Marine Weather Quiz Flashcards
A Small Craft Advisory means:
1. Small Craft are prohibited from operating in US waters due to hazardous conditions
2. Small Craft may only be operated by licensed mariners due to hazardous conditions
3. Forecast winds and seas may be hazardous to Small Craft
4. Storm conditions are imminent; all mariners should take cover
- Forecast winds and seas may be hazardous to Small Craft
NWS issues a Small Craft Advisory when wind and sea conditions might be dangerous to small craft. There is no definition of “small craft”. Ref: CCME p 128, BCME p 142.
How do surface winds circulate around a Low pressure system in the northern hemisphere?
1. Clockwise and slightly out of the Low
2. Clockwise and slightly into the Low
3. Counterclockwise and slightly out of the Low
4. Counterclockwise and slightly into the Low
- Counterclockwise and slightly into the Low
As a result of Pressure Gradient, Coriolis, and surface friction, winds spiral clockwise out of a High, and counter-clockwise into a Low in the Northern Hemisphere. Ref: BCME p 140
Wind speeds are proportional to the gradient of the isobars, which represent:
1. Lines of equal barometric pressure
2. Lines of equal wind speed
3. Lines of equal atmospheric depth
4. Lines of equal temperature
- Lines of equal barometric pressure
An isobar is a line connecting points of equal barometric pressure on a weather map. Wind speed is proportional to the gradient (tight packing) of the isobars. Ref: BCME p 140-141
Prudent mariners pay attention to and record the condition of the atmosphere and its elements. Which of these elements has the most influence on sea state?
1. Rain
2. Barometric Pressure
3. Temperature
4. Wind
- Wind
Sea state is comprised of waves (caused by local wind) and swell (caused by distant wind). Rain, pressure and temperature have some effect on seas, but wind is the primary driver. Ref: BCME p 140
A simple sea breeze scenario blows onshore and may enhance or diminish synoptic wind. Sea Breeze is caused by:
1. Ocean waters heated by the Gulf Stream
2. Convective thunderstorms moving offshore
3. Differential heating of land and sea
4. Synoptic scale pressure gradients
- Differential heating of land and sea
Land surfaces heat quickly with the sun, but water’s surface temperature remains relatively constant. This differ-ential heating of land and sea causes a thermal low over land, which is filled by higher pressure, cooler air over the sea. Ref: BCME p 146
What type of fog is caused by wind transporting warm air over cold water, and can persist even in strong winds?
1. Advection Fog
2. Radiation Fog
3. Steam Fog
4. Valley Fog
- Advection Fog
Advection fog requires some wind to advect warm air over cooler water. Once formed, it can persist with moderate or strong winds. Ref: BCME p 143
Select ALL weather parameters that would result in reduced visibility:
Fog
Heavy precipitation
Blowing sand
Smoke
ALL
Low visibility may result from fog, heavy rain, smoke or blowing sand. See “Navigation in Low Visibility” safety guidance in Ref: BCME p 143.
Which windspeed range describes Storm force winds?
15-20 kts
34-47 kts
48-63 kts
64-100 kts
48-63 kts
See the wind warnings chart and “Rule of 15s” at BCME p 142
15- Gale force
30- Small craft warning
45- Storm
60- Hurricane
In a marine forecast, the term that describes the average of the highest one third of the waves in the forecast period is:
Combined Sea State
Significant Wave Height
Crest to Trough Ratio
Rogue Wave Factor
Significant Wave Height
NWS reports seas using Significant Wave Height (SWH), which is the average of the highest one third of the ob-served or predicted seas. Ref: BCME p 142
In the midlatitude regions (approx. 30-60 degrees latitude), weather systems move from west to east. In the tropics, weather systems move:
From west to east, as in midlatitude regions
From east to west, with the tradewinds
From west to east, with the tradewinds
From North to South, due to Coriolis
From east to west, with the tradewinds
Air flows from midlatitude highs towards the equator, and is turned by Coriolis to result in the tropical tradewinds. Tropical weather systems (squalls, tropical storms) approach from windward, so from east to west. Ref: BCME p 144
What is the feature at position 1, and what type precipitation would you expect?
Warm Front, steady rain
Warm Front, thunderstorms
Cold Front, steady rain
Cold Front, thunderstorms
Warm Front, steady rain
The feature with semicircular “pips” is a warm front, showing the boundary of warm air encroaching upon cooler air, and sliding up over the cooler air. Warm fronts bring prolonged periods of steady rain. Ref: BCME p 140-141.
- What is the feature at position 2, and what type of precipitation would you expect?
a. Warm Front, steady rain
b. Warm Front, thunderstorms
c. Cold Front, steady rain
d. Cold Front, thunderstorms
d. Cold Front, thunderstorms
The feature with triangular “pips” is a cold front, depicting the boundary of cold air encroaching on warm air, pushing the warmer moist air into the atmosphere. A cold front is characterized by cumulonimbus clouds and thunderstorms. Ref: BCME p 140-141.
What is the general wind direction in the warm sector (position 3), between the two fronts?
a. Southwest
b. Northeast
c. Southeast
d. Northwest
a. Southwest
Since wInds circulate counterclockwise and into a Low in the Northern Hemisphere, the winds in the warm sector (warm air mass between warm and cold front) are generally from the southwest. After the cold front passes, winds are typically from the Northwest. Ref: BCME p 140-141
