At 06Z today, TD10 was upgraded to TS Isidore based on aircraft recon into the storm. The convection with Isidore has been amazing, even as an open tropical wave a couple days ago, but the CDO has been persistently cold during the revived TD state and now the TS state. Although the low-level center is still somewhat disorganized, the middle and upper levels are certainly well-developed, and I suspect that if the low-level center shifts under the center of the CDO, the storm could rapidly become strong. Sadly, the TMI, AMSU, and SSM/I microwave sensors on various satellites all missed the center of the system as of the latest passes, each catching it on the edge of a swath. This CDO-dominated stage of development in a Tropical Storm is best observed with microwave imagery, because it can "see" through the CDO and into precipitating regions below... able to pick up spiral bands or even an eyewall long before VIS or IR can. The 15Z advisory positions TS Isidore at 17.9N 78.7W (just 50km away from Jamaica) and moving NW at 6kts. Maximum sustained winds are still fairly weak at 40kts, and the MSLP is 1003mb. Given the present appearance of the storm, one might expect it to gain intensity a bit more quickly than it has been. A Tropical Storm Watch is in effect for Grand Cayman, a Tropical Storm Warning is in effect for Little Cayman, Cayman Brac, and Jamaica, and a Hurricane Watch is in effect for western Cuba and the Isle of Youth. Isidore is forecast to reach hurricane strength by the time he reaches Cuba early Friday morning. Once crossing Cuba and entering the Gulf of Mexico, more rapid intensification is likely, as the shear is already moderately low and expected to lessen, and the SSTs there are very warm. As a long-range possibility, one model (GFDL) has the storm hitting the Gulfport, MS area on Sunday evening as a strong CAT2 hurricane. NOGAPS hints more at a curve toward Brownsville, TX, while UKMET and MM5 virtually stall it in the central Gulf and intensify it substantially. A Canadian model has it hitting the Florida panhandle on Saturday night. Unfortunately, the latest AVN run is not in at the time of writing, and they've done well with tracks this season. So, the point is, Cuba should certainly be prepared for rough weather, but the entire Gulf coast should be watching this very closely because the future track is so uncertain. The small vortex I mentioned in yesterday's update was upgraded to TD11 at 21Z yesterday based on satellite estimates. At 09Z today, a fortuitous (for us, not them) ship observation very near the center of TD11 found 37kt sustained winds, and in combination with satellite estimates, was enough to warrant upgrading it to TS Josephine, the 10th named storm of the season. It is very small, weak, and no threat to land. As of 15Z today, she was located at 36.0N 51.4W and tracking NNE at 10kts. Intensity is 35kts and 1009mb, and it should maintain current intensity or weaken as a trough advances on it and it becomes extratropical.
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