The National Hurricane Center confirmed the development of both Tropical Storm Lee and Tropical Storm Maria Saturday, the 12th and 13th named storms of the 2017 hurricane season. Lee and Maria join Category 1 Jose, making this the second time this season with three named storms in the Atlantic Basin at the same time.
The long-term average for the Atlantic Basin is 12 named storms for the entire season, so we are well ahead of normal.
With 13 named storms as of September 16, this is the earliest date that the Atlantic Basin has reached the "M" storm since 2012. In that season, Leslie, Michael, and Nadine had all formed by mid-September. Not surprisingly, 2012 was a very active year, closing that year’s hurricane season with 19 named storms.
Over the previous dozen hurricane seasons (2005-2016), the only additional years to be this far ahead of the curve by mid-September are the 2011 and the record-smashing 2005 hurricane seasons. Because of the practice of recycling storm names every six years, we end up with the eerie coincidence of near-identical storm name lists for 2005, 2011, and this year. Differences are attributed to retirements: five retired storm names in 2005 (Dennis, Katrina, Rita, Stan, & Wilma) and one retired name in 2011 (Irene).
Lee, Maria, and Nate had all formed by mid-September in 2011, a season that ended with 18 named systems in the Atlantic. In the 2005 season, when six storms were labeled from the Greek alphabet because the 21-name list was exhausted by mid-October, Lee, Maria, Nate, and Ophelia had all formed by mid-September.
While most hurricane prognosticators were anticipating a near-to-above normal season back in the spring, we are currently on a pace to out-run most, if not all, of those pre-season forecasts.
This year's tropical activity got off to an extra early start thanks to Tropical Storm Arlene in April. By the end of June, the basin had produced three named storms already, including Louisiana's landfalling T.S. Cindy. Since August 1, activity has really kicked into high gear, with six consecutive tropical cyclones reaching hurricane strength, including three major storms Harvey (Category 4), Irma (Category 5), and Jose (Category 4).
While Harvey's lead story is the record rainfall dumped in Texas, we should not forget that Harvey made a second U.S. landfall in Louisiana, producing additional flooding rains in western sections of the Bayou State.
With two landfalls (Cindy and Harvey) already this season, Louisiana has more than made up for the four prior landfall-free seasons (2013-2016). Unfortunately, there remains plenty of time for a third “hit” before the end of November. A third landfall? That is not unprecedented: there have been five seasons since the mid-1950s with three or more landfalls for Louisiana, led by four strikes in 2002. Yet a look at Texas and Florida reminds us that the Bayou State has been spared from a true tropical disaster so far this season.
The Gulf of Mexico has had more than its share of storms already in 2017, with a half-dozen named storms already this year. On average, only about one-third of all Atlantic tropical systems form or track into the Gulf, so this year’s numbers through mid-September -- two tropical storms and four hurricanes -- are above the long-term average for a full season.
While we have passed the unofficial mid-point of the hurricane season (September 10), indications are that we should not anticipate a rapid drop-off in activity anytime soon. While not excessively warm, SSTs (sea-surface temperatures) are running a bit above normal for this time of year over the vast majority of the tropical Atlantic. In addition, we are still several weeks away from the ramp-up in mid-level wind shear that commonly occurs during the back-end of the hurricane season.
Let us be hopeful for a rapid shutdown in activity for 2017 but remain vigilant and prepared for another unwanted tropical visitor before the season ends.
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