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95 Cards in this Set

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Which 2 manuals contain detailed instructions regarding the Navy’s surface weather observation program?
NAVMETOCCOMINST 3141.2, Surface METAR Observations User's Manual,
and
NAVMETOCCOMINST 3144.1, United States Navy Manual for Ship’s Surface Weather Observations
What are the 3 temperature scales in use today?
Fahrenheit, Celsius, and Kelvin
Each time zone covers approximately how many degrees of longitude?
15° of longitude
What does the abbreviation UTC mean?
Coordinated Universal Time
What observation element should be observed last?
Pressure
How many states-of-the-sky are internationally recognized?
27
List the three general cloud forms
Cumuliform, stratiform, cirriform
Stable air is normally associated with what general cloud form?
Stratiform
The 4 processes that cool air by lifting
Mechanical Lift
Convective Lift
Convergence
Vorticity
Mid-etage clouds in the temperate regions of the earth are found between what levels?
6,500 to 23,000 feet
Define cloud variety
Variety identifies the specific appearance of the arrangement of elements within a cloud layer, the thickness of the layer, or the presence of multiple layers.
Most supplementary cloud features are associated with what type of cloud?
Cumulonimbus
The height of the base of cumulus clouds is directly related to what factor?
The amount of moisture near the surface
What is a simple rule of thumb for classifying cumulus congestus clouds as towering cumulus?
If the height of the cumulus congestus cloud appears to be twice the width of the base, it should be classified as towering cumulus.
Cumulonimbus capillatus clouds are identified by what distinguishing feature?
An anvil top
Describe 2 potentially dangerous wind phenomena associated with an outflow boundary.
Low-level wind shear & microbursts.
A wall cloud will usually form in what location of a CB cell?
The right rear quadrant with respect to CB movement
Stratus fractus clouds generally form in conjunction with what other type of cloud?
Nimbostratus
When must altostratus clouds be reclassified as nimbostratus?
When precipitation begins or when bases drop to less than 6,500 feet.
What might the formation of altocumulus castellanus or altocumulus floccus indicate?
Approaching frontal systems with conditions favorable for thunderstorm activity.
What are cirrus clouds composed of?
Ice crystals
Explain the formation of a rotor cloud.
Formed when strong winds moving across mountains set up a wavelike action in the winds downstream from the mountain. The upward moving air in the waves, if moist, is brought to saturation as it rises.
Explain the formation of a cap cloud.
Formed when moist air is forced upward by a mountain top and dissipates on the leeward side of the mountain as the moving air descends.
How is the amount of cloud layer coverage and total sky coverage measured?
In eighths of the sky
Define cloud layer
Clouds and/or obscuring phenomena aloft either continuous or composed of detached elements that have bases at approximately the same level.
Define cloud ceiling
The lowest layer that blocks 5/8 or more of the celestial dome from being seen.
Define total obscuration
Any collection of atmospheric phenomena dense enough to obscure even the portion of the sky directly overhead.
Define summation sky coverage
Sky cover at any level is equal to the amount the sky cover of the lowest layer plus the additional sky cover present at all successively higher layers (up to and including the layer being considered).
Given: Layer No.1 is 1/8 fog (SFC) Layer No.2 is 2/8 cumulus 3,000 ft Layer No.3 is 2/8 altocumulus 12,000 ft Layer No.4 is 5/8 cirrus 20,000 ft
What is the ceiling height?
12,000 feet
A cloud height of 7,550 feet would be reported as what height?
7,500 feet
What are the 4 types of visibility that may be observed?
Prevailing visibility,
sector visibility,
differing level (or tower) visibility,
& runway visual range.
Define prevailing visibility
The greatest distance that known objects can be seen and identified throughout half or more of the horizon circle.
Where can shipboard observers obtain visibility range information at sea?
Combat Information Center (CIC)
When is sector visibility reported?
When it differs from the prevailing visibility, and either prevailing visibility or sector visibility is less than 3 miles.
When is differing level visibility reported?
When the prevailing visibility is 4 miles or less.
What type of lithometeor produces a yellow or orange tinge when viewed against a brighter background?
Haze
Where are dust/sand whirls most likely to develop?
In desert regions on calm, hot, clear afternoons
What does the term “heavy sandstorm“ mean?
Blowing sand that reduces visibility to less than 5/16 of a mile.
Define sublimation
Water vapor bypasses the liquid state and goes directly from a gas to a solid.
What 3 factors are necessary for cloud formation?
Moisture, hygroscopic nuclei, and cooling
Fog may form when the temperature-dewpoint spread is how many Celsius degrees?
Four Celsius degrees or less
Fog formed by moist air moving over a cooler surface is known by what term?
Advection fog
Define the term "mist"
A fog condition that reduces prevailing visibility to between 5/8 mile and 6 miles.
Explain the formation of frost
Frost occurs when radiational cooling lowers the temperature of an object below the freezing level and ice crystals form through sublimation.
Any liquid that has a temperature below its normal freezing point but still exists in the liquid state is known by what term?
Super-cooled liquid
What distinguishes drizzle from rain?
The slow rate of fall and droplet size (less than 0.02 inch).
What type of hydrometeor is composed of hard grains of ice formed from freezing rain or the refreezing of snowflakes?
Ice pellets
If rain is accumulating at a rate of 0.25 inches per hour, how should the intensity be classified?
Moderate
What does the abbreviation LTGCA mean?
Lightning cloud-to-air
When is a thunderstorm considered to have begun?
When the first thunder is heard, or when overhead lightning is observed, and the local noise level is high enough as might prevent the observer from hearing thunder.
Ten millibars is equal to how many hectopascals?
10 hectopascals
What is meant by the term "removal correction"?
The pressure correction applied to station pressure based on the difference in height of the barometer and the runway or station elevation.
What would be the "r" factor for a shipboard barometer located 45 feet above the water line?
1.62 hectopascals or .045 inches of mercury
What is an altimeter setting used for?
It is a pressure value used by aircraft to allow correct determinations of height above mean sea level.
How is the overall trend or characteristic of pressure tendency determined?
A barograph trace or the actual recorded pressures during the period.
Define wet-bulb temperature
The lowest temperature to which an object may be cooled by the process of evaporation.
What is the normal result of air being cooled to below the dew-point temperature?
Condensation and/or precipitation
Given an air temperature of 82.5°F and a dew- point temperature of 70.0°F, calculate the dew- point depression.
12.5°F
What is meant by the term "frost-point temperature"?
The temperature, below freezing, that a parcel of air must be cooled to in order to reach saturation.
List 3 methods for manually obtaining the sea surface temperature.
Bucket method, bathythermograph method, and seawater injection method.
Explain the difference between True North and Magnetic North?
True North is in reference to the geographic North Pole while Magnetic North is in reference to the magnetic North Pole.
Winds blowing directly off the starboard beam are coming from what relative direction?
090°
How can relative winds be manually converted to true winds?
Using the CP-264/U true wind computer, a maneuvering board, or an aerological plotting chart.
How is the mean wind speed determined?
By using the arithmetic or graphical average during the 2-minute observation period.
How would the observed wind speed on a ship be affected by winds blowing from dead astern?
It would be less than the actual wind speed.
Define the term "gust"
A rapid fluctuation in wind speed with a variation between peaks and lulls of 10 knots or more observed in the lo-minute period prior to the actual time of observation.
Define the term "squall"
A sudden increase in wind speed of 16 knots or more and the sustained increase must be 22 knots or more for at least 1 minute.
Define wave height
The vertical distance from the crest to the trough of the wave
What factors will determine the maximum height of sea waves for any location?
The wind speed, the length of time the wind has been blowing, and the size of the fetch area
What would be the average wave height with a sea state of 5?
8 to 13 feet
Define wave period
The time it takes for a complete wave cycle to pass a given point
How is wave direction determined?
Wave direction is the direction the majority of waves in a group are coming from.
What is meant by the term "significant wave height"?
The average height of the highest 1/3 of all the waves present
How do swell waves differ from sea waves?
Swell waves are sea waves that have moved out of the area of formation and are more smooth and regular in appearance.
How is swell wave height determined?
By using the average height of all the swell waves present.
At approximately what temperature (Fahrenheit) would you expect rime ice to form on a ship, assuming blowing spray is present?
14°F
What elements are included in an ice accretion observation?
The source of the ice accretion, the thickness of the ice, and a determination of the rate of accumulation or melt-off.
Why does it take seawater longer to freeze than freshwater?
It is due to the salinity of seawater and the density changes in seawater caused by salinity. In addition, the freezing of seawater is slowed because of waves, currents, and tides.
When does sea ice reach a maximum in the Northern Hemisphere?
March
What is meant by the term "fast ice"?
Sea ice that is frozen solidly to the shores of islands or land masses.
Why should ships avoid operating in ice areas where rafting is occurring?
Rafting ice indicates that the ice is closing rapidly
How does pack ice normally drift in the Northern Hemisphere during winter?
It normally drifts to the right (about 30°) of the wind direction.
Where do most of the world’s icebergs originate?
Antarctica and Greenland
What is the most important influence to us in the movement of icebergs?
The prevailing sea current at the icebergs submerged depth.
What publication provides detailed instructions for reporting ice in the sea?
NAVMETOCCOMINST 3144.1
What term describes the inability of the body to get rid of excess heat fast enough to maintain an internal temperature balance?
Heat stress
Define the term "relative humidity"
The ratio of how much water vapor is in the air compared to the amount of water vapor, at the current temperature andpressure, that the air can possibly hold.
Given an air temperature of 90°F and a relative humidity of 65%, what is the apparent temperature?
105°F
What effects does the Wet-bulb Globe Temperature index (WBGT) take into consideration?
Temperature, humidity, and radiant energy
What is meant by the term "wind chill factor"?
The temperature required under no-wind conditions that will equal the cooling effect of the actual air temperature in conjunction with the wind.
What is the survival chance given a seawater temperature of 15°C and an immersion time of 3 hours?
Marginal
What does a pressure altitude lower than the actual altitude mean?
The air is more dense than normal
What happens to density altitude when the air temperature increases?
It increases density altitude
How may density altitude be calculated?
By using the Density Altitude Computer (CP-718/UM), the Smithsonian Meteorological Tables, the Density Altitude Formula, or the Density Altitude Diagram.
How does humidity affect air density?
It decreases air density