Flashcards in WO08: Atmospheric Phenomena Deck (183):
A funnel-shape cloud of condensed water droplets, associated with a rotating column of wind and extending from the base of a cloud but not reaching the ground or a water surface.
A funnel cloud that touches a land surface. (Identified by presence of bush)
A funnel cloud that touches a water surface. (Identified by presence of bush)
A local storm produced by a CB cloud and is always accompanied by lightning and thunder, usually with strong gusts of wind, heavy rain, and sometimes with hail.
What is to be reported when the vortex of a funnel-shape cloud does not (or may not) reach the ground?
Funnel cloud and its direction
When shall a tornado, waterspout, or funnel cloud be reported?
If it is within sight at the time of the observation
When shall a thunderstorm be recorded?
When thunder has been heard in the last 15 mins or overhead lightning has been seen in the past 15mins and local noise is such that it might prevent the observer from hearing thunder.
What time should be recorded for the beginning of a thunderstorm?
The time of the earliest occurrence that indicates thunderstorm activity at the station.
What time should be recorded for the end of a thunderstorm?
When it is no longer possible to report thunderstorm activity at the station for 15 minutes.
How are the beginning and end times for tornadoes, water spouts, and funnel clouds determined?
By when you first see them, and then can no longer see them. If the bush goes out of view, the tornado ends and a funnel cloud begins.
Priority of Remarks
1. General Weather Remarks
4. Hail Size
5. Runway Visual Range (RVR)
Char. of Precipitation
Not occurring at the time of observation, but is expected to begin again soon
Char. of Precipitation
Intermittent precipitation precipitation occurring at time of observation.
Funnel Cloud Abbrev.
In which cases is there a 15 minute 'leeway' for begin/end times?
Thunder, intermittent or showery precipitation, or obstruction to vision.
Order of priority for column 32
-Tornado, water spout, funnel cloud
-Frozen precipitation (Precipitations in order of decreasing intensity)
-Obstruction to vision
-Additional and vicinity phenomena
What must be recorded in the remarks column when reporting a tornado or waterspout?
Direction from station and the direction toward which it is moving
What must be recorded in the remarks column when reporting a tornado or waterspout that has been reported by the public?
Location with respect to the station or city, direction toward which it is moving, and the time at which it was observed
Lightning cloud to ground
Lightning cloud to ground Abbrev
Lightning cloud to cloud
Lightning cloud to cloud abbrev
Lightning in cloud
Lightning in cloud abbrev
Lightning (Type unkown)
What is to be recorded when the type of lightning is not known?
What must be recorder when lightning is observed?
Direction from station
If two or more types of lightning are observed, how is this reported?
Abbreviations for lighting frequency
OCNL, FRQ, CONTUS
What shall be recorded on the 2322 as unusual weather?
Damage to life or property by:
-high wind, tornadoes or hail
-thickness of ice (during freezing precipitation)
-Floods or droughts
-Other items of considerable value for climatological purposes (severe lightning)
Where on the 2322 shall unusual weather be recorded?
Column 1, and if there is not enough room, on the back of the 2322 with notes to this effect on the front.
Any product of the condensation of atmospheric water vapour that is deposited on the earth's surface is a type of precipitation.
What are the three forms of precipitation?
Water drops at 0 degrees or greater
Water drops at -0.1 degrees or less. Drops freeze on the ice accretion indicator.
Solid particles of crystals of ice.
What are the three characters of precipitation
Showery, continuous, intermittent.
-Falls from cumuliform cloud
-Begins and ends abruptly
-Usually has a short duration
-rapidly fluctuates in intensity
-sky brightens between showers
-When there is no break in precipitation for at least an hour
-When there is no break in precipitation since the beginning of the hour preceding the time of observation.
-Liquid water particles less than or equal to 0.5mm in diameter.
Rain: Precipitation of liquid water particles > 0.5mm falling in widely scattered drops.
Freezing drizzle: drizzle that freezes on impact with the ground or other objects near the earth's surface. To be reported when temperature 0.1 degrees or less.
Freezing rain: rain that freezes on impact with the ground or other objects near the earth's surface. To be reported when temperature 0.1 degrees or less.
Snow: mainly hexagonal crystals that are usually branched. At a temperature higher than about -5 degrees, the crystals become clustered to form flakes.
-White and opaque ice particles
-spherical or conical
-brittle and easily crushed
-bounce and break up on hard ground
-always occur in showers
*GS is also used to report small hail (
At what temperature do snow pellets occur?
Around 0 degrees
-very small white, opaque ice particles
-flat and elongated
-transparent or translucent ice pellets
-spherical, rarely conical
-5mm diameter or less
-bounce and make sound on impact
-2 types: a and b
Ice pellets type a
Frozen raindrops or snowflakes that melted then refroze that usually fall continuously
Ice pellets type b
-Pellets of snow encased in a thin ice layer
-droplets intercepted by the pellets
-water resulting from partial melting of the pellets
-usually fall in showers
Hail: Small balls or pieces of transparent ice with a diameter of 5-50mm or sometimes more which fall separately or fused into irregular lumps.
Small hailstones: hail that is less than 5mm and is not an ice pellet.
Ice crystals: A fall of branched ice crystals in the form of needles, columns, or plates that may seem to be suspended in the air.
-Can create luminous pillar or halo
-frequent at polar regions
-only occur at very low temperatures
-fall from cloud or a cloudless sky
Forms when water is condensed on grass and and other objects near the ground that have been cooled by radiation during the night to a temperature below the dew point of the surrounding air but is still above freezing.
Forms when air with a dew point below freezing is brought to saturation by cooling. It is a deposit of interlocking ice crystals formed by direct sublimation on objects that are usually of small diameter.
A white or milky opaque granular deposit of ice formed by the rapid freezing of supercooled water drops as the contact the exposed object
A coating of ice, generally clear and smooth, formed on exposed objects by the freezing of a film of super cooled water deposited by rain, drizzle, fog, or possibly condensed from super cooled water vapour. It is denser, harder, and more transparent than rime or frost.
Where should deposits be recorder?
They SHALL be recorded in column 41, but may be recorded in column 1 as well.
What are the four deposits?
Dew, rime, hoar frost, and glaze
What usually produces rime?
What usually produces glaze?
freezing drizzle or freezing rain
What are the units used to report snowfall?
cm and tenths ( always even numbers)
What are the units used to report snowfall water equivalent?
mm and tenths
What are the units used to report rainfall?
mm and tenths.
What are the units used to report the snow on the ground?
What is considered a trace regarding precipitation?
less than 0.2mm or 0.2cm
What is considered a trace regarding snow on the ground?
Less than 0.5cm on the ground is recorded at TR. None is recorded as 0.
What are the three intensities of precipitation?
Which form of precipitation does not have categories of intensity?
IC- Ice crystals
In which two ways are precipitation intensities determined?
By effect on visibility or by rate of fall
Which types of precipitation does intensity by visibility criteria apply to?
Light intensity by visibility criteria
Visibility of more than or equal to 5/8
Moderate intensity by visibility criteria
If alone with a visibility of 1/2 or 3/8
Heavy intensity by visibility criteria
If alone with a visibility of less than or equal to 1/4
Which types of precipitation does intensity by rate of fall apply to?
Rain, rain showers, freezing rain, hail, ice pellets
Light intensity by rate of fall criteria
2.5mm/h or less.
Moderate intensity by rate of fall criteria
2.6mm/h to 7.5mm/h
Heavy intensity by rate of fall criteria
7.6mm/h or more
When frozen precipitation is mixed or if there is another obstruction to vision present, how is the intensity determined?
By using rate of fall criteria for the water equivalent.
When there is mixed precipitation (two or more of snow, snow showers, snow grains, snow pellets, drizzle, freezing drizzle) with no other obstruction to vision, how is intensity determined?
The predominant precipitation is judged by visibility and the less dominant by rate of fall.
How is intensity determined when there is an obstruction to vision?
By using rate of fall criteria and ensuring this is consistent with visibility
Determining intensity of liquid precipitation with no measuring equipment
Take into consideration the size of the drops, the spray over a hard surface, and how quickly puddles are formed.
What is considered light rain when there is no measuring equipment available?
-Individual drops are easily seen
-There is hardly any spray when the rain lands
-Puddles form slowly
What is considered moderate rain when there is no measuring equipment available?
-Individual drops are not easily seen
-There is noticeable spray when the rain lands
-Puddles form rapidly
What is considered heavy rain when there is no measuring equipment available?
-Individual drops are not identifiable (rain in sheets)
-There is heavy spray to a height of several cm
-Puddles form very rapidy
How are hail and ice pellets intensities determined if they cannot be determined by rate of fall?
They are determined by their accumulation on the ground.
Light: slow accumulation
Moderate: rapid accumulation
Heavy: very rapid accumulation
How are drizzle, freezing drizzle, or snow grains intensities determined if they cannot be determined by rate of fall?
They are determined by their accumulation on the ground.
Light: less than 0.2mm/h
Moderate: 0.2mm/h to 0.4mm/h
At what rate of fall does freezing drizzle become freezing rain?
When the rate of fall is greater than 1.0mm/h
When there is rain or drizzle, and ice on the indicator, what shall be reported?
Freezing rain or drizzle
When it is snowing and there is hoar frost or rime on the indicator, what shall be reported?
This is a indication of fog and rime on indicator or froin shall be reported.
If additional space is required for columns 2, 3, and 4, where should the extra information be recorded?
At stations without a snow gauge, how is the snowfall water equivalent determined?
It is estimated. The snowfall divided by ten and converted to mm.
What is to be recorded if the observer is certain that the water in the rain gauge is from dew alone?
The word "dew" shall be written in brackets before the amount.
When only dew is found in the rain gauge, is this amount included in the 'total precipitation' column?
Is column 13 (total 24-hour precipitation) filled in at all stations?
No, only at those stations at which synoptic observations are transmitted.
How long can a break in precipitation last before it has to be coded again when the precipitation resumes?
How do you report increasing depth of newly-fallen snow since last main synoptic report?
- Coded when rounded value increases by 1 cm
- Reported on-the-hour, only
What does /Sss/ represent?
-S Identifies precipitation as snow
-ss Units as whole centimetres
Is snowfall reported if all the snow melts as it hits the ground?
No, /Sss/ is not reported
What does Column 9 (snowfall cm & tenths) represent?
Depth of newly fallen snow reports the amount of new snow that fell in the last 6 hours (some of which may have melted).
What does /Sss/ in Column 41 (remarks) represent?
Increasing (or accumulating) depth of newly fallen snow reports the amount of new snow that remains (after any melting that may have occurred).
When should /Sss/ by reported?
/Sss/ shall be reported only at the hours when the accumulated (rounded) value increases to equal or exceeds the previously reported value by 1 cm or more.
How do you code rainfall since last main synoptic report?
- Coded when rounded value equals or exceeds 10 mm or exceeds the previously reported value by 10 mm (rounded) or more.
- Reported on-the-hour, only
What does /Rrr/ represent?
-R Identifies precipitation as rain
-rr Units as whole millimetres
Average size of hail shall be estimated in whole millimetres
How is hail coded?
HAIL DIAM nn MM (nn is average diameter in millimetres)
Hail with a diameter of 5 mm or more
SHGS (Small Hail)
Hail with a diameter of 4mm or less
List the different components of the Type B Rain Gauge
-Mounting bracket assembly
What is the scale on the graduated cylinder and what's it capacity?
Scale is graduated at every 0.2 mm and it has a capacity of 25 mm
How to measure rainfall?
Rainfall amounts are recorded every 6 hours
-Read the lowest point of the meniscus
-Amount below 0.2 mm = trace
-If frozen, melt the ice
- Add measured amount of warm water
- Subtract amount added from measurement
Measuring Rainfall (Hail)
Hail or small hail
- Melt catch in rain gauge (some bounces out)ert
If completely covers ground:
- Invert funnel, gather stones (before they melt)
How to determine intensity with no TBRG (Tipping Bucket Rain Gauge)
Use a spare Type B Rain Gauge
Use 10 minutes intervals
What are the major components of the Tipping Bucket Rain Gauge
How much is the fill amount of the bucket in the TBRG
How to determine total rainfall using the TBRG?
-Number of steps (When the bucket fills up and swings to the other side) * 0.2 mm (Fill amount of the bucket)
-Add up the rainfall since the last synoptic
How to determine rate-of-fall intensity using the TBRG?
-Calculate over a short period (10 min)
-Convert to mm/hour
What are the three Rate-of-fall intensities for the TBRG?
-2 steps or less per 10 min is light
-3 to 6 steps per 10 min is moderate
-7 steps or more per 10 min is heavy
When do you change the TBRG chart?
-Change daily during rainfall season (whether rain fell or not) on a synoptic hour.
When is a blank TBRG chart left on the recorder?
During the snowfall season
When does a TBRG system become operational?
It becomes operational only for the day(s) of liquid (non-freezing) precipitation, and while they occur
- Charts only required on days with RA/DZ
What are the characteristic of the snow ruler?
The snow ruler is a wooden stick 1 m (or 100 cm) in length, with scale markings in increments of 0.2 cm throughout its length.
How do you measure using the snow ruler?
-Use the average ruler measurement that is undisturbed by the wind (drift)
How do you calculate water equivalent by using snowfall amount?
Divide snowfall by 10. Its water content is 1/10th of its depth.
How do you calculate water equivalent by using ice pellets?
Divide by 2. Ice pellets have water content of 1/2 its amount.
How is average snowfall to be recorded?
To the nearest 0.2cm.
How is snowfall amount determined when the snow is melting?
Use the snow/rain gauge and multiply water by 10.
What are the components of the nipher snow guage?
Shield, telescopic stand, receiver.
Nipher snow gauge shield
Inverted bell shape which minimizes the effect of turbulent winds over the receiver mouth in an attempt to obtain only the precipitation which is falling.
Nipher snow gauge telescopic stand
Cast iron coupled pipes (3" and 4") which serve to adjust, through the clamping device, the height of the receiver mouth and shield to 152cm (5ft) above the snow surface at the time.
Nipher snow gauge receiver
Copper containing lying on the mouth at the top of the inner pipe so that its opening is parallel with the top of the shield. it serves to collect all precipitation when snow is occuring. Stations have two receivers to be exchanged every 6 hours during snowfall.
How shall the amounts of snowfall and rainfall be determined using the Nipher snow gauge when both fall at the same time?
The total amount shall be calculated and snowfall and rainfall will be estimated based on the water equivalent of the snow that has accumulated on the ground.
How shall snowfall amount be determined if all of the snow has melted by the time of observation?
The amount of water collected in the snow/rain gauge shall be measured to obtain the water equivalent of the snowfall.
What types of precipitation are considered when determining depth of snow on the ground?
Snow, ice, or any other form of solid precipitation such as hail, ice pellets, or snow pellets but not ice that resulted from freezing precipitation only.
Does total depth of snow on the ground include ice layers?
Yes, for this reason, a snow stake is preferable to a snow ruler.
Things to consider when choosing an area to measure snow depth
-the heat of nearby buildings
-drifting caused by snow fences
-increased depth due to the plowing of sidewalks
When shall the snow gauge be checked?
It shall be checked and emptied whenever a measurable amount of precipitation is found in the rain gauge.
Obstruction to vision
-A meteor, other than precipitation, that reduces the horizontal visibility at eye level. May be suspended in the air or blown from the earth's surface.
Fog: Water droplets or ice crystals suspended in the air with 1/2 SM or less visibility.
Freezing fog: Supercooled water droplets suspended in the air with a visibility of 1/2 SM or less. Temperature is always below 0 and is usually between -0.1 and -30
Mist: Water droplets or ice crystals suspended in the air with a visibility of 5/8 to 6.
How can freezing fog be identified?
By rime or glaze deposits on indicator or other cold exposed objects.
What do rime or glaze indicate?
Freezing rain, freezing drizzle, or freezing fog.
Haze: a suspension of extremely small, dry particles invisible to the naked eye and sufficiently numerous to give the air an opalescent appearance.
Smoke: A suspension in the air of small particles produced by combustion. Smoke may give the sky an orangish tinge, or greenish-yellow when produced by a forest fire.
Blowing snow: Snow particles raised by the wind reducing visibility to 6 miles or less.
Heavy blowing snow: Snow particles raised by the wind reducing visibility to 1/2 mile or less when occuring alone.
Sand raised by the wind to reduce visibility to 1/2 mile or less.
Sand raised by the wind to reduce visibility to 1/4 mile or less.
Dust raised by the wind to reduce visibility to 1/2 mile or less.
Dust raised by the wind to reduce visibility to 1/4 mile or less.
Duststorm: Dust raised to great heights by a strong turbulent wind. May look like a high wide wall. Visibility at eye level is reduced to 1/2 mile or less.
Heavy duststorm: Dust raised to great heights by a strong turbulent wing. Visibility at eye level is reduced to 1/4 mile or less.
Sandstorm: Sand raised to great heights by a strong turbulent wind. May look like a high wide wall. Visibility at eye level is reduced to 1/2 mile or less.
Heavy Sandstorm: Sand raised to great heights by a strong turbulent wind. Visibility at eye level reduced to 1/4 mile or less.
Dust haze: A suspension in the air of dust or small sand particles, raised from the ground, prior to the observation, by a duststorm or sandstorm.
What is the order of priority for obstructions to vision?
-Tornado, waterspout, funnel cloud
-Frozen precipitation (precip. in order of decreasing intensity)
-Obstructions to vision
-Addiction and vicinity phenomena
When shall obstructions to vision be recorded in column 32?
Only when visibility is 6 miles or less.
Why is FZFG not usually reported when it is colder than 30 degrees?
Because usually at this temperature, the fog is made up of almost entirely ice crystals and therefore, there is no icing hazard.
If it is below 30 degrees and fog is present, how is it determined if it is FG or FZFG?
If there is evidence of ice accretion, FZFG will be reported as there is an icing hazard.
When there is a physical indication of freezing fog, what must be written in remarks?
FROIN or RIME ON INDICATOR
When shall obstructions to vision such as VA, FU, BR, BLSN be recorded in columns 2, 3, and 4?
When prevailing visibility is 6miles or less.
If you do not know what time precipitation or obstruction to vision starts or ends what should be entered in columns 3 and 4?
M for missing.
Shallow fog: visibility at eye level is not reduced
Fog patches: Scattered patches at least two metres above ground, covering less than 50% of the ground
Fog covering part of the aerodrome: More or less continuous fog bank covering at least 50% of the ground.
When particles of dust are raised by the wind in such a way that very low objects are veiled or hidden but the visibility at eye level is not appreciably restricted.
When particles of sand are raised by the wind in such a way that very low objects are veiled or hidden but the visibility at eye level is not appreciably restricted.
When particles of snow are raised by the wind in such a way that very low objects are veiled or hidden but the visibility at eye level is not appreciably restricted.
Dust/sand whirls consist of an ensemble of particles of dust or sand, raised from the ground by the wind in the form of a whirling column of varying height and a small diameter.
Volcanic Ash: Consists of fine particles of rock powder that have been blown out from a volcano.
When is additional phenomena recorded in column 32?
When it is occurring within the aerodrome perimeter.
How is a cloud of VA recorded?
As an obscuring layer based aloft using FEW, SCT, BKN, OVC
When shall windshear be reported?
When it occurs along the runway takeoff or approach path within 1500ft AGL and is considered significant to aircraft operations. It shall be reported on each SPECI until the next hourly ob.
In the vicinity: Shall be used when specific weather phenomena are observed within 5SM but are not occurring at the point of observation.