the pre-depression evolution of easterly waves in the North Atlantic
during the 1999-2006 hurricane seasons. Each pre-depression disturbance
is characterized by its absolute circulation within 125 km of the center
and by the percent area covered by convective clouds within 250 km. In
some cases positive and negative changes in convective organization are
reflected in the near-surface absolute circulation. In a composite
analysis of 50 developing cases it is found that an increase in absolute
circulation during the 72 hrs preceding NHC-classified depression stage
coincides with an increase in convective activity during the same period.
Average structure of the developing disturbance at different times
relative to depression stage will be presented. Following previous
studies of easterly wave development, the QuikSCAT data is used to
estimate the low-level detrained volume flux and budget absolute
circulation tendency. Relationships between these quantities, the
observed circulation, convective activity, and vertical shear are examined
on a case-by-case basis and for the composite disturbance.
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