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September 2013

Invest 95L Unlikely to Become Very Strong – Blustery Rain-Maker for Gulf Coast

   Posted by Levi at 6:11pm on September 18, 2013

In what seems to be the theme this year, another low pressure area has crossed the Yucatan Peninsula and made its way into the Bay of Campeche. Unlike its predecessor, Hurricane Ingrid, Invest 95L will not be able to develop quickly. A northwesterly flow aloft over the BOC, in part due to the upper ridge left behind by Ingrid, is piling up and causing air to sink in front of 95L, while simultaneously shearing the system. This is not allowing convection to develop to its north or west. Such hostile conditions will persist until around Friday night, when 95L will be aligned more with the upper ridge axis, where there will be less shear.

By this time, 95L may be within a couple hundred miles of the Mexican coast, but right now it seems unlikely to actually move inland there, as a shortwave trough digging towards the north gulf coast will erode the mid-level steering ridge to the north of 95L. The result will likely be that 95L stalls and then moves northeastward. However, true strengthening will likely remain difficult. The trough will bring a cold front towards the gulf coast, and the orientation of the front (SW to NE) suggests that 95L will become strung out to the northeast along the front, or even split into two pieces: a tropical system to the south and a baroclinic (non-tropical) system attached to the tail-end of the front. While a splitting could allow a tropical system to remain intact, with the front to the north spreading energy out, significant strengthening seems unlikely.

Another potential scenario is that instead of 95L staying separate from the front, it merges with it and strengthens non-tropically, a scenario portrayed by the UKMET. This would in some ways be analogous to Tropical Storm Lee from 2011. The strengthening would not be tropical in nature, and winds would likely not exceed low-end tropical storm force. Either of these scenarios is possible, but both would mean a blustery autumn rainstorm from Louisiana eastward, and not much more than that.

Current information on 95L including its satellite floater and model track forecasts can be viewed here. Also don’t forget to check my Facebook feed for more frequent updates than here on the blog.