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Trosum (tropical summary) -- Thursday night, September 6, 2012

By: Stu Ostro , 3:39 AM GMT on September 07, 2012

Hurricane Michael at 1305 UTC Thursday September 6. West, rather than north, is the top. Because of the nature of the polar-orbiting swath and the location of the hurricane within it, the edges of the image are a little skewed/distorted, but nonetheless it is spectacular.

Image credit: NASA/GSFC MODIS Rapid Response


- Leslie will more directly affect Bermuda this weekend as it makes its closest approach, but recent model runs are consistent in predicting the heart of the hurricane to bypass to the east. That is in contrast to Igor a couple years ago which was a solid hit, with the center passing just west and the northward-pushing wave-generating southerly fetch sweeping across the islands, plus Igor had a tropical storm force wind diameter of extraordinary size for a tropical cyclone.

- Nevertheless, Leslie has a large enough surface wind circulation to send ocean waves all the way the East Coast of the U.S. along with an elevated risk of rip currents, and fairly large swells are also already reaching Bermuda.

- Thereafter, latest model trend is for Leslie to pass over or just east of Newfoundland during midweek.


- That Isaac's primary remnant still exists so intact is interesting meteorologically, while what's most important from this point forward is what effects it has upon people. In the short term, that won't be much, as it's very asymmetric with all of the thunderstorms south & southwest of the center and thus well offshore, and the system isn't moving much. Even for mariners, sustained winds are rather weak and waves not very high. Main hazard would be lightning and brief strong gusts in thunderstorms.

- Conditions in the atmosphere are not favorable for quick organization and strengthening.

- Then it looks as if the system will get picked up by a trough aloft and a cold front as we head into the weekend and move northeast toward Florida, but by then it'll be merging with that front, at which time its window to be numbered/named will be closing. It could bring some locally heavy rain but models suggest amounts for the most part won't be too high.


- Hurricane Michael ended the absence of any major (Category 3 or higher) hurricanes so far this season in the Atlantic, and was another example of how tropical cyclones which are small in size seem to have an easier time very quickly spinning up if atmospheric conditions are conducive to strengthening. Michael is not a threat to land, and its intensity has since ebbed back down to Cat 2.


A tropical wave/low coming off Africa has a pretty good chance of eventually developing into a tropical cyclone as it moves across the Atlantic.


- Currently there are no tropical cyclones in the eastern or western Pacific.

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. Skyepony (Mod)
2:37 PM GMT on September 09, 2012
Stu~ You strike me as someone that might enjoy a good TRMM pass click pic for a very large quicktime movie of it. Welcome to WeatherUnderground!

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About stuostro

Proud to be a weather-obsessed weather geek! \m/ Senior meteorologist at The Weather Channel. If not a meteorologist, would be a DJ ♫

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