TD10 upgraded to Isidore, TD11 forms and is upgraded to Josephine.

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.

Please visit my tropical Atlantic headquarters.