Eta 6-hr vertical circulation, frontogenesis and negative EPV September 18, 06 UTC.

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Speaker Notes:

The data on this slide shows a pronounced, sloping region of frontogenesis extending from the surface up through 300 mb. As was the case with Gaston, there appears to be a break between one maximum located near the surface, and another maximum located at mid levels, however the break is not as pronounced as with Gaston. Also, as was the case with Gaston, instability (as indicated by the blue shaded, negative EPV) appears to be plentiful from the surface through 700 mb. North of the surface front, there appears to be a lack of low-level instability, however a layer of mid-level (around 700 mb) instability can be seen.