Test 3 Flashcards
The direction of surface wind is?
From high pressure towards low pressure deflected by earth’s rotation.
Tropical cyclones normally form within which of the following?
5 degrees to 15 degrees
According to Buys Ballot’s law, when an observer in the Northern Hemisphere experiences a northwest wind, the center of low pressure is located to the
northeast
You are enroute from Puerto Rico to New York. A hurricane makes up and is approaching. If the wind veers steadily, this indicates that your vessel is
in the dangerous semicircle
Low-pressure disturbances, which travel along the intertropical convergence zone are called
tropical waves
The approximate distance to a storm center can be determined by noting the hourly rate of fall of the barometer. If the rate of fall is 0.08-0. 12 inches, what is the approximate distance to the storm center
80 to 100 miles
What kind of weather would you expect to accompany the passage of a tropical wave?
Heavy rain and cloudiness
Tropical cyclones are classified by form and intensity. Which system does not have closed isobars?
Tropical disturbances
A tropical wave is usually preceded by
Good weather
Ocean swells originating from a typhoon can move ahead of it at speeds near
50 knots
The highest frequency of tropical cyclones in the North Atlantic Ocean occurs during
August, September, and October
Recurvature of a hurricane’s track usually results in the forward speed
increasing
You have determined that you are in the right semicircle of a tropical cyclone in the Northern Hemisphere. What action should you take to avoid the storm?
Place the wind on the starboard bow and hold that course.
A line on a weather chart connecting places which have the same barometric pressure is called an
isobar
A rapid rise or fall of the barometer indicates
a change in the present weather conditions.
In the Northern Hemisphere, if your vessel is in a hurricane’s navigable semicircle it should be positioned with the wind on the
starboard quarter, hold course and make as much speed as possible.
A phenomenon where the atmospheric pressure is higher than that of other surrounding regions is called
a high-pressure area; an anticyclone; or a “high”
Cyclones tend to move
parallel to the isobars in their warm sectors
The flow of air around an anticyclone in the Southern Hemisphere is
counterclockwise and outward
The dangerous semicircle of a hurricane in the Northern Hemisphere is that area of the storm
to the right of the storm’s track
You are located within a stationary high-pressure area. Your aneroid barometer is falling very slowly. This indicates a(n)
decrease in the pressure of the system
In the Northern Hemisphere which semicircle of a hurricane is the navigable semicircle?
left
The hurricane season in the North Atlantic Ocean reaches its peak during the month of
September
As a high-pressure system approaches, the barometer reading
rises
In the Southern Hemisphere the wind circulation in a high-pressure system rotates
counterclockwise and outward
The eye of a hurricane is surrounded by dense black cumulonimbus clouds which are called the
wall cloud
What enables you to estimate the bearing of a storm’s center?
Buys Ballot’s Law
The left half of the storm is called the navigable semicircle because
Both A and B
A. the wind speed is decreased by the storm’s forward motion.
B. the wind tends to blow vessels away from the storm’s track
The edge of a hurricane has overtaken your vessel in the Gulf of Mexico, and the northwest wind of a few hours has shifted to the west. this is an indication that you are located in the
navigable semicircle
The rise and fall of the ocean’s surface due to a distant storm is known as
swell
How can you estimate the position of a tropical storm’s center?
with a radio weather bulletin or weather fax
using shipboard radar
observe the wind direction and apply Buys Ballot’s Law
all of the above.
Which scale is used to estimate wind speed by observing sea conditions
Beaufort scale
You are steaming west in the North Atlantic in an extratropical cyclonic storm, and the wind is dead ahead. According to the Law of Buys Ballot, the center of low pressure lies to the
north
If it is impossible to avoid a hurricane in the Northern Hemisphere, the most favorable place to be when the storm passes is in
that half of the storm lying to the right of the storm’s path
The navigable semicircle of a tropical storm in the South Indian Ocean is located on which side of the storm’s track
Right
What is the direction of rotation of tropical cyclones, tropical storms and hurricanes in the Northern Hemisphere?
Counterclockwise and inward
What classification of tropical cyclones would have closed isobars, counter-clockwise rotary circulation, and sustained winds between 34 and 63 knots?
a tropical storm
The wind velocity is higher in the dangerous semicircle of a tropical cyclone because of the
wind circulation and forward motion of the storm
When is the peak of the hurricane season in the western North Pacific?
July through October
What is the average speed of movement of a hurricane prior to recurvature?
10 to 12 knots
You are in the Northern Hemisphere and a tropical wave is located 200 miles due west of your position. Where will the wave be located 24 hours later?
Farther away to the west
Atmospheric pressure at sea level is equal to
14.7 pounds per square inch
29.92 inches of mercury
1013.25 millibars
All of the above
What kind of pressure systems travel in tropical waves?
low pressure
A hurricane is characterized by winds of
64 knots or greater
When within 300 miles of a named tropical storm or hurricane, it is standard practice to send weather reports every
3 hours
Anticyclones are usually characterized by
dry, fair weather
The wind circulation around a high-pressure center in the Northern Hemisphere is
clockwise and moving outward from the high
What is the FIRST sign of the existence of a well developed tropical cyclone?
An unusually long ocean swell
Which kind of conditions would you observe as the eye of a storm passes over your vessel’s position?
Huge waves approaching from all directions, clearing skies, light winds, and an extremely low barometer.
In a tropical cyclone, in the Northern Hemisphere, a vessel hove to with wind shifting counterclockwise is
in the navigable semicircle
A slow rise in the barometric pressure forecasts
improving weather conditions
Generally speaking, in the Northern Hemisphere, when winds are blowing from between SE and SW the barometric reading
is somewhat lower than it would be for winds from a northern quadrant
Which of the following statements concerning frontal movements is TRUE?
A cold front generally passes faster than a warm front
If an observer in the Northern Hemisphere faces the surface wind, the center of low pressure is to his
right, slightly behind him
“Surface circulation” is another term for
wind in the lower troposphere
The Beaufort scale is used to estimate the
wind speed
The intensity of a hurricane as it reaches higher latitudes and cooler waters
decreases
What is the first visible indication of the presence of a tropical cyclone or hurricane?
an exceptionally long swell
The first cloud formations you can use to indicate the bearing of the center of a hurricane or tropical storm are
the point of convergence of the cirrus clouds
As a licensed Merchant Marine Officer you are expected to
obtain a weather forecast before setting out from port
listen to weather forecast on the radio while enroute
understand all broadcast weather warning information
All of the above
You are steaming eastward in the North Atlantic in an extratropical cyclonic storm and the wind is dead ahead. According to the law of Buys Ballot, the center of the low pressure lies
to the south
Severe tropical cyclones (hurricanes, typhoons) occur in all warm water oceans except the
South Atlantic Ocean
In a tropical cyclone in the Northern Hemisphere, a vessel hove to with the wind shifting counterclockwise would be
in the navigable semicircle
Tropical storms and hurricanes are most likely to form in the Southern hemisphere during
January through March
What is the average speed of the movement of a hurricane following the recurvature of its track?
20 to 30 knots
You are in the Northern Hemisphere and a tropical wave is located 200 miles due east of your position. Where will the wave be located 12 hours later?
Nearby to the east
The dense black cumulonimbus clouds surrounding the eye of a hurricane are called
cloud walls
A generally circular low pressure area is called a
cyclone
You can determine if your vessel’s position is in the dangerous or navigable semicircle of a hurricane by
Both A and B
A. observing whether the wind is veering or backing
B. plotting two or more recent storm positions from weather bulletins
The dangerous semicircle of a typhoon in the Southern Hemisphere is that area
to the left of the storm’s track
Weather information is available from
commercial radio broadcast
the Coast Gaurd on scheduled marine information broadcast
VHF-FM continuous marine weather broadcast provided by the National Weather Service
All the above
The process by which the temperature and/or moisture characteristics of an air mass changes is called
modification
You can expect frontal activity when two air masses collide and
there are significant differences between the temperature of each air mass
A gale is characterized by a wind speed of
34 to 47 knots
You are attempting to locate your position relative to a hurricane in the Northern Hemisphere. If the wind direction remains steady, but with diminishing velocity, you are most likely
on the storm track behind the center
If you are caught in the left semicircle of a tropical storm, in the Southern Hemisphere, you should bring the wind
on the port bow, and make as much way as possible
Weather systems in the middle latitudes generally travel from
west to east
Where is the dangerous semicircle located on a hurricane in the Southern Hemisphere
to the left of the storm’s track
A barometer showing falling pressure indicates the approach of a
Low-pressure system
A boundary between two air masses is a
front
If you observe a rapid fall of barometric pressure you should
prepare for the onset of stormy weather with strong winds
A slow, gradual fall of the barometer indicates approaching
deteriorating or unsettled weather
In the Northern Hemisphere, the largest waves or swells created by a typhoon or hurricane will be located
forward and to the right of its course
If a weather bulletin shows the center of a low-pressure system to be 100 miles due east of you, what winds can you expect in the Southern Hemisphere?
South-southwesterly
In the Northern Hemisphere, when the center of a high pressure system is due east of your position, you can expect winds from the
south to east
A tropical storm is a tropical cyclone that generates winds of
between 34 and 63 knots
When your vessel is on the track but behind the storm’s center the
Wind direction remains steady
barometer rises
wind speed decreases
all the above
Swells that have outrun the storm are produced in the
right front quadrant
What indicates the arrival of a hurricane within 24 to 36 hours?
unusually good weather with above average pressures followed by a slow fall 0f 4 millibars in six hours.
In the Northern Hemisphere, you are caught in the dangerous semicircle of a storm with plenty of sea room available. The best course of action is to bring the wind on the
starboard bow and make as much headway as possible.
The atmosphere in the vicinity of a high-pressure area is called
anticyclone
That half of the hurricane to the right-hand side of its track ( as you face the same direction that the storm is moving) in the Northern Hemisphere is called the
dangerous semicircle
In the Northern Hemisphere, an area of counterclockwise wind circulation surrounded by higher pressure is a
low
