Weather Flashcards
This implies that the wind is blowing FROM the northwest. That is, it is a northwest wind.
In our view, this is very unfortunate symbology, as to us the symbol intuitively looks like a piece of string anchored to a post and blowing in the wind. However, that “image” is backwards. One must instead of think of the circles as fish heads (or choose whatever image works for you here) with the line part as the “tail” behind it.
What is wind shear?
Wind shear is encountered in an area where two winds moving in opposite directions “rub” or mix together.
What are the two types of temperature inversions?
Two types: Ground-Based and Inversion Aloft
What is a ground-based temperature inversion?
Ground-based inversion: occurs near the ground on cold, clear nights. Since the ground radiates and cools much faster than the air above it, air in contact to the ground becomes cold while just a few hundred feet above it that temperature has changed very little. This can trap fog or smoke close to the ground and decrease visibility.
What sort of weather condition would lead to the (highly dangerous in a small aircraft) rapid accumulation of structural ice?
Freezing rain causes the greatest accumulation of structural ice.
Express 1 statute mile as RVR.
5000 RVR
What does the following mean in a METAR?
M20/
“Temperature minus twenty (degrees Celsius), dewpoint missing (not available).”
Express 3/4 mile as RVR.
4000 RVR
What are the only cloud types forecast in the Terminal Aerodrome Forecast (TAF)?
The only types of clouds reported in a TAF are cumulonimbus (thunderstorm) clouds.
What does the following METAR excerpt mean?
R12L/M1000FT
“Runway one two left R-V-R less than one thousand (feet)”
Express 4500 RVR in statute miles.
7/8 mile
Describe Cirrus Clouds.
Cirrus: These high clouds are composed almost entirely of ice crystals. They display a wispy, feathery appearance. Their base altitudes typically range from about 16,500 to 45,000 feet.
What is a trough?
A trough line is an elongated area of low pressure. It is usually associated with and is most clearly identified as an area of maximum cyclonic (anti-clockwise) curvature of the wind flow. (isobars, contours, or streamlines.)
What is the difference between an AIRMET and a SIGMET?
Both AIRMETs and SIGMETs are for ALL aircraft. However, as AIRMETs generally contain less crucial weather information than SIGMETs, pilots of large aircraft should be particularly mindful of SIGMETs.
Describe Cirrus Clouds.
These high clouds are composed almost entirely of ice crystals. They display a wispy, feathery appearance. Their base altitudes typically range from about 16,500 to 45,000 feet.
Describe Stratus Clouds.
These low clouds exhibit a fairly uniform light to dark gray appearance and typically blanket large areas of the sky. The bases of these clouds are usually found near the ground to around 6,500 feet. A stratus cloud with its base extending down to the ground is known as fog.
What are the two requirements for structural icing?
Flight through visible moisture,
Temperature (of the collecting surface) at freezing or below.
What is meant by the term “front”?
A front represents a boundary between two air masses that contain different temperature, wind, and moisture properties.
Express 1/2 mile as RVR.
2400 RVR
Express 6000 RVR in statute miles.
1 1/4 miles.
Describe the flow of winds around a low pressure system in the northern hemisphere.
Counterclockwise (cyclonically) around lower air density areas or a “low.
What does the term “precipitation” mean?
Precipitation refers to all different kinds of moisture that falls from the sky: drizzle, rain, snow, ice pellets, hail and ice crystals.
At what altitude / distance from an uncontrolled field should you expect to be able to normally pick up its ASOS / AWOS broadcast?
At uncontrolled airports that are equipped with ASOS/AWOS with ground-to-air broadcast capability, the one-minute updated airport weather should be available to you within approximately 25 NM of the airport below 10,000 feet.
Describe the flow of winds around a high pressure system in the northern hemisphere.
This convection process causes changes in the air density, and those variations cause winds. Winds flow out of higher air density areas into lower air density areas. Because of the Coriolis effect in the Northern Hemisphere, the wind flows clockwise (anti-cyclonic) around higher air density areas, called a “high,” and counterclockwise around lower air density areas or a “low.” For general reference, highs bring clear weather and lows bring stormy weather. Because this is not always true, pilots perform a thorough check of all available weather data when planning a flight.
An easy way to remember this is to picture a clock face with an “H” at its center.
What is a SIGMET?
SIGMETs (WS) are broadcasted for hazardous weather that is considered of extreme importance to all aircraft. SIGMETs (acronym for “SIGnificant METeorological information”) warn of the following weather hazards:
S: Severe turbulence
T: Terrible icing (severe icing)
I: Invisibility from dust/sandstorms
V: Volcanic ash reducing visibility
What is an AIRMET?
An AIRMET (WA) is broadcasted for weather phenomena that potentially affects all aircraft.
While applicable for all aircraft, for pilots of light aircraft especially, an AIRMET (acronym for “AIRman’s METeorological information) gives valuable information about the following conditions: moderate icing, moderate turbulence, sustained winds 30 knots or greater at the surface, widespread area with a ceiling of less than 1,000 feet and/or visibility less than 3 miles and extensive obscurement of mountains. These are important to light aircraft, as they have limited flight capabilities due to lack of equipment and/or instrumentation and lesser pilot flight experience.
Describe Nimbostratus Clouds.
Nimbostratus: Often called rain clouds, nimbostratus exhibit a uniform dark gray appearance. Their bottoms are typically blurred and indistinct due to falling rain or snow. These clouds have low bases, but may have considerable vertical development bringing the tops into the middle level range.
Describe a Terminal Forecast (TAF)
Terminal Forecasts (TAFs) are the surface weather expected at an airport (usually the larger airports). They are issued four times a day and are valid for the duration specified in them (such as 24 or 30 hours).. The last six hours are an “outlook” rather than a forecast. Each Terminal Forecast Includes a station identifier, the date/time, cloud coverage and types, and winds within a 5 mile radius from the center of the runway complex.
Here is a typical TAF (this one is for Lake Charles, Louisiana - KLCH):
000 FTUS44 KLCH 270500 TAFLCH TAF KLCH 270522Z 270606 14010KT P6SM VCSH BKN035 OVC070 TEMPO 0710 VRB20G30KT 1SM TSRA BKN010CB FM1100 25007KT P6SM SCT030 FM1800 31008KT P6SM SKC FM0000 35007KT P6SM SKC=
{{Const851:5}}
What does a Winds and Temperatures Aloft (FD) forecast provide?
The Winds and Temperatures Aloft Forecast (FD) gives an estimate of wind direction as it relates to true north, the wind speed (in knots) and the temperature (degrees Celsius) for selected levels of altitude.
What is “convection” with regards to weather?
Variation in the temperature comes from uneven heating of the Earth’s surface by the Sun.
There TAF specifies a 30% probability that. from the 1 2th day of the month at 0000Z - TRSA - Thunderstorm with moderate rain showers.
The KSTL TAF is valid for 24-hours and has four forecast time groups. The 20Z conditions are found in the first forecast time group from 1 8Z till
23Z, when conditions are forecasted to raduall chan e.
161818 16014G20KT P6SM SCT060 SCT120 TEMPO 1823 BKN120 BECMG 2324
What is an International SICMET? What sorts of weather are usually covered by international SICMETs?
International SIGMET: These SIGMETs are considered “widespread” because they must be either affecting or be forecasted to affected
area of at least 3,000 square miles at any one time.
The International SIGMET is issued for 12 hours for volcanic ash events,
6 hours for hurricanes and tropical storms, and
4 hours for a
events. Like the domestic SICMETs, International SIGMETs are also identified by an alphabetic designator from Alpha through Mike
numbered sequentially until that weather phenomenon ends.
A02 implies that this is an Automated station with a precipitation discriminator.
What is a stationary front?
A stationary front is similar to a warm front, i.e., warm air is present behind it (to its south) with cool air ahead of it (to its north). However,
while a warm front shows movement, a stationary front shows little or no movement as the cooler, more dense air remains intact and does not
retreat.
What does “TAF AMD” mean?
“TAF AMD” means that it’s an amended TAF (Terminal Aerodrome Forecast). That is, there was an original TAF for this time period, but it was
deemed necessary to issue a replacement.
What kind of weather can we expect as a (surface) warm front passes?
This causes clouds and precipitation ahead of the surface warm front, assuming enough upward motion of air parcels and available
moisture.
The 1021 is the sea level pressure atmospheric pressure in the region (associated with the high pressure area there) in millibars.
For the purposes of weather reporting and flight regulations, what constitutes a “ceiling”?
A ceiling is the height above the Earth’s surface of the lowest layer of clouds or obscuring phenomena that is reported as “broken,” “overcast,”
or “obscuration,” (“vertical visibility”) and is not classified as “thin” or “partial.” (also: not “scattered” or “few”)
What is Wind Shear?
Wind shear is the phenomenon that occurs when wind from different directions meet. It can occur at any altitude and can be horizontal or
vertical.
Describe Cumulous clouds.
C
U
P
C: Cotton-like or popcorn appearance.
U: Uneven bases and bumpy tops.
P: Powered by rising warm air (formed from ground heating).
First of all, the double blue circle in the middle represents calm surface winds as there is no “wind stick”
sticking out of it. Because the inner circle is not at all filled in, this also indicates clear skies.
The red 70 represents the current temperature, in Fahrenheit.
The green 64 represents the dew point. While a small temperature/dew point spread does not guarantee
the formation of fog (since moisture and other factors are needed), it is a key factor in the creation of fog
or low visibility conditions. A double pink equals (=) looking sign - look at Cuba and in the Chicago area to
see some fog examples and check out the relatively small temperature-dew point spreads there.
The orange “1 67” might be tricky at first, but with a little careful observation you might be able to figure it
out. This is the barometric pressure (altimeter setting). Sea-level pressure is plotted in tenths of millibars
(mb), with the first two digits (generally 10 or 9) omitted. For reference, 1 013 mb is equivalent to 29.92
inches of mercury. Below are some sample conversions between plotted and complete sea-level pressure
values:
Pilot Weather Report, over Double Eagle II Airport, Albuquerque, New Mexico, 845 UTC, remarks, Tijeras
Pass closed due to fog and low clouds, unable to fly VFR, returned to Double Eagle II Airport.
“Ceiling” is defined as the lowest cloud layer that is listed as Broken (BKN) or overcast (OVC) or as VV
(Vertical Visibility). From 1600Z (FMI 600 section), the clouds section contains only the entry “SC T 250” - or
scattered clouds at 25,000 feet. SCT clouds do not make a ceiling. Therefore, at 1 600Z, no ceiling (unlimited
ceiling) is forecast.
When talking about high and low pressure areas in the Northern Hemisphere, we often use the terms
“cyclonic” and “anti-cyclonic.” Which one is associated with which type of pressure area, and which is
clockwise and which is anti (counter) clockwise?
Anti-cyclonic means clockwise. Cyclonic means counter-clockwise. Remember that they are reversed
as such!
Winds around a high pressure system tend to be anti-cyclonic (clockwise). Winds around a low pressure
system tend to be cyclonic (anti-clockwise).
The easiest way to remember this is to picture a clock with an “H” on its face.
What is an aloft (temperature) inversion?
I: Inversion aloft (occurs higher than ground-based inversions).
C: Cold air trapped near the Earth’s surface.
I: Icing develops from freezing rain passing through cold air.
N: Numbing effects on aircraft wings.
G: Ground lift reduced drastically.
What is a Convective SIGMET?
S
L
E
E
T
S: Severe thunderstorms (due to surface winds ≥ 50 knots, hail ≥ 3/4 inch, or tornadoes)
L: Line of thunderstorms
E: Embedded thunderstorms
E: Extreme precipitation (≥ heavy precipitation affecting 40%+ of an area ≥ 3,000 square miles)
T: Turbulence, icing, and low-level wind shear (implied with any Convective SIGMET)
Define in celsius what each weather day would feel like…
A hot summer day is ____°Celsius and above
A nice spring day is about ____° Celsius
Sweater weather is in the teens (about ____° Celsius)
Jacket weather is single digits (about ____°Celsius)
Coat weather is below zero (about -____° Celsius)
A hot summer day is 30° Celsius and above
A nice spring day is about 20° Celsius
Sweater weather is in the teens (about 15° Celsius)
Jacket weather is single digits (about 05° Celsius)
Coat weather is below zero (about -03° Celsius)
Assuming the temperature at sea level is 6 degrees Celsius and a standard atmospheric lapse rate, what is
the temperature at 6,000 feet?
Altitudinal variations need to also be monitored by the pilot before and during flight. Normally in the
troposphere temperature decreases as the altitude increases. This is known as the lapse rate. The average
temperature decrease (or average lapse rate) in the troposphere is usually given as -2 degrees Celsius per
1 ,OOO feet. Sometimes, a slightly more accurate value of -1.98 degrees per 1OOO feet is used.
6 thousand feet - 0 thousand feet = 6 thousand foot difference.
6 thousand feet * -2 degrees C per thousand feet - -12 degrees difference
6 degrees minus 12 degrees C - -6 (negative six) degrees Celsius at 6,000 feet.
