Air Mass Mayhem

*Calculate the pressure difference (Δmb) and write the correct wind flow direction for Pairs 3 and 4 in the blank cells above.

Part 4: Evidence-Based Analysis

1. Based on the data in the table, what is the mathematical relationship between the pressure difference (Δmb) and the observed wind speed? Cite data from two city pairs to support your claim.

2. In Pair 3, an untrained observer predicts wind will blow from Dallas to Memphis because "Dallas comes first in the table." Use atmospheric scientific principles to refute this claim and state the actual direction.

3. Extension / Synthesis: If a strong High pressure system (1030 mb) sits over cold Ontario (cP air) and a deep Low pressure system (992 mb) sits over the Midwest, explain how the combination of pressure gradient and air mass characteristics will change the local temperature and weather in Ohio.

Investigation 1 • Page 2 of 2 Atmospheric Sciences • Middle School Science

Part 3: Table Calculations & Directions

• Pair 3 (Dallas 996 mb vs Memphis 1020 mb): Δmb = 24 mb. Direction: Memphis → Dallas (High 1020 mb flows to Low 996 mb). Speed: 18 knots.
• Pair 4 (Chicago 1032 mb vs Detroit 994 mb): Δmb = 38 mb. Direction: Chicago → Detroit (High 1032 mb flows to Low 994 mb). Speed: 35 knots.

Part 4: Scientific Reasoning Rubric Reference

• Q1: Positive relationship. A greater pressure gradient results in higher wind speed (e.g., Denver → Salt Lake Δ4 mb = 6 knots, while Chicago → Detroit Δ38 mb = 35 knots).
• Q2: Wind does not follow arbitrary listing or alphabet; fluids move down pressure gradients. Since Memphis is at 1020 mb and Dallas is at 996 mb, air flows from Memphis to Dallas.
• Q3: High pressure in Ontario will drive cold, dense cP air south toward the Low in the Midwest, causing Ohio to experience dropping temperatures, clearing skies behind the front, and northerly winds.

Mixed-Readiness Differentiation

Striving Learners (Scaffolding)

• • Provide physical arrows with "H → L" stamped on them to place over maps.
• • Highlight the first letter (m=ocean, c=land) with blue and brown pencils.
• • Pre-fill the subtraction formula: \( \Delta\text{mb} = \text{High} - \text{Low} \).

Advanced Learners (Extension)

• • Introduce the Coriolis Effect: explain why winds curve clockwise around Highs and counter-clockwise around Lows in the Northern Hemisphere.
• • Have students research Arctic (cA) air masses and compare their density to cP.

Teacher Guide • Lesson 1 (Air Mass Origins) Atmospheric Sciences • Middle School Curriculum

Map Symbol: Solid red line with semicircles pointing the direction warm air moves. Slow & Prolonged

Tracking Weather at a Fixed City

Mission Briefing

Meteorologists do not just watch fronts on a radar—they track how 5 key variables change over time at a single weather station:

Temperature

Pressure

Humidity

Precipitation

Wind Dir.

Lab Handout: Track Indianapolis as a severe cold front passes over 24 hours!

Hands-on Analysis

Part 4: Evidence-Based Data Analysis

1. Exact Timing of Passage: At approximately what time did the frontal boundary directly pass over Indianapolis? Cite at least TWO specific data points from the table as evidence.

2. Front Classification: Did a Cold Front or a Warm Front pass over Indianapolis? Justify your decision by comparing conditions at 10:00 (before) to 22:00 (after), addressing temperature, dew point, and pressure.

3. Pressure Analysis: Explain why the barometric pressure fell to its lowest point (1001 mb) right before the front passed, and then rapidly climbed to 1022 mb by 22:00.

Investigation 2 • Page 2 of 2 Atmospheric Sciences • Middle School Science

Part 4: Indianapolis Station Data Analysis

• Q1 (Exact Timing): Between 14:00 and 16:00 (around 14:00). Evidence: Pressure reached its absolute minimum (1001 mb) at 14:00, wind shifted sharply from SSW to West with severe gusts up to 48 mph, and severe thunderstorms began.
• Q2 (Front Classification): Cold Front. Before the passage (10:00), air was 74°F with a humid dew point of 66°F. After passage (22:00), the temperature plunged 30°F down to 44°F, dew point dropped to 32°F (crisp/dry), and pressure soared to 1022 mb. Only a strong cold front produces this rapid temperature plunge and clearing.
• Q3 (Pressure Curve): The frontal boundary lies in a low-pressure trough where converging air rises rapidly. Once the cold front sweeps through, the incoming polar air mass is dense and sinking (High Pressure), causing the barometer to rise steeply to 1022 mb.

Mixed-Readiness Differentiation

Striving Learners (Scaffolding)

• • Provide color highlighters: blue for temperature drop rows, red for pre-frontal rows.
• • Sentence stem: "I know a cold front passed because the temperature changed from ___°F to ___°F and the wind shifted from ___ to ___."

Advanced Learners (Extension)

• • Have students research occluded fronts: what happens when a fast-moving cold front catches up to and overtakes a warm front?
• • Ask students to calculate the rate of temperature drop per hour between 14:00 and 18:00 (5°F per hour drop).

Teacher Guide • Lesson 2 (Frontal Collisions) Atmospheric Sciences • Middle School Curriculum

Forecasting Performance Task

Team Assessment

Your Role: Lead Meteorological Forecaster

Using multi-day synoptic weather maps, you will provide a 24-48 hour probabilistic forecast for Atlanta, GA:

1. Analyze Data Measure front speed & calculate arrival

2. Range Forecast Predict temp range & rain probability %

3. Write CER Defend your forecast with scientific evidence

Take out the Performance Task Assessment Document.

Individual / Paired Task

Part 3: Scientific Explanation (CER Format)

CLAIM: State your prediction regarding how the collision of the advancing cold air mass with the existing warm air mass will suddenly alter weather conditions in Atlanta.

EVIDENCE: Cite at least THREE pieces of data from Maps 1 and 2 (e.g., front speed, pressure change, temperature plunge in St. Louis) that support your claim.

REASONING: Explain the underlying scientific mechanism (density difference, pressure gradients, condensation as warm air rises) that connects your evidence to your claim, and explain why a probabilistic range is scientifically appropriate.

Performance Task • Page 2 of 2 Atmospheric Sciences • Middle School Summative Assessment

Performance Task Exemplars & Calculations

Part 1: Frontal Motion Calculations

• Q1 (Speed): \( \text{Speed} = \frac{310\text{ miles}}{24\text{ hours}} \approx 12.9\text{ to }13.0\text{ mph} \) (Accept 12.5–13.5 mph).
• Q2 (Arrival): \( \text{Time} = \frac{140\text{ miles}}{13\text{ mph}} \approx 10.7\text{ hours} \). Adding ~11 hours to Tuesday 12:00 PM yields an arrival window of Tuesday 10:00 PM to Wednesday 1:00 AM.
• Q3 (St. Louis Evidence): Temperature plunged 21°F (from 65°F to 44°F), and barometric pressure rose sharply from 999 mb to 1024 mb (+25 mb rise), indicating a dense polar air mass took over.

Part 2: Sample Atlanta Forecast Matrix

• Tue Evening: Temp: 68°F–72°F | Rain: 80%–90% | Wind: Shifting SW to W @ 20-30 mph | Heavy storms, gusty.
• Wed Morning: Temp: 46°F–50°F | Rain: 20%–30% | Wind: NW @ 15-20 mph | Overcast, lingering drizzle, clearing.
• Wed Afternoon: Temp: 52°F–56°F | Rain: <10% | Wind: N @ 10 mph | Crisp, sunny, clear skies, rising barometer.

Part 3: Exemplar CER Response

Claim: Atlanta will experience severe thunderstorms Tuesday night as the cold front arrives, followed by a dramatic drop in temperature (15-20°F) and clearing skies by Wednesday.
Evidence: The front traveled 310 miles in 24 hours (~13 mph) and is only 140 miles away. In St. Louis, the front caused severe weather, a 21°F drop, and pressure jumped from 999 mb to 1024 mb.
Reasoning: Dense cP air wedges under humid mT air over Georgia, forcing warm air to rise rapidly. As it rises, it cools and condenses into thunderheads. Probabilistic ranges are required because frontal speed can fluctuate based on pressure gradient shifts.

Mixed-Readiness Tiered Supports

Scaffolded Support (Tier 2 / Striving)

• • Sentence Starters: "My forecast predicts rain probability will be ___% because..."
• • Pre-fill arrival formula: \( \text{Time} = \frac{140}{13} = \_\_\_ \text{hours} \).
• • Provide a checklist of the 5 weather variables (temp, pressure, humidity, rain, wind).

Advanced Extension (Tier 3 / Accelerated)

• • Ensemble Modeling: Ask students why different computer models might predict slightly different arrival times (e.g., European ECMWF vs American GFS).
• • Topography Impact: Have students evaluate how the Appalachian Mountains might slow down or alter the front's trajectory toward Atlanta.

Teacher Assessment Guide • Lesson 3 (Predicting the Storm) Atmospheric Sciences • Middle School Curriculum