A quick mid-year review of the 2016 Atlantic hurricane season

To this date, the 2016 Atlantic hurricane season has recorded twelve named storms and one tropical depression, including Hurricane Alex from January. By the end of September we will likely see the next storm develop as signs of strengthening continue with an active tropical wave (97L). Currently, 97L is located roughly 470 miles east-southeast of Barbados tracking to the west about 15-20 knots. The tropical wave will either intensify into Tropical Depression Fourteen or Tropical Storm Matthew. The 30-year average (1981-2010) for the Atlantic basin consists of twelve named storms. With two months left in the 2016 Atlantic hurricane season, one can conclude that an above average recording of named storms will likely occur.

midyear-review-graphic

Eight of the named storms have been tropical storm strength; four have been hurricanes with only Gaston classified as a major hurricane. This leads to another interesting fact. The Accumulated Cyclone Energy (ACE) computation shows that the strength and duration of the tropical cyclones of this year have been near normal, so far.

A deeper look into the seasonal trends would lead to an examination of the ENSO (El Nino-Southern Oscillation.) Observations of sea surface temperatures since early May have indicated an ENSO neutral signal. Sea surface temperatures (SSTs) near the equator are near or slightly below average in the Central PacificOcean. SSTs observed in the eastern Pacific Ocean have shown to be slightly above normal. According to Climate Prediction Center / NCEP, similar conditions will be observed through the Northern Hemisphere winter 2016-2017.

NCEP Average SST Anomalies Aug Sep 2016
The above graphic issued by NCEP, depicts a blue shaded area in the central Equatorial Pacific Ocean, which would indicate overall cooler than average SST’s from mid-August to mid-September.

This ENSO signal is important to tropical weather forecasters since it can indicate a reason for the presence of vertical wind shear. In this case of a neutral ENSO signal, wind shear measurements are more likely to be close to normal.  However, wind shear has been a factor through the season for impeding the strength of various tropical cyclones throughout the Atlantic. One example is the harsh wind shear environment that weakened the most recent storm, Tropical Storm Lisa.

One last glance at the image will reveal warmer than average sea surface temperatures throughout the Atlantic basin. This extra oceanic heat content is one factor that could be evidence to support an above average tropical season.

The Atlantic hurricane season runs from June 1 – November 30.

 

Sources:

Acknowledgments: NOAA National Hurricane Center, NOAA NCEP/Climate Prediction Center

http://wilkensweather.com/WWT_Outlook_2016_Final.pdf

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/enso.shtml#forecast

http://www.nhc.noaa.gov/text/MIATWSAT.shtml