Joaquin may converge with another slow-moving storm in the East to add to a serious flooding situation into early next week.
According to AccuWeather Chief Meteorologist Elliot Abrams, “The dry spell and local drought conditions will be washed away by heavy rain and flooding.”
Small stream and urban flooding are a given in this case. How significant river flooding becomes will depend on duration, intensity and location of the subsequent rounds of rain.
The nearly week-long pattern has the potential to put some neighborhoods of major cities under water and can flood some communities along streams.
According to AccuWeather Meteorologist Brett Rathbun, “Very heavy rainfall fell across a large portion of the East on Tuesday, causing localized flash flooding.”
Joaquin Becomes a Hurricane
“Rainfall amounts between 3 and 5 inches fell across western Pennsylvania, including Pittsburgh,” Rathbun said. “Rainfall amounts between 2 and 4 inches fell across parts of Virginia.”
Cumulative rainfall through Monday may reach 1 foot in some places.
The rainfall will occur in several stages through early next week. Each stage will bring the risk of flash and small stream flooding. Each subsequent stage will increase the coverage and severity of flooding, as well as the extent of travel delays and disruptions to outdoor activities.
The first round of drenching rain, associated with a slow-moving storm, will sweep steadily northeastward through Wednesday. Much of this rain will be absorbed by the dry ground. However, too much rain will fall too fast for the ground to totally absorb in all areas.
This first batch of rain will deliver 1-3 inches and is forecast with locally higher amounts.
During the first batch, the heaviest rain will fall across New England and neighboring Canada on Wednesday.
According to AccuWeather Senior Meteorologist Brett Anderson, “From part of Maine to portions of New Brunswick, Nova Scotia and Prince Edward Island, up to 6 inches (150 mm) of rain will produce significant flooding and potential road closures into Wednesday night.”
A break in the rain is likely from late Wednesday through Thursday across the Northeast. Water levels on small streams will recede, while some of the major rivers will begin to rise a bit.
The second round of rain will begin right along the Atlantic coast and will spread slowly westward from Thursday afternoon through Saturday.
This second batch is likely to cause significant urban flooding and major travel delays from Raleigh, North Carolina, and Norfolk, Virginia, to New York City and Boston, as well as farther west to part of the Interstate 81 corridor.
Rain will collect on streets and highways, while low cloud ceilings and poor visibility will impact flights in and out of the major airports.
Where the soil became saturated with the first round, more rapid runoff and small-stream flooding will occur. Noticeable rises are likely along the Delaware, Susquehanna, Connecticut and Potomac rivers. However, still water levels along many of the major rivers may stay below flood stage through Friday.
Football fans heading to area high school and college football games may not only have to contend with pouring rain, but also muddy parking lots.
Joaquin’s impact may come into play during the third round of rain, which could arrive sometime between Sunday and Monday.
Joaquin became a Category 1 hurricane on Thursday morning and will remain a hurricane as it brings rain and wind to the central Bahamas.
By Thursday afternoon, Joaquin will begin to track northward and will strengthen to a Category 2 hurricane sometime between Thursday night and Friday.
There is the potential for another round of small stream flooding and perhaps flooding of unprotected areas along the major rivers. River flooding is often delayed and may not occur until after all of the rain has ended.
While the situation is not likely to become another Sandy, Irene or Isabelle, coastal flooding is a significant threat from the Carolinas to Maine, including in some of the inland bays and tidal rivers.
Satellite Loop of Joaquin (Image/NOAA).
The period from Saturday into next Tuesday will bring onshore winds strong enough to cause coastal flooding, beach erosion and rough surf. How severe this becomes will depend on whether a non-tropical storm acts alone or joins forces with Joaquin or its moisture.
Those along the immediate East Coast from North Carolina into southern New England should make preparations for coastal flooding regardless of Joaquin.