Good morning! The tropics are active this morning with a couple of areas of interest on the map in the short term: one in the Caribbean and another the remnant low of Tropical Storm Colin. Briefly, what happened yesterday with Colin was simply a case of the storm running before it could walk. What I mean by this is that everytime thunderstorms tried to form near the center of circulation, the center ran out to the west ahead of the convection -- causing the process to start anew each team. Tropical systems become organized when they move more slowly and the thunderstorms near the center act to lower the pressure near the center; forcing more air into the center of circulation and then upward in a continuous process of thunderstorm formation. With the storm moving westward at 20+ mph, this just couldn't happen. Also, the storm was affected by wind shear yesterday and, since it wasn't particularly well organized, this is all it took for Colin to degenerate.
This morning, conditions are still not favorable for redevelopment in the short term with wind shear increasing near the storm due to an area of low pressure to its north, but as this wind shear weakens over the next couple of days and Colin moves west-northwestward, the potential is there for reorganization. Colin is also expected to slow down as it hits a weakness in the ridge of high pressure north of it; this likely will also aid in reorganization. On the second image I attached, you can see the "spin" about 5,000 feet above the ground (orange colors east of Puerto Rico); while Colin does not have an organized center of circulation in the low levels, it's still a fairly solid system aloft.
Where are Colin's remnants headed? Most of our forecast models continue to say that an area of low pressure aloft will form off the east coast later this week and be strong enough and far enough south to carry Colin out to sea and away from the east coast. Two things to watch for will be the strength of the trough and also the strength of Colin. Generally, a weaker system will be guided more toward the west with the low level steering currents while a stronger system would be guided more toward the north (out to sea) by the upper level steering currents. We'll likely know which route Colin (or Colin's remnants) take by tomorrow or Friday as we see how strong the trough of low pressure is along the east coast. Bottom line is that Colin is not dead yet and it's still a system worth paying attention to.
Elsewhere in the tropics, there's a disturbance a bit south of Puerto Rico this morning in the Caribbean. While there are a lot of thunderstorms associated with it, there's not much in the way of mid level or low level rotation thus any development here should be slow in the short term. Farther out into the Atlantic, there was a burst of dry, dusty air over the past few days that moved into the central Atlantic behind Colin, this should limit development in the eastern Atlantic for the next day or two. Beyond that, though, several waves are poised to move off the west coast of Africa, all worth watching is the general pattern in the Atlantic enters a phase of upward motion.
Brian
