2013 Hurricane Season: Where do we stand?

BATON ROUGE, LA (WAFB) - So far, so good.

But a quick review of the 2013 season through the end of July shows that the tropics are off to a relatively busy start in the Atlantic Basin, supporting the pre-season consensus projections for another busy Atlantic Hurricane Season.

Two storms have already visited the Gulf -- T.S. Andrea and T.S Barry -- but neither was a landfall threat for the Bayou State. Andrea rolled into Florida's Big Bend, making landfall on the evening of June 6th with peak winds estimated at a respectable 65 mph; Barry made landfall on the Mexico Gulf Coast on June 20th near Veracruz with maximum winds of 45 mph.

The Gulf has been 'quiet' through July, but this is no time to let your guard down. From a historical perspective, the season hasn't really started yet. If tomorrow was October 1st, that would be one thing. But a sports analogy with the current tropical timeline suggests that the "regular season" is only just about to begin, with the "playoffs" more than a month away.

True, Louisiana's has suffered some early-season tropical bombs in the past, most notably 1957's Audrey. But 1-in-5 of Louisiana's landfalls occur in August with nearly half (47%) of Louisiana's tropical hits coming in September.

The past three hurricane seasons -- 2010, 2011 and 2012 -- have been very active in the Atlantic, with 19 'named' storms in each of the seasons. That number '19' is not only well-above the long-term average of '11' posted by the National Hurricane Center (NHC), but it ties as the third highest storm count ever for the Atlantic Basin! Back-to-back-to-back ... the three prior seasons rank among the six 'busiest' hurricane seasons in more than 100 years. That has got to make you sit up and take notice!

And then, when we compare the current storm count through July 2013 with those three prior seasons through the end of July (Table 1, attached), one can't help but conclude that we are on a path for another very busy season.

As many as 19 storms for 2013? Well, probably not. (Wonder what the Vegas odds are running for a 4th consecutive season with 19 'named' in the Atlantic? Even the 3-in-a-row must have paid-off nicely!)

But something in the mid to upper 'teens -- as called for by a number of prognosticating groups -- sure seems like a solid bet.

There is something else to notice about our busy seasons of 2010, 2011 and 2012: while storm counts were quite high, the number of Gulf 'visitors' tended to run below expectations from a purely statistical sense.

On average, roughly 1-in-3 'named' storms spend at least some time in the Gulf of Mexico. With 19 'named' storms, those statistics imply that we would expect 6 or more storms in the Gulf. Yet the numbers in the Gulf for all three prior seasons were well-below that.

Part -- but certainly not all -- of the explanation may be attributed to the position and strength of the Atlantic High.

The Atlantic High is a surface high pressure system that shifts position as well as expands and contracts through the course of the tropical season. It is a major "steering" feature for tropical systems -- tropical storms and hurricanes tend to 'run around' the outer edge of the high.

An expanded, well-developed Atlantic High tends keep low-latitude tropical systems (those closer to the equator) running along an east-to-west track, often sending them into the Caribbean and eventually the Gulf. However, when the Atlantic High contracts (shrinks in size) or shifts towards the eastern Atlantic, tropical systems will often begin to turn to the northwest and north sooner, often missing the Caribbean, the Gulf and with a little luck, even stay out over the 'open' water and miss the U.S. Eastern Seaboard.

A review of the tropical track maps for 2010, 2011 and 2012 shows that a majority of 'named' storms in those three seasons tended to form over -- and remain over -- the open Atlantic, suggesting that the preferred configuration of the Atlantic High for much of the time during those three seasons was a 'contracted and/or eastward-shifted' high pressure center.

But the role of the Atlantic High is steering storms must be examined on a storm-by-storm basis.

During 2010, a series of systems did track through the Caribbean, indicating periods of a well-developed ridge of high pressure which drove these storms directly into Central America before they had chances to re-curve towards the Gulf. (Louisiana suffered no tropical 'hits' in 2010.)

2011's T.S. Lee was a serious rainmaker for Louisiana and much of the eastern U.S. -- but remember, Lee formed in the Gulf, and well, had to go inland somewhere.

Then there is unforgettable Isaac in 2012, a storm that seemed almost destined to hit Louisiana as it slowly tracked on a near-direct northwestward path towards us.

Those storms considered -- showing that Louisiana didn't go unscathed during these three seasons -- one still might conclude that Gulf tropical activity was somewhat lower than expected given the overall basin activity for the past three hurricane seasons.

So what's the take-away?

So far this season, the Atlantic High has been showing some signs of leaning towards an "expanded, westward-shifted" configuration that increases the potential for storms getting into the Gulf. Of course, there are no guarantees on how the Atlantic High might behave in the coming months -- and unfortunately, our forecasting skill for the size and location of the Atlantic High barely extends out more than 7 to 10 days.

But the two latest storms of the 2013 season -- Chantal and Dorian -- both tracked along west-northwest paths, indicative of a solid steering component to their north. Even over the past few days, the remnants of defunct Dorian continued to slowly move to the west, a sign that the Atlantic High was still a steering factor.

As we get into the heart of the hurricane season -- August, September and October -- we could see more storms showing signs of becoming Gulf 'visitors' compared to the recent past.

So let's remain watchful -- and review our family and business preparedness plans -- while the Gulf behaves, if only for the time being.

We've had two Gulf storms already in 2013, but they may just be the equivalent of a "pre-season" warm-up.

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