12-18-24 - Warm through the New Year + a visit with Craig Cogil from National Weather Service!

Dec 18, 2024

This episode is a long one, but so good, with a lengthy visit with Craig Cogil at the National Weather Service in Johnston. We're so grateful for all of Craig's time and insights!

Forecast Discussion

• A system moving through tomorrow will bring snow to northern Iowa, with 1-2 inches expected north of Highway 20.
• Strong winds and colder air will follow.
• The 8-14 day outlook shows high confidence in above-average temperatures, potentially reaching the 40s.
• There's a slight chance of above-average precipitation, likely in liquid form due to warmer temperatures.

Climate Trends

• December has been warming in recent years, with less snow and more mixed precipitation events.
• The beginning of December 2024 has been close to normal in temperature and slightly drier than average.

Recent Weather Events

• An ice storm occurred on Friday, December 13th, affecting areas including Omaha, Des Moines, and Ames.
• The timing of the ice storm during evening commute in Omaha led to significant impacts.

Forecasting Challenges

• Predicting mixed precipitation (sleet, freezing rain) is particularly challenging due to the complexity of temperature profiles and freezing lines.
• Small changes in temperature or location can significantly affect the type of precipitation experienced.
• Latent heat release during phase transitions can complicate forecasts by warming surface air more quickly than anticipated.

 

Tornado Climatology and Technology

• The conversation then shifts to discussing tornado climatology and the evolution of weather technology.
• The official tornado climatology database started in 1950.
• Early records (1950s-1970s) only noted tornado occurrences without ratings.
• In the mid-1970s, a project retroactively rated tornadoes from 1950 onwards using newspaper archives and photos
• The Fujita scale for rating tornadoes was introduced in the mid-1970s
• There's been an apparent increase in tornado numbers over time, largely due to improved detection and reporting methods

Radar Technology Evolution

• Weather radar technology evolved from repurposed World War II equipment.
• The first dedicated weather radar network, WSR-57, was introduced in 1957.
• This was followed by WSR-74 in 1974, which came in different frequency bands (S-band and C-band)
• S-band radars (10 cm wavelength) are better at penetrating heavy precipitation, while C-band radars (5 cm wavelength) are more easily attenuated