26 July 2003

26 July 2003 – Flight 815

Research Flight from GXY

Pilot: Tom Warner

T.O. 23:49 UT

T.D. 01:08 UT

A broad 500 mb ridge covered the continental US. By noon cumulonimbi were developed over the mountains with anvils streaming to the N. By mid-afternoon a few towers went up to the N of CHILL, but could not break the cap and collapsed. They were possibly associated with a surface front dropping through the area. Anvil began to overspread the area from the mountain convection to the SW. By 23:15 UT there was a significant cell on south end of the towers to the N with 60 dBZ below the melting level. By 23:40 when the aircraft was being started, there was 60 dBZ to 40 kft MSL in a cell at 330 deg/30 nmi from CHILL.

After takeoff, the pilot noted cloud base at 13.5 kft MSL. At 00:03 he was passing N of a hail shaft at 16 kft and turning onto the 330 deg radial towards CHILL. The 1^st cloud pass ended at 00:12 and a reverse course took him back through to the NW. After this pass he loitered to warm the engine a bit, then headed back to the SE. At 00:30 he was out on the SE end and reversed course to make another pass to the NW. This pass was complete at 00:37 when he dropped to 16 kft and headed back through to the SE. At 00:43 he had completed the SE-bound pass and was re-entering the cloud on a NW course, noting graupel and small hail. At this time cloud tops were still > 50 kft MSL. At 00:50 he was out on the N side and reversing course to repenetrate to the S. At 00:56 he was out and descending on his return-to-base. He caught a few additional precipitation shafts as he descended, mainly from new cells on the S end of the area of convection. At 01:06 he made his last pass through a precipitation shaft on his way in to GXY.

The pilot reported peak hail size was ~ nickel-size, with some soft and some hard. Peak rates of climb in updrafts were ~2500 fpm. CHILL personnel report that CHILL reflectivities were ~3 dB too high.

The DMT liquid water sensor element #R3N-0922-8 was broken on this flight. It was an uncoated one and had been installed since the beginning of the Greeley deployment. All imaging probe data look good, although heaters on the ICE-Q plates on the HVPS probe were apparently not working and may have caused some problems with the HVPS sampling volume. Hail apparently has interrupted the heater circuitry after many flights when it has been hitting the plates. The aircraft pitot de-ice also was out.