SPC mesoanalysis: Effective Inflow Base?

[Dave Kaplow]

I notice that when you check SRH at the SPC mesoanalysis site the graphic now also shows something called "effective inflow base" that's measured in meters above ground level. What exactly is this parameter measuring, and how is it calculated? I tried a search but I couldn't really find much information about this particular index. There is some reference to "Effective Inflow Layer" here (PDF), which I assume means the same thing as Effective Inflow Base... But I was wondering if someone could tell me in less technical terms what the significance of the EIB parameter is, and how it's meant to be used. Thanx.

 

[Kiel Ortega]

I am sure Rich can elaborate more, but the Effectie Inflow Layer is the layer in which parcels meet some CAPE/CINH standard; it's meant to show where parcels in a thuderstorm are probably originating. I assume EIB is the bottom of the layer---so the lower the EIB, the more likely the storm is sfc based. So the best use would be for tornado potential of storms.

 

[Rich Thompson]

I notice that when you check SRH at the SPC mesoanalysis site the graphic now also shows something called "effective inflow base" that's measured in meters above ground level. What exactly is this parameter measuring, and how is it calculated? I tried a search but I couldn't really find much information about this particular index. There is some reference to "Effective Inflow Layer" here (PDF), which I assume means the same thing as Effective Inflow Base... But I was wondering if someone could tell me in less technical terms what the significance of the EIB parameter is, and how it's meant to be used. Thanx.
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Dave,

The "effective inflow base" is an estimate of how close to the ground a storm is drawing inflow air. The color filled area on the graphic shows where storms are "elevated" and unable to process the near ground air mass.

It's calculated by lifted each data point on a sounding and comparing the lifted parcel CAPE/CIN values to the threshold values of 100 J/kg CAPE and -250 J/kg CIN. If the CAPE is equal to or larger than 100 J/kg, and the CIN is smaller than 250 J/kg, then that data point is part of the effective inflow layer. The same procedure is continued on each level moving upward until a lifted parcel is found that violates the CAPE/CIN constraints. If a sounding has no parcels with at least 100 J/kg CAPE, or the "cap" is too strong, then there's no effective inflow layer (and hopefully no storms in such an environment).

It might make more sense to see it plotted on a sounding:

http://www.spc.noaa.gov/exper/soundings/06062500_OBS/

The effective inflow layer is plotted in purple to the left of the temperature and dewpoint plots.

Rich T.

 

[Blake Michaleski]

Very cool. Thanks for the explanation Rich.

 

[Dave Kaplow]

Yes, thanks Rich, that was a great explanation and exactly what I was looking for. Thanks for taking the time to reply. Now that I know a bit more about it, I can see why this was added to the mesoanalysis page. It's an interesting and very useful graphic. You guys continue to do an incredible job with that page, and for that matter with the SPC site in general.