AMS Minutes: October 18, 2016
The University of Georgia Chapter of the American Meteorological Society welcomed speaker Steve Nelson on September 18, 2016 in the Geography Building on the UGA campus. Chapter-funded food was served as chapter members assembled, and Mr. Nelson prepared for his presentation. The meeting was called to order at 5:30 PM by chapter president Ian Boatman.
President Ian Boatman began the meeting by reminding those going to the upcoming AMS conference to finish their registrations for the conference. He then introduced the guest speaker, Steve Nelson, who is the Science and Operations Officer at the National Weather Service office in Peachtree City. He is a forecaster, but he also researches computer systems and helps develop weather models for the National Weather Service. Furthermore, he studies local severe weather events and winter weather occurrences.
Mr. Nelson spent the majority of his presentation discussing the severe flash flooding that took place in Athens, Georgia this past August. There were actually two events that caused this flooding; one took place on the evening of August 17th and the other took place the following evening on August 18th. To begin, Mr. Nelson showed many of the models used by the National Weather Service that reflected the data of the radar and various derived products from that evening. He then proceeded to describe how the forecasted setup did not coincide with the severe flooding events that transpired. In fact, the National Weather Service was only predicting approximately .10 inches of rain on each of these days. Mr. Nelson then went on to discuss the mathematical equation behind flooding; he showed that the combination of foreword motion and storm propagation cancels out the movement of the storm and can cause rain to persist for hours. This similar setup took place in Athens, Georgia on the evenings of August 17th and 18th. Mr. Nelson showed an atlas chart that provides a general guideline for issuing flood warnings based on time and rainfall amounts. Based on the table and climatological data, he admitted that the Peachtree City office fell short in issuing a timely flash flood warning for this event. Mr. Nelson explained that major issues that could have contributed to this slow response were the temporary short staffing of their National Weather Service forecast office, and the fact that the greatest severity of the event occurred during the shift change at the office. Nonetheless, he reiterated that neither of these factors should have lead to the late warning.
Mr. Nelson noted that although this was certainly a flash flooding event, the impacts on the affected area could have been much worse. The Athens region really only experienced a handful of isolated effects. For instance, there was a road closure that lasted for a few hours, and a bowling alley that collapsed due to water loading. He reiterated that the combination of the amount of rain that fell in such a short time with the hilly Athens terrain could have made for a much worse scenario. Mr. Nelson finished his presentation by briefly discussing various opportunities for students interested in working for the National Weather Service, from volunteering to collaborative research to scholarships. Finally, he took a few questions from chapter members and stayed for a group photo.
President Ian Boatman adjourned the meeting at 7:00 PM.
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