It's a wrap - almost. September comes to a close this week. What can we expect weather-wise in the coming days? Meteorologist Sean Sublette has the details in this edition of Shift Ahead.More
If you’ve gotten sick of summer-like temperatures in the Northeast through September, fear not. A cold front – coupled with some serious tropical moisture and a ridge in Canada – is kicking them to the curb and setting up more fall-like conditions for the region starting on Tuesday.
Of course, the cooler weather also comes with a deluge soaking of rain. Up to 8 inches of rain is possible in that region over the next five days. The ground it will be falling on is dry as the East Coast has seen very little rainfall since August. That’s led to a 1,200-mile stretch of flash flood watches and warnings from North Carolina to Maine. What’s more, a tropical storm could spin up into the region this weekend or early next week, adding to the watery woes.
A complex set of factors is driving the seasonal shift. A cold front sweeping out of the Midwest will draw up tropical moisture from the Gulf of Mexico and Atlantic on Tuesday, providing the first dose of heavy rain. It will also cause temperatures to drop 10-20°F compared to Tuesday’s highs.
But rather than leave the region completely, the front will stall offshore thanks to a huge ridge of high pressure in Canada blocking its exit.
An atmospheric logjam like this is a recipe for extreme weather, and in this case, heavy rains will be the outcome as more rain streams up the Eastern Seaboard through the end of this week. The heaviest rain will be in the Appalachians and southern New England where a month-and-a-half of rain could fall in the next 5-7 days.
Heavy rainfall events are on the rise across the U.S., particularly the Northeast. The region has seen heavy rainfall events increase by 71 percent since 1958, the largest increase of any region in the country. [check your local climate trends]
That’s consistent with climate change projections, which show that a warmer atmosphere will hold more moisture. Eventually, the atmosphere reaches a breaking point and major deluges are the result. Last year, Pensacola, Fla. made headlines when a record-setting 15.55 inches of rain fell in a day including a one-hour stretch where 6 inches of rain fell.
While forecasts for the current system hitting the Northeast don’t indicate that Pensacola-levels of rain are likely to fall, the system is still cause for flooding concerns. On the bright side, the cooler, wetter weather will help the region out of drought and could help kickstart fall foliage season.
Oh, and about that tropical storm spinning in the Atlantic. Joaquin formed on Monday night, and while the Northeast is not in the National Hurricane Center cone of probability at this time, it could to see impacts this weekend. That hints at the loads of uncertainty about the storm’s track and NHC has “very low” confidence in Joaquin’s track and intensity at this time. Models show a wide spread of possibilities for the storm from making landfall anywhere between the Mid-Atlantic and Maine to curving out to sea in the next few days.
However, a number of models do steer it to the Mid-Atlantic and the storm is worth keeping an eye on into the weekend, especially as the forecast becomes clearer.
Sean Sublette contributing reporting to this article.