Meteorology Practice Questions

1. Standard atmospheric pressure at sea level is approximately:

• A.1013 millibars (29.92 inches of mercury)✓
• B.850 millibars (25.10 inches of mercury)
• C.1100 millibars (33.00 inches of mercury)
• D.760 millibars (22.40 inches of mercury)

Why: Standard sea-level pressure is 1013.25 mb, equal to 29.92 inches of mercury or 14.7 psi. Readings are compared against this value; well below it indicates a low-pressure system.

2. In the Northern Hemisphere, the 'dangerous semicircle' of a tropical cyclone is:

• A.The left side relative to the storm's track
• B.Directly behind the storm
• C.The eye itself
• D.The right side relative to the storm's direction of movement✓

Why: Facing the direction the storm is moving, the right-hand semicircle (in the Northern Hemisphere) is the dangerous semicircle: winds are stronger there, and they tend to blow a vessel into the storm's path. The left side is the navigable semicircle.

3. A fast-moving cold front in summer can produce a squall line. A squall line typically forms:

• A.Behind the cold front, parallel to it, up to 50 miles to the rear
• B.Directly along the cold front surface boundary
• C.Ahead of the cold front, up to 200 miles in advance✓
• D.At the warm front boundary well ahead of the cold front

Why: Squall lines often develop ahead of fast-moving cold fronts, sometimes up to 100–200 miles in advance, where atmospheric instability and wind shear in the pre-frontal warm sector trigger severe convective activity before the front itself arrives.

4. A vessel transiting from the Gulf Stream to the Labrador Current region notices dense fog forming rapidly. The MOST probable cause is:

• A.Radiation fog formed over the cold Labrador Current during clear nights
• B.Sea smoke generated by warm Gulf Stream air over the frigid Labrador Current
• C.Advection fog as warm, moist Gulf Stream air moves over the cold Labrador Current✓
• D.Frontal fog associated with a cold front pushing south across the Grand Banks

Why: The Grand Banks is one of the world's foggiest regions due to classic advection fog: warm, humid Gulf Stream air (70-80°F) moves northward and encounters the cold Labrador Current (35-40°F), cooling to its dew point and producing persistent, dense advection fog.

5. When comparing readings between a mercury barometer and an aneroid barometer aboard ship, any difference is MOST likely due to:

• A.Calibration error or index error in the aneroid instrument✓
• B.The aneroid using a different unit of measurement
• C.Mercury barometers reading too high in cold weather
• D.The aneroid barometer not compensating for diurnal variation

Why: Aneroid barometers can develop index error over time due to metal fatigue in the sensing capsule; regular comparison against a mercury barometer or a certified standard and applying the resulting correction is standard practice.