OUPV Marine Weather and Tides 2 — Questions and Answers
Question 1: What weather condition is indicated by a rapidly falling barometer?
- Fair weather approaching
- A storm or severe weather approaching (Correct answer)
- Fog is likely
- No significant change expected
Correct answer: A storm or severe weather approaching
A rapidly falling barometric pressure indicates approaching storm conditions, typically with strong winds and precipitation.
A rapidly falling barometer (more than 0.04 inches per hour) indicates an approaching low-pressure system with potentially severe weather including strong winds, heavy rain, and rough seas. The rate of fall correlates with storm intensity.
Question 2: What is a spring tide?
- A tide that only occurs during the spring season
- A tide with the greatest range between high and low water, occurring during full and new moons (Correct answer)
- An unusually low tide caused by offshore winds
- A tide caused by river flow in the spring
Correct answer: A tide with the greatest range between high and low water, occurring during full and new moons
Spring tides produce the highest highs and lowest lows due to the combined gravitational pull of the sun and moon when they are aligned.
Spring tides occur approximately every two weeks during full and new moon phases when the sun, moon, and Earth are aligned. This alignment combines the gravitational forces, producing the greatest tidal range.
Question 3: What does a veering wind mean?
- A wind that shifts direction counterclockwise
- A wind that shifts direction clockwise (Correct answer)
- A wind that increases in speed
- A wind that suddenly stops
Correct answer: A wind that shifts direction clockwise
A veering wind shifts clockwise. This typically indicates improving weather conditions in the Northern Hemisphere.
A veering wind changes direction clockwise (e.g., S to SW to W to NW). In the Northern Hemisphere, a veering wind typically indicates the passage of a cold front or a high-pressure system approaching. A backing wind (counterclockwise shift) often indicates deteriorating conditions.
Question 4: How do you calculate the height of tide at a specific time between high and low water?
- Divide the range by the number of hours
- Use the Rule of Twelfths or NOAA tide table predictions (Correct answer)
- It changes linearly at a constant rate
- Subtract the current depth from the charted depth
Correct answer: Use the Rule of Twelfths or NOAA tide table predictions
The Rule of Twelfths approximates tidal rise and fall, which is not linear. NOAA tide tables provide more precise predictions.
The Rule of Twelfths approximates tidal change: 1st hour 1/12, 2nd hour 2/12, 3rd hour 3/12, 4th hour 3/12, 5th hour 2/12, 6th hour 1/12 of the total range. For more accurate predictions, use NOAA tide tables.
Question 5: What is a sea breeze and when does it typically occur?
- An offshore wind at night
- An onshore wind during the day caused by differential heating of land and water (Correct answer)
- A wind caused by tropical storms
- A constant trade wind near the equator
Correct answer: An onshore wind during the day caused by differential heating of land and water
A sea breeze is a daytime onshore wind that occurs because land heats faster than water, creating a pressure differential.
Sea breezes develop on sunny days when land heats faster than adjacent water. The warm air over land rises, creating lower pressure, while cooler air over the water flows onshore. Sea breezes typically begin mid-morning, peak in the afternoon, and can reach 10-15 knots.
Question 6: What weather phenomenon creates the most dangerous conditions for small vessels in coastal waters?
- High clouds
- Thunderstorms with their associated gusty winds, lightning, and reduced visibility (Correct answer)
- Steady light rain
- Morning fog in summer
Correct answer: Thunderstorms with their associated gusty winds, lightning, and reduced visibility
Thunderstorms produce sudden severe wind gusts, dangerous lightning, intense rain reducing visibility, and steep confused seas.
Thunderstorms are the most dangerous weather for OUPV operations because they combine multiple hazards simultaneously: wind gusts exceeding 60 knots, lethal lightning, near-zero visibility, and confused seas. Microbursts can produce destructive downdraft winds.
OUPV Marine Weather and Tides 2
What weather condition is indicated by a rapidly falling barometer?