Earth Systems Science · Module 3

6 a.m.: a storm is strengthening offshore. What do you tell the city?

Warm Gulf water can make a storm strengthen overnight. Someone must decide before the science is finished.

These slides give you the science to make that call and defend it.

Start → Jump to my project Formula sheet
A storm growing over warm Gulf water before dawn A scene, not to scale. On the left is a coastal city and a clock reading 6:00 a.m. Offshore, a towering storm cloud with a flat anvil top stands over the Gulf. The top layer of the sea is warm, at least 26.5 °C down to about 50 m, with cooler water below. Moist air flows in along the sea surface, rises in the storm, and condenses, releasing the heat that powers the storm. Rain falls from the cloud base. coastal city 6:00 a.m. vapor condenses: heat released anvil top moist air flows in warm Gulf layer: 26.5 °C or more, ~50 m deep cooler water below
Hurricane Beryl regained hurricane strength and reached 80 knots in the hours before landfall near Matagorda, Texas, on 8 July 2024.

Start here · The big picture

One engine: the Sun heats Earth unevenly, and air and water carry the heat

Four parts of Module 3, from hours to decades Four panels joined by arrows. Part 1, Air and clouds, led by Cloud Makers: a column of air with a cloud forming where it cools to its dew point. Part 2, Weather, led by Weather Station: wind blowing from high pressure toward low. Part 3, Storms and sea, led by Storm and Sea: a thunderstorm over warm ocean. Part 4, Climate, led by Climate Desk: decades of temperature records. A time axis runs underneath from hours to decades. Air and clouds Part 1 Cloud Makers H L Weather Part 2 Weather Station Storms and sea Part 3 Storm and Sea Climate Part 4 Climate Desk hours (a cloud, a storm) decades (a climate)

Four parts, one driving question.

Your team leads one part and teaches it. The class needs all four to make the 6 a.m. call.

Start here · How to use these slides

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Part 1 · Cloud Makers lead this part

The air and its water

  • Name the gases and layers of the air.
  • Trace how sunlight heats the ground, then the air.
  • Find the temperature high above you.
  • Find relative humidity and dew point.
  • Predict the height of a cloud base.
Rising air cools until a cloud forms Warm air rises from sunlit ground, cools as it climbs, and a flat-based cloud forms at the height where the air reaches its dew point. dew point reached rising air cools

Part 1 · Key idea

Dry air is 78% nitrogen and 21% oxygen

What 100 parts of dry air are made of A grid of 100 squares, one per percent of dry air by volume. 78 squares are nitrogen (78.08%), 21 are oxygen (20.95%), and 1 is argon (0.93%). Carbon dioxide is 427.55 parts per million (about 0.04%), far too small for one square. Water vapor is not part of dry air; it varies and is typically about 1%. Nitrogen, N₂ 78.08% Oxygen, O₂ 20.95% Argon, Ar 0.93% Carbon dioxide, CO₂ 427.55 ppm: 4 in 10,000, too small for one square Water vapor varies; typically about 1%
Each square is 1% of dry air by volume.

The atmosphere is the thin layer of gases held to Earth by gravity.

Nitrogen and oxygen stay steady. Water vapor changes from place to place, and it feeds every cloud and storm.

Part 1 · Key idea

Weather happens in the bottom layer, the troposphere

Temperature through the layers of the atmosphere A graph of temperature against height from 0 to 110 km. In the troposphere, from the ground to 6 to 20 km, temperature falls from about 17 °C to about −51 °C. In the stratosphere, up to 50 km, it rises to about −15 °C because ozone forms there. In the mesosphere, up to 85 km, it falls to about −120 °C. In the thermosphere above, it rises again, up to 2,000 °C near the top. 020406080100 −120−80−400 temperature (°C) height (km) Troposphere: all weather Stratosphere ozone forms: warms with height Mesosphere Thermosphere warms, up to 2,000 °C tropopause: 6–20 km up 17 °C −51 °C −15 °C −120 °C

The troposphere is the lowest layer, where air cools with height and all weather forms.

Above it, the stratosphere warms with height. Storm tops stop there and spread into flat anvils.

Part 1 · Key idea

Earth reflects about 29% of sunlight and absorbs the rest

Where the average 340 watts per square metre of sunlight goes Averaged over the whole planet, about 340 watts of sunlight arrive on each square metre at the top of the atmosphere. About 100 (29%) is reflected to space by clouds, ice, and bright ground. About 77 (23%) is absorbed by the air. About 163 (48%) is absorbed by the land and ocean surface. A stacked bar shows the three parts adding to 340. reflected clouds, ice, bright ground absorbed by air absorbed by land and ocean Where 340 W/m² of sunlight goes ≈ 100≈ 77≈ 163 reflected 29%air 23%surface 48% global, yearly average · bar length = W/m²

Albedo is the fraction of sunlight a surface reflects. Earth's is about 0.29.

The 71% that is absorbed heats the air, land, and sea, and drives every wind and current.

Part 1 · Key idea

Sunlight heats the ground, and the ground heats the air

Three ways heat moves into the air 1, radiation: sunlight crosses space and warms the ground. 2, conduction: the warm ground heats the thin layer of air touching it. 3, convection: cooler, denser air sinks on both sides and pushes the warm air up in a rising bubble. 1 2 3 radiation conduction convection warm air cool air sinks sunlit ground warms first

Air is heated mostly from below, so the troposphere is warmest at the bottom.

  • Radiation: sunlight crosses space and warms the ground.
  • Conduction: warm ground heats the air touching it.
  • Convection: denser air sinks around warm air and pushes it up.

Part 1 · Key idea

Warm air does not rise by itself: denser air pushes it up

Cold air outweighs warm air, so it pushes warm air up Left: a balance holds one cubic metre of 30 °C air with a mass of 1.16 kg and one cubic metre of 0 °C air with a mass of 1.29 kg, both at sea-level pressure. The cold side sits lower. Right: a warm bubble in colder air. The push on its bottom is larger than the push on its top, so the net push is upward. That net push is buoyancy. 30 °C 1.16 kg 0 °C 1.29 kg 1 m³ of air each, sea-level pressure warm air smaller push down bigger push up from colder air cold, dense air

Buoyancy is the upward push that denser surrounding air gives a lighter parcel.

A cubic metre of 30 °C air has 0.13 kg less mass than one at 0 °C. Take the colder air away, and the warm air goes nowhere.

Part 1 · Key idea

Four numbers describe any air

Air pressure falls with height A graph of air pressure against height in the standard atmosphere. Pressure is 1013 hPa at sea level, 795 at 2 km, 617 at 4 km, 472 at 6 km, 357 at 8 km, 265 at 10 km, 194 at 12 km, 142 at 14 km, and 104 at 16 km. Half of the air lies below about 5.6 km, where pressure is about 500 hPa. 0481216 02505007501000 air pressure (hPa) height (km) half the air is below 5.6 km (about 500 hPa) 1013 hPa at sea level
  • Temperature (°C): how fast the molecules move.
  • Air pressure (hPa): the weight of the air above you.
  • Density (kg/m³): mass packed into each cubic metre.
  • Humidity: how much water vapor the air has.

Part 1 · Key idea · Practice Gym classroom model

Climb 1 km and the air cools about 6.5 °C

Average temperature against height in the troposphere A straight line falls from 15 °C at sea level by 6.5 °C for every kilometre: 2 °C at 2 km, −11 °C at 4 km, −24 °C at 6 km, −37 °C at 8 km, and −50 °C at 10 km. The air reaches 0 °C at about 2.3 km. 0246810 −50−30−10015 temperature (°C) height (km) 2 °C−11 °C−24 °C−37 °C−50 °C 0 °C at 2.3 km −6.5 °C for every km

The lapse rate is how fast temperature drops as you go up.

Averaged worldwide, it is 6.5 °C per km in the troposphere. Real days vary, so a measured rate can be larger or smaller.

Practice Gym modelT = T₀ − 6.5 × h

Standard troposphere, T = 15.04 − 0.00649 h (h in metres, up to 11,000 m): NASA Glenn, Earth Atmosphere Model. Classroom model: Practice Gym, Module 3, lapse-rate items.

Part 1 · Worked example · Practice Gym classroom model

How cold is it 6 km above a 28 °C afternoon?

A 6 km column of air above a 28 °C surface A height ruler from 0 to 6 km beside a tall cloud. At the ground the thermometer reads 28 °C. At 6.0 km, 39 °C colder, it reads −11 °C, cold enough for ice crystals in the cloud top. 0246 km −11 °C 28 °C 39 °C colder ice crystals
Surface
T₀ = 28 °C
Height
h = 6.0 km
Lapse rate
6.5 °C per km (average)
  1. RuleT = T₀ − 6.5 × h
  2. Cooling6.5 °C/km × 6.0 km = 39 °C
  3. Subtract28 °C − 39 °C = −11 °C
  4. Read itBelow freezing: tall clouds grow ice up there.
Answer

About −11 °C. Check: higher is colder, so the answer must be below 28 °C.

Part 1 · Key idea

Relative humidity compares the vapor in the air with saturation

Saturation is a balance, not a full sponge Two closed jars of water. At 10 °C, few molecules escape and the vapor stops building at 9.4 grams per cubic metre, where as many molecules condense back as evaporate. At 30 °C, molecules evaporate faster, so the balance settles at 30.4 grams per cubic metre. Warm air does not hold water like a sponge; the balance point is higher. 10 °C balance at 9.4 g/m³ 30 °C balance at 30.4 g/m³ up arrows: evaporating · down arrows: condensing

Saturation is the vapor level where condensing balances evaporating. It rises steeply with temperature.

Relative humidity (RH) = vapor in the air ÷ saturation × 100.

Saturation values: Practice Gym table, from water's saturation vapor pressure (CRC Handbook of Chemistry and Physics, “Vapor Pressure of Water”). NWS Glossary: relative humidity.

Part 1 · Worked example · Practice Gym table

Find the relative humidity and dew point of 30 °C air

The Practice Gym saturation table as a bar chart Bars show saturation vapor content: 9.4 grams per cubic metre at 10 °C, 12.8 at 15 °C, 17.3 at 20 °C, 23.0 at 25 °C, 30.4 at 30 °C, and 39.6 at 35 °C. The 30 °C bar is filled to 17.3, the vapor actually in the air: a relative humidity of about 57%. A dashed line at 17.3 meets the top of the 20 °C bar, so the dew point is 20 °C. 9.412.817.323.030.439.6 10 °C15 °C20 °C25 °C30 °C35 °C 17.3 dew point 20 °C saturation vapor content (g/m³) by air temperature
Air
30 °C
Vapor in it
17.3 g/m³
Table
saturation values in the chart
  1. Read the tableSaturation at 30 °C = 30.4 g/m³
  2. RH17.3 ÷ 30.4 × 100 = 56.9% ≈ 57%
  3. Dew point17.3 g/m³ saturates at 20 °C
  4. Read itCool this air by 10 °C and droplets form.
Answer

RH ≈ 57%; dew point 20 °C. Check: RH is under 100%, and the dew point is below the air temperature.

Part 1 · Key idea

A cloud forms where rising air cools to its dew point

Rising air closes in on its dew point A graph of temperature against height from 0 to 2 km. Air starts at 30 °C with a dew point of 22 °C. As it rises, its temperature falls 9.8 °C per km and its dew point falls about 1.8 °C per km, so the 8 °C gap closes by 8 °C per km. They meet at 1.0 km, about 20 °C: the cloud base. Above it, the cloud keeps rising and cools more slowly. 00.51.01.52.0 15202530 temperature (°C) height (km) cloud base: 1.0 km air: −9.8 °C/km dew point: −1.8 °C/km 30 °C 22 °C inside the cloud: cools more slowly

Dew point: the temperature at which air becomes saturated.

Rising air expands and cools, closing in on its dew point. Then condensation wins: vapor turns into droplets on specks of dust and salt.

Classroom quick estimatecloud base ≈ 0.125 km × (T − dew point)

Part 1 · Worked example · Classroom quick estimate

How high is the cloud base on a muggy afternoon?

Cumulus clouds with flat bases at 0.75 km A ground station reads an air temperature of 32 °C and a dew point of 26 °C, a 6 °C spread. Puffy clouds overhead share a flat base at 0.75 km, marked on a height ruler from 0 to 1 km. 00.250.51 km base: 0.75 km air 32 °C dew point 26 °C
Air
32 °C
Dew point
26 °C
Rule
0.125 km per °C of spread
  1. Spread32 °C − 26 °C = 6 °C
  2. Height6 °C × 0.125 km/°C = 0.75 km
  3. Convert0.75 km = 750 m
  4. Read itMuggy air has a small spread, so clouds form low.
Answer

Cloud base ≈ 0.75 km. Check: 0.75 ÷ 0.125 = 6 °C, the spread you started with.

Part 1 · Key idea

Millions of cloud droplets merge to make one raindrop

From cloud droplet to raindrop Left: a raindrop drawn about 100 times as wide as a cloud droplet, which appears as a tiny dot beside it; a million droplets merged make a drop 100 times as wide. Right: droplets collide and merge as they fall through the cloud. A drop falls out once it is heavy enough to beat the updraft holding it up. raindrop ≈ 100× as wide cloud droplet 10⁶ droplets → 100× the width collide, merge updraft falls

Cloud droplets are too small to fall. They grow by bumping into each other and merging.

When a drop is too heavy for the updraft, it falls as precipitation: rain, snow, sleet, or hail.

Part 1 · Key idea

Clouds are named by shape and height

Cloud families by height Three bands of sky. High clouds, made of ice crystals: wispy cirrus. Middle clouds: altocumulus puffs and a gray altostratus sheet. Low clouds: flat gray stratus and heaped cumulus. A cumulonimbus thunderstorm cloud rises from the low band through all three and spreads into an anvil at the top. HIGH · iceMIDDLELOW cirrus altocumulus altostratus stratus cumulus cumulo- nimbus

Ten basic types, sorted by how high they sit.

  • Cumulus: heaped. Stratus: layered.
  • Cirrus: wispy, high, made of ice.
  • Nimbo- or -nimbus: brings precipitation.

Part 1 · Common mistakes

Three air-and-water mistakes that cost points

Cold air sinks on both sides and pushes warm air up warm
✗ Mistake

“Hot air rises on its own.”

✓ Fix

Denser air around it sinks and pushes it up. No denser air, no rise.

Evaporation and condensation balance at a higher level when warm =
✗ Mistake

“Warm air holds more water, like a sponge.”

✓ Fix

Warmth speeds evaporation, so vapor balances at a higher level. Cooling to the dew point lets condensation win.

Subtract the cooling: 28 minus 39 is minus 11 28 + 39 = 67 °C ✗ 28 − 39 = −11 °C ✓
✗ Mistake

“6 km up is 28 + 39 = 67 °C.”

✓ Fix

Air cools with height, so subtract: T = T₀ − 6.5 × h.

Part 1 · Check yourself

Your turn: humidity and cloud base

Air at 25 °C has 12.8 g/m³ of vapor. Saturation at 25 °C is 23.0 g/m³. What is the relative humidity?

Show the answer

A, 56%. RH = 12.8 ÷ 23.0 × 100 = 55.7% ≈ 56%. B divides the wrong way (23.0 ÷ 12.8); RH can never pass 100% in this model. C is 100 − 56, the room left before saturation. D divides by the temperature (12.8 ÷ 25).

Surface air is 28 °C with a dew point of 24 °C. Using the classroom quick estimate, where is the cloud base?

Show the answer

B, 0.5 km. Spread = 28 − 24 = 4 °C; 4 × 0.125 km = 0.5 km. A uses the dew point alone (24 × 0.125). C uses the air temperature alone (28 × 0.125). D divides 4 by 0.125 instead of multiplying.

Part 2 · Weather Station lead this part

Weather on the move

  • Explain how uneven heating makes winds.
  • Find a pressure gradient from two stations.
  • Predict which way Earth's spin turns the wind.
  • Read highs, lows, and fronts on a map.
  • Measure weather and judge a forecast.
A surface weather map Isobars curve around a high and a low. A cold front with triangles runs south from the low, and a warm front with half circles runs east. L H

Part 2 · Key idea

The same sunbeam covers twice the ground at 60° latitude

Sunlight is concentrated at the equator and spread thin near the poles Two equal beams of sunlight strike a curved Earth at noon on an equinox. At the equator the beam lands on one unit of ground. At 60° north the same beam strikes at a slant and spreads over two units, so each square metre gets half the energy. The tropics take in more energy than they lose, the poles lose more than they take in, and winds and currents carry heat toward the poles. equator 60° N same beam same beam spreads over 2 units lands on 1 unit tropics: energy surplus pole: deficit air and ocean carry heat poleward noon on an equinox · 1 ÷ cos 60° = 2

Sunlight is concentrated near the equator and spread thin near the poles.

The tropics gain more energy than they lose; the poles lose more than they gain. Winds and currents carry the extra heat poleward.

Part 2 · Key idea

Earth's spin breaks one giant loop into three cells

The three circulation cells from the equator to the North Pole A slice of the troposphere from the equator to 90° north. In the Hadley cell, 0° to 30°, air rises at the equator, flows poleward high up, sinks near 30°, and returns along the surface. In the Ferrel cell, 30° to 60°, the loop turns the other way, kept going by passing storms rather than by heating. In the polar cell, 60° to 90°, air rises near 60° and sinks at the pole. Rising air brings clouds and rain at the equator and near 60°; sinking air brings dry weather and deserts near 30° and cold, dry air at the pole. Hadley heat-driven Ferrel turned by storms Polar heat-driven 0°30°60°90° N rising: rainy(ITCZ) sinking: dry,deserts rising:stormy sinking:cold, dry latitude, equator to North Pole

Rising air at the equator sinks near 30° and flows back along the surface: the Hadley cell.

Ferrel cell 30–60°, polar cell 60–90°. The middle cell is turned by passing storms, not by heating.

Part 2 · Key idea

Winds are named for where they come from

Earth's surface wind belts A globe with lines at 30° and 60° north and south. Between 0° and 30° north, northeast trade winds blow toward the equator; between 0° and 30° south, southeast trade winds do the same. They meet at the ITCZ, a rainy belt along the equator. Between 30° and 60°, westerlies blow from the west toward the poles. Beyond 60°, polar easterlies blow from the east. Houston sits near 30° north, at the edge of the trades and the westerlies. polar easterlies westerlies northeast trades ITCZ: rainy belt southeast trades westerlies polar easterlies Houston 30°60°30°60°

A northeast trade wind blows from the northeast toward the equator.

Trades meet at the ITCZ (intertropical convergence zone), a rainy belt. Westerlies carry most mid-latitude weather from west to east.

Part 2 · Key idea

Wind blows from high pressure toward low pressure

Isobar spacing sets the strength of the push A high-pressure area on the left and a low on the right, with isobars labelled 1024 to 1004 hPa every 4 hPa between them. In the top half the isobars are close together, so pressure changes fast and the push from high to low is strong. In the bottom half they fan out, so the push is weak. 102410201016101210081004 H L strong push weak push isobars close isobars far apart

Isobars are map lines joining places with equal air pressure.

The pressure gradient is how fast pressure changes with distance. Tighter isobars mean a bigger push and stronger wind.

Part 2 · Worked example · Practice Gym

How strong is the push between two stations?

Two stations 400 km apart Station A reads 1024 hPa and station B reads 1008 hPa, 400 km to the east. Isobars at 1020, 1016, and 1012 hPa lie between them. Air is first pushed from A toward B, then Earth's spin turns it to the right in the Northern Hemisphere. 102010161012 A · 1024 B · 1008 push: high → low turned right (south) 0200400 km
Station A
1024 hPa
Station B
1008 hPa
Distance
400 km · Northern Hemisphere
  1. Difference1024 − 1008 = 16 hPa
  2. Hundreds of km400 km ÷ 100 km = 4
  3. Gradient16 hPa ÷ 4 = 4.0 hPa per 100 km
  4. DirectionPushed from A toward B, then turned right.
Answer

4.0 hPa per 100 km. Check: 4.0 × 4 = 16 hPa, the difference you started with.

Part 2 · Key idea · Practice Gym rule

Earth's spin bends long journeys: right in the north, left in the south

Coriolis deflection in each hemisphere A globe spinning from west to east. In the Northern Hemisphere, air heading south bends to its right, toward the west, and air heading north bends to its right, toward the east. In the Southern Hemisphere, air heading north bends to its left, toward the west. Air moving along the equator goes straight: no deflection there. Dashed lines show the straight paths; solid curves show the bent paths. Earth spins west to east North: bends right South: bends left equator: no turn 0° matters only over hundreds of km and hours

The Coriolis effect deflects anything moving freely over long distances.

Right of its motion in the Northern Hemisphere, left in the Southern, zero at the equator. It grows with speed and latitude.

Part 2 · Worked example · Practice Gym rule

Why does the trade wind blow from the northeast?

Air heading south bends west A compass. Air starts moving due south toward the equator. Facing south, your right hand points west, so the air bends toward the west and ends up moving toward the southwest. It arrives from the northeast: a northeast trade wind. NSWE straight path bent toward the west arrives from the northeast facing south, right hand → west
Motion
due south, toward the equator
Where
Northern Hemisphere
Rule
bend right of the motion
  1. Face itFace south, the way the air moves.
  2. Find rightYour right hand points west.
  3. BendThe air curves west: it now heads southwest.
  4. Name itWinds are named for where they come from: the northeast.
Answer

A northeast trade wind. Check: moving toward the southwest means coming from the northeast.

Part 2 · Key idea

Fronts are where two air masses meet

A cold front lifting warm, moist Gulf air A cross-section. Cold, dry air from Canada, a continental polar air mass, wedges under warm, moist air from the Gulf, a maritime tropical air mass. The warm air is forced up steeply along the front, cools, and builds tall storm clouds. Below, the map symbols: a cold front is a line with triangles, a warm front a line with half circles, each pointing the way the front moves. cold, dry air from Canada warm, moist air from the Gulf forced up: tall clouds, storms cold front warm front map symbols point the way the front moves

An air mass is a huge body of air with about the same temperature and humidity.

At a front, denser air wedges under lighter air and lifts it. Rising air cools, so fronts bring clouds and rain.

Part 2 · Key idea

Every weather instrument gives a reading with a unit

Thermometer

Temperature, °C.

Barometer

Air pressure, hPa.

Anemometer

Wind speed, m/s.

Wind vane

Points to where wind comes from.

Rain gauge

Rain depth, mm.

Hygrometer

Relative humidity, %.

Upper airWeather balloons can climb past 35 km, radioing readings twice a day from 92 U.S. sites.

Part 2 · Worked example · Weather Station build

How deep will 100 mL stand in a round cup?

A round rain-gauge cup holding 100 mL A straight-sided cup 7.0 cm wide, so its radius is 3.5 cm and its base area is 38.5 square centimetres. 100 mL of water stands 2.6 cm, or 26 mm, deep, read on a ruler taped to the side. 7.0 cm wide r = 3.5 cm 026 mm 100 mL base area 3.14 × 3.5 × 3.5 = 38.5 cm²
Cup width
7.0 cm, so r = 3.5 cm
Water
100 mL = 100 cm³
Circle area
3.14 × r × r
  1. Base area3.14 × 3.5 cm × 3.5 cm = 38.5 cm²
  2. Depth100 cm³ ÷ 38.5 cm² = 2.6 cm
  3. Convert2.6 cm × 10 mm/cm = 26 mm
  4. Read itMark 26 mm on the ruler: that line means 100 mL.
Answer

About 26 mm. Check: 2.6 cm × 38.5 cm² ≈ 100 cm³.

Part 2 · Key idea

Read a surface map: highs, lows, and fronts

A low with its fronts and a high, Northern Hemisphere A sketch of a surface map, not a real day. Around the low (1000 hPa), wind spirals counterclockwise and inward; the air rises, making clouds and rain. A cold front with triangles trails southwest from the low, with a band of rain along it. A warm front with half circles runs east. Around the high (1024 hPa) to the northwest, wind spirals clockwise and outward; the air sinks, bringing fair weather. 100010041024 H L high: air sinks, spreads out: fair weather low: air spirals in, rises: clouds, rain sketch, Northern Hemisphere

Around a low, air spirals in and rises: clouds and rain. Around a high, air sinks and spreads out: fair weather.

Across Texas, these systems usually travel from west to east.

Part 2 · Key idea

The cone shows where the centre will probably go, not how big the storm is

A hurricane track forecast cone A storm offshore moves northwest toward the coast. Forecast centre positions for days 1 to 5 sit inside circles that grow with time; the cone is drawn around the circles. Each circle is sized so that two-thirds of past official track errors fell inside it. The storm's own wind field, drawn as a dashed circle, is a separate thing from the cone, and a town outside the cone can still get wind, rain, and surge. Day 12345 a town outside the cone can still get wind, rain, surge land Gulf storm's wind field (size)

A forecast gets less certain the farther ahead it looks, so the circles grow.

Each circle holds two-thirds of past track errors. Impacts can reach hundreds of miles outside the cone.

Part 2 · Key idea

A watch says possible; a warning says expected

Hurricane watch and warning lead times A timeline in hours before tropical-storm-force winds (39 mph or more) arrive. The hurricane watch is issued 48 hours ahead, the hurricane warning 36 hours ahead. Preparation fits in the time before the winds arrive; after that, working outdoors becomes dangerous. −48 h−36 h0 h WATCH possible WARNING expected tropical-storm- force winds arrive time to prepare and leave too late Hurricane winds: 74 mph (64 kt) or more. Tropical-storm-force winds: 39 mph (34 kt) or more.

A hurricane watch: hurricane winds are possible. A hurricane warning: they are expected.

Both are timed to the first tropical-storm-force winds, because preparing outside gets dangerous once they arrive.

Part 2 · Common mistakes

Three weather mistakes that cost points

A west wind blows from the west toward the east WE west wind
✗ Mistake

“A west wind blows toward the west.”

✓ Fix

Winds are named for where they come from. Currents are named for where they go.

A sink is far too small for the Coriolis effect 50 cm1,000 km
✗ Mistake

“Coriolis spins my sink drain.”

✓ Fix

It needs hundreds of kilometres and hours. A sink's swirl comes from how the water moved first.

Impacts reach outside the cone
✗ Mistake

“We are outside the cone, so we are safe.”

✓ Fix

The cone tracks only the centre. Wind, rain, and surge reach far beyond it.

Part 2 · Check yourself

Your turn: gradient and deflection

Map A: stations read 1012 and 1000 hPa, 300 km apart. Map B: 1020 and 1008 hPa, 600 km apart. Which map has the stronger wind?

Show the answer

A. Map A: 12 ÷ 3 = 4.0 hPa per 100 km. Map B: 12 ÷ 6 = 2.0. The steeper gradient wins. B has it backwards: more distance spreads the same drop thinner. C ignores distance. D: the gradient, not the pressure itself, drives wind.

Air moves due north in the Southern Hemisphere. Which way does the Coriolis effect turn it?

Show the answer

B. Southern Hemisphere: turn left. Facing north, your left hand points west. A uses the northern rule. C is true only at the equator. D turns left but reads the compass wrong.

Part 3 · Storm and Sea lead this part

Storms and the sea

  • Name the three things every thunderstorm needs.
  • Calculate the energy a storm's rain released.
  • Explain why warm water alone cannot make a hurricane.
  • Explain how wind and density move the ocean.
  • Stack water masses by density.
A thunderstorm over a warm sea A tall storm cloud with an anvil top and lightning stands over the sea. The sea has a warm top layer over colder, denser water.

Part 3 · Key idea

Every thunderstorm needs moisture, instability, and lift

The three ingredients of a thunderstorm 1, moisture: water vapor flows in from the warm Gulf. 2, instability: once lifted, the air stays warmer than its surroundings, so it keeps rising in a strong updraft. 3, lift: a front, a sea breeze, or hills push the first air upward. The storm's top spreads into an anvil at the tropopause. tropopause 1 2 3 moisture instability: keeps rising lift: a front cold air wedges in warm Gulf water anvil
  • Moisture: water vapor to fuel the cloud.
  • Instability: lifted air stays warmer than the air around it, so it keeps rising.
  • Lift: a front, a sea breeze, or hills push the air up first.

Part 3 · Key idea

Condensing vapor heats the rising air, so the storm feeds itself

A rising parcel compared with the air around it A graph of temperature against height, an example day. The surrounding air cools 7 °C per km from 30 °C at the ground. A rising parcel starts at 30 °C and cools 9.8 °C per km until its cloud base at 1 km. Inside the cloud, released latent heat slows its cooling, and at about 2.4 km, the level of free convection, it becomes warmer than its surroundings. From there it rises on its own to about 11.6 km, where it spreads into the anvil. Below 2.4 km it needs a push from a lift. 04812 −50−30−101030 temperature (°C) height (km) cloud base level of free convection anvil top parcel warmer: rises on its own needs a push rising parcel surrounding air
Example day. The Circulation Engine's Storm Mode draws these curves for the settings you choose.

Condensation releases latent heat: about 2.5 million joules per kilogram of water.

That heat keeps the updraft, the rising core of the storm, warmer than the air around it, so it keeps climbing.

2.5 × 10⁶ J/kg is the classroom value (Practice Gym), the value near 0 °C; near 25 °C it is about 2.44 × 10⁶ J/kg, the 2,430 J/g Module 1 used (CRC Handbook of Chemistry and Physics, “Enthalpy of Vaporization of Water”). NWS Glossary: latent heat.

Part 3 · Worked example · Practice Gym

How much energy did a storm's rain release?

Rain over 100 square kilometres A storm rains 25 mm over a square 10 km on each side, an area of 100 square kilometres. Inset: 1 mm of rain over 1 square kilometre is 1,000 cubic metres, which is 1,000,000 kg of water. 10 km × 10 km = 100 km² 25 mm of rain 1 mm × 1 km² = 1,000 m³ = 10⁶ kg
Rain
25 mm over 100 km²
Mass rule
1 mm over 1 km² = 10⁶ kg
Latent heat
2.5 × 10⁶ J/kg
  1. Mass25 × 100 × 10⁶ kg = 2.5 × 10⁹ kg
  2. Energy ruleE = m × L
  3. Multiply2.5 × 2.5 = 6.25, and 10⁹ × 10⁶ = 10¹⁵
  4. RoundE = 6.25 × 10¹⁵ J ≈ 6.3 × 10¹⁵ J
Answer

About 6.3 × 10¹⁵ J released into the air. Check: 6.25 × 10¹⁵ J ÷ 2.5 × 10⁶ J/kg gives back 2.5 × 10⁹ kg.

Part 3 · Key idea

Severe storms bring large hail, damaging wind, or tornadoes

Inside a severe thunderstorm A sketch of a large thunderstorm. A strong, rotating updraft carries hailstones up and around until they are too heavy and fall. Rain-cooled air rushes down and spreads out as a gust front of damaging wind. Under the rotating updraft, a tornado reaches the ground. Severe means hail at least 1 inch wide, gusts of 58 mph or more, or a tornado. rotating updraft tornado gust front: damaging wind hail grows, then falls
Sketch, not to scale.

A thunderstorm is severe when it makes hail at least 1 inch wide, gusts of 58 mph or more, or a tornado.

A tornado is a rotating column of air reaching from the storm to the ground.

Part 3 · Key idea

A hurricane needs warm deep water, low shear, and distance from the equator

Three conditions a hurricane needs Panel 1, warm water: the sea is at least 26.5 °C from the surface down to about 50 m. Panel 2, low wind shear: a storm stays upright when winds change little with height, below about 10 m/s; strong shear tilts it and tears it apart. Panel 3, spin: the storm must be at least about 500 km, or 5°, from the equator, where the Coriolis effect is too weak to start it spinning. 0 m50 m ≥ 26.5 °C cooler below 1 · warm water low ✓ high ✗ 2 · low wind shear 0° too little spin ≥ 5° (≈ 500 km) ✓ 3 · enough spin

Wind shear is a change in wind speed or direction with height. Strong shear tilts a storm and tears it apart.

These conditions are necessary but not enough. Most disturbances in good conditions never become hurricanes.

Part 3 · Key idea

A hurricane is a heat engine that runs on warm sea water

Cross-section of a hurricane A cross-section, not to scale. Warm, moist air spirals in along the sea surface toward the centre. It rises in the eyewall, where its vapor condenses and releases heat. At the top, air flows out in all directions. In the calm, clear eye, air sinks. Strong winds stir the sea and bring up cooler water from below, so a storm that stalls in one place cools its own fuel. eye calm, sinking eyewall: heat released warm, moist air spirals in warm layer: the fuel outflow at the top stirred-up cooler water cooler water below

A hurricane is a tropical cyclone with winds of at least 74 mph.

Warm water evaporates into the inflow. Condensation in the eyewall releases the heat that drives the winds. Over cool water or land, the fuel runs out.

Part 3 · Key idea

Winds drag the sea surface into giant loops

The subtropical gyres of one ocean basin An ocean basin between two continents, simplified. Trade winds push water west along the equator. In the Northern Hemisphere the loop turns clockwise: a fast, narrow, warm current such as the Gulf Stream runs north along the west side, westerlies push the water east, and a slow, wide, cooler current returns south along the east side. In the Southern Hemisphere the loop turns counterclockwise. equator clockwise counter- clockwise trades push west westerlies push east Gulf Stream: warm, fast, narrow cool, slow, wide
Simplified basin. The real Gulf Stream averages about 6.4 km/h.

A gyre is a huge loop of surface currents driven by the wind.

Five subtropical gyres turn clockwise in the north and counterclockwise in the south. The west side of each carries a fast, warm current.

Part 3 · Key idea · Practice Gym classroom model

Cold, salty water is dense and sinks

Seawater density from temperature and salinity A chart with salinity from 33 to 37 ppt across and temperature from 0 to 30 °C up. Sloping lines join water of equal density in the classroom model, from 1024 kg/m³ for warm, fresher water at the top left to 1029 kg/m³ for cold, salty water at the bottom right. Three water masses are marked: B, 25 °C and 34 ppt, about 1024.0; C, 10 °C and 35 ppt, 1027.0; A, 4 °C and 36 ppt, about 1028.7. 102410251026102710281029 0102030 3334353637 salinity (ppt) temperature (°C) B · 1024.0 C · 1027.0 A · 1028.7 denser
Lines of equal density, kg/m³, from ρ ≈ 1027 + 0.78(S − 35) − 0.15(T − 10).

Salinity is how much salt is dissolved in seawater, in parts per thousand (ppt).

Cold, salty water sinks near the poles and feeds the thermohaline circulation, a deep conveyor that takes about 1,000 years per lap.

Part 3 · Worked example · Practice Gym classroom model

Which water mass sinks to the bottom?

Three water masses stacked by density A tank with three layers. On top, B: 25 °C, 34 ppt, about 1024.0 kg/m³. In the middle, C: 10 °C, 35 ppt, 1027.0 kg/m³. On the bottom, A: 4 °C, 36 ppt, about 1028.7 kg/m³. B · 25 °C, 34 pptC · 10 °C, 35 pptA · 4 °C, 36 ppt 1024.01027.01028.7 warm, fresher: floatscold, salty: sinks density in kg/m³
A
4 °C, 36 ppt
B
25 °C, 34 ppt
C
10 °C, 35 ppt
Model
ρ ≈ 1027 + 0.78(S − 35) − 0.15(T − 10)
  1. A1027 + 0.78 + 0.90 = 1028.7 kg/m³
  2. B1027 − 0.78 − 2.25 = 1024.0 kg/m³
  3. C1027 + 0 − 0 = 1027.0 kg/m³
  4. StackDensest on the bottom: A, then C, then B on top.
Answer

A sinks to the bottom. Check: A is coldest and saltiest, so both terms raise its density.

Part 3 · Common mistakes

Three storm-and-sea mistakes that cost points

Warm water plus strong shear: the storm is torn apart shear ✗
✗ Mistake

“Warm water alone makes a hurricane.”

✓ Fix

It also needs low shear, distance from the equator, and moist air. Even then, most never form.

Condensation releases heat into the air + heat vapor → droplets
✗ Mistake

“Condensation cools the cloud.”

✓ Fix

Condensation releases heat; evaporation absorbs it. That released heat drives the updraft.

Subtract 0.15 kg per cubic metre for each degree above 10 +0.15(T − 10) ✗ −0.15(T − 10) ✓
✗ Mistake

“Warmer water is denser.”

✓ Fix

Warming makes water expand, so it gets less dense: subtract 0.15 for each °C above 10.

Part 3 · Check yourself

Your turn: density and storm energy

Use the Practice Gym model. Which water sinks to the bottom? X: 20 °C, 35 ppt. Y: 5 °C, 34 ppt. Z: 15 °C, 37 ppt.

Show the answer

B. X: 1027 + 0 − 1.5 = 1025.5. Y: 1027 − 0.78 + 0.75 = 1027.0. Z: 1027 + 1.56 − 0.75 = 1027.8, the densest. A looks only at temperature; Y's low salinity cancels its cold. C has it backwards: warm water floats. D: different densities layer instead of mixing.

A storm drops 10 mm of rain over 400 km². How much heat did the condensation release?

Show the answer

C. Mass = 10 × 400 × 10⁶ = 4.0 × 10⁹ kg; E = 4.0 × 10⁹ × 2.5 × 10⁶ = 1.0 × 10¹⁶ J. A is the mass in kg, not the energy. B forgets that each mm over 1 km² is 10⁶ kg. D divides by 2.5 × 10⁶ instead of multiplying.

Part 4 · Climate Desk lead this part

Climate: the long pattern

  • Tell weather from climate.
  • Explain why some weather keeps coming back.
  • Explain what sets a place's climate.
  • Put numbers on the ice-albedo feedback.
  • Read El Niño with a running average.
Many years of readings make a climate A wiggly line of yearly temperatures over many years, with a smooth average line through it. years →

Part 4 · Key idea

Weather is one day; climate is 30 years of days

Daily highs scatter around the 30-year normal A sketch, not station data. Dots for one year of daily high temperatures scatter above and below a smooth band, the 30-year normal for each date. One dot falls far below the band: a single cold snap. It is weather; it does not move the normal. one cold snap: weather 30-year normal JFMAMJJASOND daily high temperature sketch, not station data

Weather is the state of the air right now. Climate is its pattern over decades: averages, ranges, and extremes.

NOAA's official normals average 30 years, now 1991–2020.

Part 4 · Key idea

Floods, droughts, heat waves, and cold waves keep coming back

Four recurring weather hazards and what sets them up Four panels. Flood: a storm stalls and keeps drawing in Gulf moisture, as Harvey did over Texas in 2017. Drought: a high-pressure area sits for weeks; sinking air blocks rain. Heat wave: a dome of high pressure warms the air beneath it day after day. Cold wave: an Arctic air mass flows south across the plains. stalled storm Flood H Drought H Heat wave Arctic air Cold wave same machinery each time: highs, lows, and air masses that stall or surge

Recurring hazards come from the same machinery: air masses, highs, and lows that stall or surge.

A drought is a long shortage of water that harms people, animals, or plants over a wide area.

Part 4 · Key idea

Wind makes cold air feel colder

Wind chill at an air temperature of 20 °F National Weather Service wind chill values for 20 °F air: 13 °F with a 5 mph wind, 9 at 10 mph, 6 at 15, 4 at 20, 3 at 25, 1 at 30, 0 at 35, and −1 °F at 40 mph. The air temperature stays 20 °F; only how fast skin loses heat changes. −551525 010203040 wind speed (mph) feels like (°F) air temperature 20 °F 20 mph wind: feels like 4 °F 13 −1

Wind chill is how cold the air feels on exposed skin.

Moving air carries heat away from skin faster. At 20 °F (−7 °C), a 20 mph wind feels like 4 °F (−16 °C).

Part 4 · Key idea

Latitude, water, height, and mountains set a place's climate

Four controls on a place's climate A west-to-east cross-section, not to scale. Latitude sets how much sunlight arrives. A coastal city beside the ocean has mild seasons. Moist ocean air blows inland and rises over a mountain range, cooling about 6.5 °C per km, so the windward slope is cloudy and rainy and the peak is cold. Descending air on the far side warms and dries, leaving a dry rain shadow. An inland city far from the ocean has hot summers and cold winters. 1 2 3 4 latitude: how much sun coast: mild height: colder rain shadow: dry inland: big swings moist air
  • Latitude sets how much sunlight arrives.
  • Nearby ocean softens heat and cold.
  • Height cools: about 6.5 °C per km.
  • Mountains wring rain from rising air and leave a dry rain shadow behind.

Part 4 · Key idea

Water warms and cools slowly, so coasts swing less

Energy to warm 1 gram by 1 °C A bar chart. Warming 1 gram of water by 1 °C takes 4.18 joules. Warming 1 gram of quartz, the mineral of most sand, takes about 0.74 joules, less than a fifth as much. Below, a sketch: a coastal city's temperature swings gently through the year, while an inland city at the same latitude swings much more. Joules to warm 1 g by 1 °C water sand 4.18 J 0.74 J coastal city: gentle swing inland city: big swing sketch of one year, same latitude

Specific heat is the energy needed to warm 1 g of a substance by 1 °C.

Water needs over five times what sand needs. So the sea heats and cools slowly, and coastal cities get milder seasons.

Part 4 · Key idea

Two knobs set Earth's temperature: albedo and greenhouse gases

The albedo knob and the greenhouse knob Two panels. Albedo knob: sunlight arrives; bright surfaces such as clouds and ice reflect part of it straight back to space, and the ground absorbs the rest. More reflection means a cooler Earth. Greenhouse knob: the warm ground gives off infrared. Greenhouse gas molecules in the air absorb it and send it out in every direction, including back down, while some escapes to space. More greenhouse gas means a warmer surface. ALBEDO knob reflected ground absorbs ice more reflection → cooler GREENHOUSE knob some escapes gas absorbs, re-emits warm ground gives off infrared more gas → warmer surface

Greenhouse gases, such as water vapor and carbon dioxide, absorb infrared from the surface and send part of it back down.

More reflection cools Earth. More greenhouse gas warms the surface.

Part 4 · Worked example · Climate Desk

How much more sunlight does open ocean absorb than sea ice?

The same sunlight on sea ice and on open ocean 300 watts per square metre of sunlight falls on each surface. Bare sea ice with an albedo of 0.60 reflects 180 and absorbs 120. Open ocean with an albedo of 0.06 reflects 18 and absorbs 282, about 2.4 times as much. Arrow widths match the numbers. 300 in300 in 180reflected18reflected sea ice · albedo 0.60 absorbs 120 ocean · albedo 0.06 absorbs 282 W/m² · arrow width matches the number
Sunlight
300 W/m² on each
Sea ice
albedo 0.60
Open ocean
albedo 0.06
  1. Ice absorbs300 × (1 − 0.60) = 120 W/m²
  2. Ocean absorbs300 × (1 − 0.06) = 282 W/m²
  3. Compare282 ÷ 120 ≈ 2.4 times as much
  4. Read itMelting ice exposes dark water, which absorbs more and melts more ice.
Answer

About 2.4 times as much. Check: absorbed + reflected = 300 each (120 + 180; 282 + 18).

Part 4 · Key idea

A feedback loop turns a small change into a bigger one

Two warming feedback loops Left, the ice-albedo loop: Earth warms, sea ice melts, darker ocean is exposed, more sunlight is absorbed, and Earth warms more. Right, the water-vapor loop: warmer air, more evaporation and more water vapor, more infrared absorbed and sent back down, and warmer air again. Both are positive feedbacks: they amplify the first change. Ice-albedo loop Earth warms sea icemelts darker oceanexposed more sunlightabsorbed Water-vapor loop warmer air more watervapor more infraredsent back down

A feedback is a loop where a change causes more of itself (positive) or pushes back against itself (negative).

Melting ice and rising water vapor both amplify warming.

Part 4 · Key idea

Slow changes in Earth's orbit pace the ice ages

The three Milankovitch cycles Three panels. Orbit shape, or eccentricity: Earth's path stretches from nearly round to slightly oval and back, about every 100,000 years. Tilt, or obliquity: the axis leans between 22.1° and 24.5°, about every 41,000 years. Wobble, or precession: the axis traces a slow circle, which shifts the seasons along the orbit, about every 23,000 years. orbit shape ≈ 100,000 years tilt: 22.1°–24.5° ≈ 41,000 years wobble ≈ 23,000 years each changes where and when sunlight falls

Milankovitch cycles shift where and when sunlight falls, over tens of thousands of years.

They set the rhythm of the ice ages. They are far too slow to explain the warming of the last 150 years.

Part 4 · Key idea

El Niño: the trade winds weaken and warm water slides east

The equatorial Pacific, normal and during El Niño Two slices of the equatorial Pacific from Asia and Australia on the left to South America on the right. Normal: strong trade winds blow west and pile warm water in the west, where air rises and rain falls; cold water wells up in the east. El Niño: the trades weaken, warm water spreads east, the rain shifts east, and the cold upwelling weakens. The Niño 3.4 box, from 170° W to 120° W, is where NOAA measures it. Normal strong trades warm pool cold upwelling El Niño weak trades Niño 3.4 box warm water spreads east AsiaS. America

El Niño is the warm phase of a Pacific cycle; La Niña is the cool phase.

El Niño raises wind shear over the Atlantic, so Atlantic hurricane seasons are often quieter.

Part 4 · Worked example · Climate Desk

Is the Pacific in an El Niño yet?

Monthly values and three-month running averages Bars show five monthly sea-surface temperature differences from normal: +0.2, +0.4, +0.7, +0.8, and +1.0 °C. Dots show the three-month running averages, plotted at the middle month: +0.43, +0.63, and +0.83 °C. A dashed line marks the +0.5 °C El Niño threshold; two of the three averages are above it. +0.5 °C threshold 0.430.630.83 +0.2+0.4+0.7+0.8+1.0 month 12345 bars: monthly · dots: 3-month average
Months 1–5
+0.2, +0.4, +0.7, +0.8, +1.0 °C
Threshold
above +0.5 °C
NOAA rule
5 overlapping 3-month seasons in a row
  1. Months 1–3(0.2 + 0.4 + 0.7) ÷ 3 = 1.3 ÷ 3 ≈ +0.43
  2. Months 2–4(0.4 + 0.7 + 0.8) ÷ 3 = 1.9 ÷ 3 ≈ +0.63
  3. Months 3–5(0.7 + 0.8 + 1.0) ÷ 3 = 2.5 ÷ 3 ≈ +0.83
  4. JudgeTwo averages pass +0.5, but NOAA needs five in a row.
Answer

Warming toward El Niño, not yet an official episode. Check: 0.43 × 3 ≈ 1.3, the sum of months 1–3.

Part 4 · Common mistakes

Three climate mistakes that cost points

One cold point does not move a long trend
✗ Mistake

“One freezing week proves the climate is cooling.”

✓ Fix

One week is weather. Climate is decades of averages and extremes.

An outlook counts storms; it does not say where they land
✗ Mistake

“A quiet season outlook means our coast is safe.”

✓ Fix

Outlooks count storms; they do not say where storms hit. One storm is enough.

A gas molecule sends infrared in every direction
✗ Mistake

“Greenhouse gases trap heat like a lid.”

✓ Fix

They absorb infrared and send it out in all directions, some back down, so the surface runs warmer.

Part 4 · Check yourself

Your turn: rates and coasts

From 2006 to 2015, global sea level rose 3.6 mm per year. At that rate, about how long does it take to rise 10 cm?

Show the answer

C. 10 cm = 100 mm; 100 ÷ 3.6 ≈ 28 years. A divides 10 by 3.6 without changing cm to mm. B multiplies 3.6 × 10. D multiplies 100 × 3.6. Rate source: NOAA Climate.gov, Global Sea Level.

Why do coastal cities have milder summers and winters than inland cities at the same latitude?

Show the answer

A. Water needs over five times the energy sand does to warm by 1 °C, so the nearby sea damps both extremes. B: same latitude means about the same sunlight. C: sea salt in air stores almost no heat. D: coasts are usually low, and height would only make them colder.

Part 5 · Every team · Storm Room

Use it in your project

“With only the data available at six in the morning, what do you tell a coastal city?”

  • Issue forecasts that cite their data.
  • Make a call and name who carries the risk.
  • Brief a family in three minutes.
  • Keep an honest field journal.
Open the Storm Room project Project Library
The four Storm Room deliverables Four cards: a forecast desk log with three timed issuances, a decision brief weighing the call against the outcome, a three-minute briefing video, and a field journal. forecast desk logdecision briefbriefing videofield journal 123

Use it · Storm Room · Forecast desk log

Every forecast names the data it was built on

How to lay out the forecast desk log A log with five columns: time issued, centre position, intensity, confidence, and the data you read. Three rows are the three issuances, each written at its own time. A last row, written after the event, verifies each issuance against what happened, including the ones that missed. ISSUEDCENTREWINDSCONFIDENCEDATA I READ Issue 1Issue 2Issue 3 timetimetime lat, lonkt or mphhigh · med · lowadvisory #, buoyreading, map time VERIFICATION · written after the event Issue 1 vs what happened · Issue 2 vs … · Issue 3 vs … Name the misses honestly, and the data that misled you.
Turn in
Forecast desk log · Assessment Center, typed
Do
Three timed issuances: position, intensity, confidence, and the data behind each. Then one verification line per issuance.
Data
NHC advisories · Buoy 42035 · WPC map
Slides
Cone · Hurricane needs · Gradient

Use it · Storm Room · Consequence and decision brief

Name the call, the limit that forced it, and who carries the risk

Every protective call has a cost if you are wrong A two-by-two table. Rows are the call: evacuate early, or wait and shelter. Columns are the outcome: the storm hits, or it misses. Evacuate and it hits: people are out of harm's way. Evacuate and it misses: money is spent, and people may trust the next order less. Wait and it hits: people are caught by water and wind. Wait and it misses: costs are saved. Your brief names which cell your call risks, and who pays for it. storm hitsstorm misses evacuateearlywait andshelter people out ofharm's way money spent;next order maybe trusted less people caughtby water, wind costs saved Who pays in your worst cell: drivers, hospitals, families?
Turn in
Decision brief · Assessment Center, typed
Do
State the call and its criteria. Name the constraint that bound it: lead time, roads, cost, shelters, medically fragile residents. Say who carries the risk.
Data
NHC watch and warning · Fort Bend County · Ready.gov
Slides
Watch or warning · Cone

Standard: HS-ETS1-3, evaluate a solution against criteria and trade-offs. Fort Bend County's guidance: “Run from the water, hide from the wind.”

Use it · Storm Room · Briefing video

Three minutes a family can follow on a phone

A three-minute briefing in four beats A storyboard of four phone screens. 0:00 to 0:30, what is coming. 0:30 to 1:30, where and when, with your own map that shows the cone is not the danger zone. 1:30 to 2:30, what to do now. 2:30 to 3:00, how sure you are and when the next update comes. 0:00–0:300:30–1:301:30–2:302:30–3:00 what is comingwhere, whenwhat to do nowhow sure we are your own mapnext update
Turn in
Briefing video · Studio Turn-In, video file
Do
On camera, give your forecast and your call with your own graphics. Plain words; say how sure you are.
Check
Play it on a phone at full volume. Could a family with no science background act on it?
Slides
Cone · Watch or warning · Engine

Use it · Storm Room · Field journal

Write each entry before you know how the storm ends

The seven parts of one journal entry A journal page with seven numbered parts: 1 header, 2 today's question, 3 raw record, 4 method log, 5 sense-making in progress, 6 dead ends, and 7 handoff. After the last project day comes a closing retrospective. 1 · Header: date, day, role 2 · Today's question 3 · Raw record, with units 4 · Method log 5 · Sense-making in progress 6 · Dead ends (required) 7 · Handoff after the last day: closing retrospective
Turn in
Field journal · Note Studio, one note named for the project
Do
One seven-part entry per project day, then a closing retrospective. Never rewrite an old call; add a new entry.
Why
Hindsight is the enemy of an honest forecast log.
Slides
Units on every reading · Desk log

Use it · Storm Room · Your team's build

The slides your build and teach-back need

Cloud Makers · cloud station

Balloon bottles, a dew-point can, a rain maker.

Weather Station · instruments

Read four instruments; make a forecast and check it.

Storm and Sea · tank and vortex

Layers that sink, wind that drags, stirring that cools.

Climate Desk · test bench

Fan on a cup, sand against water, ice on black and white.

Circulation EngineIts readouts are model evidence: “When we changed ___, the ___ changed.” Open the lab

Use it · The rest of the year

Module 3 shows up in every other project

Part 6 · Reference · Formula sheet

Every Module 3 formula and rule on one page

Albedo

absorbed = in × (1 − albedo)

Earth: 340 W/m² in, albedo ≈ 0.29. Ice 0.5–0.7, ocean 0.06. Example

Lapse rate (Practice Gym)

T = T₀ − 6.5 × h

°C and km. Subtract: higher is colder. Example

Relative humidity

RH = vapor ÷ saturation × 100

Dew point: where vapor = saturation. Example

Saturation table (g/m³)

10 °C 9.4 · 15 °C 12.8 · 20 °C 17.3 · 25 °C 23.0 · 30 °C 30.4 · 35 °C 39.6

Cloud base (classroom)

≈ 0.125 km × (T − dew point)

Rising air cools 9.8 °C/km until saturated. Example

Pressure gradient

Δp ÷ (distance ÷ 100 km)

hPa per 100 km; tighter isobars, stronger wind. Sea level 1013 hPa. Example

Coriolis rule

right (N) · left (S) · none at 0°

Winds named from; currents named to. Example

Rain gauge

depth = volume ÷ area

1 mL = 1 cm³; circle area = 3.14 × r × r; 1 cm = 10 mm. Example

Storm energy (Practice Gym)

E = d × A × 10⁶ kg × 2.5 × 10⁶ J/kg

d in mm, A in km². Example

Seawater density (Practice Gym)

ρ ≈ 1027 + 0.78(S − 35) − 0.15(T − 10)

kg/m³; S in ppt, T in °C. Densest sinks. Example

El Niño test

3-month average > +0.5 °C

Five overlapping seasons in a row. Example

Hurricane gates

Sea ≥ 26.5 °C to ~50 m · ≥ ~500 km (5°) from the equator · shear < ~10 m/s. Watch 48 h, warning 36 h. Slide

Constants

Air 1.29 kg/m³ at 0 °C, 1.16 at 30 °C · latent heat 2.5 × 10⁶ J/kg · water 4.18 J/(g·°C) · 1 hPa = 100 Pa.

Part 6 · Reference · Vocabulary

Module 3 words, in plain language

Atmosphere
The layer of gases held to Earth by gravity.
Troposphere · Stratosphere
The lowest layer, where weather happens; the ozone-warmed layer above.
Albedo
The fraction of sunlight a surface reflects.
Radiation
Energy carried as light across space.
Conduction · Convection
Heat passed by touch; heat carried by moving fluid.
Buoyancy
The upward push from denser surroundings.
Air pressure
The weight of the air above, in hPa.
Humidity · Relative humidity
Water vapor in the air; vapor ÷ saturation × 100.
Lapse rate
How fast temperature drops with height.
Saturation
Vapor level where condensing balances evaporating.
Dew point
The temperature at which air becomes saturated.
Condensation
Vapor turning into liquid droplets.
Precipitation
Rain, snow, sleet, or hail that falls.
Hadley cell
The loop rising at the equator, sinking near 30°.
Trade wind
Steady wind blowing toward the equator.
ITCZ
The rainy belt where the trade winds meet.
Isobar
A map line joining equal air pressure.
Pressure gradient
How fast pressure changes with distance.
Coriolis effect
Deflection by Earth's spin: right in the north.
Air mass
A huge body of air with similar temperature and humidity.
Front
The boundary where two air masses meet.
Forecast
A prediction with a stated confidence.
Watch · Warning
Hurricane winds possible (watch) or expected (warning).
Instability · Updraft
Lifted air keeps rising; the rising core of a storm.
Latent heat
Energy a phase change absorbs or releases.
Severe
Hail ≥ 1 inch, gusts ≥ 58 mph, or a tornado.
Tornado
A rotating column of air touching the ground.
Wind shear
Change in wind speed or direction with height.
Hurricane
A tropical cyclone with winds of 74 mph or more.
Gyre
A huge wind-driven loop of ocean currents.
Salinity
Dissolved salt in seawater, in ppt.
Thermohaline circulation
Deep ocean flow driven by temperature and salt.
Weather · Climate
The air right now; its pattern over decades.
Drought
A long water shortage that causes harm.
Wind chill
How cold moving air feels on skin.
Rain shadow
The dry side of a mountain range.
Specific heat
Energy to warm 1 g by 1 °C.
Greenhouse gas
A gas that absorbs and re-emits infrared.
Feedback
A loop where a change grows or shrinks itself.
Milankovitch cycles
Slow orbit changes that pace ice ages.
El Niño · La Niña
Warm and cool phases of a Pacific cycle.

More wordsLook up any term in the Ascent Lexicon.

Part 6 · Reference · Trustworthy data

Real data for your project, from the people who measure it

Cite itWrite the source, the link, and the date and time you read it. Live data changes every hour.

Part 6 · Ready for your project?

Three last checks

Surface air is 20 °C. At 6.5 °C per km, what is it 4.0 km up?

Show the answer

B. 20 − 6.5 × 4.0 = 20 − 26 = −6 °C. A adds the cooling. C cools for only 1 km. D forgets to start from 20 °C.

Sea 30 °C, low shear, but the storm sits at 2° N. Why no hurricane?

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A. Hurricanes need to be about 5° (500 km) from the equator, where the Coriolis effect can start the spin. B: 30 °C is well above 26.5 °C. C: low shear helps storms. D: hurricanes form over open ocean.

Your town is just outside the cone. What should your briefing say?

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C. The cone shows the likely track of the centre; the centre has left it about a third of the time, and impacts can reach hundreds of miles beyond. A, B, and D each treat the cone as the danger zone.

You made it through Module 3

Now go make the call

Practice the math, run the Circulation Engine, then build, brief, and defend your call.

Storm Room project Practice Gym · Module 3 Circulation Engine Module 3 page
A forecast desk at dawn A map with a forecast cone pointing at the coast, a barometer dial, and a clock at 6:00. hPa 6:00 a.m.