Friday, May 27, 2016

Tropical or Subtropical Development off Southeast Coast Becoming More Likely

May 27,2016
An area of low pressure northeast of the Bahamas may become a tropical or subtropical depression or storm Friday into the weekend, and may soak parts of the Southeast coast during the Memorial Day weekend.
On Friday morning, the National Hurricane Center (NHC) said that this system now has a 90 percent chance of developing into a subtropical or tropical depression or storm in the next two days. The Air Force Reserve is scheduled to send a plane on Friday afternoon to gather information on the developing low pressure system.
The area of interest has also been designated as Invest 91-L by the NHC. This naming convention is used by the NHC to identify features they are monitoring for potential future development into a depression or storm.
(MORE: What is an Invest?)
Here's what we know right now.
(MORE: Atlantic Hurricane Season Forecast)

Tropical or Subtropical Development Factors

A surface low pressure system has developed northeast of the Bahamas and is moving towards the northwest. This low pressure system is one of the ingredients required for a tropical or subtropical depression or storm to form. The other ingredient is persistent shower and thunderstorm activity collocated with the low.

Current Satellite View
Thunderstorm activity should organize around that central of circulation throughout the next day or so. This will be partially due to weakening upper-level winds as the system moves in the general direction of the Southeast coast. Slightly cooler water temperatures may limit intensification on Saturday.

Computer Model Track Forecast
While most computer model forecast guidance depicts that a low pressure system will move toward the Georgia or South Carolina coastline, there remains questions about how well organized it will be. The low will be passing over the warmer waters of the Gulf Stream, and environmental conditions are generally favorable for development.

What is the Upshot of All of This?


Saturday Forecast
No matter whether a tropical or subtropical depression or storm develops or not, there will likely be some impacts along the Southeast coast.
Those impacts will mostly be increased rainfall and the potential for rip currents and high surf for parts of the Southeast coast during the Memorial Day weekend.
(MORE: Holiday Weekend Outlook)
If you have plans to hit the beach along the Southeast coast this holiday weekend, we don't suggest canceling plans yet. Check back with us at weather.com. We will continue to watch this situation closely, and will provide updates over the next few days.

Sunday Forecast
(FORECAST: Virginia Beach | Hatteras | Myrtle Beach | Daytona Beach)
The next named storm of the 2016 Atlantic Hurricane Season will be given the name Bonnie.
If you recall, we already had the “A” named storm this season. Hurricane Alex was a rare January storm that formed in the eastern Atlantic Ocean and impacted the Azores.
(MORE: Florida's Lucky Hurricane Drought)

Southeast Coast is Typically an Early Season Area to Watch

This map shows the typical formation areas and tracks for named storms in June.
The area off the Southeast coast, as well as the Gulf of Mexico and northwest Caribbean, is a part of the Atlantic basin where early-season tropical or subtropical storm development is most likely.
That said, it's not a very active time of year for storms to form compared to the peak August-October period. For example, only one named storm forms during June every other year, on average.
(MORE: Where June Storms Develop)
Recent seasons have had activity before the start of June.
Last May, Tropical Storm Ana formed off the Southeast coast before making landfall near Myrtle Beach, South Carolina, with minor impacts.
In 2012 two named storms, Alberto and Beryl, formed during May off the Southeast coast. Beryl would go on to make landfall in northeast Florida, while Alberto moved out to sea.
(MORE: When Hurricane Season Starts Early)

Difference Between Subtropical and Tropical Storms

A subtropical depression or storm exhibits features of both tropical and non-tropical systems, with a broad wind field, no cold or warm fronts, and generally low-topped thunderstorms spaced some distance from the center.
Subtropical cyclones typically are associated with upper-level lows and have colder temperatures aloft, whereas tropical cyclones are fully warm-core, and upper-level high-pressure systems overhead help facilitate their intensification.
Because of this hybrid nature, the National Hurricane Center still issues advisories and forecasts (i.e. projected path) for subtropical depressions and storms and assigns a number or name much like a regular tropical depression or tropical storm.
Occasionally, if thunderstorms cluster close enough and persist near the center, latent heat given off aloft from the thunderstorms can warm the air enough to make the storm a fully tropical storm.
When that happens, the wind field will tighten closer to the center. Of course, this would also open the door to further intensification.

MORE: Hurricanes From Space - Satellite Imagery

No comments:

Post a Comment