Eta 6 hour forecast cross section of frontogenesis and ageostrophic circulation vectors, valid 1/6/05 18 UTC.

frontogenesis cross-section

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Speaker Notes:

By 18 UTC, a shallow layer of frontogenesis is indicated over eastern Pennsylvania, indicating that the frontal zone had become very shallow in that area by that time (a shallow layer of cold air remained near the surface). The lower branch of the associated circulation was still resulting in a northerly ageostrophic flow.

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