No sooner did the calendar crack May than we had to start worrying about a potential tropical system forming off the coast of the southeastern United States later this week. Anyone who lives near the coast from Florida to North Carolina needs to keep a close watch on this system. Here’s what you need to know to stay ahead of what could become Ana.

First thing’s first...

Hurricane season doesn’t begin until June 1, but every couple of years, we deal with tropical/subtropical storms forming in the Atlantic or Caribbean a few weeks before the season begins. Despite the impending end-of-the-world scare takes from certain websites, this is nothing new or unprecedented, nor is it a worrisome omen of danger to come this summer.

In fact, if this system becomes Tropical (or Subtropical) Storm Ana, it will form in the exact spot that storms should form in May if they form at all. Just take a look at some storms in recent history:

  • Tropical Storm Alberto formed off the South Carolina coast in May 2012, reaching peak winds of 60 MPH.
  • Tropical Storm Beryl formed in Alberto’s wake, in the same spot just a week or so later, with maximum winds reaching 70 MPH. Beryl is the storm pictured above, swirling just off the coast of Florida.
  • Tropical Storm Arthur formed off the coast of Belize in May 2008 with winds of 45 MPH.
  • Subtropical Storm Andrea formed off the coast of Georgia in May 2007 with 60 MPH winds.
  • Tropical Storm Ana spun-up near Bermuda in April 2003 with winds of 60 MPH.
  • Hurricane Alma developed in the Caribbean in May 1970, reaching category one status with 80 MPH winds.
  • Hurricane Able became a powerful category three hurricane with 115 MPH winds back in May 1951, coming very close to the Outer Banks of North Carolina.

If this storm joins the ranks, it’s rare, but nothing new.

The Setup

Now that we’ve gotten that out of the way, let’s take a look at the factors that could go into developing this system. There is an area of disturbed weather over the Caribbean at this hour, which is very slowly making its way north towards the southeastern United States. The disturbance will cross the very warm Gulf Stream as it interacts with relatively low levels of wind shear and high moisture, allowing it to develop into a low pressure system.

This morning’s run of the GFS model for Wednesday morning shows that the system should have (or be close to having) a closed low pressure center at the surface just off the eastern coast of Florida. It will gradually develop as it crosses the warm waters of the Gulf Stream, becoming either a subtropical or fully tropical storm. The GFS, for what it’s worth, shows the system developing a warm core through at least 500 millibars as early as Thursday morning.

A tropical cyclone is one that has a tight cluster of thunderstorms near its center that derives its energy from air heated by the warm waters below. Tropical cyclones are warm-core storms, meaning that the air through the center of the storm is warmer than the air outside of the storm.

A subtropical storm, on the other hand, is a cyclone that has both tropical and non-tropical characteristics. Subtropical storms aren’t completely warm-core systems, and the convection and strongest winds might be considerably displaced from the center of circulation. Subtropical systems are close enough to tropical systems that the National Hurricane Center assigns them names and issues forecasts/advisories on them.

Some subtropical systems manage to transition into fully tropical systems, and a couple have gone on to cause great amounts of damage. Last year’s Hurricane Fay was a great example of this—the system began life as a subtropical depression that strengthened into Subtropical Storm Fay, which transitioned into Hurricane Fay before making landfall in Bermuda.

Track

Assuming it develops, where will Ana wind up going? It depends on which model you want to believe. The latest run of the GFS brings it pretty close to the coast of the southeast before steering it into South Carolina, while this morning’s run of the European model shows the storm staying much farther off the coast and straying away from land before dissipating once it exits the influence of the Gulf Stream.

Tropical cyclone track forecasts have gotten much better over the years, but the system usually needs to form for the models and forecasters to get a better handle on where the storm will go. If you live anywhere near the coast in the Southeast, you need to keep a close eye on this system.

Effects

Even a relatively weak system could cause headaches (or worse) for people affected by the storm’s impacts. Here’s a quick look at what to expect if/when the storm forms:

High Surf/Rip Currents: Even if the system stays relatively far away from land, coastal areas will still be affected by high surf and rip currents. The risk for these two hazards will grow with the storm’s size and strength, so a stronger, larger storm will create greater oceanic risks than would a smaller, weaker system. Make sure you know how to survive a rip current if you’re heading to the beach later this week (or ever, really).

Heavy Rain: The threat for heavy rain grows the closer the storm gets to land. The latest rainfall forecast from the Weather Prediction Center shows that the storm could produce some pretty heavy rainfall just off the coast of South Carolina, which could easily nudge ashore if it makes landfall. Heavy rain over a short period of time increases the likelihood of flash flooding, which is especially dangerous for motorists. Please don’t drive through a flooded roadway—not only will your family suffer with your loss, but first responders will have to risk their lives to recover a corpse who didn’t quite make it.

Winds: Winds shouldn’t be too big of an issue in this case, but even marginally gusty winds can take down weak tree limbs and topple trees/power poles that are in loose, moist soil.

Tornadoes: In the event that the storm approaches shore, tornadoes can and do form in the rain bands of landfalling tropical systems. It’s a low risk at this point, but it’s another hazard that residents both on the coast and inland should keep an eye on, just in case.

Forecasts/Advisories

The National Hurricane Center doesn’t issue regular forecasts until hurricane season begins on June 1, but they’re issuing “special tropical weather outlooks” every day around 11:00 AM EDT until this system forms or dissipates.

If it does develop, the NHC will issue forecasts and advisories at least every six hours, but they’ll bump the frequency up to every three hours if it’s close enough to land. And, as always, I’ll have updates and analysis here at The Vane as warranted, if you’re into that sort of thing. (You are.)

[Images: NOAA, NASA, Tropical Tidbits, author]

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