Tropical Development Possible as Dying Front Stalls off the Southeast Coast

Jon Erdman
Published: July 22,2015

The 2015 Atlantic hurricane season has taken a bit of a backseat to a hyperactive Pacific Ocean, at times, featuring up to six tropical cyclones at once recently.
Despite that, we're watching an area near the Southeast U.S. coast for potential development in the coming days.
(MORE: Expert Analysis | Hurricane Central)
Let's break down what we know now.

Setup For Potential Tropical Development

 

 

 

 

 

 

 

 

The Setup

Meteorologists look for patterns in both upper-air and surface computer model forecasts when identifying potential weather scenarios in the extended range, say, beyond three days or so.
(MORE: What to Expect in July in the Tropics)
Heading into the final week of July, one such pattern, in particular, is drawing our interest.
A frontal boundary is expected to stall out from near Bermuda southwestward to near the northwest Bahamas, across the Florida peninsula to the eastern Gulf of Mexico.
These boundaries help focus clusters of showers and thunderstorms over the mainland in the spring, summer and fall, and the same can be true, at times, in the Gulf of Mexico as well as the subtropical Atlantic basin.
Computer guidance also suggests a weak area of low pressure in the upper levels of the atmosphere may form near the Florida peninsula or eastern Gulf of Mexico. This upper-level spin may help boost the formation of showers and thunderstorms.
The front's location over the warm Gulf stream and northeast Gulf of Mexico water only adds low-level warmth and moisture to the air, increasing instability, or the ability to generate convection.

Origin locations of Atlantic Basin named storms from July 21-31, based on climatology since 1950. Note the number of tropical cyclones that have formed in late July in the Gulf of Mexico and southwest Atlantic Ocean, off the Southeast coast of the U.S.

Rainfall Forecast

One or more areas of low pressure may eventually form at sea level along that stationary front somewhere off the Southeast coast or in the eastern Gulf of Mexico.
If a cluster of showers and thundershowers can














develop in the same place as a low-pressure center and persist, it may eventually develop into at least a tropical depression by next week.
If one does form, it may get drawn north or northeastward, but it is far too soon to speculate which areas may be affected next week.
Regardless of whether a tropical depression or storm develops, thunderstorms may be more numerous, particularly during the afternoon and evening, from the eastern and northern Gulf Coast into Florida this weekend into next week, with a threat of locally heavy rain and flash flooding.
(FORECASTS: Orlando | Daytona Beach | Destin)
This is a relatively common early-season pattern known to generate tropical cyclones near the U.S. coast.
Despite high wind shear squashing any chance of tropical development in the Caribbean Sea, the Atlantic Basin has manufactured three named storms so far this season, all either close to, or landfalling in, the U.S.
On Mother's Day weekend, Tropical Storm Ana was the earliest East Coast landfall on record.
A little more than a month later, Tropical Storm Bill soaked an already saturated southern Plains, Ozarks and Ohio Valley.

2015 Atlantic hurricane season named storm tracks, as of July 21, 2015.

Finally, a disturbance that originated from a Midwest thunderstorm cluster sprouted convection over the Gulf Stream and developed into Tropical Storm Claudette on July 13.
Last July, Hurricane Arthur formed in this same general area, off the southeast U.S. coast, pounding eastern North Carolina and southeast Virginia on the July 4th holiday weekend.
If you have vacation plans next week from the northern and eastern Gulf Coasts to Florida and the Southeast coast as far north as the Outer Banks of North Carolina and southeast Virginia, don't cancel them yet.
But, do check back with us at weather.com, Weather Underground, and The Weather Channel for the latest on this situation.

MORE: Tropical Storm Ana - May 2015