Weather phenomena can be wild and unpredictable. From hurricanes to heat waves, these events shape our climate and impact our lives. Understanding them helps us prepare for nature's extremes.

Severe storms, temperature swings, and precipitation extremes are key players in weather systems. They're influenced by atmospheric patterns and can cause major disruptions. Knowing the science behind them is crucial for forecasting and safety.

Severe Storms

Tropical Cyclones and Hurricanes

• Tropical cyclones are low-pressure systems that form over warm tropical oceans and have sustained winds of at least 74 mph (119 km/h)
  • Characterized by a warm core, closed low-level circulation, and a central "eye" of calm weather surrounded by the eyewall where the strongest winds and heaviest rainfall occur
• Hurricanes are a type of tropical cyclone that form in the North Atlantic Ocean, central North Pacific Ocean, or eastern North Pacific Ocean
  • Powered by heat from the sea, evaporating water increases their power (latent heat of condensation)
  • Categorized by wind speed using the Saffir-Simpson Hurricane Wind Scale from Category 1 (74-95 mph) to Category 5 (157 mph or higher)
• Bring heavy rainfall, strong winds, storm surges, and can cause extensive damage to coastal areas (Hurricane Katrina in 2005)

Tornadoes and Thunderstorms

• Tornadoes are violently rotating columns of air extending from a thunderstorm to the ground, often appearing as a funnel-shaped cloud
  • Winds can exceed 300 mph (480 km/h) and cause severe damage along a narrow path
  • Most common in the United States, particularly in "Tornado Alley" (Texas, Oklahoma, Kansas, Nebraska)
• Thunderstorms are characterized by the presence of lightning and thunder, caused by the rapid upward movement of warm, moist air
  • Can produce heavy rainfall, strong winds, hail, and occasionally tornadoes
  • Severe thunderstorms can lead to flash flooding, damaging winds, and large hail

Cyclones and Anticyclones

• Cyclones are low-pressure systems characterized by inward spiraling winds that rotate counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere
  • Associated with cloudy, rainy weather and can bring strong winds and storms
• Anticyclones are high-pressure systems with outward spiraling winds that rotate clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere
  • Associated with calm, clear weather and light winds
  • Can lead to heat waves or cold waves depending on the season and location (Siberian High in winter)

Extreme Temperature Events

Heat Waves

• Prolonged periods of excessively hot weather, often combined with high humidity
  • Defined based on local climate, but typically when temperatures are well above average for an extended period
• Can cause heat stress, heat exhaustion, and heat stroke, particularly among vulnerable populations (elderly, children, outdoor workers)
  • Urban areas are more susceptible due to the urban heat island effect, where concrete and asphalt surfaces absorb and radiate more heat than natural surfaces
• Examples include the European heat wave of 2003 and the Russian heat wave of 2010

Cold Waves

• Prolonged periods of excessively cold weather, often accompanied by snow and ice
  • Defined based on local climate, but typically when temperatures are well below average for an extended period
• Can cause hypothermia, frostbite, and damage to infrastructure (frozen pipes, power outages)
  • Particularly dangerous for homeless populations and those without adequate heating
• Examples include the North American cold wave of 2014 and the European cold wave of 2012

Precipitation Extremes

Blizzards and Heavy Snowfall

• Blizzards are severe winter storms characterized by strong winds (35+ mph), blowing snow, and low visibility (less than 1/4 mile)
  • Can lead to whiteout conditions, making travel extremely dangerous
• Heavy snowfall events can disrupt transportation, damage infrastructure, and cause roof collapses
  • Lake-effect snow occurs when cold air moves over warmer lake waters, causing heavy, localized snowfall (Great Lakes region)

Drought

• Prolonged periods of abnormally low rainfall, leading to water shortages and dry conditions
  • Can be meteorological (lack of precipitation), agricultural (insufficient soil moisture), or hydrological (reduced streamflow and groundwater levels)
• Impacts include crop failures, wildfires, and water scarcity for communities and ecosystems
  • Long-term droughts can lead to desertification and ecological changes (Dust Bowl in the 1930s)

Flash Floods

• Rapid flooding caused by heavy rainfall or rapid snowmelt, often in low-lying or urban areas with poor drainage
  • Can occur within minutes to hours of the rainfall event, leaving little time for warning or evacuation
• Dangers include fast-moving water, debris flows, and damage to infrastructure (bridges, roads)
  • Flash floods are a major cause of weather-related fatalities worldwide (2021 European floods)

Atmospheric Circulation Patterns

Frontal Systems

• Fronts are boundaries between air masses of different temperatures and densities
  • Cold fronts occur when colder air advances and displaces warmer air, often bringing thunderstorms and rapid temperature drops
  • Warm fronts occur when warmer air advances over colder air, often bringing steady precipitation and gradual temperature rises
  • Stationary fronts occur when neither air mass is advancing, leading to prolonged periods of cloudy, wet weather
• Frontal systems are associated with mid-latitude cyclones and are a major driver of day-to-day weather variability in many regions
  • The meeting of cold, dry continental air masses and warm, moist maritime air masses along frontal boundaries can trigger severe weather events (Nor'easters along the US East Coast)