Clark
(Meteorologist)
Thu Aug 11 2005 08:16 PM
Re: looks pretty strong for a minor tropical storm

Irene is more or less holding her own this afternoon. The colder cloud tops are really obscuring things in trying to find where the low-level center is located. Add in that the circulation is not very large at all and it becomes even more difficult. Here's my best guess as to the structure and setup of the storm right now...

On visible imagery, cloud motions north of the main cloud pass are rapidly going from east-southeast to west-northwest, but not curving around into the storm's center. This gives further credence to the idea of a small circulation and is also likely one of the two regions where the strongest winds are associated with the storm. Cloud motions to the south of the storm at low levels are sprialing inwards, but not at a strong clip. With low clouds curving around to a N-S orientation near the current convective blowup at about 25.5N/62.5W, this suggests the center is further west of that mass. The speed of these low clouds, particularly further to the west, suggests that the circulation is not well define on the south side...but it is and has been closed per visible satellite imagery over the past week, just too small to accurately be captured as a closed low by the QuikSCAT passes at times.

The colder cloud tops on the western edge of the storm (looking at about 25.5-28N, 63.5-65W) are largely cirrus clouds; there is little convection associated with them at this point. An outflow boundary is racing to the NW out of this region, clearly evident on visible satellite imagery and an indicator of the collapse of the convection in this area several hours ago. I would expect cloud tops in this area to warm over the coming hours before convection redevelops there later tonight. In the meantime, some colder cloud tops are building to the east and southeast of the center of circulation; these will likely persist for some time as well.

Given the satellite appearance, the mid-level center would appear to be in the middle or on the eastern edge of the "colder" cloud tops to the NW of the deep convection, somewhere near 26-26.5N/63.5W. The actual low-level center is likely displaced from there, albeit not to a huge degree, and is located near 26N/64W, give or take. It is possible that there are multiple swirls rotating around the larger center, but we don't have accurate enough data to make that call at this time.

Given the current structure of the storm, winds are likely still around 50mph, given no improvement in the satellite signature of the storm and nothing else to suggest that winds are any higher at this point, cloud track and QuikSCAT winds included in that. Slow strengthening is still possible, but I don't see any rapid deepening likely in the near term. Think Emily, before it got to the islands, and that's probably a good marker for how this storm may try to get organized.



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