Forecast Discussion 9/15

Short term- main focus is on development of a low off the east coast of Florida.  Sfc analysis shows a low forming on the end of a frontal region in the Atlantic.  Models in general agreement on the formation of this system, and it's track to the north-northwest.  Phase analysis shows this system expected to have warm-core characteristics, at least initially and/or for the 24 hrs or so.  This is supported by  upper air obs which show a very slight T max over the developing cyclone.  However, shear is high, and the system is baroclinic in nature, so it is not expected to develop into a tropical storm.  A shift to a completely cold core system is expected as it begins to move north.  That said, it could still have some tropical characteristics, and GRIP scientists are planning several missions to the system over the next couple days.  This system will remain fairly stationary located just north of or over the Bahamas for the next 18-24 hours.

Elsewhere, PG-24 continues to be associated with a few showers, but no development is expected due to high shear and little to no organization of the system to begin with.  Ex-Fred continues to develop thunderstorms in a dirunal cycle.  Rotation is clearly visable on satellite, but little to no deep convection is associated with the center.  Fred continues to be in an area of high shear, however shear could decrease over the next few days.  Global models conflict with Fred, GFS kills Fred within the next 2 days, while NOGAPS and CMC show a low reaching the vicininty of Florida 144 hours out.  It is worth noting that NGP and CMC runs are from 00Z, while GFS has been updated to 6 Z (12Z CMC shows a weaker Fred, but still does not appear to outright kill it).  Cyclone Tracking page does not track Fred for the GFS, but does for the CMC and NGP.  12Z NAM also tracks a low in the area where Fred is expected to be begining 9/18 00Z.  Finally, PG-26 continues to be associated with thunderstorms and is moveing west.  It is not well organized at this time and shear is high, but satellite imagery hints at a low lever circulation, and NHC has noted that slow development is possible.  Most models kill PG-26, with the only exception being CMC, which keeps a very weak system around past 7 days, following Fred. 

Global models also suggest possibility of a system behind PG-26, (PG-27?) that could potentially develop in the long term.