How thunderstorms, tornadoes and hurricanes form

Grade 9 Science Worksheet

Circle the best answer.

1. Read this first

   Card

   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. Surroundings at 3 km: 4 °C.

2. 1.

   A parcel starts at 30 °C with a dew point of 22 °C. Bo lifts it to 3 km. How warm is it, and does it keep rising?

   • 20 °C, which is 16 °C warmer than its surroundings, so it keeps rising
   • 8 °C, which is 4 °C warmer than its surroundings, so it keeps rising
   • 0 °C, which is 4 °C colder than its surroundings, so it sinks back
   • 12 °C, which is 8 °C colder than its surroundings, so it sinks back
3. 2.

   a dry parcel cools 10 °C per km. Surroundings at 1.5 km: 14 °C. Air at 28 °C is forced up a slope to 1.5 km. Jun compares it with the 14 °C surroundings. Does lift alone start a storm?

   • Yes: the parcel is 13 °C, 1 °C warmer than its surroundings, so it keeps rising
   • Yes: the parcel is 18 °C, 4 °C warmer than its surroundings, so it keeps rising
   • Yes: air that cools while rising gets warmer than the air around it
   • No: the parcel is 13 °C, 1 °C colder than its surroundings, so it needs more lift or heating

4. Winds above one spot, both from the southwest

   8 m/s at the ground and 28 m/s at 6 km. Card: shear of about 20 m/s or more from the ground to 6 km favors supercells.

5. 3.

   Milo finds the shear from the ground to 6 km. Does it favor a supercell?

   • No: 8 m/s at the ground is too weak to count as shear
   • No: both winds blow from the southwest, so there is no shear
   • Yes: 28 − 8 = 20 m/s, which reaches the 20 m/s mark
   • Yes: 28 + 8 = 36 m/s, which is above the 20 m/s mark
6. 4.

   Noah orders the steps that give a supercell its rotating updraft. Which order is correct?

   • Shear rolls air into a horizontal tube, then the updraft tilts it upright
   • Shear tilts the updraft upright, then rain rolls it into a horizontal tube
   • Earth's spin rolls air into a horizontal tube, then the updraft tilts it upright
   • The updraft rolls air into a horizontal tube, then shear tilts it upright
7. 5.

   NOAA says supercell updrafts can top 160 km/h. What is that in m/s, by Pia's math?

   • About 576 m/s
   • About 44 m/s
   • About 160 m/s
   • About 2.7 m/s

8. Four ocean areas (example data)

   Area	Latitude	Water at 50 m (°C)	Wind shear (m/s)
   A	2° N	28.0	4
   B	14° N	27.5	5
   C	14° N	27.5	18
   D	14° N	24.0	5

9. 6.

   Ren needs warmth to 50 m (26.5 °C or more), low shear and a latitude over 5°. Which area can support a tropical cyclone?

   • Area C, which is warm and far enough from the equator
   • Area A, which has the warmest water at 50 m
   • Area D, which has low shear and is far from the equator
   • Area B, which passes all three tests

10. Two disturbances over warm water (example data)

    Disturbance	Latitude	Water at 50 m (°C)	Wind shear (m/s)
    P	3° N	29.5	4
    Q	15° N	28.0	4

11. 7.

    Tala compares the disturbances. Which one can spin up into a tropical cyclone, and why?

    • P: the warmest water, 29.5 °C at 50 m, wins over latitude
    • Q: at 15° N the Coriolis effect is strong enough to help start rotation
    • P: the equator spins fastest, so it starts rotation well
    • Q: its lower water temperature leaves less heat to spin up the storm

12. 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

13. 8.

    NHC reports sustained winds of 105 knots (1 knot = 1.15 mph). Which category does Esme name?

    • Category 1, since 105 knots is about 91 mph
    • Category 2, since 105 reads directly as 105 mph
    • Category 4, since 105 knots is about 158 mph
    • Category 3, since 105 knots is about 121 mph

14. Winds of one storm (example data)

    Hour	Sustained winds (mph)
    0	75
    12	95
    24	115

15. 9.

    Rapid intensification means a gain of 35 mph or more in 24 hours. Did Ari's storm do it, and which categories did it span?

    • Yes: it gained 40 mph in 24 hours, going from Category 1 to Category 3
    • No: it gained just 20 mph in the first 12 hours, under 35 mph
    • No: winds above 74 mph are steady, so a gain of 40 mph does not count
    • Yes: it gained 40 mph in 24 hours, going from Category 2 to Category 4
16. 10.

    A hurricane is about 300 miles wide with an eye about 30 miles wide. What share of its area does Kira say the eye covers?

    • About 10%, the same as the ratio of the widths
    • About 0.1%, one tenth of the ratio of the widths
    • About 33%, since the eye is one third of 100 miles
    • About 1%, since area goes with the square of the width