guest]

The weather in the local area looks a bit interesting this week. NWS has a chance of tstms everyday this week with the possibility of severe tstms on Thursday and Friday -- large hail being the factor.

Yep, the weather radio sitting in my room is ready for some action! I do not know how much you regard the NWS' Weekly Hazards Assessment, but the product has a wedge of svr wx for a good chunck of Nebraska, South Dakota and parts of Iowa and southwest Minnesota for Mar 26-29.

MCAPEs are going to be abundant I have got a feeling...

[senorpepr]

I saw that wedge earlier today. It may have a possibility of verifing. Looking at the models, a lot of the parameter will be met this week for severe weather. We'll have to see as each model run comes in, though. At this point... hail looks very possible within the Omaha area.

[Guest]

Going to be looking forward to the convective outlooks tomorrow as well as the area Hazardous Weather OUtlooks.

[FLwxGuy]

Mike, I found the following at SPC's website:

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MUCAPE (Most Unstable Convective Available Potential Energy) is a measure of instability in the troposphere. This value represents the total amount of potential energy available to the most unstable parcel of air found within the lowest 300-mb of the atmosphere while being lifted to its level of free convection (LFC). No parcel entrainment is considered. The CAPE calculation uses virtual temperatures, but the CIN value does not. SPC forecasters have noted that non-virtual CIN calculations tend to define areas of weak cap more accurately than if the virtual temperature was considered.

That pretty much covers the background info on MUCAPE, but there is a critical thing left out in the SPC description.

Like the best LI (lifted index), MUCAPE is best suited for use when dealing with a shallow cool (or relatively stable) layer close to the boundary layer, which would make surface based CAPE values unrepresentative of the instability present above the shallow stable layer. the same thing goes for surface based LI values.

similarly, the Showalter index is fairly useful when dealing with low level stability.