Met Office C-130 Hercules Aircraft Flight A647 on the 24th January 1999. This flight was over Mid-Wales.

Aircraft Scientist's De-brief Log

Flight No :- A647 Date :- 24th January, 1999

1. Assessment of the flight

A partly successful sortie.

This was the second flight in the UTLS campaign. The intention being to study the dynamics and chemistry associated with a warm front.

A flight track was set up along a line orientated 010°/210° overhead the Aberystwyth MST radar site. We flew 4 legs of this pattern:-

1. From position "A", a Profile was flown northwards from FL50 to FL200, ending at position "B", At FL110, we crossed the frontal boundary into warmer, moister air.

2. From the northern point "B" we then flew south to "C" at FL200. At this point we started a Profile down to FL50. Again we crossed the frontal boundary at FL110. We continued southwards on this track at FL50 to the southernmost point, "D". Between "C" and "D", there were many layers of cloud and also a marked clearance between 50.85N, 4.97W and 50.56N, 5.111W. South of this we then started to see precipitation falling out of some of the clouds above us.

3. Heading north from "D", we profiled up to FL165 then remained at this level all the way to "B". We remained in cloud throughout the Run.

4. A stepped profile was then carried at "D" heading W then E so that we would have the maximum amount of time on this leg at FL100. The northern edge of the front was now up in this area. We started the Run in the colder air but passed the frontal boundary at 1330. This time, it wasn't so clear cut. Varying amounts of liquid water were seen on this Run. It froze on the wipers and leading edges of the wings.

The CO and Ozone parameters showed very little variations throughout these four legs.

This concluded the Aberystwyth part of the sortie. We were now positioned such that we could fly inbound to Chilbolton on the 282°T radial. We descended to FL65 to start the first leg. The temperature was now -5°C and we started to sample ice columns amongst the liquid water. Shortly after starting on this run we contacted 'Radsearch' on the radio to check the plan. They informed us that they could see no precipitation on the radar and requested that we finish the sortie as soon as possible. The run was aborted at this point and we landed at RAF Lyneham 20 minutes later.

2. Summary of the weather conditions

A waving frontal system was approaching the UK from the south west early on Sunday morning. The northern edge of the warm front moved from about mid to north Wales during the first 3 hours of the flight. In this region the front appeared quite active. Further south, around the Bristol Channel, there was much less activity and less cloud. Winds were SW'ly with speeds of 20kts near the surface and 70kts at height.