storm warning pressure indicators Practice Questions

1. A NWS Small Craft Advisory for wind is typically issued when sustained winds are forecast to reach:

• A.18 to 33 knots✓
• B.34 to 47 knots
• C.48 knots or higher
• D.10 to 17 knots

Why: The NWS issues a Small Craft Advisory when sustained winds of 18–33 knots (or seas of 4–7 ft, depending on region) are forecast, indicating conditions hazardous to small craft.

2. A Storm Warning is issued when sustained winds are forecast to reach:

• A.48 to 63 knots✓
• B.34 to 47 knots
• C.64 knots or higher
• D.25 to 33 knots

Why: A Storm Warning is issued by the NWS for sustained winds of 48–63 knots; winds of 64 knots or higher result in a Hurricane/Typhoon Warning for tropical systems.

3. In the Northern Hemisphere, if a mariner observes a rapidly falling barometer combined with a backing wind (shifting counterclockwise), this most likely indicates:

• A.A low-pressure center is approaching from the west or southwest✓
• B.A high-pressure ridge is building overhead
• C.A cold front is passing with brief showers expected
• D.A sea breeze circulation is developing

Why: A rapidly falling barometer signals an approaching low-pressure system, typically tracking from the west or southwest in mid-latitudes. By Buys Ballot's Law in the Northern Hemisphere (back to the wind, low on your left), a backing wind (counterclockwise shift) places the observer NORTH of the storm's track, with the low center passing to the south.

4. According to Buys Ballot's Law, if you stand with your back to the wind in the Northern Hemisphere, the low-pressure center will be located:

• A.To your left and slightly ahead✓
• B.Directly behind you
• C.To your right and slightly behind
• D.Directly in front of you

Why: Buys Ballot's Law (Bowditch): in the Northern Hemisphere, standing with your back to the wind, the low-pressure center lies to your left. Because surface friction makes the wind cross the isobars and flow toward the low (inflow), the angle from your back-to-wind direction is LESS than 90 deg (under 8 points), placing the low to your left and slightly ahead — i.e., forward of abeam — rather than directly abeam or behind.

5. A vessel is in the path of a tropical cyclone. The barometer has fallen to 980 mb. Based on pressure alone, which action is MOST appropriate?

• A.Immediately execute storm avoidance maneuvers and seek shelter or sea room✓
• B.Continue on course; 980 mb indicates only moderate conditions
• C.Reduce speed by half and wait for conditions to deteriorate before altering course
• D.Log the reading and monitor for the next scheduled forecast broadcast

Why: 980 mb represents a significant depression well below normal and may indicate a tropical cyclone of hurricane intensity; at this pressure, immediate evasive action is required since conditions will worsen rapidly as the center approaches.