Advanced Weather Topics Quiz

Tropical cyclones extract heat energy from warm ocean water. Higher SSTs and deeper warm water (high ocean heat content) provide more sustained energy for intensification. The storm doesn't 'use up' the warm water as quickly when warmth extends deeper.

The jet stream is driven by temperature contrast between the Arctic and lower latitudes. As the Arctic warms faster, this contrast weakens, the jet stream slows and meanders more, and blocking patterns (stalled weather systems) become more frequent.

Storm surge adds on top of existing sea level. Higher baseline sea level means even an identical storm on the same track produces more coastal flooding. This effect applies immediately and compounds as sea level continues rising.

Living coral builds up reef structure. When coral dies and collapses, previously charted depths may change significantly. Charts based on older surveys of living reef systems may show incorrect depths in actively degrading reef areas.

The traditional rules (south by November 1, north by June 1) remain good guidance but with less margin than historically. Pre-season and post-season storms are more common, making the shoulder periods riskier than the historical record alone suggests.

El Niño warms the central/eastern Pacific, increasing upper-level winds (wind shear) over the tropical Atlantic. This shear disrupts tropical cyclone formation and maintenance, generally suppressing Atlantic hurricane activity.

While total storm counts vary year to year with ENSO, the proportion of Atlantic hurricanes reaching Category 4 or 5 has increased, and rapid intensification events (35+ mph gain in 24 hrs) have become more frequent as ocean heat content rises.

Sea level rise increases mean water depths at open-water locations but infrastructure (docks, fuel docks, entrance channels) may not have been maintained to match. Verify with current tide gauge data and the marina directly.

Pre-season tropical activity (before June 1) has become more common. Late May departures that historically were well outside tropical storm risk now have a measurably higher probability of encountering early-season activity.

La Niña cools the central Pacific but warms the western Pacific, and generally increases activity in the western Pacific typhoon basin. It also reduces Atlantic wind shear, increasing Atlantic hurricane activity. Both effects are relevant to passage planning in their respective oceans.

Coral bleaching events kill reef-building organisms. As coral structures die and collapse, previously surveyed depths change — often becoming shallower as rubble accumulates. Charts based on older surveys of living reef systems may be dangerously inaccurate.

The Fastnet low tracked south of the predicted track and underwent explosive cyclogenesis (deepened ~27 mb in 24 hours). 1979 NWP models could not capture this accurately. Modern models would perform substantially better, though rapid intensification remains difficult.

Analysis of boat behavior in the Fastnet storm suggested that boats hove to or lying ahull experienced fewer catastrophic capsizes than those running off, possibly because running boats encountered waves at more dangerous angles.

Long-period Southern Ocean swells entering the shallow (50-70m) Bass Strait and combining with short-period storm waves creates wave steepness far beyond what either wave system would produce alone. The same physics applies in other shallow areas with conflicting swell systems.

Crews who retired early — before conditions became extreme — generally survived. Those who continued past the point where retreat was safe ultimately required rescue. Competitive pressure delaying retirement decisions was a recurring factor in losses.

Both the Andrea Gail and El Faro cases involved commercial pressure — fishing income and cargo schedule — influencing decisions to continue into deteriorating or forecast dangerous conditions. This human factor is not unique to commercial operations.

The El Faro captain was using forecast data that had been superseded. More current products — which he had access to — showed Joaquin tracking toward his route. Model initialization time and data freshness are critical: always use the latest run.

Both inquiries found that sailors who abandoned intact or only partially damaged vessels for liferafts had worse outcomes than those who stayed aboard. A floating vessel provides more shelter, visibility, and survival resources than a raft in extreme conditions.

Commitment bias is strongest when you're invested in a plan and under pressure. Pre-defined thresholds — 'if conditions reach X, we do Y' — established before departure remove the in-the-moment negotiation that bias exploits.

Gale warnings were issued, but the low's southward track shift and explosive deepening (to 963 mb) produced conditions far worse than the warnings indicated. The forecast underestimated both track and intensification.

Long-period Southern Ocean swells propagating northward into the shallow (50-70m) Bass Strait combined with steep local storm waves to produce extreme sea steepness — more dangerous than wave height alone.

The NTSB found the captain was using forecast data that had been superseded by newer products showing Joaquin's track shifting toward his route. Using the most current model run — not older cached data — is a fundamental requirement.

Both inquiries documented cases where sailors died in life rafts while their vessels were later found afloat. The principle 'step up into the life raft' — meaning leave only when the vessel is sinking or on fire — is directly derived from these findings.

Commitment bias — continuing a plan despite evidence it should be abandoned — appears in all four cases: race position, fishing income, cargo schedule. Pre-defined, non-negotiable decision thresholds are the structural defense against this bias.

At sea (sea level), compare your barometer reading against the nearest airport METAR or ASOS station report (which is always sea-level corrected). The difference is your calibration error — adjust or apply mentally.

A sustained fall of 2+ mb/hour indicates rapid cyclogenesis or fast approach of an intense system. This is a serious warning requiring immediate weather reassessment and plan evaluation.

Aneroid barometers use a mechanical linkage that can stick slightly, holding the pointer at a previous position. Tapping gently frees the linkage so the pointer settles at the actual current pressure.

Ultrasonic anemometers measure wind by timing sound pulses, eliminating mechanical wear and stall speed issues. Their fast response is particularly valuable for gust detection. They can misread in heavy rain, which is their main limitation.

Apparent wind combines true wind and boat velocity. Sailing upwind, boat motion adds to apparent wind speed (reads higher than true); sailing downwind, boat motion subtracts from apparent wind (reads lower than true). The navigation computer converts apparent to true wind.

A temperature-dew point spread of ≤2°F means the air is extremely close to saturation. Fog is actively forming or imminent. Take immediate action: reduce speed, activate nav lights, prepare fog signals.

Spread = 70 – 55 = 15°F. Cloud base ≈ 15 × 225 = 3,375 feet. This indicates cumulus with moderate base height — reasonable conditions without significant ceiling concerns.

Warm fronts bring warm, moist air. As relative humidity increases ahead of the front, the dew point rises toward the air temperature, decreasing the spread. Decreasing spread combined with falling pressure and backing winds is the classic warm front sequence.

In an integrated network, raw sensor data feeds multiple derived calculations. A calibration error in the wind direction sensor propagates as a consistent error through all wind-direction-dependent displays and calculations.

Airport METAR data is sea-level corrected. If your barometer reads 6 mb low, calibrate it (adjust the calibration screw) or apply a +6 mb mental correction to all future readings. Uncorrected barometers give misleading pressure trend data.

Sailing downwind, the boat moves away from the wind, reducing apparent wind speed relative to true wind. Apparent = True – boat speed (simplified, for a dead run). 35 kts apparent – 10 kts boat speed ≈ 25 kts true wind.

A 2°F temperature-dew point spread means the air is extremely close to saturation. Fog is actively forming or imminent. Immediate action: reduce speed, activate navigation lights, prepare fog signals per COLREGS.

A systematic direction discrepancy between instrument and observation suggests a calibration offset in the wind direction sensor. This error will propagate through all NMEA 2000 calculations using wind direction data.

Classic warm front approach: slowly falling pressure (starts gentle), wind backing (S→SE→E), rising humidity (decreasing T-Td spread), slow temperature rise. Combining barometer, wind, and humidity data recognizes this before visual cloud signs become obvious.