Wind waether

Weather

Short-term atmospheric conditions like rain, wind, and temperature.

Climate

Long-term average of weather patterns over decades or more.

Air Pressure

Force of air molecules pressing down on Earth; air flows from high to low pressure.

High Pressure System

Descending air → compresses, warms, dries → clear skies.

Low Pressure System

Rising air → expands, cools → forms clouds and precipitation.

Pressure-Gradient Force

Wind is driven by differences in pressure; closer isobars = faster winds.

Isobars

Lines of equal pressure on a map; spacing shows pressure gradient strength.

Coriolis Force

Earth's rotation deflects moving air: right in the N Hemisphere, left in the S.

Friction

Slows wind near Earth's surface; affects wind speed and direction, especially over land.

Adiabatic Processes

Rising air expands and cools, sinking air compresses and warms.

Hadley Cell

Warm air rises near the equator at the ITCZ, cools, condenses, and forms clouds, moves poleward aloft, sinks at ~30° latitude, warming and drying, creates deserts, and returns to equator as surface Trade Winds.

Ferrel Cell

Air rises at ~60° latitude where warm air from the south meets cold air from the north (Polar Front), moves equatorward aloft, sinks at ~30°, reinforcing high pressure zones, and returns poleward as surface Westerlies.

Polar Cell

Cold air sinks at the poles, moves equatorward at the surface as Polar Easterlies, meets warm air at ~60° latitude, forcing air to rise, rising air cools and forms clouds/precipitation, and returns to poles aloft to sink again.

ITCZ (Intertropical Convergence Zone)

Region at the equator where Hadley cells converge; warm air rises, causing clouds and rain.

Wind Naming Rule

Winds are named for the direction they come from (e.g., Westerlies come from the west).

Differential Heating

Uneven heating of land vs. ocean shifts wind belts seasonally, driving monsoons and pressure zones.

Polar Front

Zone at ~60° latitude where cold Polar Cell air meets warm Ferrel Cell air; a region of frequent storms and frontal systems.

Columbus' Voyage

Used Trade Winds to sail west and returned via Westerlies. Early navigation took advantage of global wind patterns.

Monsoon

A seasonally reversing wind system that brings wet and dry periods, especially in South Asia.

ITCZ (in Monsoons)

The Intertropical Convergence Zone shifts with the seasons, pulling in moist or dry air. Moves north of the equator in the summer, south of the equator in the winter.

Summer Monsoon (India)

Land heats → low pressure → moist ocean air flows in, bringing heavy rain.

Winter Monsoon (India)

Land cools → high pressure → dry air flows out to sea, causing dry conditions.

North American Monsoon

Weak monsoon in late summer; moist air from Gulf and Pacific brings rain to U.S. Southwest.

Climate Change & Monsoons

Warming disrupts timing and strength of monsoons, causing floods, droughts, or delays.

Tropical Cyclone

Large rotating storm formed over warm oceans; includes hurricanes, typhoons, and cyclones.

Hurricane

Tropical cyclone in the North Atlantic or Eastern Pacific.

Typhoon

Tropical cyclone in the Western Pacific.

Cyclone

Tropical cyclone in the Indian Ocean or South Pacific.

Formation Zone

5°-35° latitude N or S; requires SST ≥ 26.5°C and no Coriolis near the equator.

Storm Steering

Guided by Trade Winds near equator and Westerlies at higher latitudes.

Hurricane Naming

Set by World Meteorological Organization; alphabetical list, alternating male/female names.

How do we Measure Hurricanes?

Once a storm reaches tropical storm strength (≥39 mph), it is tracked and classified using the Saffir-Simpson Scale.

Saffir-Simpson Scale

A 1-5 rating system that classifies hurricanes based on sustained wind speeds.

Category 1

Lowest wind speeds, usually minimal damage.

Category 5

Highest wind speeds (157+ mph), catastrophic damage.

Hurricane Development

Storms progress from a tropical depression → tropical storm → hurricane once sustained winds reach 74 mph.

Tropical Depression

A developing storm system with organized thunderstorms and winds less than 39 mph.

Tropical Storm

A stronger system with winds from 39-73 mph; the storm is named at this stage.

Hurricane Anatomy - Eye

Calm center of the storm with sinking air and clear skies.

Hurricane Anatomy - Eyewall

Surrounds the eye; strongest winds and heaviest rain occur here.

Hurricane Anatomy - Rainbands

Spiral arms of thunderstorms extending outward; can stretch hundreds of miles.

Rotation Direction

Cyclones rotate counterclockwise in the Northern Hemisphere, clockwise in the Southern Hemisphere due to the Coriolis effect.

Storm Damages - Storm Surge

Coastal flooding caused by strong winds pushing ocean water onshore, often most deadly.

Storm Damages - Freshwater Flooding

Intense rainfall leads to inland flooding, even far from the coast.

Storm Damages - Wind Damage

Strong winds knock down trees, powerlines, and buildings — especially in the eyewall.

Storm Damages - Embedded Tornadoes

Small tornadoes can form within rainbands, adding to damage unpredictability.

Safety Valve for Earth's Climate?

Releasing built-up heat from warm ocean waters and transporting it toward the poles.

Bhola Cyclone (1970)

Deadliest cyclone in recorded history, Bangladesh; estimated death toll: 300,000 to 500,000 people.

Hurricane Katrina (2005)

Costliest Hurricane in the U.S.; main impact: catastrophic flooding in New Orleans after levee failures.