Cloud Base Heights and convection

In the case of convection, it is typically assumed that ceilings are low because of the often heavy rain associated with it. This morning the Cloud Base Height product was explored in this situation. A small area of convection formed in Chicago O'Hare's airspace as the sun rose and progressed NW over Lake Michigan. It wasn't particularly intense convection but showed a very pretty satellite signature in the 1-minute SRSOR imagery from GOES-14.

The CBH imagery was overlaid:

20160818 1430 UTC Visible imagery and Cloud Base Heights.

Higher ceilings, upwards of 25,000+ feet were indicated by the CBH in the area of cirrus blowoff, which makes sense. In the SW portion of the cell, ceilings dropped off dramatically to ~3,000 feet. Radar data was also overlaid with the CBH to determine where precipitation was falling.

20160818 1430 UTC composite reflectivity and Cloud Base Heights

The radar clearly shows the core of most intense rainfall and higher dBZ values corresponding to the lower ceiling heights in the CBH. Again, this makes sense. To look confirm further, the flight rule categories were examined as well.

20160818 1430 Visible imagery and observed flight rule categories

Observed flight rule categories actually on showed a few stations observing IFR conditions, while the CBH low ceiling covered more area. This is likely due to the way that ceiling heights are estimated in convection. Near the convective core a cloud is typically composed of thick ice. This makes estimating ceiling heights in the normal fashion extremely difficult if not impossible as estimating thickness through something the satellite cannot 'see' through is impossible. So, instead it uses the level of the LCL.

There were likely areas of LCL ceiling estimation in the core. However, the overall pattern of the CBH product was accurate. Higher ceiling in the cirrus blowoff areas with significantly dropping ceilings in and around the main core of the cells.