Category Archives: Tropical Wave

Danielle, Earl etc.

As of 5:00 a.m. EST on 26 August 2010 Hurricane Danielle, a category 2 (Safir-Simpson scale) tropical cyclone was located at lat 23.4N log 54.9W some 860 miles to the southeast of Bermuda, moving toward the northwest at 16 mph with maximum sustained winds of 105 mph and a minimum central pressure of 968 mb. The current track for Danielle is projected to gradually turn toward the north and then the northeast keeping the storm over open waters over the next 3 – 4 days, however the storm should be near Bermuda by this Saturday 28 August.

Satellite view of the eastern Atlantic for the aviation industry on 26 August 2010 at 2:00 a.m. EST. Visible are Tropical Storm Earl and a couple of tropical waves over equatorial Africa.
Satellite view of the Atlantic basin for the aviation industry on 26 August 2010 at 5:45 a.m. EST shows hurricane Danielle and Tropical Storm Earl moving in tandem.

At the same time following behind hurricane Danielle some 1700 miles to the southeast we find Tropical Storm Earl located at lat 15.2N long 34.8W, tracking west-northwest at 16 mph with maximum sustained winds of 45 mph and a minimum central pressure of 1004 mb. The forecast is for this cyclone to maintain its current course over the next 3 – 4 days to then gradually start turning toward the northwest by north and eventually recurb toward the north/northeast. In any case, at the present rate of travel the storm should be near the Bahamas early next week and, depending on when the projected recurbing of its track takes place, it may come close to the Florida or Atlantic USA coastline by Wednesday 1 September 2010.

Following behind Earl, some 800 miles to the east is a large Tropical Wave over the eastern Atlantic waters just southwest of the Cape Verde islands, and 900-1000 miles east of that is another tropical wave over equatorial Africa, moving westward toward the Atlantic. Looking farther east over equatorial Africa, the Arabian sea and the Indian Ocean several embrionic and large tropical waves are visible. It is clear the assembly-line is busy and in motion sending impulses into an environment that will convert them to tropical waves, which will then be launched over the eastern Atlantic waters to hitch a ride along hurricane alley, where several factors and prevailing conditions may contribute to cyclogenesis – the generation of yet another storm or hurricane for the 2010 Atlantic hurricane season that is now entering what historically has been the most active month. At the moment conditions appear to indicate an increase in activity and favorable conditions over the past few days, only time will tell if these forecasts will become reality or not.

Satellite view of the eastern Atlantic and a portion of equatorial Africa on 26 august 2010 shwoing water vapor in the atmosphere. Tropical storm Earl is visible to the left of the picture and also two tropical waves moving westward over equatorial Africa.
26 August 2010 Satellite view of the Atlantic basin showing water vapor in the atmosphere, which helps in visualising the environment in which hurricane Danielle and tropical storm Earl are moving.

Hurricane Danielle is currently moving within an atmospheric environment of mostly dryer air; this condition can be see on the satellite picture on the left above, where the browns and darker shades identify dryer air, however on the same picture we can also see how Danielle is pulling moisture from far away to the south where the Caribbean and Central American region are loaded with high moisture conditions. What is interesting to note is that Tropical storm Earl is facing some of the same dryer atmosphere surrounding Danielle, but when you look east of Earl you can see how the eastern Atlantic and western equatorial Africa have quiet a high moisture content in the atmosphere; you can see this clearly on the picture above on the right. What conclusions can we draw from these atmospheric conditions around Danielle, Earl and the tropical waves following them? Could it be that the higher moisture content in the atmosphere over the eastern Atlantic and equatorial Africa, offers more ‘fuel’ to fire-up storms and rain and otherwise generate more atmospheric activity within those tropical waves, so that the potential for tropical cyclone generation might be increased?

The Tropics are Hot!

Satellite view of Hurricane Danielle under visible light on 25 August 2010 at 12:15 p.m. EST

  Back on 20 August we posted comments about Hurricane Alley Traffic, and in 22 August we posted Beware of the Tropics!. Today on 25 August 2010 we see several of the concerns expressed in those postings becoming real hazards. What was then Tropical Depression #6 is now Hurricane Daniellein the middle of the tropical north Atlantic following a track that may keep it away from land as it recurbs toward the north and eventually the northeast. The large tropical wave we alerted about as it emerged from equatorial Africa, over the warm waters of the eastern Atlantic south of the Cape Verde Islands, is now Tropical Depression #7 riding along ‘hurricane alley’ on what appears, at least for now, a more westerly track than Danielle followed before, which could spell potential trouble ahead for Caribbean nations and even South Florida or the mid-Atlantic mainland USA a few days from today.

Projected track for Hurricane Danielle over the next five days as estimated by the Office of Naval Research, U.S. Navy


Global mosaic, a composite of several satellite images, showing the Atlantic and Indian oceans, and a portion of the eastern Pacific. Two hurricane, one tropical depression and several tropical waves are visible in this view. Here we see both 'hurricane alley' and the 'tropical wave assembly line' in action.

As if Danielle and TD #7 were not enough, there is already another quite large tropical wave just now coming over the eastern Atlantic waters south of the Cape Verdes, and a couple more tropical waves following behind it at regularly spaced intervals. What we are seeing is the tropical wave assembly line in equatorial Africa kicking into a higher gear generating tropical waves, fueled by the heat and high moisture content in the atmosphere and trade winds pushing storms westward over Africa from the Indian ocean.

Dramatic as this higher level of activity is it should not be surprising, after all the most active period of the annual Atlantic hurricane season historically has taken place in late August and September, so we still have plenty of tropical activity in front of us. As it is, over the past few weeks planet Earth has had a ‘belt’ of disturbed tropical weather around it just to the north of the equator, as illustrated by the composite satellite view that follows:

Composite full-disk satellite view of Earth's western hemisphere showing the belt of tropical weather circling the planet just north of the equator.

While this is in progress we must take a look at the eastern Pacific just south of the equator off the coasts of Peru and Ecuador, where surface waters  have temperatures averaging 15 degrees Celsius with even colder surface waters nearer the land. What we are seeing is a typical La Nina event, part of the Pacific ocean ENSO (El Nino Southern Oscillation) phenomenon, which traditionally creates a favorable environment for tropical cyclone generation (cyclogenesis) over the tropical north Atlantic ocean. How much will the current La Nina contribute to hurricane development in the Atlantic depends on several other factors and remains to be seen. However, the mere fact of an unfolding La Nina combining with all the tropical activity already being generated in the Indian ocean, over equatorial Africa and along hurricane alley in the Atlantic, should sound the alert for all of us who reside along the coastal regions of the Western Atlantic, the Caribbean and the Gulf, to pay attention, be prepared, and to always practice MITIGATION.  Relative to this it is critical that we all keep in mind that there is no such a thing as just a minor hurricane, every hurricane is capable of causing plenty of damage on building, infrastructure and property, and when it comes to a major hurricane (category 3 or higher on the Safir-Simpson scale) all it takes is one making landfall over a vulnerable community to cause major damage or even a disaster.

Map showing sea surface water temperature in the Atlantic, Caribbean, Gulf and eastern Pacific basins. The darker shades of brown in the Gulf and southeast of the Caribbean identify waters above 30 deg. Celsius. The green colors and a touch of blue off the coast of Peru shown the much cooler waters marking the unfolding La Nina event.