AWWS - Aviation Weather Web Site / User's Guide

• 3.1 alphanumeric products (standard bulletins and for some products, plain language one)
• 3.2 graphical products (maps, charts) and
• 3.3 ASEP products.

• AIRMET;
• SIGMET;
• PIREP;
• METAR / SPECI;
• TAF;
• Upper Winds (FD) and
• NOTAM.

3.1.1 SIGMET

The SIGMET amends a Graphic Area Forecast (GFA). The SIGMET is a short-term weather warning issued when hazardous conditions occur or are expected to occur. They are numbered sequentially i.e. A1, A2, etc. SIGMETs are in force until updated or canceled. These messages describe hazardous weather conditions up to and including FL600.

The weather conditions for which a SIGMET is issued are as follows:

• area of active thunderstorms
• line of thunderstorms
• severe squall line
• hurricane/tropical storm
• moderate or heavy hail
• severe turbulence (not associated with convective cloud)
• severe icing (not associated with convective cloud)
• marked mountain waves
• widespread sand or dust storm
• volcanic ash cloud
• low-level wind shear
• tornado or waterspout

The SIGMET bulletins are produced in abbreviated plain language using standard meteorological abbreviations listed in the Environment Canada (EC) Manual of Abbreviations (MANAB).

Example of a SIGMET message:
WSCN02 CYUL 010058
CYUL SIGMET C7 VALID 010100/010500 CYUL-
WTN AREA BOUNDED BY 5000N04800W - 5000N04200W - 4500N03600W -
4500N04200W - 5000N04800W. MODERATE TO SEVERE TURBULENCE FORECAST
FL320 TO FL400. OBSERVED BY SEVERAL AIRCRAFT. AREA MOVING EASTWARD
15 KTS. WKNG.
END/HJT/KET

The weather conditions for which an AIRMET is issued are as follows:

• IFR weather (broken or overcast cloud condition less than 1,000 ft above ground level (AGL) and/or visibility less than 3 statute miles);
• Freezing precipitation (not requiring a SIGMET);
• Moderate icing (not associated with convective clouds);
• Moderate turbulence (not associated with convective clouds);
• Thunderstorms (unorganized);
• The surface mean wind speed, over a large area, increases to 20 knots or more, or gusts increase to 30 knots or more, when lighter winds were originally forecast; or
• The difference between the forecast and observed wind direction is greater than 60 degrees.

The AIRMET bulletins are produced in abbreviated plain language using standard meteorological abbreviations listed in the Environment Canada (EC) Manual of Abbreviations (MANAB).

Example of an AIRMET message:

WACN31 CWEG 311950
AIRMET A1 ISSUED AT 1950Z CWEG-
AMEND GFACN31 CWUL 311745 ISSUE
WTN AREA BOUNDED BY /5042N12114W/30 W KAMLOOPS -/4911N11933W/OLIVER - /5019N11850W/30 NE KELOWNA - /5042N12114W/30 W KAMLOOPS. WTN AREA FQT VSBYS 1-3SM -SN OBSERVED. AREA MOVG EWD 20 KTS AND VSBYS GRADUALLY IMPROVG AFT 21Z. END/GF

3.1.3 PIREP

A PIREP, or Pilot Report, is a bulletin transmitted by a pilot, either in flight or on the ground. It can describe flight parameters or weather conditions observed by the pilot.

A PIREP can contain some or all of the following elements:

• location of the aircraft
• time
• flight level
• type of aircraft
• cloudiness
• temperature
• wind
• turbulence
• icing
• remarks

The remarks section is a free format area where pilots can describe other relevant information.

On AWWS, a PIREP can also be viewed in plain language:

UACN10 CYFS 181008 EG UA /OV YFS 044022 1000 FL 140 CLIMBG /TP BE9L /SK 120 BKN XXX /RM A SCT LYR OVR HORN PLATEAU AT 140 ASL -VIA YZF FSS-
PIREP LOCATION 62.02N  120.70W	DATE - TIME 18 JULY 2001 - 1000 UTC	FLIGHT LEVEL 14000 FEET
TYPE OF AIRCRAFT BE9L BEECH AIRCRAFT CORP. KING AIR (LIGHT)	CLOUDINESS BROKEN BASE 12000 FT	TEMPERATURE
WIND	TURBULENCE	ICING
REMARKS /RM A SCT LYR OVR HORN PLATEAU AT 140 ASL -VIA YZF FSS-

Under normal circumstances, remarks are not translated into plain language because they are free format in nature.

The main elements contained in a METAR are as follows:

• correction code;
• METAR/SPECI/LWIS identifier;
• station identifier;
• date stamp;
• wind information;
• prevailing horizontal visibility;
• present weather;
• cloud group;
• temperature/dew point;
• altimeter setting and
• remarks.

Describing all these parameters in detail is beyond the scope of this guide. For more information, please consult the Meteorological Service of Canada web site:

Example of a coded METAR:
METAR CYGP 181100Z 25002KT 15SM FEW040 BKN240 12/11 A3010 RMK SC1CI1 SLP194=

On AWWS, a METAR or a SPECI can also be viewed in plain language:

METAR CYGP 181100Z 25002KT 15SM FEW040 BKN240 12/11 A3010 RMK SC1CI1 SLP194
METAR	LOCATION CYGP - GASPE A QUE	DATE - TIME 18 JULY 2001 - 1100 UTC
WIND 250 TRUE @ 2 KNOTS	VISIBILITY 15 STAT.  MILES	RUNWAY VISUAL RANGE
WEATHER	CLOUDINESS FEW CLOUDS (1/8 - 2/8) 4000 FT BROKEN CLOUDS (5/8 - 7/8) 24000 FT	TEMP / DEWPOINT 12 C / 11 C
ALTIMETER 30.10 IN HG	RECENT WEATHER	WIND SHEAR
REMARKS RMK SC1CI1 SLP194= CLOUD WITH OPACITY: STRATOCUMULUS 1/8  CIRRUS 1/8  SEA LEVEL PRESSURE: 1019.4 hPa

The main elements contained in a TAF are:

• bulletin identifier;
• amendment/correction code;
• aerodrome identifier;
• date stamp;
• period of coverage;
• wind information;
• prevailing horizontal visibility;
• present weather;
• cloud group;
• temporary or permanent change groups and
• remarks.

Describing all these parameters in detail is beyond the scope of this guide. For more information, please consult the Meteorological Service of Canada web site.

Example of standard format TAF:
TAF CYUL 181124Z 181212 01005KT P6SM SCT040
FM1500Z 04008KT P6SM SCT040 TEMPO 1822 BKN040
BECMG 0204 04003KT SKC
RMK NXT FCST BY 15Z=

FD are alphanumeric forecasts of wind and temperature aloft for various altitudes. They are produced for over 140 sites across Canada. The flight levels available are

• for the low level: FL030, FL060, FL090, FL120, and FL180, and
• for the high level: FL240, FL300, FL340, FL390, FL450, and FL530.

The FD bulletins are prepared to meet aeronautical requirements for flight planning and to prepare documentation for flights in Canada, between Canada and the US, Greenland, Mexico and the Caribbean. The bulletins for low levels are prepared by the Canadian Meteorological Centre (CMC) while the high-altitude forecasts are prepared by the National Weather Service (NWS) of the United States.

They follow the format ddfftt, where dd is the wind direction (true), ff is the wind speed (in knots) and tt is the temperature (in degrees Celsius).

Subtracting 100 knots from the speed and adding 50 to the direction indicate wind speeds from 100 to 199 knots. For example, 240 degrees @ 130 knots is coded 7430. Speeds in excess of 199 knots are coded as if they were of 199 knots (e.g. winds of 90 degrees @ 210 knots are coded 5999, as would winds of 199 knots). Finally, wind speeds less than 5 knots are indicated by 9900.

The example below shows winds and temperatures in the lower levels, and the table explains the various codes used and how to decode them:

FCST BASED ON 051200 DATA VALID 060000 FOR USE 21-06

	3000	6000	9000	12000	18000
YVR	2523	2631-02	2536-09	2560-14	7503-25
YVV	0224	3609-05	2811-08	2769-14	2789-26
YWG	2610	9900+00	2612-03	2525-10	2562-23

  interpretation of the previous example :

FD Coded	FD Decoded
2523	Wind at Vancouver at 3,000 ft above sea level (ASL) 2500 true at 23 knots
9900+00	Wind at Winnipeg at 6,000 ft above sea level (ASL) light and variable, temperature 000C
7503-25	Winds at Vancouver at 18,000 ft above sea level (ASL) 2500 true (75-50=25) at 103 knots (03+100=103), temperature -250C
859950 (Generic Example)	Winds 3500 true (85-50=35) at 199 knots or greater, temperature -500C

FD forecasts are generated automatically twice a day at the Canadian Meteorological Centre (CMC) for the low levels, and at the National Weather Service (NWS) of the United States for the high levels. The low-level FD bulletins are amended (if necessary) 4 times a day when the upper air analyses of 00, 06, 12 and 18UTC are prepared. In AWWS, all forecasts for a given point are combined into one table:

Example of Upper Winds forecast by the Canadian Meteorological Centre for flight level <= FL180.
Winnipeg Man.

STN YWG -		for use	3000	6000	9000	12000	18000
FDCN01 CWAO FCST BASED ON 090000 DATA VALID 090600		05-09	3310	3216+15	3023+07	3030+01	2945-10
FDCN02 CWAO FCST BASED ON 090000 DATA VALID 091200		09-18	3216	3019+13	2922+06	2934+00	3047-10
FDCN03 CWAO FCST BASED ON 090000 DATA VALID 100000		18-05	3417	3419+10	3230+07	3236+03	3146-08

NOTAM :

A NOTAM is an aviation notice distributed by means of telecommunication- containing information concerning the establishment, condition or change in any aeronautical facility, service, procedure or hazard, the timely knowledge of which is essential to personnel concerned with flight operations.

To retrieve NOTAM from the Aviation Weather Website (AWWS), you need to enter the appropriate Aerodrome or NOTAM file identifier (4-letter ID).

The user guide below explains the NOTAM options offered on this web site. For general information on the Canadian NOTAM system itself, you can consult the "NOTAM Canadian procedure manual" (Section Publication of this website) and AIM.MAP 5.6.8

NOTAM Files :

There are 3 categories of NOTAM files to be consulted for complete flight planning. They are:

Additional NOTAM option :

Note : Under certain conditions, as explained above, being familiar with this section only, before commencing a flight, does not meet CAR 602.71 and AIM-RAC 3.3 requirements. Please review all pertinent NOTAM files for complete information.

BC Seasonal VFR Route Forecasts :

VFR route forecasts are available for the routes from Hope to Lytton and from Hope to Princeton, in south-western British Columbia. These route forecasts include Terminal Advisories for Hope and Princeton as well as the aviation weather, for VFR flying, along two primary routes from the coast to the interior of British Columbia. Forecasts are issued four times per day at 1400, 1700, 2000 and 2300Z, valid for six hours with an outlook for the remainder of the day.

VFR route forecasts are issued for the summer season represented by the period during which British Columbia observes daylight savings time. The last forecast of each day contains an outlook for the following morning. VFR route forecasts are amended as required.

• Significant Weather Prognosis Charts (SIGWX HI, MID LVL and Atlantic);
• North Atlantic Turbulence Forecast Charts (N ATLC TURB);
• Flight Conditions Charts;
• Surface Analysis Charts (SFC ANALYSIS);
• Upper Air Analysis Charts (UPR AIR ANALYSIS);
• Graphic Area Forecast (GFA);
• Local Graphic Forecast (LGF);
• Upper Wind Charts (FL<= FL180, FL240, FL340, FL390 and FL450);
• Satellite Imagery;
• Radar Imagery
• Aviation Weather Camera Images and
• Canadian Turbulence Forecast Charts.

Volcanic Ash information is available in alphanumeric and / or graphical format.

High level SIGWX charts are valid at specific fixed times: 0000, 0600, 1200, and 1800 UTC. They show significant en-route weather phenomena (including icing, turbulence and convective activity) over a range of flight levels from FL250 to FL630 (about 380 to 75 hPa) over Canadian airspace. This product is issued by the National Weather Service (NWS) of the United States.

The significant weather elements are defined by the World Meteorological Organization (WMO) and the International Civil Aviation Organization (ICAO), and include:

• thunderstorms and cumulonimbus clouds
• tropical cyclones
• severe squall lines
• moderate or severe turbulence
• moderate or severe icing
• widespread sand storms and dust storms
• well-defined surface convergence zones
• surface fronts with speed and direction of movement
• tropopause height
• jets streams
• volcanic eruptions

This product is issued by the National Weather Service, which is the American counterpart to the Meteorological Service of Canada (MSC).

Example of a Significant Weather Prognosis High Level Chart. View the chart.

Mid level SIGWX charts are valid at specific fixed times: 0000, 0600, 1200, and 1800 UTC. They show significant en-route weather phenomena (including icing, turbulence and convective activity) for FL100 to FL240 (700-400hPa) over Canadian airspace.

Example of a Significant Weather Prognosis Mid Level Chart. View the chart .

The North Atlantic significant weather chart covers the low and middle level (from surface to 400 hPa) significant weather for aviation operations over the N. Atlantic . . The chart contains forecast positions of surface pressure centres, surface fronts and clouds with icing expected; positions of tropical storms and hurricanes are indicated when applicable. Significant icing and turbulence areas are included as well as freezing levels. These charts are prepared twice a day, and are valid approximately 11 hours after issue times (valid times are either 0000 UTC or 1200 UTC).

Example of a North Atlantic Sig Wx chart.. View the chart

These products are issued by the Canadian Meteorological Aviation Centre (CMAC) of Environment Canada.

The significant weather elements described in the forecast include:

• thunderstorms and cumulonimbus clouds
• areas of organized cloud
• tropical cyclones or hurricanes
• severe squall lines
• moderate or severe turbulence
• moderate or severe icing
• widespread sand storms and dust storms
• surface fronts with speed and direction of movement
• freezing level

The North Atlantic Turbulence prognostic displays areas of moderate to severe turbulence, associated with both the jet stream and convective clouds, between FL280 and FL430.

This product was created for the Gander Automated Air Traffic System (GAATS), at the request of NAV CANADA, to assist the Gander Area Control Centre (ACC) in defining the tracks used to separate aircraft when they cross the Atlantic. The chart uses non-standard symbols to depict the following elements:

• areas of turbulence
• motion of the areas of turbulence (direction and speed)
• characteristic of the areas of turbulence (increasing in intensity, decreasing in intensity, staying the same)
• horizontal position of the jet core (the centre of the jet stream)
• altitude of the jet core
• motion of the jet core (direction and speed)
• tops of convective clouds

The product is issued 3 times a day, at 1030, 1715 and 2230 UTC. The first product is used to prepare Eastbound tracks for that evening (valid at 0000UTC). The second product is an update of the first (valid at 0000UTC). The last issue is used to prepare Westbound tracks (valid at 1100UTC).

Example of a North Atlantic Turbulence Forecast Chart (N ATLC TURB) Eastbound and Westbound.

The information is depicted in terms of flight categories:

• red for Instrument Flight Rules (IFR),
• yellow for Marginal Flight Rules (MVFR) and
• green for Visual Flight Rules (VFR).
  

By default, the METAR information is shown. To display a TAF, the user must first select a valid time: 1800, 0000, 0600 or 1200 UTC. The program then displays the worst flight category expected at that time.

For example, in the following TAF for St. John's (Newfoundland), the TEMPO section shows that between 1800 and 2000 UTC, IFR conditions are expected for part of the time. Since these conditions are worse than the main conditions shown in the first portion of the TAF, St.John's will be shown in red.

TAF CYYT 091131Z 091212 26005KT P6SM SCT030 BKN070 TEMPO 1215 5SM
-SHRA BR BKN030 OVC070
FM1500Z 18005KT P6SM -RA SCT004 BKN030 TEMPO 1820 2SM -RA BR
OVC004
FM2000Z 16005KT 1/2SM -SHRA FG VV002
FM0900Z 16010KT 3SM -SHRA BR OVC010
RMK NXT FCST BY 18Z=

The user can zoom on the map by simply clicking in the area of interest.

Example of a flight conditions chart. View the chart.

The surface analysis chart shows the mean sea level pressure field at a given time, along with the position of high and low pressure centres and fronts. These analyses are produced 4 times a day, at 0000, 0600, 1200 and 1800 UTC by the Canadian Meteorological Centre (CMC) of Environment Canada.

The isobars (or curving lines joining points of equal pressure) are drawn automatically by computer at every 4 hPa (4 millibars) intervals. Please note that 1 millibar = 1 hectopascal (hPa). Fronts (transition zone between two air masses) are added manually. Other annotations can be present on the analysis:

• "NEW" indicates a newly formed feature;
• "QS" stands for "quasi-stationary" and means that the feature did not change position in the past 6 hours.

Example of a Surface Analysis Chart (06UTC). View the chart.

The "history" of a low pressure centre can also be indicated if the low has existed for more than 6 hours. The history is shown by a series of circles connected by a dashed line:

In this example, a 996 hPa low pressure centre is shown to be moving toward the southeast. Its pressure went from 1001 hPa 18 hours prior to the analysis, to 1000 hPa 12 hours prior to the analysis, to 999 hPa 6 hours prior to the analysis.

On AWWS, you can retrieve the most current analysis, or the analysis that was produced 6 hours before.

3.2.6 Upper Air Analysis (UPR AIR ANALYSIS)

Upper air analysis charts are produced automatically by computer, and are generated twice a day, at 0000 and 1200 UTC. They are available for 4 levels: 250, 500, 700 and 850 hPa. They are very specialized products that show temperatures, wind speed and pressure "heights" at given levels in the atmosphere. Please note that 1 millibar = 1 hectopascal (hPa). The hPa unit is used at the Canadian Meteorological Centre (CMC) on the charts.

The analyses shown on AWWS are highly technical products that meteorologists use in the preparation of their forecasts. While a detailed explanation on the interpretation of these charts is beyond the scope of this manual, a brief description can be given.

Example of a 250 hPa Upper Air Analysis: this analysis shows the position and strength of the jet stream. It also shows the height pattern at this pressure level and the temperature.

Example of a 500 hPa Upper Analysis: this analysis shows the height pattern at this pressure level, the temperature and the winds. It can be used to identify the presence of upper lows. It also gives meteorologists a way to determine areas where the temperature of the atmosphere is increasing or decreasing, which is one of the way to evaluate the potential for development of surface low pressure systems.

Example of a 700 hPa Upper Air Analysis: this analysis shows the height pattern at this pressure level, the temperature and the winds.

Example of a 850 hPa Upper Air Analysis: this analysis shows the height pattern at this pressure level, the temperature and the winds. The temperature analysis can be helpful in defining precipitation types at the surface.

There are two types of Graphic Area Forecast (GFA) charts (to be used together):

• clouds & weather (CLDS, WX)
• icing, turbulence and freezing levels (ICG, TURB& FZLVL)

Each GFA must cover three valid times: T + 0 hr, T + 6 hr and T + 12 hr. This means that each GFA issue consists of 6 separate charts. The clouds and weather chart of the last set contains a worded instrument flight rules (IFR) outlook extending over the next 12-hour period.

The GFA uses codes from METAR/TAF and symbols and abbreviations are consistent with those found in the MET section of the Aeronautical Information Manual (AIM) of Transport Canada. All heights are Above Sea Level (ASL) unless indicated; cloud bases and tops are indicated; visibility is always included, and if expected to be greater than 6 miles is shown as P6SM; winds are included only if greater than 20 knots or with gusts to 30 knots or more.

Examples:

• Clouds & Weather portion of a Graphic Area Forecast (GFA) for the Ontario/Quebec (GFACN33) region and
• Icing, Turbulence and Freezing level portion of a Graphic Area Forecast (GFA) for the Ontario/Quebec (GFACN33) region.

The Local Graphic Forecast (LGF) is a single graphic product describing the most probable weather conditions (clouds, weather and low level turbulence) expected to occur between the surface and 10,000 feet over a given area at a specific time (the valid time) only. Clouds, weather and turbulence information, are described in the “text box” on the right side of the product.

The “look and feel” of the LGF is similar to the GFA; however, it does NOT replace the GFA. The LGF is a specially designed product focusing on the needs of pilots in a defined geographic area.

More specifically, the West Coast VFR LGF has been designed to meet the needs of the Pacific coastal aviation community under Visual Flight Rules (VFR) only. Therefore, icing in clouds is NOT included. Also, a description of the sea state over open seas is described in the “text box” on the right side of the product.

West Coast VFR LGF format and information:

•  Each issue depicts three forecast times: T+0, T+3 and T+6 for each domain.

•  The last product of the day contains an outlook for the following morning.

•  Codes are consistent with METAR/TAF codes.

•  Symbols and abbreviations are consistent with those found in the MET section of the Aeronautical Information Manual (AIM) of Transport Canada and with the GFA. (http://www.tc.gc.ca/CivilAviation/publications/tp14371/MET/3-1.htm#3-3)

•  All heights are Above Sea Level (ASL) unless otherwise indicated.

•  Cloud bases and tops (other than convective tops) below 10,000 feet are indicated.

•  Convective tops are explicitly stated.

•  Visibility is always included. If it is expected to be greater than 6 miles, then it is shown as P6SM.

•  Relevant synoptic features and the speed and direction of such features are indicated; winds are included only if equal to or greater than 20 knots or with gusts to 30 knots or more and associated with turbulence.

•  Freezing levels at 2500 foot intervals are depicted.

•  Areas of non-cloud related icing, when applicable, are depicted (e.g. freezing precipitation, freezing spray, freezing drizzle etc.). Icing in clouds is NOT depicted.

•  Low level turbulence (e.g. mechanical, low level wind shear and lee wave below 10,000 feet asl) are depicted.

•  Symbols are used to depict precipitation (rain, snow, freezing rain, freezing drizzle, ice pellets, snow pellets) as well as to depict thunderstorm, fog and turbulence. Intensity symbols (moderate and severe) are also used, where appropriate.

NOTE: In the LGF, orange dashed lines depict organized areas of low ceilings or visibilities.

West Coast VFR LGF Issue times and geographical coverage areas :

•  Issue times: 1500, 1800, 2100 and 0000 UTC.

•  There are three distinct embedded areas covering the entire Pacific coast of British Columbia . They comprise of the North Coast , Central Coast and South Coast domains.

This chart provides temperature and wind forecasts, in graphical format, for a given flight level. The information is divided into discrete geographical areas: East, North and West. The information presented on this chart is essentially the same as the information contained in FD bulletins. The major difference, however, is that only one flight level can be consulted at a time, given the graphical representation of the information. The information is generated by computer and is derived from numerical weather prediction models.

Example of a Upper Winds Chart for the East Region for FL180. View the chart.

Winds aloft are computer prepared and contain forecast wind direction and speed as well as forecast temperatures. Wind direction is from true north. Temperature is in whole degrees Celsius and assumed to be negative above 24,000 feet. The National Weather Service (NWS) of the United States produces these charts 4 times/day. They are valid at: 00, 06, 12 and 18 UTC. The levels 18,000 feet and above are pressure altitudes.

On AWWS, the levels FL240, FL340, FL390 and FL450 are available.

Example of a Upper Winds Forecast Chart for FL240. View the chart.

Example of a Upper Winds Forecast Chart for FL340. View the chart.

Example of a Upper Winds Forecast Chart for FL390. View the chart.

Example of a Upper Winds Forecast Chart for FL450. View the chart.

3.2.11 Satellite Imagery

This section of AWWS displays satellite imagery for the area of interest, in either visible (VIS) or infrared (IR) wavelength. Two types of satellites are used: geostationary (GOES) and polar orbiting (HRPT).

Geostationary satellites orbit the Earth at about 36,000 km of altitude over the equator. They are called geostationary because their position does not change with respect to a point on the surface. Polar orbiting satellites orbit the earth at an altitude of approximately 850 km. Since they complete one orbit every 105 minutes, the satellites circle the earth 14 times a day. Because of the orbital shift resulting from the planet's rotation, they move west by approximately 2 time zones per orbit.

In a visible image (VIS), objects can be seen because they reflect the light incident upon them from the sun. This implies that these images can only be used during daylight hours. It also means that the appearance of the objects will change during the course of the day, since the angle of the incident light will also change. Clouds generally appear better defined on visible images. Banks of fog can readily be recognized and large, cumuli form cloud can cast shadows on lower neighbors. The resolution on visible images is about 2 km at the equator and deteriorates farther north.

Infrared imagery (IR) is not as straightforward to interpret, because it shows heat instead of light. Because this imagery records radiation that is emitted from objects, they can be used at night. An estimate of the temperature of the objects in the scene can be obtained by matching their shade to the temperature scale on the left side of the image (temperatures are in degrees Celsius).

Given that there is a correlation between altitude and temperature (the lapse rate), it is possible to estimate cloud top height from their temperature.

Because they use emitted radiation, interpretation of infrared (IR) images is not always straightforward. For example, cirrus clouds are thin, and let infrared radiation from lower levels go through. This can sometimes "contaminate" the temperature of the cloud depicted on the image, since it represents an average of the temperature of the cloud top and the objects underneath. In these circumstances, clouds will appear lower than they actually are. Similarly, fog, which can sometimes be quite shallow, can be very difficult to pick out on an infrared (IR) image since its temperature can be nearly identical to that of the ground below it. In the case of a temperature inversion, where the temperature aloft is warmer than at the ground, clouds can even appear as dark objects. The resolution on infrared (IR) images is about 4 km at the equator and deteriorates farther north.

Example of visible (VIS) satellite imagery. View the satellite visible image.

Example of an infrared satellite imagery. View the satellite infrared image.

Satellite Animation (GOES Images Only)

GOES satellite images can be animated using the playback controls at the top of the satellite page. The default animation period is set to 3 hours, but a 6-hour animation is also available.

The displayed satellite image will be, by default, the latest in the series of satellite images available for animation. The time interval between images is either 1 hour or 30 minutes, depending on which satellite product is selected. Please keep in mind that visual satellite images ( VIS ) are only available during daylight hours.

To animate the series of GOES satellite images, you first need to click the "Play" button in the playback controls. In addition, you can view the images individually by manually stepping through the animation sequence using the “Next Image”.

The Playback Controls are as follows:

  Play Button : Used to "play" or activate the series of images in the loop.

  Pause Button : Used to "stop" the series of images in the loop.

 First Image : Used to loop back to the first image in the series.

  Previous Image : Used to step backward one image at a time.

  Next Image : Used to step forward one image at a time.

  Last Image : Used to loop ahead to the last image in the series.

  Increase Speed : Increase the speed of the animation in the loop of images.

  Decrease Speed : Decrease the speed of the animation in the loop of images.

For more information on satellite imagery, please consult the Frequently Asked Questions (FAQ) about satellite from Environment Canada web site.

This section of AWWS shows radar imagery, in terms of precipitation rate (PCPN rate) or echo tops, at different geographical scales.

There are three geographical scales available:

• national composite for all of Canada;
• regional composite for the following regions: Pacific, Western, Ontario, Quebec and Atlantic; and
• single site radar.

For each of those scales, two types of imagery are available:

• precipitation rate (PCPN rate; a measure of the instantaneous precipitation rate, in cm/hour for snow and mm/hour for rain); and
• echo tops (the height above the ground at which the radar echoes were detected).

Example of a regional composite that shows the echo tops:View the radar image.

Example of a regional composite that precipitation rate: View the radar image.

Radar Animation

Animation of radar images is a helpful tool for assessing precipitation movement and development.

Using the playback controls at the top of the radar page, up to 3 hours of radar images can be animated. The default animation period is set to 1 hour.

The displayed radar image will be, by default, the latest image available in a series radar images available for animation. The time interval between images is 10 minutes. To animate the series of images, you first need to click the "Play" button in the playback controls. In addition, you can select the images individually by manually stepping through the animation sequence using the “Next Image”.

The Playback Controls are as follows:

  Play Button : Used to "play" or activate the series of images in the loop.

  Pause Button : Used to "stop" the series of images in the loop.

 First Image : Used to loop back to the first image in the series.

  Previous Image : Used to step backward one image at a time.

  Next Image : Used to step forward one image at a time.

  Last Image : Used to loop ahead to the last image in the series.

  Increase Speed : Increase the speed of the animation in the loop of images.

  Decrease Speed : Decrease the speed of the animation in the loop of images.

For more information on radar imagery, please consult Environment Canada web site.

Weather cameras (Wx Cam) are a supplement to existing meteorological information and provide a colour picture of local weather conditions with the date and time (UTC) that the image was taken superimposed on it.  Wx Cam pictures are updated every 10 minutes.  Where there is a co-located Automated Weather Observation System (AWOS), the most recent METAR or SPECI observation will also be superimposed upon the weather camera picture.

A typical Wx Cam suite will consist of 2 or 3 fixed-view weather cameras. Cameras are usually placed at aerodromes, but may also be located in areas of challenging terrain that are frequently transited by VFR flights.

The interpretation of Wx Cam pictures is facilitated by corresponding reference images for each camera orientation. Reference images are ''clear sky'' pictures with arrows pointing at prominent landmarks, indicating their distance and height from the camera. Reference images are to be compared with the real-time pictures in order to get a better appreciation of the prevailing weather situation.

Past images are also displayed under historical images, so that a weather trend may be discerned.

Weather briefers at NAV CANADA Flight Information Centers also have access to the Wx Cam images, allowing for simultaneous viewing and discussion of these products with pilots.

The following is a summary of the features of the Canadian Turbulence Forecast chart:

Area: Includes the entire Canadian Domestic airspace from the North Pole southward, with extended coverage to the area 100 NM south of the Canada - US airspace boundary.

Vertical coverage: from FL280 to FL430 inclusive.

Forecast Period: 12 hours.

Issue/Valid Times: 10:30 UTC (valid 00:00 UTC) and 22:30 UTC (valid 12:00 UTC )

Canadian Turbulence Forecast Chart Contents:

1. Forecast areas of turbulence including those associated with gravity shear waves, thunderstorms, and orographic flow. Three categories will be defined: MDT, MDT-SEV and SEV. Each area will have an associated velocity (arrow for direction, speed in KT indicated), and a special symbol which shows whether it is strengthening or weakening. The symbol is a circle with either a "+" or a "-" in it. The base and/or top of the turbulence level is included (in hundreds of feet). The abbreviations "BLO" or "ABV" may be used.
   
   
2. Forecast jet stream axis. This axis will be independent of jet speed and level. The jet axis is drawn for upper winds of 50kt or greater. A "J" inside a square indicates the position of a jet core.  Immediately below the core is the flight level of the jet, in hundreds of feet (e.g. FL340). Immediately below that is the wind speed of the jet core, in kt (e.g. 134KT)
   
   
3. Areas of CB tops at or above FL 280 (with modifiers ISOL, FEW, SCT or FRQ).
   
   
4. The primary label at the upper right side of the chart includes the issue time and valid time, with the words (FOR FL 280 -430).
   
   
5. The secondary label at the upper right side of the chart states "Moderate or greater turbulence is possible vicinity and above CB tops".
   

3.2.15 Volcanic Ash Information

The Volcanic Ash information available on AWWS system is composed of bulletins and charts:

• Canadian Volcanic Ash Advisory bulletins (FVCN CWAO header);
• Canadian Volcanic SIGMET (WVCN);
• Alaska Volcanic Ash Advisory bulletins (FVAK PANC header);
• Washington Volcanic Ash Advisory bulletins (FVXX KNES header) and the
• Ash density prognostic charts from the Montreal Volcanic Ash Advisory Centre (VAAC) CANERM Model (CANadian Emergency Response Model).

Example of a Canadian Volcanic Ash Advisory bulletin (FVCN CWAO header):
FVCN01 CWAO 131828
VOLCANIC ASH ADVISORY
ISSUED 1828 UTC 13 MARCH 2001 BY THE MONTREAL VAAC

CLEVELAND 2001-001 ALEUTIAN_IS 5249N16957W
(LAT/LON IN DEGREES AND MINUTES)

BACKGROUND INFORMATION:
CLEVELAND - ALEUTIAN_IS (1101-24-)
SUMMIT HEIGHT 1730 METERS

PLEASE SEE FVAK20 PANC 131802 ISSUED BY ANCHORAGE VAAC
WHICH DESCRIBES CONDITIONS OVER OR NEAR THE MONTREAL VAAC AREA OF RESPONSIBILITY.

Example of Washington Volcanic Ash Advisory bulletins (FVXX KNES header):
04:13
FVXX20 KNES 240400
VOLCANIC ASH ADVISORY
ISSUED: 2001 MAR24/0400 VAAC: WASHINGTON

VOLCANO: TUNGURAHUA 1502-08
LOCATION: 0128S 7826W AREA: ECUADOR

SUMMIT ELEVATION: 16480 FT (5023 M)

ADVISORY NUMBER: 2001/43

INFORMATION SOURCE: GOES-8 VISIBLE AND INFRARED AND MULTISPECTRAL IMAGERY. GEOPHYSICAL INSTITUTE IN QUITO.

ERUPTION DETAILS: VOLCANIC ASH CLOUD AT 23/1530Z.

DETAILS OF ASH CLOUD: NO EVIDENCE COULD BE FOUND OF ASH FROM YESTERDAYS BRIEF EMISSION TO FL290. NO ASH WAS DETECTED IN EITHER VISIBLE SATELLITE IMAGERY AT 23/2115Z OR IN INFRARED AND MULTISPECTRAL IMAGERY THROUGH 0345Z.

TRAJECTORY: N/A .

OUTLOOK: SEE SIGMETS.

THIS WILL BE THE FINAL MESSAGE ISSUED FOR THIS EVENT.

REAL TIME SATELLITE IMAGERY AND VOLCANIC ASH ADVISORIES OFTEN ACCOMPANIED BY A MAP DEPICTING ASH LOCATION ARE AVAILABLE AT INTERNET URL ADDRESS HTTP://WWW.SSD.NOAA.GOV/VAAC/WASHINGTON.HTML
(ALL LOWER CASE EXCEPT /VAAC/)

PLEASE REFER TO SIGMETS FOR CURRENT WARNINGS.

TURK

Charts

Each chart consists of 6 panels. Each panel presents the average ash density forecast for an atmospheric layer at a specific time. The first chart depicts a 6- and 12-hour prognostic while the second chart depicts an 18- and 24-hour prognostic. Occasionally, the Canadian Meteorological Centre (CMC) may transmit prognostic charts valid at 30-36, 42-48, 54-60 and 66-72 hours.

The charts are usually available approximately within one hour after the beginning of the execution of the Emergency Response Model (CANERM). The results are based on the last execution of the Global Model (i.e. 00 UTC or 12 UTC). The forecast time, the date and the time of validity as well as the atmospheric layer for which the forecast is valid are indicated above each of the panels.

This volcanic ash information (bulletins and / or charts) will be sent as default in the user's request (Route, Regional or Local Data) if any volcanic ash information is available on the site.

Example of a VAAC Chart Output (18-, 24-hour forecast). View the chart.

For more information about the Montreal VAAC centre, consult the Environment Canada Web site.

3.2.16 Comox Weather Charts

There are three different Comox weather charts; surface analysis, significant weather prognosis and surface prognosis. Each chart provides weather coverage for an area that includes the Canadian west coast, Eastern Pacific Ocean and Gulf of Alaska. Comox weather charts are provided on a best-available basis courtesy of the Department of National Defence (DND).

Comox Surface Analysis

The surface analysis chart is issued 4 times daily at approximately 00Z, 06Z, 12Z and 18Z. It contains MSL pressure (isobars), synoptic features (highs, lows, fronts), organized areas of precipitation and wind velocity indicators.

Comox Significant Weather Prognosis

The significant weather prognosis is issued twice daily; once as a 12-hour prognosis and again as an 18-hour prognosis. Each chart contains clouds & weather data, synoptic features (highs, lows, fronts), organized areas of precipitation and dashed lines indicating the freezing level.

Comox Surface Prognosis

The surface prognosis consists of a 24-hour depiction and a 36-hour depiction. The 24-hour and 36-hour charts are issued twice daily and contain forecasts of MSL pressure (isobars), synoptic features (highs, lows, fronts), organized areas of precipitation and wind velocity indicators.