It came close to happening about 10 days earlier in North Philly. But this time the storm cluster was even bigger, stronger, and slower moving.
According to the Iowa, Northeast Philly Airport got 2.42 inches of rain out of their total of 3.99 inches in just ONE HOUR, between 5 and 6 p.m. That’s a record for that spot. Yet that was about 7 miles from the maximum rainfall spot in Croydon of 10.28 inches.
The below graphics from the NBC10 radar were about four hours apart. That’s not much movement!
And this is the National Weather Service graphic showing the radar estimates of rain totals:
And here is the NBC10 version with the cities labeled more clearly:
A rare FLASH FLOOD EMERGENCY was issued by the National Weather Service due to the life-threatening nature of the flooding. This was no “typical” flash flood. In fact, the NWS estimated this to be a “100-year flood." That means the odds of this happening are only one percent in any given year.
MORE TO COME?
The answer to that question is “yes," but not likely this week. The atmosphere is drying out a bit, and any storms that do develop have a better chance of actually moving.
In the longer term, the warming climate will cause these types of floods to become more numerous and even more extreme. It’s simple science: warmer air holds more moisture, which gives us the potential of heavier rain. This is NOT “the new normal” as some people call it. The “normal” 20 years from now will feature more flash floods, with more records falling.
Speaking of records, my research has shown the following at Phila. International Airport:
PHILLY RAIN RECORDS SINCE 2010
This is no coincidence. This was not a “freak event." Events like this are localized (some parts of the Philly area didn’t even get a drop of rain yesterday). But we keep “loading the dice” to come up “flash flood” more and more in the years and decades to come.