Regional And Mesoscale Meteorology Team
Daily Satellite Discussion
Monday July 28, 1997
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Hurricane Danny was a small Category 1 hurricane which moved
very slowly to the NNE across extreme SE Louisiana, then over the open
Gulf waters and into Mobile Bay where it was located during the SRSO.
The SRSO period, just after sunrise, showed a cloud covered eye that was
well defined in the IR. Overshooting eyewall convective tops could be
tracked. Aircraft reconnaissance measured near steady intensity with
MSLP of 987 mb and max 1-min surface winds of 65-70 knots during the
SRSO. This is also a good case to show cyclonic cirrus outflow,
becoming anticyclonic at larger radii.
The sequence of imagery used to derive the winds was from 13:04z to 13:09z. There were 8 1-minute interval images . The red wind barbs were derived from tracking convective overshooting maxima cyclonically around the eye. The short time interval permits tracking of clouds that can quickly change shape and would be unrecognizable in traditional 15 or 30 minute data. The green barbs reflect the anticyclonic cirrus outlow, in the outer regions of the storm.
The rapid scan imagery presents benefits for obtaining manually tracked winds. The reduced time interval allows for accurate tracking of individual clouds in a rapidly changing mesoscale convective environment because the clouds are able to maintain similar coherent structure between successive images.
Carol Vaughn