Academic journal article Journal of College Science Teaching

Cancel the Cardinals Home Opener?! Lessons in Melting and Evaporation

Academic journal article Journal of College Science Teaching

Cancel the Cardinals Home Opener?! Lessons in Melting and Evaporation

Article excerpt

The St. Louis Cardinals are scheduled to play their home opener the next day and Megan Riley, a young meteorologist who works for a private weather consulting firm, is responsible for developing the weather forecast. It's looking like she may need to change her prediction from rain to snow. Students work in groups to analyze information presented in each part of this interrupted case and decide whether they want to update their forecast: keep it as rain, or revise it to snow.


The case

Part I -- The problem

Megan Riley, a meteorologist with Weather Innovations, Inc. (WINC), had just arrived on the evening shift. The time was 3:30 p.m. on April 9th. Among the locations for which WINC (and Megan) needed to create a forecast was St. Louis, Missouri. When she had left the night before, her two-day forecast included rain for St. Louis, but it didn't look like enough to spoil the home opener for her favorite baseball team, the Cardinals. Now a day later, with the opening pitch less than 24 hours off, Megan was more concerned.

"What do you think about snow in St. Louis?" Megan asked Sean, her supervisor.

He shook his head. "No way, Meg. It's gonna be too warm. It was awfully cold last night, but a warm front is approaching quickly from the south. That warm air will arrive later tomorrow, but the clouds tonight will trap enough heat to make whatever falls come down as rain."

"But the surface layer is still really dry," Megan replied. "All the way up to about 1,200 meters."

"And ...?" Sean demanded.

Sean could be a little intimidating, but Megan charged ahead, undaunted.

"And the wet bulb temperatures are near freezing across that area," she replied. "Plus, wet bulb temperatures don't change much with height over St. Louis."

"Do you realize that it's mid-April, in St. Louis, and you're talking about snow?" Sean pressed her.

"Yes, I do," Megan replied. "But I'll show you the analyses I've done so far. Really Sean, we could have a rain-to-snow changeover in St. Louis during the night."

"Well, we'll both be in hot water if you're wrong, Meg," he said. "We've got a lot of St. Louis contracts, including your beloved baseball team, those Redbirds. There's a lot on the line.... I'll give you until 6 p.m. to prove it. See me then."


* What is Megan concerned about?

* What information does the wet bulb temperature provide?

* How can the wet bulb temperature influence precipitation type?


Part II -- Making a convincing case for snow, 6 p.m.

Most of the St. Louis news broadcasts were already on the air, including Megan's TV station client, and they were reporting her earlier forecast of rain. That particular station didn't have a trained meteorologist on staff. They had opted instead to use a "weathercaster" who had great delivery--and no sense whatsoever for the science involved. It might not have been the best move for the station, but it kept Meg employed. As it was, this weathercaster was still using Megan's old forecast. "Not a problem," she thought to herself. "There's still the 10 o'clock news." Megan collected her notes and went to find Sean.

As Megan prepared herself to see her supervisor, she reviewed her argument. The weather map showed that St. Louis was still under the influence of a high pressure system, but it was retreating toward the east. Fronts and a new storm center loomed over the Rockies, and radar had detected precipitation already in northwestern Missouri, although it wasn't expected in the St. Louis area until dawn the next day (see Figure 1).

Megan also noted the surface conditions at 6 p.m. in St. Louis, where the temperature was 42 degrees Farenheit and the dew point temperature 17 degrees Farenheit. This was a rather large dew point depression, but it also meant a surface wet bulb temperature of about 33[degrees]F. …

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