Two tropical waves east of the Antilles show promise, with one having the potential of becoming a newsmaker...
Satellite and surface observations indicate that there are two disorganized clusters of convection associated to two tropical waves east of the Lesser Antilles. These are embedded directly in the ITCZ, thus halting any quick tropical development for the time being.
The waves are interacting directly with the ITCZ. The likelihood of tropical depression of storm formation soon is LOW, for now (see below):
An overview from CIMSS data products reveals that upper-level winds are relatively favorable, with shear of less than 15 kts in the area. An upper-level ridge is present near 12N, 45W, and its expected to track westward close to our system of interest. The upper-level low NE of Puerto Rico is expected to slowly track westward, away from the wave. This may be key in the possible tropical cyclone development once it nears the Caribbean in two to three days.
Saharan Air Layer (dust) is expected to lessen its burdening effects, when compared to a few weeks ago. This means there will be a more significant amount of instability present in the environment, especially as our system moves further west. However, it is an inhibiting factor at the moment for tropical cyclogenesis to happen (see below).
Track an intensity prospects:
Lots of discrepancies past Puerto Rico...
It does seem like this system may have the potential of becoming a significant threat to land (e.g. Antilles and US coastline). Numerical models agree on a general WNW track that may bring the disturbance over the Caribbean Sea, just south of Puerto Rico, then slowing down and turning NW in response to a weakness in the ridge near Florida/Bahamas. The ridge to its north will be eroded by a trough that will emerge off the eastern seaboard. This trough is currently located over the Northern Plains (see below).
Despite the effects of this trough, it appears that it wont be enough to make CRISTOBAL (?) recurve away from North America. A general NW track seems more plausible, due to the presence of a weak ridge (500mb) over the Dixie Alley. That said, the potential of a Gulf coast tropical storm or hurricane threat early next week is within the realm of possibilities, as of now.
Intensity-wise, things are far more complicated than with track. Its intensity will depend on many factors that are hard to forecast at this moment, such as:
1) Land - effects of land interaction (e.g. if it passes over 10,000 ft mountains in Hispaniola)
2)Stability - how much dry air will entrain in its structure
3 Shear - vertical shear (which appears to be quite favorable)
4) Other potential structural changes that may or may not favor intensification.
Personally, I consider this system to have a decent chance of becoming a hurricane at some point, if it develops. Despite this, we have plenty of time to track it.
Models vary their track from a Louisiana/Mississippi hit called by 12Z GFS and CMC global models, to a recurvature just east of Florida by the 12Z NAVGEM (Navy global model). The strength of the trough and its extent to the south are the drivers of the different model track solutions.
For reference, attached is an image of the 12Z GFS that Brian McNoldy (RSMAS/Miami) adapted showing the forecast track for this solution:
It is way to early to tell, plenty of time to observe.
For now, it can be said that a strong tropical disturbance, perhaps a tropical storm, may be near Puerto Rico (likely to the south) near Friday, and moving across the Caribbean during the weekend.
Greensboro, NC (8/19/2014) 1:44 pm
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