2 Sep 2010 DC-8 Platform Scientist Report (Earl) - Ed Zipser

2 Sep 2010 DC-8 Platform Scientist Report (Earl) - Ed Zipser

DC-8 GRIP Flight 13   4th Flight into Earl   Sept 2, 2010
Takeoff ~ 1600 UTC;   Land ~ 2350 UTC    7.8 hours

The main objective of this flight was to document the changes in the structure
of Earl and its near-environment since the previous flight 24 hours earlier.
The pattern was changed before takeoff to a "butterfly", with 3 full passed through
the storm rotated by 60 degrees.  (Chris Jennison calls this the radiation warning
pattern, perhaps more realistic than a butterfly)

Another reason for the last-minute change to a butterfly pattern was to simplify the
pattern and make it easier for the Global Hawk to plan flight legs directly
above ours.  We had to take account of the 100 knot difference in flight speeds
(345 kn for GH, 450 kn for DC-8), and the way this was done was for the GH
to do the same but shorter legs, aiming for true coincidence in the eye and
eyeball.  The first coincident leg was W-E, with the GH diverting about 25 nm
to the south at the eye to avoid a region with lightning. The second was 030 - 210 deg
and was almost exactly coincident.  This was especially interesting because of
a partial inner and outer eyeball, a structure that persisted throughout the flight,
with the inner eyeball slowly collapsing and the outer eyeball becoming somewhat
better organized.

All instruments worked well on this flight.  About 35 dropsondes were released, all
but 3 providing good data.  At times, it appeared that the eye was tilted toward the north
(best guess) with height, and some of the eye centers estimated by minimum wind speed
being well to the SSW of the apparent eye on the IR images.  The wind circulation at
flight level (FL330 and FL350) gradually weakened with time.  Maximum wind at flight
level noticed on the display was 70 knots in the SSW wall on the 2nd pass.  

On the return leg back to FLL, we descended to FL250 east of Florida, noticed a dust
layer in the lowest 2 km, and did a reverse leg to descend and then proceeded toward
FLL in the dust at FL50.

A few images from the flight follow.

1. 1647Z:  DC-8 and Global Hawk preparing to line up for the W-E pass.

2. Pilot's radar showing approach to the eye at 2030Z, with partial inner and outer eyewalls

3. APR-2 image showing stratiform, then convective echoes in the NNE-SSW approach to the eye, about 2030Z

Ed Zipser, Platform Scientist