Ground based radar

During Elena's slow loop in the Gulf, the center was within 200 km of the WSR-57 radar at Apalachicola, FL (AQQ) from 22 UTC 31 August through 07 UTC 2 September.  1,142 complete scans of Elena's eyewall and inner rainbands were made during this 34 hour period with as little as 23 s between scans.  In order to have a uniform time step between radar images and to focus on the mesoscale aspects of the reflectivity field, the scans were linearly interpolated to five-minute intervals.  Only the closest two scans to the time in question were weighted and used to compute the interpolated scan.  If there were no scans within five minutes of either side of the prospective interpolated time, no scan was calculated and a gap appears in the data.

Below are two scans from the AQQ radar.  The image on the left is from 2205 UTC 31 August when Elena was a disorganized, but strong category 2 hurricane.  The image on the right is from 1755 UTC 1 September as Elena was approaching peak intensity (~56 m s-1).

The location of the AQQ radar can be seen in both images as the open white circle and surrounding high reflectivity values due to ground clutter (upper left corner of left image; north-northwest of Elena's center in right image).  In order to analyze the changes in reflectivity with time in Elena, the radar location and surrounding clutter were eliminated by removing a box centered on the radar.  The removed area was then filled by bilinearly interpolating from the surrounding data points.