Thursday, 29 June
T-28 Flight 761
Project Flight 14
Take Off ~ 22:32 GMT
Return to Base: 23:55 GMT
Pilot: Tom Root
The mission began with the target an explosively-growing cell 34 nmi northeast of CHILL. The aircraft climbed to the northwest and began working the southern flank of the storm. The storm was producing nickel-sized hail and a small tornado at this time. The pilot noted severe turbulence, continuous lightning, and dime-size hail. After 3 passes at ~6 km, ice accumulation necessitated a descent below the freezing level to shed the ice. After regaining altitude, the aircraft completed 2 more passes, north-to-south then south-to-north behind (to the east of) the convective region on the upshear end of the storm. The very last pass was through the main weak echo region under which a F0 tornado was spinning at the time.
As the aircraft lined up to land, the engine began to seize. The aircraft made it onto the runway still generating some power, but the engine quit during rollout.
This was a vigorous storm with peak updrafts at 6 km exceeding 30 ms -1, severe turbulence, heavy icing, and hail up to quarter size. There was a tandem electrical balloon sounding into the storm around 23:18, and a second launch into the updraft 30 minutes later. Updrafts inferred from balloon ascent rate were ~30 m s-1 at 6 km and 50 m s-1 at 8 km.
Radar reflectivities exceeding 60 dBZ reached to altitudes exceeding 30 kft. The storm moved only slowly eastward at first, then turned rightward as it became a full-fledged supercell. It was in the STEPS eastern Doppler lobe for more than 2 hours. Hail up to golf ball size was reported on the ground near I-70 as it moved southward over it. The tornado lasted 23 min and the funnel near the ground had a diameter of ~100 m.
The LMA reported frequent IC lightning and an apparently inverted electrical structure (negative over positive) during the early part of the flight. The CG rate increased dramatically as the tornado touched down, the storm became definitely supercellular, and its motion veered to the right. The CG polarity was totally positive during the period of the tornado. A lightning-free hole is evident in the LMA data over the updraft region at this time.
Most instruments performed well. The HVPS was intermittent, but obtained
some data in interesting regions. The DMT liquid water sensor was lost during
the second pass. Icing and fogging caused some problems for some of the optical
instruments at times.
This was the final flight during STEPS for the T-28.