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Don moving towards Texas; Next up 91L/Emily

By: louisianaboy444 , 5:52 PM GMT on July 29, 2011

Thanks for reading this is my afternoon Tropical report.


Well Don has behaved himself and has actually been more of a benefit then harm. A strong high pressure system located on the U.S. Southeast mainland is bringing brisky Northeastly shear to this system and thus has hampered it. This might strengthen a tad more before landfall but that now is starting to look doubtful. I am calling this a 50-55 mph storm hitting just south of Corpus Christi. Hopefully once it hits land it can spread out its moisture field and at the very least enhance the moisture and instability to hopefully give Texas some much needed rainfall.

Our Next System

Our next system is out in the Central Atlantic located roughly around 8N 42 W. Looking at the latest CIMSS wind maps I have concluded that this system does have a closed Low-Level Circulation but is still embedded in the Intertropical Convergence Zone. This can be seen by this graphic:

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The convergence in this area is still very elongated in nature which tells me it is still of this convergence zone. Also you can see it by this also:

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Look at the 10N Latitude line. You can see a band of uniform Easterly winds. This is the ITCZ but it does look like this system is trying to bend the wind flow counterclockwise which you can also see by this map which shows me that its trying to break away and become its own seperate entity. Also if you look out in the Central Atlantic about 20N you can see a weak upper level trough. This along with the Easterly winds just North of the system is bringing lots of dry air into the region. This can also clearly be seen by this map:

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The Areas of dark shading is drier air

This could be one factor that the system may have to deal with as it traverses towards the Islands. Overall Wind shear for the next 48-60 hours looks very minimal and my feeling tells me this could be at least a Tropical storm by Sunday or Monday right when it will be crossing into the Islands.

Now the big question is where will it go? Well as it has taken me awhile to anaylsis things I will say that the graphics i'm about to show you are from the 06Z GFS not the 12Z but are still pretty valid.
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This image is from 114 Hrs out on the GFS Vertical wind shear product. This can be used to see features that may steer storms. First off you can see our system in the NE Caribbean just south of Puerto Rico. What I concluded is that not one trough will try to tug it north but indeed two. Look good at the bottom circle I have outlined. This is a shortwave trough just North of our system. These shortwaves reside around 700-500mb just as our system will. Looking at the loop this shortwave begins to tug our system Northward.

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Looking at this next graphic what actually happens is this shortwave gets absorbed by the longwave trough off the coast of the NE U.S. and amplifies it. This amplified trough is the reason why the GFS predicts the storm recurving out into the Atlantic.

So my thoughts are this. If the shortwave helps to amplify this trough and the storm gathers strength then this idea of a recurvature is absolutely possible. But if this trough appears to come out flatter and weaker then advertised(which has been happening more than not) and the system stays weaker then the trough could have little affect on it thus we could end up having big trouble for the Caribbean. It is still early in the game and we have lots of time to watch this system. But right now I would have to give this system a 60-70 percent chance of forming with a 30 percent possibilty that this could be our first hurricane. That may be going out on a limb but I believe this will be our first big storm that Africa will throw at us the next few months.

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

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1. TropicalAnalystwx13
8:12 PM GMT on July 29, 2011
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