Invest 97L a Development Threat this Week – Will Bring Heavy Rain To the Greater Antilles

   Posted by Levi at 10:45pm on September 2, 2013

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Invest 97L remains elongated today, with the main low centered just north of Barbados, but the overall circulation extending for hundreds of miles WSW and ENE of that location. The system has made no westward progress during the last 24 hours due to low pressure feeding back in a favorable environment near the lesser Antilles. The system should eventually assume a general WNW motion. Due to slower movement than expected, 97L is likely to gain latitude as the subtropical ridge to the north is weakened by a front off of the Carolinas in a few days, and interaction with the greater Antilles appears likely. Heavy rains will be the main concern for the mountainous areas of Puerto Rico, Hispaniola, and Cuba as the system moves somewhat lethargically northwestward. Although the exact track of the system remains uncertain due to its broad nature and vulnerability to center reformations, the system is expected to end up in the general vicinity of Cuba or the Bahamas in 4-6 days. This solution is supported by the 12z runs of the ECMWF and UKMET.

The current environment around 97L remains rather favorable, with anticyclonic wind flow aloft, and a deep moisture field from the surface to 700mb. The main impediment to development remains the system’s elongated structure, being exacerbated now by interaction with another low pressure system to the ESE that is closing distance with 97L. As the system moves westward, development, if any, is expected to be slow, as the system will take time to consolidate, and the central Caribbean trade winds tend to cause low-level divergence and hostile conditions for tropical waves. Potential interaction with Hispaniola and Cuba may also hamper development. However, if 97L can consolidate over open water north or south of the big islands, the environment will become mostly favorable for development of a tropical cyclone late this week and possibly into next week once the system gets farther west and north. With a disturbance this large, we are in a bit of a wait and see game to see if it consolidates, and if so, where and when.

Elsewhere, a tropical wave moving across central America into the western Gulf of Mexico will be monitored for potential development in an unstable atmosphere. For now, no computer models show significant development. A tropical wave is forecasted by most of the global models to develop off of Africa in about a week from now. This will be discussed more once the timetable gets closer.

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