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It's August 15th

August 15, 2016

75 days in, five storms down, the 2016 Hurricane Season may still just be getting started. Colorado State hurricane expert Dr. Phil Klotzbach pointed this out Sunday on Twitter.


NOAA updated their seasonal forecast Thursday, stating that 2016 is likely to be the most active Atlantic hurricane season since 2012. Records have already been broken this year, but NOAA says an additional 7 to 12 named storms are still possible, of which three to six may become hurricanes.


Why August 15th

The official start of the Atlantic Hurricane Season was June 1st, but there is a notable rise in the frequency of activity after August 15th.  Nearly two-thirds of all hurricanes in the Atlantic Basin develop between August 15 and October 15th.


Storm Frequency-FPBS


The main reasons for the annual uptick in activity are warmer waters, more favorable atmospheric conditions, and an increase in tropical waves moving across the Atlantic. However, it’s not always that simple.

Uncertainty is higher than normal this year, as indicated by NOAA’s five-storm spread in predictions. The average margin of error on tropical storm forecasts is three in an August update. [1] One of the main reasons for the uncertainty is the potential development of La Nina, which is the opposite phase of an El Nino pattern. During La Nina, favorable atmospheric conditions tend to develop in the Caribbean and Western Atlantic, which in turn enhances tropical cyclone activity. At the season’s start, climate models suggested a nearly 80% chance of La Nina formation by the fall. That confidence has recently slipped to just 55-60%.[2]


La Nina Forecast-FPBS


Dr. Gerry Bell, lead seasonal hurricane forecaster at NOAA’s Climate Prediction Center, says many storms may not survive the trip across the Atlantic this year.

“Less conducive ocean temperature patterns in both the Atlantic and eastern subtropical North Pacific, combined with stronger wind shear and sinking motion in the atmosphere over the Caribbean Sea, are expected to prevent the season from becoming extremely active.”


What to Look for Next

Reliable weather models are beginning to show an uptick in convection associated with tropical waves moving off the west coast of Africa in about 6 to 10 days. This is very normal this time of year, and many meteorologists refer to it as the “Cape Verde Season” since the waves usually pass just to the south of the Cape Verde Islands. Whether or not the waves are able to survive the long journey across the Atlantic and mature into a cyclone is largely determined by day-to-day fluctuations in pressure and wind patterns at the time.




Large amounts of shear, the difference in wind speed or direction with height, is one of the most common (and most recent) explanations for why a tropical storm or hurricane struggles to strengthen or even fails to survive. The recent dissipation of El Nino has resulted in less shear across portions of the Atlantic Basin overall, but other factors such as water temperatures and the presence of dry air aloft can also play a role in inhibiting tropical cyclones. Regardless, even a “near-normal” year might seem more active to some considering how relatively quiet the previous three seasons have been.

Even during an inactive season, major hurricanes can form and leave a lasting impact. Examples of this include Hurricanes Andrew (1992) and Alicia (1983), which are constant reminders to residents in South Florida and Southeast Texas that it only takes one storm to seem like an active year. Only four tropical storms formed in 1982 and seven in 1992, which were both well below the 30-year average of 12.

The Florida Public Radio Emergency Network, home to the mobile app Florida Storms, provides on-demand and hazards-based weather information to all Florida public radio media. 



Editor's Note: Meteorologist Jeff Huffman contributed in part to this story.
[1] https://ams.confex.com/ams/pdfpapers/167939.pdf
[2] http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf
Sources include nearest National Weather Service office, National Hurricane Center, and the Florida Public Radio Emergency Network (@FloridaStorms).
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