How thunderstorms, tornadoes and hurricanes form
Grade 9 Science Worksheet - Challenge Me
Circle the best answer.
Read this first
Two warm, humid days (example data)
Day Surface (°C) Dew point (°C) Air at 2 km (°C) A 33 24 20 B 28 22 10 Note: A dry parcel cools 10 °C per km, a cloudy one 6 °C per km, and cloud base is 125 m per °C between air temperature and dew point.
A student says any warm, humid day brings a thunderstorm. Using the card rules, Bo lifts a parcel on each day to 2 km. Which reply is best?
- No: on day A the parcel, about 16.5 °C, is colder than the 20 °C around it
- No: on day B the parcel is about 13 °C, colder than the 10 °C around it
- Yes: on day A the parcel is about 21.8 °C, warmer than the 20 °C around it
- Yes: both days are warmer than 20 °C at the surface, so both days are unstable
Card
Earth's spin gives a turning rate of about 0.0001 per second at midlatitudes. A tornado with 50 m/s winds at a radius of 100 m turns at 50 ÷ 100 = 0.5 per second.
A student says tornadoes spin because of Earth's spin alone. Luz compares the two turning rates. Which reply is best?
- No: a tornado turns about 500 times faster than Earth's effect, so shear and the updraft supply the spin
- No: a tornado turns about 5,000 times faster than Earth's effect, so shear and the updraft supply the spin
- Yes: a tornado turns 5,000 times slower than Earth's effect, so Earth sets the spin
- Yes: Earth's effect is small, but it adds up across a whole storm and starts the spin
Heat = mass × 4,186 J per kg per °C × temperature change. Water weighs 1,000 kg per m³. A passing storm cools the top 50 m of the ocean by 2 °C. How much heat does Esme say each square meter loses?
- About 210 MJ per square meter
- About 0.42 MJ per square meter
- About 4,200 MJ per square meter
- About 420 MJ per square meter
A hurricane crosses into water below 26.5 °C with winds of 100 mph, and loses 12 mph a day (model data). After how long does Tala expect it to drop below 74 mph?
- After about 2.2 days
- After about 8.3 days
- After about 0.5 day
- After about 6.2 days
Kira wants to test whether warm water or low shear matters more for a tropical cyclone forming. Which comparison best isolates water temperature?
- The same disturbance on two days, with shear and water both changing
- Two disturbances with equal shear and latitude, but different 50 m water
- One disturbance with warm water and low shear, compared with a cold, calm sea
- The two warmest disturbances, whatever their shear and latitude
One hurricane weakening (example data)
Hour Winds (mph) Shear (m/s) Water under the eye at 50 m (°C) 0 110 5 28 12 100 6 24 24 80 6 24 Two explanations for the weakening: stronger shear, or colder water. Ren reads the table. Which do the data support?
- Colder water: shear stayed near 5 to 6 m/s while the water under the eye fell from 28 to 24 °C
- Neither: winds fall whenever a storm lasts longer than 12 hours
- Stronger shear: it rose from 5 to 6 m/s just as the winds fell
- Both equally: each changed by about the same share between hours 0 and 12
Radar shows heavy rain in a storm. Pia asks if its updraft rotates, which would make it a supercell. Which radar evidence would best show that?
- Very heavy rain across the whole storm
- A tall cloud top reaching 12 km
- A storm that lasts longer than 30 minutes
- Winds moving toward and away from the radar, side by side at the same height
Four days (example data)
Day Moisture Instability Lift Storm 1 yes yes yes yes 2 yes yes no no 3 yes no yes no 4 no yes yes no Zee reads the table. Which summary of thunderstorm formation fits all four days?
- Lift matters most, since the two days with lift both had storms
- Moisture alone makes storms, since three of the four days had moisture in them
- Any two ingredients together make a storm, as on days 2, 3 and 4
- A storm formed only on the day with moisture, instability and lift together
Four stretches of one storm's track (example data)
Stretch Water at 50 m (°C) Shear (m/s) Winds (mph) 1 29 5 60 to 100 2 29 20 100 to 80 3 25 5 80 to 70 4 land 5 70 to 45 Ari reads the table. Which summary of what strengthens and weakens a hurricane fits all four stretches?
- It strengthens whenever shear is low, whatever the water below
- It weakens only over land, since water and shear never matter
- It strengthens only with warm deep water and low shear together; lose either one, or cross land, and it weakens
- It strengthens whenever the water is warm, whatever the shear
Saffir-Simpson Hurricane Wind Scale (NHC)
Category Sustained winds (mph) 1 74 to 95 2 96 to 110 3 111 to 129 4 130 to 156 5 157 or higher Milo reads the scale. Which summary of what the scale rates fits the table?
- It rates peak wind alone, in uneven bands: 15 mph for Category 2, 27 for Category 4
- It rates the total size of the storm, using bands that grow by 15 mph
- It rates wind, rain and storm size together, in bands that are each exactly 20 mph wide
- It rates peak sustained wind alone, in equal bands that are 20 mph wide