This Photo by Unknown Author. Licensed under CC BY-SA


By Captain Michel Treskin

Editor Jennifer J. Lacelle

June 17, 2021

I remember my father predicting the weather better than the meteorologist on TV. Every time he predicted adverse weather I would question him… he was right 95% of the time.

After so many years as a pilot, I can now say that I read the sky just like my father did.

Weather forecasting is not an exact science, but it is an extraordinarily complex and extremely difficult discipline in which to be accurate. Aviators constantly rely on the current weather they can see, the forecast at the destination, and the departure airport’s report.

When the weather is well below the landing system, which will ensure a safe landing, we need to have an alternative airfield to land just in case we can’t at the destination. Pilots are meteorologists as well; we get a weather package before each flight, and it covers all aspects of our planned route plus alternative routes.

Zones in the Sky

The earth is surrounded by a layer of air which we breath and weather system develops. The weather is confined inside this layer which is called the atmosphere. The top of the layer, depending where on the globe you look, varies between 35-50 thousand feet. This limit is called the troposphere. Above that layer, its cold and deprived of any clouds, and no weather forms.

Photo by Unknown Author. Licensed under CC BY-SA-NC

Weather is affected by gigantic air masses moving around our planet. This air mass could come from the Artic or Antarctic, which are super cold and normally descends the lower regions in the wintertime.


In reverse, the air mass could be tropical: full of moisture and hot. Anything coming from the desert, would be dry. So, all these air masses are moving around by high level winds (Jetstream) and by the rotation (Coriolis) of the earth. These big airmasses are basically broken down into fronts that could be cold or warm.

Because we live in an envelope of air, we will be affected by different air pressure. The low pressure is always associated with weather (cloud, rain, snow, stormy and windy).

This Photo by Unknown Author. Licensed under CC BY-SA

High pressure is always the best with blue sky, little wind and some puffy clouds — if close to water. That’s why a barometer in your house can be a good predictor. If the pressure goes up, better weather ahead. If the pressure starts coming down, the weather is changing for the worse.


The weather forecaster will have all the information in front of him and he will have to determine what these patterns will do in the next 24-36 hours. Most of the time, a computer is using specific algorithms to predict what the weather will be.

How accurate are they? Well, I think that we can all answer that question. One time or another, we all have been duped by a forecast, and it never happened how they described on the radio or TV.

However, knowing some basic meteorology can make you somewhat of an expert and maybe impress some of your friends (or your next date).

Looking outside and seeing blue skies with no clouds is a good indication that the air is dry. You need moisture to have cloud formations. No cloud = good weather. It doesn’t matter if the temperature is hot or cold.

Though, it might matter if you live close to water, and because of daytime heating the water will evaporate and as it climbs in the atmosphere. However, it will cool down and clouds will form. This is called sublimation.

This Photo by Unknown Author. Licensed under CC BY-SA-NC


These clouds can develop into some big, occasionally mean, clouds called Cumulus Nimbus, or CB for short. These are the ones aviators hate to see in the weather or forecast.

They can rise up to the edge of the atmosphere (Tropopause) and rarely, but it happens in the warmer latitude of our planet, where these giants climb well above the tropopause and climb as high as 50 thousand feet.

Commercial airplanes cannot fly over them, and must go around them. One CB can be over 200 miles wide, so making these kinds of detours can be extremely costly in time and fuel.


When you see those type of clouds, you can easily forecast strong winds and rain, or even hail. The good news is they move rapidly and if conditions are right, they will disappear quickly. (Over development)


This Photo by Unknown Author is licensed under CC BY-SA

Most of the clouds are called Cumulus. Those white puffy clouds you see everyday that sometimes resemble animals or other forms are cumulus clouds. Depending on how high they are, they will either be called Strato Cumulus (low height), Alto Cumulus (medium height) or Cirrus Cumulus (high clouds)

When the sky is blue and there are no clouds, you can safely predict good weather for the next 36-48 hours. If the sky is blue but you can see thin, almost see through, high clouds (cirrus clouds), then you can with certainty predict a change of weather, rain or snow, is coming in the next 24-36 hours because a low-pressure front is on its way.

When you see low clouds in the sky, and they’re visibly moving, then you might be able to predict stormy weather. Alternatively, a front has just passed and it’s a 50% gamble that it might clear up or get worse.

This Photo by Unknown Author. Licensed under CC BY-SA

Another trick to know about the changes is if you turn your back to the wind. Your left side will be the low-pressure area, and that’s where you have bad weather. On your right side will be the high-pressure area, where the weather is nice.

If it’s a clear windy day, turn your back to the wind. Your left shows the bad weather somewhere out there on the horizon (you might be able to see those cirrus clouds), while on your right is where you want to go with the good weather over the horizon.

This Photo by Unknown Author. Licensed under CC BY-SA

Dynamics of Fog

Predicting fog is a hard one, and in order to foresee, there needs to be two ingredients. One: the air has to be 100% saturated in moisture. Two: a wee bit of air movement to stir said air.

Too much wind = no fog.

No wind = no fog.

It has to be just right. Once daytime heating begins, the air will start to dry, and the fog will disappear. When we talk about outside air temperature, we always include the temperature where the air would be 100% saturated. This temperature is called Dew point.

For example, if it is 20 degrees outside, the dew point could be 15 degrees. When the temperature and dew points are the same or close to, then fog could be coming depending on wind.

In aviation, we have the luxury of having all the info required to make our journey safe. We always have the actual weather — look outside — and we always have a forecast.

Unfortunately, this forecast is not 100% reliable and that is why we always have other airports with their weather (alternate airfields) in case our destination predicted weather that’s worse than forecast. We always have 2-3 alternate airports in our planning in case we need to divert.

Have fun with weather and remember where the good weather is.

Be safe.

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