Clark
Meteorologist
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Quieter Tropics, but for how long?
Tue Aug 16 2005 12:55 AM
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The Atlantic and East Pacific, on a whole, are relatively quiet this evening. Irene is headed out to sea, Fernanda has met its fate in cooler waters, while Greg and TD 10 have succumbed to stronger shear. But, there still remain a few areas worth watching in the next few days.
First off, Irene. As expected, Irene has perked up in intensity as it began to move towards warmer waters and accelerated ever-so-slightly towards the north and east. It has likely peaked in intensity and should begin to weaken from here, mainly a result of increasing upper-level shear, and later due to cooler SSTs once it crosses 40N. The NHC track looks pretty good from here on out, only desiring to shift it slightly further east as a result of a continued eastward motion over the past day or so and relatively little to turn it more northward in the short-term. Overall, however, the storm should ultimately become extratropical within 2 days or so and head off towards Greenland & Iceland as a vigorous extratropical storm.
Meanwhile, former TD 10 is doing it's best Irene impression, maintaining an impressive low-level circulation despite losing most of it's convection to southwesterly shear on a regular basis. However, it does continue to develop convection, something likely helping to maintain the circulation, and as we've seen this year in real-life and in laboratory experiments, these systems can be incredibly resilient to shear. It's still got another day or two before it escapes the gallows of the upper trough and enters a region more favorable for development, but both current atmospheric conditions and model projections agree that the environment should become more favorable once it draws closer towards the Lesser Antilles. Whatever system is there should pass just north of the islands, though it may come reasonably close enough to kick up some surf on north-facing beaches.
As of right now, I would put odds of TD 10 redeveloping at about 50/50. It continues to maintain itself in the face of some hostile conditions (this morning's QuikSCAT pass showed some 35-40kt uncontaminated winds, while recent TRMM and Windsat microwave imager passes suggest decent low-level banding features) and there is support for the main vortex to maintain itself over the next few days in the model guidance. Where it goes beyond 3 days depends upon the strength and orientation of the subtropical ridge and how strong the storm is at that point, with the usual caveats of a weaker disturbance being more likely to head towards the west applying. Model guidance is split, with some models turning it back more towards the west with others turning it northward in conjunction with a weakness in the ridge, so it remains to be seen what happens -- particularly given a very weak disturbance at this point. In other words, stay tuned. If and when it redevelops, we'll have a better idea of where it may go, and I'll update at that point.
A new tropical wave coming off of the coast of Africa looks decent, though it has a little dry air to deal with ahead of it. This dry air is relatively confined, however, and should pose little impediment to tropical development a week or so down the road. Nevertheless, this wave will likely meet much the same fate as the one that preceded it, maintaining a weak signature for a day or two before gradually weakening. It's in waves further down the line, currently over Africa, where the next Cape Verde system likely lies. Model guidance is unanimous in bringing a strong wave off of the coast of Africa in 4-5 days; given the concurrence among the model, it'll be one to watch. Elsewhere, lowering pressures (at least the potential thereof) in the W. Caribbean and Bay of Campeche bear watching, though conditions are currently unfavorable for development.
Out in the East Pacific, Fernanda has lost all of it's convection and is now just a low-level swirl of low clouds amidst a stable environment. The projected west-southwest motion never materialized quite as much as expected, due to a slightly stronger storm and slightly weaker upper ridge, leading to it entering this environment. Water temperatures at this latitude are unfavorable for redevelopment until nearer to Hawaii, quite a distance for this system to have to travel; coupled with the stable environment with sinking motion throughout the column that the system has entered into and I believe this may be all we see from this storm. It's another story towards demise with Greg, which, much like ex-TD 10, is still sprouting convection -- it's just being sheared to death. Initially being sheared by Fernanda to the west, now it is being sheared by a large disturbance just off of the coast of Mexico to the east. Unless the shear abates, which does not appear likely in the next few days, this system is likely done as well. Little movement is expected with Greg, with a westward track being the general trend. The system (invest 99E) off of the coast of Mexico bears watching for development, but it is currently rather large and will take some time to get organized. Upper-level conditions and water temperatures are favorable for the next day or two, so it has a chance. There's a weakness in the steering currents near Baja California, but a general west-northwest motion is likely in the short-term. And, finally, like in the Atlantic, there is some agreement in the models for another system to spin-up in the East Pacific in the long-term, something not out of the realm of possibility given the favorable atmospheric conditions and favorable climatological factors at play. Again, it may be a broken record by now, but it too is one to watch for.
More later in the week...
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