Could potential storm Isaac wreak havoc at Republican convention?


GFS model simulations showing a tropical system over Florida August 27-28 during the beginning of the Republican National Convention (StormVistaWxModels.com)

Before anyone gets alarmed or excited, consider forecasts of the path and intensity of tropical systems this far out have essentially no skill. As our tropical weather specialist Brian McNoldy said earlier: “In the 5-7 day period and beyond, weather details become fairly unpredictable.”

If this model defeats the long odds against it and is somehow right, organizers say they’re ready for the possibility of a hurricane Isaac during the convention according to a report from ABC News:

The Republican National Convention, Secret Service and federal, state and local authorities have been planning for a “multitude” of hurricane scenarios for “well over a year,” said Bryan Koon, Florida’s emergency management director. RNC spokesman James Davis would not give details of those plans, saying only that they are “focused completely on having a great convention.”

Since 1852, the Tampa area been hit by 27 hurricanes including 6 during the month of August the ABC News report said.

Colorado State University Tropical Meteorology Project has developed a tool that shows the historic probability of a named storm affecting the region around Tampa is 20 percent in any given season. The odds of a direct hit near Tampa is around 3 percent.

Jeff Masters of wunderground, who wrote a detailed blog post on the risk of a storm hitting Tampa during the convention, says the risk of a highly disruptive the storm that would trigger evacuations during the convention itself is smaller:

“[H]istory suggests that the odds of a mass evacuation order being given during the 4-day period that the Republican National Convention is in town are probably around 0.2%,” he wrote.

But if powerful hurricane did strike the Tampa Bay region - either during the convention or some other time - the effects could be devastating.

Climate Central’s Andrew Freedman ranked Tampa-St. Petersburg the most vulnerable U.S. city to hurricanes ahead of Miami and New Orleans. He noted 125,000 people live below 6.5 feet above high tide, which a large storm surge could overwhelm.

“In St. Petersburg alone, there are more than 45,000 homes that lie below 6 feet in elevation, and would likely be vulnerable to a storm surge of that magnitude or greater,” Freedman wrote.


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For the most part, the Tampa region has dodged the bullet with landfalling storms in recent years. While a number of storms have brushed the area, the last direct hit from a hurricane occurred in 1946 (a category 1 storm). Not since 1921 has a major hurricane (category 3 or higher) struck the region. The storm of October 20-21, 1921 produced a 10.5 feet storm surge which would cause massive flooding today, including at the convention site.

The bottom line is that Tampa is “due” in a sense to deal with a destructive hurricane. But the odds of a direct hit at any given time are very small.


European model simulation of where tropical disturbance or potential “Isaac” could be in 9 days, as illustrated by the different circles. (StormVistaWxModels.com/Matt Rogers)

The various members of the European forecast model “ensemble” (shown to the right) provide a fair representation of where this system might be in 9 days - essentially anywhere from the western Gulf of Mexico to the central Atlantic. There’s a huge spread.

In other words, this disturbance could harmlessly turn out to sea, even if it ever earns the name Isaac and becomes a formidable storm.

Inauspiciously, several storms beginning with the letter “I” have caused trouble along the Atlantic and Gulf coasts in the last decade, namely Isabel (2003), Ivan (2004), Ike (2008), and Irene (2011). The World Meteorological Organization retired all of these storms due to their toll on life and property.

The odds of a hurricane smacking Tampa during the convention may be long, but chances are if it does, another I-named storm will deliver the blow.

Jason is currently the Washington Post’s weather editor. A native Washingtonian, Jason has been a weather enthusiast since age 10.

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