Reading Weather Patterns — Practice · Grade 9 Science

Chapter: Atmosphere & Weather

What this practice covers

By the end of Reading Weather Patterns you should be able to:

11 questions, multiple choice, numeric and written answer, each with a worked explanation.

Vocabulary used: isobar, station model, meteorologist, prevailing westerlies, relative humidity, dew point.

Problem 1

On a weather map, a line connecting all points with the same air pressure is called a(n)...
  1. Isobar
  2. Isotherm
  3. Front
  4. Station model
Answer and explanation

Isobar

Isobars connect points of equal air pressure — 'iso' means equal and 'bar' refers to pressure.

Problem 2

Which instrument measures air pressure?
  1. Barometer
  2. Anemometer
  3. Hygrometer
  4. Rain gauge
Answer and explanation

Barometer

A barometer measures air pressure; an anemometer measures wind speed, a hygrometer measures humidity, and a rain gauge measures precipitation.

Problem 3

In the mid-latitudes, including New York State, weather systems generally move...
  1. From west to east
  2. From east to west
  3. From north to south only
  4. Randomly, with no general pattern
Answer and explanation

From west to east

The prevailing westerlies and the jet stream generally steer mid-latitude weather from west to east.

Problem 4

Isobars on a weather map are packed very closely together over a region. What does this most likely indicate?
  1. Strong winds, due to a big pressure difference over a short distance
  2. Calm winds, because the pressure is very steady
  3. An approaching heat wave with no wind
  4. That the map has an error
Answer and explanation

Strong winds, due to a big pressure difference over a short distance

Tightly packed isobars mean pressure changes quickly over a short distance, and bigger pressure differences drive stronger winds.

Problem 5

A barometer reads 1020 mb at 6 a.m. and 1002 mb at noon, six hours later. By how many millibars did the pressure fall?
Answer and explanation

18 mb

1020 − 1002 = 18 mb. That's a fairly rapid fall, often a sign that stormier weather is on the way.

Problem 6

A front moves 180 km between maps taken 6 h apart. Find its average speed and one forecasting limit. Explain the reasoning in your own words.
Answer and explanation

30 km/h over the measured interval; a later arrival estimate needs continued observations.

Average speed=180/6=30 km/h.

Future speed or direction can change, so straight extrapolation is an assumption.

Response criteria

  • Use the stated conditions.
  • Show the evidence or calculation.
  • Explain the conclusion and any stated limitation.

Problem 7

A radar image shows precipitation moving east. What extra information improves arrival-time prediction? Show the reasoning, not just the conclusion.
Hints

A forecast is conditional and updated with new evidence.

Answer and explanation

Distance to the location and movement speed/direction over successive images, with allowance for growth or decay.

Problem 8

Why should forecast confidence be lower farther into the future?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

Initial-state uncertainty and evolving interactions can amplify differences in predictions.

Problem 9

Agreement about passage can coexist with uncertain arrival timeAgreement about passage can coexist with uncertain arrival timeFront movement from initial position (km)03060901200123Forecast lead time (h)Model A: 40 km/hModel B: 30 km/h
Original illustrative constant-speed front trajectories for timing comparison. They are not an operational forecast ensemble or a calibrated probability interval. The record distinguishes event agreement from uncertainty about timing.
Interpret the supplied visual model. At a place 60 km ahead, what arrival times do the two supplied models imply?
Answer and explanation

1.5 h at 40 km/h and 2 h at 30 km/h, assuming steady speed along the stated path. Actual movement can evolve.

The curves share an initial position and direction but differ in slope. The vertical axis is travel distance, not temperature or precipitation probability.

1.5 h at 40 km/h and 2 h at 30 km/h, assuming steady speed along the stated path. Actual movement can evolve.

Response criteria

  • Read the labeled quantities, reference frame or objects correctly.
  • Explain the relation between the visual evidence and the mechanism.
  • Keep the drawing’s stated assumptions and limits in the conclusion.

Problem 10

A front is 90 km from a town. Model A gives steady motion 30 km/h and model B 45 km/h. Calculate the two arrival times and define a fair observation-based timing check.
Answer and explanation

A gives 3 h and B 2 h. Record the forecast issue time, defined passage indicator/location and predicted intervals, then compare with later observations using the original criteria. Changing criteria after the event undermines verification.

A gives 3 h and B 2 h. Record the forecast issue time, defined passage indicator/location and predicted intervals, then compare with later observations using the original criteria. Changing criteria after the event undermines verification.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the physical mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

Problem 11

OpenSciEd table for Chanute Martin Johnson Station, Kansas, with observation times, temperature in degrees Fahrenheit, relative humidity percent, wind speed and gust in miles per hour during the Fort Scott hail case.
Actual historical station record from the Fort Scott case, OpenSciEd 6.3. Use the 3:52 PM and 4:52 PM rows and distinguish the wind-speed and gust columns. Observed station weather in the Fort Scott case · OpenSciEd · 6.3 Weather, Climate & Water Cycling, Lesson 2, source, CC BY 4.0. Figure excerpt rendered from the PDF and resized for the web.
Using the actual station record, calculate the changes from 3:52 PM to 4:52 PM in temperature (°F and °C), relative humidity (percentage points) and wind speed (mph). For a temperature difference, Δ°C = Δ°F × 5/9. Explain what these simultaneous changes support and why they do not by themselves prove a particular front, exact hailfall location or complete cause.
Answer and explanation

Temperature changes from 68 to 59 °F: −9 °F, equivalent to −5 °C. Relative humidity changes from 68% to 78%: +10 percentage points, not a 10% relative increase. Wind speed changes from 12 to 30 mph: +18 mph. The observations support a changing atmospheric situation at the named station; mapped front/pressure, wind direction, moisture and event-location evidence would help test causes. A humidity increase alone does not prove more water vapor, because saturation conditions change with temperature.

Read matching times and the correct source columns before subtracting.

Subtract later minus earlier: 59−68 = −9 °F; multiply the difference by 5/9 to obtain −5 °C. Do not subtract 32 when converting a temperature difference.

Compute 78−68 = 10 percentage points and 30−12 = 18 mph; gusts are a separate column.

State the station scale and time interval, then request independent mapped/process evidence rather than claim a unique cause.

Response criteria

  • All changes use later minus earlier and retain correct units.
  • Temperature-difference conversion and percentage-point distinction are correct.
  • The inference is limited to the stated record and identifies evidence needed for a causal explanation.

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