AIRMET Tango: Turbulence, Strong Surface Wind and Shear
AIRMET Tango is the rough air advisory. It gathers three hazards that all come from the same source, moving air, and warns about them across a wide area.
It goes out on a fixed clock, next to Sierra and Zulu. Like them, it covers a wide area. It does not tell you about one field.
What triggers an AIRMET Tango
Three separate triggers, any one of which is enough on its own.
The first is moderate turbulence. That means the aircraft gets moved off its path. People feel a firm pull against the belts. Loose items shift. The aircraft stays under control the whole time.
The second is a surface wind of 30 knots or more, held rather than gusting.
The third is low-level wind shear that no storm caused. It sits below 2000 feet above the ground.
As with every AIRMET, the conditions have to cover a wide area before the advisory is issued.
Why moderate is the ceiling
The turbulence trigger stops at moderate, and that is deliberate rather than an oversight.
Severe turbulence is not an AIRMET. It is a SIGMET. The two products split at the point where a hazard stops being a problem for some aircraft and becomes a problem for all of them.
So a Tango tells you the air is rough enough to matter to light aircraft, to passengers, and to anybody hand flying. It does not tell you the air is dangerous to a transport jet.
If you see a SIGMET for turbulence instead of, or alongside, a Tango, that is a real step up. That is a new product with a new level of risk. Treat it as one.
The surface wind trigger
Thirty knots of sustained surface wind looks modest written down. Over a wide area it is not.
For a light aircraft it is often beyond the crosswind limit at any runway not pointing into it. It makes taxiing awkward and tie-downs necessary.
It also rarely comes alone. Wind that strong at the surface is being dragged down from above, and dragging it down means mixing. That mixing is mechanical turbulence, and it fills the lowest few thousand feet with the bumps that make approaches hard work.
Near hills the same wind produces rotor and wave, which is why a Tango over mountainous terrain deserves more respect than the same advisory over flat ground.
Low-level wind shear, the non-convective kind
The shear trigger is narrower than it first appears, and the word non-convective is doing the work.
Shear from a thunderstorm is covered by convective products. What Tango covers is shear from everything else: a low-level jet running above a cool surface layer, a strong inversion, a sea breeze front, or a frontal surface passing through.
It happens below 2000 feet, which is exactly where an aircraft is slow, low and configured. A sudden loss or gain of headwind there changes airspeed at the worst possible moment.
Unlike turbulence, this one is often invisible. Smooth air, no cloud, no clue, and then the airspeed moves twenty knots.
Using it in planning
Tango is a good product for deciding how a flight will feel and a poor one for deciding whether to go.
The area is large and the conditions inside are uneven. Read it to know that rough air is on the menu, then look to PIREPs for what pilots actually met, and at what levels.
That pairing works well. The AIRMET gives you the region and the expectation. A run of PIREPs gives you the altitudes where it was smooth and where it was not.
If the reports and the advisory disagree, the reports are more current. An AIRMET is valid for six hours and the air changes faster than that.
What it does not cover
Two gaps are worth naming, because both catch people out.
It does not cover severe turbulence. That is a SIGMET. So a Tango is a floor on the rough air, not a cap on it.
It does not cover storm turbulence either. Air near a thunderstorm is handled by the convective products, and it can be far worse than anything a Tango would warn you about.
There is a third gap that is not a rule but a fact. Wave and rotor near hills are patchy by nature. A wide area advisory smooths over that, so the worst spots inside a Tango can be much worse than the word moderate suggests.
Verdict on AIRMET Tango
Treat AIRMET Tango as a heads-up about moving air in three forms: bumps, surface wind, and shear down low.
Moderate is its ceiling, so a Tango is never the worst case. Check whether a turbulence SIGMET exists as well, weigh the advisory against current PIREPs for your levels, and give it extra weight if your route crosses high ground.
Frequently asked questions
What does AIRMET Tango cover?
Three hazards. Moderate turbulence, sustained surface winds of 30 knots or more, and non-convective low-level wind shear. Any one of them over a wide enough area triggers the advisory.
What is the turbulence threshold for an AIRMET Tango?
Moderate. Severe turbulence is not an AIRMET at all, it is a SIGMET, because the severity crosses the line where the hazard threatens all aircraft rather than only lighter or slower ones.
What counts as low-level wind shear here?
Non-convective shear below 2000 feet above ground, strong enough to affect an aircraft on approach or departure. Shear caused by thunderstorms is covered by convective products instead.
Is 30 knots of surface wind really a hazard?
Sustained, over a wide area, yes. It is a crosswind problem for light aircraft, a ground handling problem, and it usually comes with mechanical turbulence in the lower few thousand feet.
How does AIRMET Tango differ from a SIGMET?
Severity. Tango covers moderate turbulence, which is hazardous to some aircraft. A SIGMET covers severe and extreme turbulence, which is hazardous to all of them, and it is issued as needed rather than on a schedule.