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September 2013

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

If you are having trouble viewing the embedded video below, try the direct Youtube link.

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.




  • stefanie says:

    Thanks Levi. 🙂

  • Kim says:

    Thanks Levi!!

  • Brandon says:

    Thanks Levi

  • Mike says:

    Great Video Levi!

    Do you think that there is any chance that with a system that has provided this much uncertainty thus far, if it does develop, could be any threat to the gulf coast, or the US coast at all? It seems that the general consensus seems to be that in a few days it will curve to a more northerly direction, but i know that with systems that have yet to develop it can be tricky to predict, especially when there is no aircraft data on it yet.

    • Levi says:

      It is definitely within the realm of possibility that the US could see weather from this system down the road, but that is a long way away.

  • jrrp says:

    nice video

  • Matt says:

    Love these updates! you should do one every day!

  • CapeFearCaner says:

    Thanks Levi, it will be interesting to see if it can find a way to make it across the high mountainous terrain of Hispaniola without being shredded to pieces. If it can, I think it has a shot at developing into something of significance.

  • rod bertelsen says:

    Best to you. Been tuned into your analyses for years. Thoughtful, well presented; sometime wrong in hindsight; sometimes brilliant. Getting a slow moving system like 97L into a good prediction is one of the most challenging a met could ever have. again – best to you.

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