From our student pilot days on, we’ve learned that airframe and propeller icing ranks high on the danger scale. Fly in icing conditions and you can expect that even small ice accretions can cause significant losses of lift, reductions of the stall angle of attack, plus increases in weight. These accretions are the product of supercooled (subfreezing yet still liquid) cloud droplets or precipitation that flash-freeze on wings, propellers, and any other airframe projection. The results are buildups defined by standardized icing accretion rates.
Back in the 1970s I had a job flying new Cessna singles from the factory in Wichita to Cessna Pilot Centers along the East Coast. One flight was especially memorable because it involved flying through a rapidly developing frontal complex that featured a large area of aggressive, building thunderstorms. Not something you want to do in a Cessna 152 with a single nav/com, no transponder, no Stormscope, and certainly no datalink weather capability.
So much of meteorology is a matter of scales. Weather can be as small as a brief onshore flow of wind (an example of a microscale event) or as big as a 3,000-nautical-mile dip in the jet stream (definitely a global scale event).
You probably don’t think much about such exotic processes as supercooling or changes in states of matter if you fly into a cloud or precipitation this winter. Unless maybe you were a chemistry major.
The internet is loaded with aviation weather websites and other related aids in flight planning, but one of the most popular has been run by the National Weather Service’s Aviation Weather Center (AWC) on aviationweather.gov.
Pilots like to take potshots at weather forecasters—especially those who make terminal area forecasts (TAFs). Let a ceiling prediction of 1,000 feet turn out to be 3,000 feet—or 3,000 to 1,000 feet—and pilots are likely to complain that forecasters don’t know what they’re talking about.
Mention “wind shear” to a pilot, and he or she will most likely think of the dangerous sort of wind shear that happens close to the surface, on approach or takeoff.
We all know the unofficial advice about flying in convective weather: avoid all cumulus cloud buildups by at least 20 nautical miles. This is called “visual avoidance”—a nontechnical term meaning “stay far enough away that you can easily manage a safe passage around actively growing clouds.” It’s a simple rule, and yet I’m betting that many of us violate it on a more or less regular basis—especially on cross-country flights. Confession: I have.
When did winter arrive this season? For the northeast quadrant of the nation, there was little doubt. The sequence of events began on November 29, when a huge Canadian air mass descended from Ontario and Manitoba, delivering surface temperatures in the 30s to the Great Lakes states.
Atmospheric modeling is a big reason for the increasing accuracy of weather forecasts. So much so that today’s 10-day forecasts are often as accurate as the three-day forecasts of 10 years ago. How does this accuracy come about?
Pilot or not, it’s a safe bet that everyone learns this meteorological tidbit at an early age: Hot air rises. Actually, it’s not a tidbit at all. It’s a very big deal when thunderstorm season rolls around. Warm, humid air near the surface does indeed rise with the heat of the day—or when a front causes warmer air to move in—and as it rises, moisture condenses into clouds that grow until thunderstorms occur. But there are caveats.
What did we do to get weather information before smartphones? Calling Flight Service or going online were the most popular—or only—options. But now we carry the weather with us on our iPhones, Androids, or tablets, giving us on-the-go accessibility to a wide range of aviation weather information. There must be hundreds of aviation weather apps out there, and if you’re like me, you have more than one of them running on your smartphone.
Repeat after me: Divergence aloft means convergence at the surface. This fact is central to the dynamics within the areas of fastest winds aloft. These are found in the streaks and cores of 100-plus-knot winds embedded within the jet stream, which encircles the poles and undulates as it flows from west to east (in the northern hemisphere).
The issues surrounding the dangers of airframe icing are many and complex, but pilots need to bear just a few essential things in mind when it comes to winter weather flying. Here’s one way of assessing the more important action items for preflight and inflight ice-avoidance.
Is a weather briefer’s mentionof “VFR not recommended”—or “VNR”—worth keeping as part of a standard weather briefing? After all, any diligent pilot should be able to determine if marginal VFR, IFR, or otherwise hazardous weather conditions are challenging enough to invoke a go/no-go decision.
This past winter, it seemed like hardly a day passed without dire warnings about the dreaded polar vortex. Reports of its vicious cold—coupled with its sudden, unannounced arrival—made sure that Americans lived under the fear of suddenly freezing mid-stride. Its billing as a singular phenomenon, as if it were a lone, angry, rogue vortex, only amped up the uncertainty.
Gordon Lightfoot’s song The Wreck of the Edmund Fitzgerald mentions a November Great Lakes storm it calls “the witch of November…with gales that come early,” complete with “slashing” gales and freezing rain.
