CURRENT LOCATION: Tied to a mooring ball near Cayo Pirata, in Ensenada Honda, Culebra, Puerto Rico

18 18.400' N, 065 17.842' W

O.K., hurricane season doesn't officially start until tomorrow, but I have already been studying the National Hurricane Center (NHC) website each morning for the past week. It has been mostly a boat-bound week this week, due to the holiday crowds (mentioned in a previous post) and some less-than-ideal midweek weather carried in along our very first tropical wave (to be discussed below).

They have added some good stuff to the NHC website this year, including the continuation and enhancement of last year's Experimental Graphical Outlook. I am elated to report that this product will be updated 4 times per day this year (last season it was only twice per day). This, combined with the Tropical Weather Discussion, should give us the tools we need to monitor potential tropical cyclones and make important decisions in time for appropriate action. [Note the term 'tropical cyclone' is an umbrella term which describes tropical depressions, tropical storms, and hurricanes]

One of the things we will be watching closely are tropical waves. Tropical waves are frequently the precursors to the tropical cyclones which form during the North Atlantic hurricane season (which runs from June 1st through November 30th). A tropical wave is an oblong low pressure system, generally stretching lengthwise in the north-south direction, which rolls off the Sahara Desert in Africa and marches westward across the Atlantic. As it travels along near the equator, it interacts with the Inter-Tropical Convergence Zone or ITCZ. Although the title is a mouthful, the ITCZ is fairly simple to understand. It is the region where the tradewinds from the southern hemisphere meet the tradewinds from the northern hemisphere. The result is the movement of a lot of hot, moist air upward into the atmosphere. This massive vertical motion, or convection, can be the catalyst for change within the tropical wave. Alone, the tropical wave is a non-circulatory system; however, certain interactions with the ITCZ can cause the wave to begin to spin. When that happens, we are looking at a tropical cyclone.

The graphic below shows the position of several tropical waves and the ITCZ at this point and time:



Three orange lines, labeled 'TRPCL WAVE' can be seen between our location in the Eastern Caribbean and the coast of Africa. You can also see the position of the ITCZ (which looks like a red ladder with slanted rungs). Although we will probably be watching several westbound waves form off the coast of Africa each week throughout the summer and fall, most will not form tropical cyclones.

As you can see in the graphic above, a fourth orange line appears near the Yucatan Peninsula off the eastern coast of Mexico and Belize. This wave passed over us earlier this week, in its non-circulatory form. It brought with it cloudy skies, enhanced tradewinds, and a little bit of rain. It was a small splash of cold water on the smiling face of Paradise. This little dose of weather reality shook us from the growing belief that every day here offers a 99% chance of blue skies and sunshine.

As much as we had just the tiniest ripple in the perfect weather we have experienced these last months, at least we are 1,500 miles away from the first named system of the Atlantic season, tropical storm Arthur. Not only that, but Arthur is headed west (we hope). Arthur is an odd one, as he started in the Pacific and hopped across Central America into the Caribbean (contrary to all I wrote above). With any luck, maybe he will be both the first and last named storm of the season. A healthy splash of reality, though, suggests that we should be prepared to see some of the following names over the next few months: