Killer weather

• We measure pressure in hectopascals (HPA)
• High pressure systems in the Northern Hemisphere have air movement that is clockwise, while in the Southern Hemisphere, it is anticlockwise
• Low pressure systems are associated with air rising, air converging, and precipitation, while high pressure systems are associated with air sinking, air diverging, and clear skies
• Cyclones are associated with low pressure systems, while anticyclones are associated with high pressure systems
• A tornado is a rotating column of air extending from a thunderstorm
• Tornadoes are most commonly formed in severe thunderstorms called supercell thunderstorms
• Tornadoes form where cold dry polar air meets warm moist tropical air, creating an unstable atmosphere
• Tornadoes can form any time during the year, but in the USA, most form in May
• Tornadoes have occurred on every continent except Antarctica, with about 75% of them happening in the United States
• The Enhanced Fujita Scale ranks tornadoes by their damage, with EF5 being the highest degree of damage
• Tornadoes come in three different sizes: weak, strong, and violent, based on their size, duration, and wind speeds
• Most South African tornadoes have been observed in Gauteng, the Free State, KwaZulu-Natal, and the northern region of the former Transkei
• Meteorologists rely on weather radar to provide information on developing storms and can predict a tornado's touchdown about 20 minutes in advance
• Tornado safety tips include moving to a basement or interior room, staying away from windows, and having a disaster plan in place
• During a tornado:

  • Go to a basement. If you do not have a basement, go to an interior room without windows on the lowest floor such as a bathroom or closet
  • If you can, get under a sturdy piece of furniture, like a table
  • If you live in a mobile home, get out as they offer little protection against tornadoes
  • Get out of automobiles and do not try to outrun a tornado in your car
  • If you’re outside, go to a ditch or low-lying area and lie flat in it
  • Stay away from fallen power lines and damaged areas
• If you’re at school during a tornado:

  • Schools in tornado-prone areas should have a disaster plan and frequent drills
  • Basements offer the best protection
  • Schools without basements should use interior rooms and hallways on the lowest floor away from windows
  • Crouch down on your knees and protect your head with your arms
• After a tornado:

  • Stay indoors until it is safe to come out
  • Check for injured or trapped people without putting yourself in danger
  • Watch out for downed power lines
  • Use a flashlight to inspect your home
• A tornado is associated with low pressure conditions
• Definition of a heat wave:

  • A prolonged period of excessively hot weather, which may be accompanied by high humidity
  • Heat waves are measured relative to the usual weather in the area and normal temperatures for the season
  • The World Meteorological Organization defines a heat wave as 5 or more consecutive days of prolonged heat with daily maximum temperatures higher than the average by 5°C or more
• Formation of heat waves:

  • High-pressure systems are associated with clear conditions and stable, sinking air
  • The sinking air warms by 1°C/100m, creating a dome cover that traps heat underneath, leading to a heat wave
• Heat waves in South Africa:

  • Heat wave temperature thresholds over South Africa
• Impacts of heat waves:

  • Health impacts include heat cramps, heat exhaustion, heatstroke, hyperthermia, hospitalizations, and even death
  • Indirect health effects can alter human behavior, disease transmission, and impact critical infrastructure
  • Other impacts include environmental, agricultural, infrastructure, wildfires, and economic consequences
• Heat waves are associated with high pressure conditions
• Heat wave precautions:

  • Stay indoors in a well-ventilated or air-conditioned room
  • Wear protective clothing if working outside and take regular breaks
  • Avoid strenuous activities and wear cool, lightweight clothes
  • Stay hydrated by drinking plenty of liquids and avoid alcohol
  • Restrict outdoor playtime for children and provide extra care for the elderly and infants
• Criterion for determining a heat wave by the South African Weather Service:

  • Maximum temperature at a town must meet or exceed 5 degrees C above the average maximum temperature of "the hottest month" for that place
  • This condition must persist for 3 days or more
• A detailed map of the "heat wave threshold" has been compiled for ease of use by SAWS meteorologists, using the latest climatological data
• The heat wave threshold is the maximum temperature that needs to be met or exceeded for a heat wave to occur
• Low pressure= Pressure lowest in the middle
• High pressure = Pressure highest in the middle
• EF0:

  • Wind speed: 105–137 km/h
  • Example of damage: Light damage. Peels surface off some roofs; some damage to gutters or siding; branches broken off trees; shallow-rooted trees pushed over
• EF1:

  • Wind speed: 138–178 km/h
  • Example of damage: Moderate damage. Roofs severely stripped; mobile homes overturned or badly damaged; loss of exterior doors; windows and other glass broken
• EF2:

  • Wind speed: 179–218 km/h
  • Example of damage: Considerable damage. Roofs torn off well-constructed houses; foundations of frame homes shifted; mobile homes completely destroyed; large trees snapped or uprooted; light-object missiles generated; cars lifted off ground
• EF3:

  • Wind speed: 219–266 km/h
  • Example of damage: Severe damage. Entire stories of well-constructed houses destroyed; severe damage to large buildings such as shopping malls; trains overturned; trees debarked; heavy cars lifted off the ground and thrown; structures with weak foundations blown away some distance
• EF4:

  • Wind speed: 267–322 km/h
  • Example of damage: Devastating damage. Well-constructed houses and whole frame houses completely leveled; cars thrown and small missiles generated
• EF5:

  • Wind speed: >322 km/h
  • Example of damage: Incredible damage. Strong frame houses leveled off foundations and swept away; automobile-sized missiles fly through the air in excess of 100 m; high-rise buildings have significant structural deformation; incredible phenomena will occur
• Impact on health services:

  • Increased ambulance call-outs and slower response times
  • Increased number of hospital admissions
  • Storage of medicines
• Increased risk of accidents:

  • Drowning
  • Work-related accidents
  • Injuries and poisonings
• Increased transmission of:

  • Food and waterborne diseases
  • Marine algal blooms
• Potential disruption of infrastructure:

  • Power
  • Water
  • Transport
  • Productivity
• Health impacts of exposure to extreme heat:

  • Heat illness: dehydration, heat cramps, heat stroke
  • Accelerated death from respiratory disease, cardiovascular disease, other chronic diseases (mental health, renal disease)
  • Hospitalization: respiratory disease, diabetes mellitus, renal disease, stroke, mental health conditions