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How to Predict
Hurricane Seasons
Why some are Weak - Why some are Strong

              Hurricane Landfalls

                             Predicted 6 Months in Advance

  Sandy - Harvey - Irma - Dorian - Michael   Barry - Mathew - Florence



What Determines the Strength of a Hurricane Season

where Hurricane Landfalls will occur



Research by GWO has found that Four primary predictable variations can greatly control hurricane landfalls and the number of hurricanes and named storms. As discussed below, the four greatest influences are the position and strength of the Azores-Bermuda High, the occurrence or non-occurrence of an El Niño, climate change cycles of ocean water temperatures, and just as important as an El Niño or La Niña is the ClimatePulse Cycles that can induce activity or suppress activity during a season.


1.    El Niño - Neutral Conditions or La Niña

An El Niño typically suppresses a hurricane season by causing above normal wind shear in the upper atmosphere, thus disrupting the formation of storms. 

A major factor in predicting the number of storms for the season is the El Niño.  Will there be an El Niño Southern Oscillation (ENSO) during the hurricane season, or will it be what we call ENSO Neutral conditions halfway between an El Niño or La Niña in the tropical South Pacific Ocean. The El Niño is a global coupled ocean-atmosphere phenomenon, and when an El Niño is in place, Atlantic Ocean tropical cyclone activity is typically less than average due to stronger winds in the upper atmosphere.  The stronger wind tends to cause wind shear and hinder development and/or strength of tropical cyclones. Conversely when a La Niña or neutral conditions are in place, Atlantic Ocean tropical cyclone activity is enhanced (see section 3.1 for the GWO El Niño, La Niña outlook).


2.    ClimatePulse Cycles

GWO has found that ClimatePulse Cycles can be just as disruptive as an El Niño, and for the same reason.  Three good examples are 2009, 2013 and 2014.

In 2009 an El Niño occurred and the season was limited to 9 named storms and 3 hurricanes. In 2013 and 2014 Climate Pulse hurricane suppression cycles caused an abnormally strong Azores-Bermuda High pressure center to settle more southward than normal, thus pushing the Inter-tropical convergence zone more southward as well.  These events caused an atmospheric circulation that allowed above normal Sahara Desert sand to be blown off Africa westward over the eastern Atlantic.  This caused a dry atmosphere in the central and eastern Atlantic, and a hostile environment in this breeding ground for hurricanes and tropical storms.  GWO was the only organization to predict these occurrences in 2009, 2013 and 2014.

3.    Climate Change and Cycles of Sea Surface Water Temperatures

The temperature of the sea surface also has an influence during a season.  The ocean surface temperatures fluctuate from cooler than normal to warmer than normal as determined by a 70-year ocean and climate warming cycle, and climate cycles in general. Is the ocean temperatures running above or below normal this season - and where is it occurring.    Warmer temperatures provide more favorable conditions for development of stronger storms and more major hurricanes, whereas colder ocean temperatures lead to less intense storms.



4.    Position and Strength of the Azores-Bermuda High

Another major factor in predicting seasonal hurricane tracks is the average position and strength of the “Azores-Bermuda High”, which is also known as the North Atlantic (Subtropical) High Pressure Center (Anticyclone).  Much like the North Pacific High off of the west coast of the United States, the Bermuda-Azores high is what meteorologists call a large “semi-permanent” area of high pressure center.  Semi-permanent means it is normally in that location, but does meander from time to time.  The Bermuda-Azores High is found south of the Azores in the Atlantic Ocean, at the Horse latitudes. 


As seen in Figure 1.1, the clockwise wind flow and atmospheric steering currents around the high determines the eventual path of tropical cyclones during the Atlantic Hurricane Season.  However, the High Pressure center meanders in position from season to season, thus influencing the tracks of tropical cyclones (hurricanes and tropical storms).  For example; if the ridge of the High is displaced to the north, this can lead to devastating storm paths such as the one taken by the New England Hurricane of 1938.  If the High is strongly displaced to the south such as it did in 2014, the strong ridge of high pressure will also displace the Inter-tropical Convergence Zone to far south and thus cause more African sand to be blown off of Africa, thus making a hostile eastern Atlantic environment that cause abnormally fewer storms to form in the middle and eastern tropical Atlantic region (ITCZ is favorable area for storm development). 

Figure 1.1 below depicts the Azores-Bermuda semi-permanent area of high pressure that meanders in latitude and longitude from one season to the next.  Clockwise wind circulation around the high sets up steering currents for hurricanes.  Changes in position of the high in latitude and longitude will change the steering currents from year to year, and also determine how much Sahara Desert sand is blown off of Africa.


4.    More ....

The variables discussed in the paragraphs above are very important when it comes to predicting what will happen during upcoming hurricane seasons.  But the major variable has not been discussed yet, the one that is the primary mechanism that puts all these variables in place for a given season, and what changes these variables from one season to the next. 


GWO has pioneered in identifying the Primary Forcing Mechanism (PFM) that controls the Earth’s Natural Climate Pulse, which in turn influences the average location of the Bermuda High and the formation or non-formation of the ENSO El Niño and La Niña. The Climate Pulse is associated with many climate cycles - including Global Warming.  GWO has noted a direct correlation of the Climate Pulse Cycles to periods of higher or lower tropical activity, such as the low activity in 2013 and 2014 . GWO has also correlated historical hurricane landfalls to the Climate Pulse Cycles to perfect highly accurate hurricane landfall models for 11 prediction zones along the coastal areas of the United States from New England to northern Mexico.


Referring to the graph in Figure 1.1; GWO was the only organization to correctly predict that the 2009 hurricane season “would” have an El Niño, and that the 2010, 2011, 2012, 2013 and 2014 seasons would “not” have an El Niño.  GWO was also the only organization to predict very destructive seasons in 2016 and 2017.


The 2013 and 2014 hurricane seasons were not suppressed by an El Niño, but instead by the Climate Pulse Hurricane Suppression Cycle (CPHSC).  The CPHSC is a cyclical 2-year cycle that returns approximately every 4 to 7 years and is often associated with El Niño events, but if it occurs without an El Niño it normally causes abnormally strong wind shear and diminished hurricane seasons much like an El Nino does.   In 2013 did not have an El Nño, but persistent CPHSC wind shear caused the weakest hurricane season since the 2009 El Niño,  season and the 5th weakest season in 60 years.  Then the second year of the CPHSC cycle caused a relatively weak (but near normal) number of hurricanes and major hurricanes in 2014, and no El Niño occurred.

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