Posted on

A review of weather reports for pilots

Mountain wave cloud from the edge of the rocky mountains

Let’s review some basic concepts in meteorological reports for Pilots.

Cloud cover: measured in oktas, or out of eighths of the sky coverage:

  • SKC – sky clear of cloud
  • Few 1-2 out of 8
  • Scattered 3-4 out of 8
  • Broken 5-7 out of 8
  • Overcast 8 out of 8 – full sky coverage

METAR: Aviation routine weather reports are coded weather observations that are taken each hour at over 200 aerodromes and other locations in Canada.

SPECI: Special Weather Reports – these amend METAR observations, whenever weather conditions fluctuate or are below criteria.  What are these criteria?

  • Sky condition: (1) the cloud ceiling height changes either up or down from 1500 feet, 1000 feet, 500 feet, 300 feet or 100 feet, or to the published IFR limits for that aerodrome. Also, (2) the first occurrence of cloud under 1000 feet is noted.
  • Precipitation
  • Temperature: if above 20 degrees, an increase of 5 degrees; or if the temperature decreases to 2 degrees or colder.
  • Visibility: up or down any of these thresholds: 3 SM, 1.5 SM, 1 SM, 3/4 SM, 1/2 SM, or the limits for the aerodrome.
  • Wind: Wind doubles to exceed 30 knots, or shifts.
  • Severe weather: thunderstorm, tornado, funnel cloud.
  • Other: these can be incidents at the aerodrome, such as an accident or a special request from a weather forecast office, or if the weather observer feels it’s just to take initiative to issue this alert.

TAF: Terminal area forecast. Limited to aerodromes where METARS and SPECIs are published.  There are about 180 TAFs in Canada.  Generally prepared four times daily with up to 30 hour validity.

GFA: Graphical Area Forecast. There are seven GFA areas in Canada, these weather charts depict the most probable weather conditions expected to occour on the ground up to FL240 (flight level 24,000 feet).  There are six charts prepared for every period, issued daily at 2330, 0530, 1130 and 1730 UTC, valid from 0000, 0600, 1200 and 1800 UTC respectively.   Each chart has 12 hours of forecasting plus a 12 hour IFR outook, giving us a total of 24 hours of forecasting.  Of the six GFAs listed for each forecast period, three contain cloud and weather information and three contain icing, turbulence and freezing levels.

The GFA can also be amended by AIRMETs or SIGMETs. AIRMETs are short term weather advisory for aircraft in flight, alerting pilots to possible hazardous flying conditions, but not severe enough to require a SIGMET.  SIGMETS  are short term warnings of certain potential hazardous weather phenomena, and are limited to more serious hazards which are important to all types of aircraft.

FDs – These provide upper level wind forecasts. They are provided for seven specific regions in Canada, and are further broken down for specific areas.  Forecast for the 3000, 6000, 9000, 12,000 and 18,000 foot levels are provided, and these are the low-level FDs. They are also given for flight levels above 18,000 feet (FL180).

Radar: Radar is provided on the Environment Canada webpage. It will show you developing precipitation. It is very accurate.

Satellite: Satellite is shown on the AWWS webpage, and is useful for long term weather forecasting and planning. You can use it to find low and high pressure systems. Recall that air rotates clockwise around a high and counterclockwise around a low.

PIREP: Pilot reports can be filed at any time. They should be regularly checked for your region. In fact, one that I received from a controller at Calgary terminal saved me from going into an area of severe turbulence.

A sample RVR for CYBW (Springbank)
A sample RVR for CYBW (Springbank)

RVR Index: Another great tool is the RVR index. The Runway Visual Range shows real time the current wind speed and direction at your chosen aerodrome. It is so accurate I often check it when I am already at the airport getting ready for a flight.  The image on the left it shows a sample of what you will see.  The wind speed and direction is displayed according to the magnetic compass.  Here the wind is blowing from 130 at 9 knots.  The wind direction is overlayed with the actual runways to get a sense of where exactly the wind is coming from, and if we can expect a crosswind.  In fact the cross wind component for each runway is calculated in a table next to the image.  Wind given is the average for each minute.

 

It is important to understand how to read these reports and understand how they are created.  After awhile, it becomes second nature.   Pilots after all, are lifetime students of weather.

Posted on 1 Comment

A student of weather

A student of weather.

Being a pilot means being a student of weather – all the time.

Weather is so fickle in Alberta that you quickly learn how much flying depends on it.

I did my ground school for my PPL a few years ago at Centennial Flight School in Edmonton City Centre airport.  After years of putting it off, I’m finally getting myself in gear to study for my ground school exam.  It’s harder once you’re done ground school and have had a long break from the theory in the lectures. And one of the most challenging topics is weather.  Things like instruments, aerodynamics, aircraft engines, navigation and air law, are more practicable, and used more often on a day to day basis. Many students struggle with weather theory the most.

Because I backcountry ski and climb, I feel like I already have a very close relationship with weather, specifically mountain weather. But in no other discipline will you have a more direct relationship with weather that you do when you fly.  It determines whether you can actually go up or not, and your safety while up in the air.  There is no ‘waiting out’ the weather once you make that decision to go up.

Weather determines whether or not we can fly VFR (with visual reference to the ground).   Fog will ground many of us.  Stay far away from thunderstorms, avoid icing and turbulence.  Mountain waves can be deadly. We need to know how wind shear affects aircraft performance.  Each airplane has a design limit for maximum cross wind – we need to be aware of these limits.

Air Command Weather Manual - by National Defense Canada
Air Command Weather Manual – by National Defense Canada

What are some of the best study aids for weather?

I want to share one of the most useful resources for studying weather I’ve recently discovered: the Air Command Manual which is published by National Defense Canada.  My instructor suggested I purchase it and I am really happy I did.  I find it very comprehensive and easy to follow: important sections are broken down into a series of lectures that can be easily referenced and reviewed.  In addition, an accompanying workbook can also be purchased in which you can test your knowledge in each specific area.  I find it a really great way to review and re-learn the specific weather topics. I have been using it every day since I got it, in preparation for the weather portion of my PPL written exam.

 

Aeronautical Information Manual (AIM), published by Transport Canada.
Aeronautical Information Manual (AIM), published by Transport Canada.

Transport Canada’s Aeronatical Information Manual (AIM) is also a very good source of weather information. It presents all of the weather products for aviation, in detail.  It tells us when the reports are published and for what areas, how long they are valid for and what all the various symbols and abbreviations are on the charts.  It is an invaluable study tool. This book is updated regularly and in fact, says on the cover when it is valid. For example, my old AIM book which is pictured was valid from October 22, 2009 to April 8, 2010. This book comes with your ground school kit when you sign up for ground school.

And of course,  the flying “bible”for Canadian pilots, “From the Ground Up” has a very good and detailed weather section, giving us the theory and application.  This also comes standard with your ground school kit.

These books can be referenced again and again, even once you are done your exams and have your license.  Certain areas, particularly when it comes to weather theory are easy to forget and these books exist so they can be easily referenced.  These books should be used regularly in your aviation career.

But of course, the best teacher is actually practical experience. Having all these resources is great but getting out and flying in all sorts of weather conditions, those we can manage of course, is indispensable.

Being a pilot means being a lifetime student of weather.

Review your weather reports!

Many different flight instruction books are available on Amazon