Could it be #13 over the horizon?

View of the southeastern USA and adjacent Atlantic waters from the GOES satellite, on 5 September 2011, showing tropical cyclones KATIA and LEE

An active month of August, in tropical cyclone terms, is over and now as we move forward into September the  most active month of the season, based on the historical record, a few things are happening in the Atlantic basin.   Tropical storm LEE continues its rather slow march toward the northeast dumping copious rain over Louisiana, Mississippi, Alabama, Tennessee, the Florida panhandle, Georgia and the Gulf of Mexico. KATIA is once again a hurricane as it moves northwest and begins a slow turn to the north and eventually the northeast.

Color-enhanced infrared satellite view of most of the tropical Atlantic basin where in addition to active tropical cyclones KATIA and LEE we also see a large tropical wave moving westward along hurricane alley

Looking east toward the far-away eastern Atlantic, there is a large tropical wave some 500 kilometers southwest of the Cape Verde Islands moving westward over hurricane alley, which appears to be getting stronger and better organized as it progresses toward a favorable environment of warm waters and low wind shear ahead. Will this be the 13th named tropical cyclone of the 2011 Atlantic hurricane season? Where will it be two or three days from now? How intense will it be then? Does it pose any threat to the USA? These are all valid questions, which meteorologists and scientists at NOAA will be trying to answer as they monitor and track this system in order to issue three and five-day forecasts once, and if, this system becomes a tropical cyclone. For now suffice it to say that the National Hurricane Center and other divisions of NOAA are already watching this specific tropical wave closely, and so will we.

Atlantic-wide water-vapor satellite view showing tropical cyclone activity on 5 September 2011

In fact, we will continue monitoring this specific tropical wave so that we can report any development that could be of interest to vulnerable communities in the Caribbean and Gulf sub-basins, and in the coastal USA along the Atlantic. Toward that end we will also continue to keep an eye on the rest  of the tropics in the Atlantic and on a worldwide basis to share any knowledge gained from our observations.

Composite full-disk satellite view of Earth's western hemisphere, on 5 September 2011, showing a disconitnuity in the so-called 'belt of tropical activity' that normally circles the planet this time of the year

Speaking of sharing knowledge, I believe it is interesting to share that today there appears to be a “break” in what I have named the belt of tropical activity that usually circles the entire planet during the northern hemisphere summer. We had seen a branching of the belt earlier this year, with a secondary branch going off toward the northwest and then north over the central Atlantic. Today, 5 September 2011, we see that same “branch” chasing after Hurricane Katia, but there is also a cut-off of the belt in the middle of hurricane alley leaving a discontinuity all the way to northern South America where the belt starts again and continues around the Pacific and beyond. I believe this specific condition is a reflection of how active the tropics have been this year, while it also highlights the difficulties associated with forecasting where one specific storm will go or how strong it might be five days from now, which in turn makes us all admire how accurate most predictions of Atlantic tropical cyclones’ center tracks have been in 2011 as well as how much track predictions have improved in accuracy over the past ten years.

Relative to how much NOAA’s hurricane center-track forecasting has improved in recent years, and how such improvement contributes to much more effective decision-making by the emergency management community in hurricane-vulnerable communities along the coastal USA, I found it somewhat disheartening that some media chose to highlight the somewhat inaccurate forecast of the intensity of Hurricane IRENE as it approached the northeastern USA rather than the quite accurate track forecast that allowed many communities to avoid evacuations of the coastal region and many more to prepare with plenty of time for the upcoming impact. This only shows how much there is still to learn about what an impact of a hurricane really means, and how the fixation on a number in a scale can be so misleading with respect to what damage to expect from the impact of a hurricane. We certainly have seen our share of “minor” hurricanes or “just a category 1”, so-called by the media, which have caused enormous damage and unheard of human suffering. In fact hurricane IRENE is one such example; as of today damages have reached more than $13.0 billion, the death toll is nearing 50, and close to 1.0 million residents along 13 states still remain without electrical power on this 2011 Labor Day. I would argue the media would do well in learning more about what we all need to do to improve how to inform a vulnerable public about what the impact of an approaching hurricane could bring to a given community, something that the Saffir-Simpson scale was not designed to do, rather than on the difficulties that remain in hurricane-intensity forecasting. NOAA is the first to acknowledge that much work remains to improve intensity forecasting, and it is working hard in continuing to improve in this regard.

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One Response to Could it be #13 over the horizon?

  1. Ricardo says:

    Well, I believe Mother Nature is addressing the question I posed on my posting above; the tropical wave riding along hurricane alley has now been classified as a tropical depression by the National Hurricane Center and it is expected to become a tropical storm within the next 24-48 hours. Conditions ahead of the projected track appear favorable for further development beyond that time frame. Initial forecast-model runs indicate a center track just north of the Virgin Islands and Puerto Rico and a generally west by northwest progress over the next 3 to 5 days. But, as it’s been pointed out before there is wide uncertainty beyond thethree-day forecast, so we’ll have to wait and see how various atmospheric components interact and affect the area of influence surrounding this storm. We’ll keep you posted. In the mean time all interest in the Antilles, the Bahamas, Florida and the Mid-Atlantic USA need to monitor this system carefully over the next few days.

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