Tag Archives: Thermocline

Are Tropical Cyclones around the Corner?

15 May 2011 marked the official start of the 2011 Hurricane Season in the eastern Pacific basin, and in less than two weeks on 1 June 2011 we will officially inaugurate the 2011 hurricane season in the Atlantic basin.

As we keep an eye on the tropics for any signs of potential tropical cyclone development along hurricane alley, the Caribbean, the Gulf of Mexico and the west-central Atlantic, as well as the eastern east Pacific, we note tropical waves on the move from equatorial Africa toward the west and areas of disturbed weather, which may eventually become threats to communities through the larger basin. Geostationary (GOES) satellites provide frequently updated imagery 24 hours a day year round, such as the one shown above [courtesy of NASA] where a large region of disturbed weather is clearly seen to the north of the U.S. Virgin Islands moving westward toward the USA mainland, which will collide with a front pushed by the jet stream toward the northeast by north. This image also shows quite a bit of tropical activity further south near the equator.

A color-enhanced infrared GOES satellite image, shown below [courtesy of NASA], also taken on 18 May 2011 shows the cell of disturbed weather mentioned above in more detail.

 On the image above notice how the large cell of disturbed weather over the west-central Atlantic is moving generally westward toward a collision with a storm system near the USA Atlantic coastline, which is being pushed by the jet stream toward the east by northeast. From this image it may be deducted that in the absence of a jet stream coming so far south and pushing toward the east by northeast, the cell over the west-central Atlantic might very well continue moving toward USA land where it may cause copious rain and possibly coastal flooding over the next 36-48 hours.

Meanwhile over the far eastern Atlantic, to the south of the Cape Verde islands, we are more and more everyday seeing tropical waves generated by the assembly line that is active over equatorial Africa, which eventually feed into the hurricane alley that channels them toward the Caribbean and the western Atlantic. Some of these tropical waves are shown on the satellite image of 18 May 2011 shown below:

A better overall perspective of tropical activity over the eastern Pacific and Atlantic-wide basin, which may at some point have the ability to impact the USA as well as several other countries, can be gained by the full-disk satellite image of Earth’s western hemisphere on 18 May 2011 that is shown below:

On the satellite image above the yellow outline across the Earth’s disk identifies the belt of tropical weather that circles the planet, and which when this image was taken on 18 May 2011 was clearly positioned to the north of the equator where it may already be capable of affecting the trajectory of tropical waves, which may impact the USA and other interests in the Caribbean and Gulf.

The overall perspective of tropical cyclone risk can be complemented by the map of sea surface temperature from 17 May 2011, which shows hurricane alley, the Caribbean and Gulf as well as the eastern-east Pacific have already reached a thermocline that is favorable for cyclogenesis. This map of sea surface temperature is shown below:

The above sea surface temperature map [courtesy of NOAA] also shows the effect of the La Nina [ENSO] event still active off the coast of Peru, where the green and yellow color identify the much cooler waters of the La Nina event. The historical record has shown that a La Nina event creates an atmosphere-ocean environment that is more conducive toward tropical cyclone generation in the Atlantic basin.

Finally, I believe it is important to take a closer look at tropical activity over the eastern Pacific off the coasts of Central America and Mexico where a satellite image on 18 May 2011 shows several large cells of rain and storms and otherwise disturbed weather that are active in that region. This region of the Pacific has seen quite a bit of storm activity the same as the junction between Panama and northern South America (Colombia and Venezuela), which has resulted is repeated incidents of heavy rains and thnderstorms over most of the area over the past several weeks. This is a pattern that developed in 2010 driven by La Nina, which appears to be repeating in 2011. The satellite image that follows below, showing the eastern Pacific near Central America on 18 May 2011 illustrates the commentary made before:

With such widespread tropical activity, and so many of the triggers for tropical cyclone development already present in these basins, i.e.: warm and warming surface waters, tropical waves and areas of disturbed weather, areas of low atmospheric pressure etc., it is clear possible tropical cyclone development may occur at any time from now on, so it becomes imperative we remain prepared, pay attention and continue to practice mitigation!