RPL Exam Meteorology: Complete Study Guide for CASA Weather Questions

Meteorology consistently accounts for 5–8 questions in the RPL theory exam — more than any single aerodynamics subcategory. Students who treat weather as "common sense" often get caught by specific CASA definitions and the way questions are framed. This guide covers the exact meteorology knowledge CASA tests, with the common question types for each area.

The ICAO Standard Atmosphere

The International Standard Atmosphere (ISA) is the baseline for almost all performance calculations and altimeter settings. Know these values cold:

• Sea-level pressure: 1013.2 hPa (29.92 inHg)
• Sea-level temperature: 15°C
• Temperature lapse rate: 2°C per 1,000 ft (up to the tropopause)
• Tropopause height: approximately 36,000 ft in mid-latitudes

The exam tests this in questions about density altitude: "If the OAT at 5,000 ft is +5°C and ISA temperature at 5,000 ft is +5°C, what is the density altitude?" The answer is that density altitude equals pressure altitude under ISA conditions.

Atmospheric pressure and altimeter settings

Three altimeter settings are tested in every RPL exam cohort. Understanding when and why each is used is essential for both the exam and real-world flying.

• QNH — altimeter set to read altitude AMSL. Used below the transition altitude. When ATC says "set 1016", they mean QNH 1016.
• QFE — altimeter set to read height above the aerodrome. Altimeter reads zero on the ground. Rare in Australia but examined.
• Standard setting (1013.2 hPa) — used above the transition altitude, gives Flight Level readings.

Common trap question: "An aircraft descends from FL85 to 8,500 ft AMSL. The QNH is 1020. When should the pilot change from standard setting to QNH?" The answer is at the transition altitude, which is typically 10,000 ft in Australia.

Pressure systems and wind

Know the relationship between pressure systems and wind direction in the Southern Hemisphere, which is opposite to the Northern Hemisphere. This distinction is frequently tested in the CASA exam.

• Anticyclone (High): pressure increases toward the centre. Wind flows anticlockwise and outward in the Southern Hemisphere. Associated with stable, fine weather.
• Depression (Low): pressure decreases toward the centre. Wind flows clockwise and inward. Associated with cloud, rain, and frontal activity.

Buys Ballot's Law (Southern Hemisphere): stand with your back to the wind, and low pressure is to your right. This is a commonly examined point — don't confuse it with the Northern Hemisphere rule, where low pressure is to your left.

Fronts

Fronts represent boundaries between air masses of different temperature and density. CASA tests the weather sequences associated with each front type. Understanding the progression of weather before, during, and after frontal passage is essential for scenario-based questions.

Cold front

A cold front occurs when cold air undercuts warm air, forcing it rapidly upward. The associated weather and characteristics are:

• Steep cumulus and cumulonimbus development, heavy showers, thunderstorms, and turbulence
• Rapid deterioration during passage, then rapid clearance afterward
• Wind shift: veers (clockwise) as the front passes in the Southern Hemisphere
• Temperature drops sharply after passage

Warm front

A warm front occurs when warm air overrides cold air at a shallow angle. The weather sequence and hazards are:

• Gradual deterioration — cirrus → cirrostratus → altostratus → nimbostratus → steady rain
• Gradual improvement after passage, with temperature rising
• Key hazards include embedded thunderstorms, freezing rain, low cloud, and poor visibility

Occlusion

An occlusion forms when a cold front catches a warm front, lifting the warm air completely off the surface. The result is complex weather with multiple frontal characteristics occurring together.

Cloud types and formation

Classify clouds by altitude and formation process. CASA uses ICAO cloud families, and you are expected to know the approximate altitude range and characteristics of each.

Family	Cloud types	Altitude (approx)
High	Cirrus, Cirrocumulus, Cirrostratus	Above 20,000 ft
Middle	Altocumulus, Altostratus	6,500–20,000 ft
Low	Stratus, Stratocumulus, Nimbostratus	Below 6,500 ft
Convective	Cumulus, Cumulonimbus	Any altitude

Key distinction: Cumulonimbus (Cb) is the most hazardous cloud type. CASA questions on Cb test knowledge of lightning, severe turbulence (updrafts exceeding 100 kt), hail, icing, and the requirement to give these cells a wide berth.

Fog

Three fog types are examined in the RPL theory exam. Each has distinct formation conditions that CASA tests directly.

• Radiation fog: forms overnight when the ground radiates heat, cooling the air to dewpoint. Requires clear skies, light wind, and high humidity. Common in valleys. Burns off after sunrise.
• Advection fog: warm moist air moves over a cold surface. Common coastal fog. Not limited to nights and can persist for days.
• Steam fog: cold air moves over warm water. Rising vapour looks like steam. Common over rivers in winter.

Thunderstorms

Thunderstorms are one of the most examined hazard topics in the RPL exam. CASA expects you to know the three lifecycle stages and the specific hazards associated with each.

1. Cumulus stage: strong updrafts only; no rain reaching the surface yet.
2. Mature stage: most severe — both updrafts and downdrafts are present, with heavy rain, lightning, and hail.
3. Dissipating stage: downdrafts predominate and precipitation eases.

CASA questions on thunderstorms test avoidance procedures, windshear on approach (microburst), and the fact that hazardous weather associated with a Cb cell can extend well beyond the visible cloud base.

Icing

Structural icing forms when supercooled water droplets (liquid water below 0°C) freeze on impact with the airframe. Two conditions must be present simultaneously:

• Visible moisture (cloud, rain, or drizzle)
• OAT between approximately -20°C and +5°C (peak danger: 0°C to -10°C)

Types examined include clear ice (most dangerous — dense and hard to shed), rime ice (opaque and rough), and mixed ice.

Carburettor icing is different — it can form in clear air at OAT up to 38°C when humidity is high, due to the combined venturi cooling and fuel evaporation effects. CASA tests carburettor icing on hot, humid days as a common trap. Per the VFRG, the conditions for carburettor icing extend well above freezing — don't assume it only happens in cold weather.

Wind shear

Wind shear is a rapid change in wind speed or direction over a short distance. Low-level wind shear below 2,000 ft is the most operationally dangerous and is the focus of most CASA exam questions.

• On approach: headwind shear to tailwind causes airspeed and lift loss, creating a potential undershoot.
• On take-off: tailwind shear to headwind causes initially slower performance, followed by a lift gain.
• Microburst: an intense downburst within 4 km that creates a headwind then tailwind on approach, causing airspeed anomalies and rapid descent.

VMC minima — what you must know

While visual meteorological conditions (VMC) minima might seem like an "operations" topic, the exam frequently frames them around weather scenarios. You need to know the following values for the relevant airspace classes and altitudes.

• Class G below 3,000 ft AMSL or 1,000 ft AGL (whichever is higher): clear of cloud, in sight of ground or water, and 5,000 m visibility.
• Class G above that level but below 10,000 ft: 5,000 m visibility, 1,500 m horizontal and 1,000 ft vertical from cloud.
• At or above 10,000 ft: 8 km visibility, 1,500 m horizontal and 1,000 ft vertical from cloud.
• Class D (all heights): 5,000 m visibility, 600 m horizontal from cloud, 1,000 ft above cloud, and 500 ft below cloud.

These are commonly tested via scenario questions — for example: "Given the following METAR, can you legally depart VFR?" This is frequently tested in the CASA exam.

TAF and METAR reading

CASA expects you to decode TAF (Terminal Area Forecast) and METAR (current conditions) elements. The following are the most commonly examined codes.

• Wind: 18015KT = 180° at 15 kt. 18015G25KT = gusting 25 kt.
• Visibility: 9999 = 10 km or more. 0800 = 800 m.
• Cloud: FEW = 1–2 oktas. SCT = 3–4 oktas. BKN = 5–7 oktas. OVC = 8 oktas (overcast). Height is given in hundreds of feet AGL: BKN025 = broken at 2,500 ft.
• Weather codes: RA = rain. TS = thunderstorm. FG = fog. BR = mist. SHRA = shower rain. PO = dust/sand whirls — note this code can appear in forecast products (TAFs), not just METARs.
• TEMPO/PROB30: TEMPO = temporary fluctuations lasting less than 1 hour each occurrence, but can repeat. PROB30 = 30% probability.

Windsock interpretation

A common meteorology-adjacent question involves reading the windsock at an aerodrome. Know these approximate wind speeds for each windsock position.

• Fully extended (horizontal): wind approximately 25–30 kt
• At 45° below horizontal: wind approximately 15 kt
• Hanging limp: calm or very light wind

Don't confuse these values — a common exam mistake is quoting 15 kt for a fully extended windsock, when 15 kt is actually the approximate speed at 45°.

Density altitude

Density altitude affects aircraft performance — the higher the density altitude, the worse the performance. It increases with the following conditions:

• High elevation (lower pressure)
• High temperature (air expands and becomes less dense)
• High humidity (water vapour displaces denser air molecules)

Formula approximation: density altitude ≈ pressure altitude + (ISA deviation × 120 ft per °C). CASA questions give you a set of conditions and ask whether take-off performance will be better or worse than the Pilot's Operating Handbook (POH) data.

Common exam traps

The following are the most frequently missed meteorology points in the RPL theory exam. Review these carefully before your exam sitting.

• Southern Hemisphere wind rotation around a Low is clockwise (not anticlockwise as in the Northern Hemisphere). Buys Ballot's Law: back to the wind, low pressure is to your right.
• QNH decreases with altitude; standard pressure (1013.2 hPa) is used above the transition altitude, not below.
• Carburettor icing can form at OAT up to 38°C — it is about humidity and the venturi/fuel evaporation effect, not ambient temperature alone.
• Radiation fog forms under clear skies — cloud cover prevents the ground heat loss needed for formation.
• TEMPO changes last less than 1 hour each occurrence, but can repeat throughout the TEMPO period.
• A fully extended windsock indicates 25–30 kt, not 15 kt.
• VMC minima change with altitude and airspace class — learn the specific values for Class G and Class D.

How meteorology fits the RPL exam

The RPL theory exam is administered by CASA, runs for 2 hours, and requires a 70% pass mark. Meteorology questions frequently use scenario-based framing — you will be given conditions and asked to predict weather or determine whether a flight can proceed VFR, not just recall definitions. The only way to get comfortable with this format is through practice questions. The Pilot Exam has 100+ meteorology questions in the RPL bank, including chart and TAF interpretation questions that mirror the real CASA format.

Related Resources

• Meteorology Study Guide
• How to Read a TAF
• All RPL Exam Topics