2012 Atlantic Hurricane Season Birdseye Discussion #89A (Special Update)

By: NCHurricane2009 , 3:56 PM GMT on August 27, 2012

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...AUGUST 27 2012...11:50 AM EDT...
This special update is written concerning Tropical Storm Isaac. At 11 AM EDT...Isaac was churning straight NW across the eastern Gulf of Mexico...located at 25.7N-84.7W. Maximum sustained winds at the center are 65 mph...as Isaac refuses to strengthen into a hurricane (75+ mph max winds).

The northwest track lies perfectly in the middle between my track and NHC's track generated at 5 PM EDT yesterday (see Figure 1 at this link for yesterday's 5 PM EDT forecast graphic). The northwest track also lies precisely on the most recent 11 AM EDT NHC graphic forecast track. The northwest track is Isaac repsonding to a low-level ridge weakness associated with central US surface front (see discussion #89...paragraph P1 of mid-latitude discussion for info on this feature). With this information...we are highly certain that the center of Isaac should make landfall near Buras, Louisiana (in the SE corner of the state) sometime Tuesday afternoon...with rainfall and gusty winds arriving well-in-advance of that time due to the large size of the storm. Storm surge impacts should already be in progress across the Gulf (worse closer to the storm center)...and will be getting worse over time near the expected landfall area. Any mandatory evacuations on the US Gulf coast should be obeyed for your safety...due to storm surge potential from Isaac's large wind field that is capable of stirring up a large amount of water. As we saw during Hurricane Ike of September 2008...it does not take an intense tropical cyclone to make big storm surge...but rather a large sized wind field also works in doing this.

Intensity-wise...it appears that Isaac should have been modeled as a large and broad-cored tropical cyclone incapable of quick intensification...also similar to what we saw with Ike of 2008 when he entered the Gulf. Like Ike....Isaac has traveled over quiet a bit of land (for example over Haiti) before entering the Gulf...and to begin with Isaac had a hard time establishing a tight core before Haiti. So perhaps it is no suprise then he is haivng a hard time establishing a tight core after Haiti. With this information...I no longer expect Isaac to become a major hurricane (115+ mph max winds). In fact...he may not ever get stronger than category 1 (75 to 95 mph max winds).

On an interesting note...despite the unusually high number of Atlantic storms so far this year...none have succeeded in become a major hurricane (115+ mph max winds).

Return to full discussion #89 for my info on the rest of the Atlantic tropics.

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