berrywr
(Weather Analyst)
Tue Aug 10 2010 05:05 AM
Attachment
94L - Beginning to Organize

Early good morning to all...I don't believe the organization with 94L is tropical at this time. The upper low off the coast of Melbourne, FL is dropping shortwave energy from north to south and filling the area of subsidence with moisture aloft to the north of the system. Current satellite imagery as of 10/05Z has the system beginning to develop SW of the earlier location of the Invest center of circulation.

Per NHC discussion there is the possibility in the short term of this system being a hybrid/subtropical system and I agree with this assessment has suppor from the upper level low will have a role in its development. This broad area of low pressure is not the same low that was near 27N 86W...it has dissipated as it moved south. This new area is located at 24N 84W and is sagging slowly south with steering currents currently aloft NNE to SSW.

Looking ahead at the upper level charts the upper level low to the system's east will ride along with the system to landfall which suggest we won't be dealing with an entirely tropical system. Initially the system will be a slow mover; perhaps near stationary for the first 24 to 36 hours and this will allow the ULL to phase with it aloft. 94L and the ULL are progged by the models to then move WNW across the GOM and a landfall on the upper TX/W LA coast late Thursday/early Friday this week.

Mid-Continental ridge remains over the Mid-South initially and retrogrades west to the 4 corners region with its axis extending east along the Mid-South and SE USA states with easterly flow aloft along the Gulf coast. There is another cutoff low extending from the progressive east coast long wave trough...inverting itself about 300 nm south of Bermuda and the Bermuda ridge east of it and not a player in the evolution of this system. Upper low continues to move north over TX into the central US and dissipating as it becomes elongated at this time.

courtesy of the NHC Glossary:

A subtropical cyclone is a non-frontal low pressure system that has characteristics of both tropical and extratropical cyclones. This system is typically an upper-level cold low with circulation extending to the surface layer and maximum sustained winds generally occurring at a radius of about 100 miles or more from the center. In comparison to tropical cyclones, such systems have a relatively broad zone of maximum winds that is located farther from the center, and typically have a less symmetric wind field and distribution of convection.

There is a wiki on subtropical cyclones and it has excellent information about these types of storms; it can be found at: http://en.wikipedia.org/wiki/Subtropical_cyclone



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