Beware of the southwest flow aloft!

Meteorological history repeats itself.

Surface analysis depicting a weak low pressure spreading an easterly flow over southern Ontario. An upper trough supporting this low, spread 25 to 45 knot southwest winds aloft at 3,000 to 5,000 feet.

Surface analysis depicting a weak low pressure spreading an easterly flow over southern Ontario. An upper trough supporting this low, spread 25 to 45 knot southwest winds aloft at 3,000 to 5,000 feet.

Part of our approach briefing is to include potential threats. While flying from Copenhagen, Denmark to Toronto I chimed in with, “YYZ’s TAF is forecasting a southwest flow for two hours after this northeast flow. There could be a strong southwest flow aloft.” Silence ensued among the other three pilots and I could hear them thinking, “what is the skipper talking about?” I broke the silence by joking, “my meteorological senses were tingling.” Sure enough ATC mentioned a strong southwest flow aloft with winds shifting to easterly at 1000 to 1500 AGL. The B787 radar was also painting purple wind shear, a rarity.

Buffalo’s upper air sounding clocked the winds southwest 25 to 40 knots at vectoring heights for Toronto. (Buffalo is the closest upper station). When the flow aloft is a strong tailwind, ATC can have a tough time with it. They also want you to get down and slow down. Something very difficult to do in an airliner without significant drag. Luckily, the 787 has “big boards” compared to the Airbus “credit cards” used for speed brakes. The F/O flying this leg couldn’t slow the slippery wing so he disengaged the A/P and rode the glide slope a little high. The well executed maneuver allowed final flap.

I wrote about this very scenario catching a supervisor by surprise some 15 to 16 years ago. It’s mentioned in both weather books. Weather does repeat itself!

The F/O greased it on in a light northeast flow coupled with a wet runway. A wet runway is a pilot’s favourite, but not too wet!

I did mention after we landed about how my meteorological senses were right and that no one buys my books. Hint, hint guys. Even if you have 15, 000 to 20,000 hours, which both my F/O’s had, they could use a refresher.