Strong stratification of winds can occur over the U.S. at any time of the year, but they are most common in the winter and early spring. And this has been one heck of a year for strong winds over most of the country.
The mission was to fly from my home base at Muskegon on Lake Michigan down to Kansas City. The general forecast called for temperatures at our home in Grand Haven, Michigan, to jump from around 30 degrees on Monday to well up into the 50s on Tuesday, and even higher on Wednesday. That just doesn’t happen in early March unless the wind starts really humping from the southwest to bring in the warm air.
The winds aloft forecast on the aviationweather.gov site that NOAA and the FAA operate called for an astonishing 60, 70 and even 80 knots of southwesterly at 3,000 feet for most of the way along my trip to Kansas City.
We are all geared up to think that winds at higher altitudes will be stronger than low, because that is the norm in a typical weather pattern. I dreaded checking the winds forecast at a usable IFR altitude but much to my surprise, the wind velocity fell off dramatically with altitude. By 9,000 feet the area of wind forecast to be at 80 knots at 3,000 feet was down to 30 knots. The 12,000 foot chart showed even lighter winds. It was a classic stratified wind setup.
I am no meteorologist, but I have spent thousands of hours slogging along in piston airplanes flying in the unpressurized altitudes of 12,000 feet and below. When the wind is markedly stratified you have lots of time to observe if you’re flying westbound in a little airplane because you will not be getting anywhere fast.
There are undoubtedly many ingredients necessary to create a powerful wind stratification such as I was encountering on my way to Kansas City, but the most important element is temperature inversion. When the air stops cooling with elevation—and often warms dramatically with altitude when the inversion is powerful—the winds and weather divert from their normal habits. With an inversion winds close to the surface can be much stronger than winds thousands of feet up.
I am sure the cold ground of winter and early spring add to the effectiveness of an inversion and help to channel strong wind into a narrow range of altitudes. Wind stratification can occur at just about any altitude, but this time of the year the lower altitudes are usually where you find the layer of highest wind velocity.
Powerful wind stratification usually creates turbulent layers where the high velocity layer of air transitions into the slower moving air above or below. And we all need to expect the possibility of windshear during takeoff and landing because the surface wind is usually many knots slower than the wind just hundreds of feet up. The terminal forecast for Kansas City had surface winds at 180 degrees at 18 knots, but the wind shear alert called for winds at 2,000 feet to be from 210 degrees at 60 knots. At St. Louis the forecast had the wind at 1,300 feet above the airport blowing at 50 knots while at the surface the wind was just 13 knots.
It turned out that the forecast was very accurate. On climb out from Muskegon the wind increased to 66 knots by 3,000 feet and the air temperature was 10 degrees C warmer than on the surface. I climbed to 10,000 feet where the air cooled off and the wind velocity was cut in half—but still on the nose.
The stratified wind condition was in full force at Kansas City as I approached to land at the big airline airport there, MCI. As I tracked the glideslope down to Runway 19R the airspeed began to increase dramatically. Even with the power at near idle the airspeed was up to 150 knots just to stay on the glideslope, and that is the gear extended limit speed. Increasing wind on approach is the classic warning of windshear because at some point that rapidly increasing wind is likely to end and the sinking will began. And it did.
Lucky for me the average wind direction was right down Runway 19 so the landing wasn’t all that dramatic, but an E-RJ behind me on approach apparently got an onboard windshear warning because the crew aborted the approach and climbed with that dramatic way nose up attitude all jet crews practice every year in the sim as the best way to escape a windshear encounter.
The stratified wind conditions were still in place when I returned to Muskegon the next day and at about 800 feet above the runway the wind was blowing 66 knots compared to gusts of 39 at the surface. Those last few hundred feet were a wild ride and tested the crosswind capability of a Baron. I hope the winds return to normal sometime soon.