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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.




  • Kim says:

    Thanks Levi! Have a good afternoon!

  • harry kane says:

    Thank You Levi, Glad to know you feel this one won’t be much of a threat as far as winds go. Lets hope for the best and let the good people in Texas have some much needed rainfall. Most likely will fall in the soggy southeast states.

  • Andrew says:

    Thanks Levi.
    Do you think it’s possible that all the tropical moisture that has been pulled northward out of the south western Atlantic in a plume over the eastern seaboard combined with dry air pulled off both the CONUS and Sahara by the very large Azores/Bermuda high prevented air from piling up and essentially caused the lack of a Cape Verde storm season?

    Or is possible that the warm Atlantic AMO is over

    • Levi says:

      The AMO is still positive. The overall distribution of SST anomalies may have weakened the local Hadley cell and contributed to less activity, but there were likely multiple factors involved. It will require a post-season analysis.

    • Eric (weather advance) says:

      From what I can tell, +AMO as a whole since mid 2000s peak is in general weakening trend, mainly in response to solar cycles, which AMO shows a strong relationship to (specifically TSI) “Normally”, AMO cycle will lasta 25-30 years or so, but since we’re experiencing one of the weakest solar cycles in centuries, it’s plausible to conclude that low solar cycles are accelerating us towards a -AMO, which is due to make a comeback, within the next 5 years. Once that happens should see a turndown in Atlantic activity similar to what occurred in the 1960s & early 70s when we last entered -AMO period. Another likely consequence will be hurricane strikes will shift away from the east coast & will go towards the Gulf of Mexico like it did in1900s & 1960s. Interestingly, those time periods were the worst for the Gulf of Mexico, with the 1900 Galveston hurricane, 1961’s hurricane Carla, 1967’s Beulah which almost came into south Texas as a cat 5, luckily hit south of border in Mexico, & 1969’s Camille. Perhaps a cooling AMO, cold PDO focuses upward motion outside deep tropics, & if the Gulf is generally warm, this sets up a generally favorable landfalling pattern there. As Levi said, this season will require extensive work to figure out exactly what went wrong with predictions, but honestly I’d prefer to be wrong anyway because #1 fewer hurricane strikes on the US than predicted saves lives & lots of $$, & #2 the best way to learn & advance ourselves in meteorology, hurricane prediction, or even science in general is to be wrong, in fact, many of our best discoveries in science have come from failed hypothesis or initial predictions, regardless of the failed predictions this season, which may seem bad now, this will surely significantly advance our understanding of tropical phenomena not just in the Atlantic, but also on a global scale as well, with global ACE index near record lows.

  • wxhstrn74 says:

    I’ve enjoyed your very informative…sometimes a bit over zealous…narratives & writings on tropical systems. Extremely well analyzed and impressive.

    Here’s one I’ll bet you never heard about….check out my blog.

    Hurricanes in Michigan??? Along with…Hurroncane!

  • derayka says:

    Thanks for the in depth analysis; if I wanted to be spoon fed I’d get my info from the local channels. Carry on and do what you feel is right.

  • Tim Perkins says:

    Levi: What are your thoughts now on 95L? (P.S. – I know you must be incredibly busy…forgive me if this intrudes on your time…)

  • WXheights says:

    Heads up on potential sub-trop like hybrid east coast weekend including a left hook potential alla “Sandy” (ECMWF 1 and CMC 2) interesting modeling

  • patrick says:

    Update, Update, Update!

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