May 25, 1994

Vortex Aircraft Mission #3

Flight ID

940525I

Flight Track:


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Flight Crew:

Chief Scientist: Watson/Ziegler         Flight Director:  Damiano
Doppler Radar:   Shepherd/Atkins        Pilots:           Tichnor/Tennesen
                                                          Kennedy
Cloud Physics:   Jacobs                 Data Technician:  Pradas
Observer:        Martin                 Systems Engineer: Lynch
Observer:        OKC firefighters
Media:           Irish Air Letters (2)


Takeoff Time: 1908 UTC                  Landing Time: 0145 UTC
Official Mission Duration: 6.9 hrs
Number of Data Tapes Used:  Radar: 3    Cloud Physics: 1        Video: 2

Data Systems Log


Radar Data System Log   Time On(UTC)    Time Off(UTC)   Comments
Tape #1                 1942                            Start LF only
                        2027                            Start TA
                                        2058            Radar down
Tape #2                 2105                            Start radar REC
                                        2149            Radar stopped
Tape #3                 2209                            Radar REC
                                        0128            Radar Off
                                                        Suggestion made by
                                                       Lynch to slow tail
                                                         to 9 RPM

Cloud Physics Log       Time On(UTC)    Time Off(UTC)   Comments
                        2024            0050            Recycle tape when
                                                        checked

Summary:

Initial plan was to fly toward Lubbock, TX, sample the low-level inflow structure, and proceed into convective mode when storms begin to develop. Just prior to takeoff, EFF reported convection northwest of Lubbock. The repeater power supply was removed prior to takeoff. Therfore, no repeater operations today.

Takeoff was at 1908 UTC; descended to 1000' AGL southwest of Childress, TX and flew westward along 34 N to near Muleshoe, TX. We then proceeded southward to 33 45' N; then eastward to just north of Lubbock. Along these tracks, winds gradually shifted from east to southeast and finally, from the south at 20-30 kts the farther westward we went.

At 2040 UTC, we proceeded northbound to setup convective patterns on a large cell 24 nm northeast of Plainview, TX. We worked the cell with mainly east-west (6) tracks along the south side of the echo. We had great difficulty staying with the main cells as they tracked eastnortheast and new growth developed along the southern flank. The ground teams reach the storms at approximately 2130 UTC. The radars malfunction several times. We were probably locked out by intervening convection while the storm was tornadic between 2200 and 2230 UTC. It appeared that we had 'too much of a good thing', i.e., too many 'weak echo vaults', too much new growth on the southern flank. All in all, we made 20 Doppler passes on 4 sets of supercells. By 0000 UTC, convection appeared to redevelop as our area became smaller and smaller as convection closed in on us. Using classic chasers term, we were caught in the 'bears cage'. At 0040 UTC, Phil Kennedy (pilot) asked Barry Damiano, the flight director, 'What's the plan?' We escaped to the south through weaker convection and lowering anvil precipitation. We continued southeast, climbing to FL240, remaining in anvil until our descent into OKC. We discharged several times, even at -14C. Landing was at 0145 UTC. It was a very bumpy flight with moderate turbulence for more than half the flight.

Irv Watson

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