Forecast Discussion 9/22

All remains quiet along the Atlantic Front.  Ex-Fred, which is now merely a wave, is located off the coast of South Carolina, and will likely be making "landfall" within the next day or so.  Convection is still associated with ex-Fred, but it is not nearly as extensive today as it has been in the past 2 days.  Convection associated with a baroclinic zone / stationary front is located roughly 15 degrees east of Fred, but is not tropical in nature, and is not associated with any kind of significant low level vorticity.  To the south, convection fired up overnight in the vicinity of Cuba, and is associated with some vorticity, but it is so weak that it is not being 'Marsupial Tracked'.  East of that system is ex-98L, which continues to be an elongated vort max with no clear center.  At 21Z yesterday, QuickSCAT showed a circulation center in the southwest portion of the elongated max, but this was not clear in the 9Z pass this morning.  Furthermore, the center is almost completely devoid of convection, although convection is still associated with the northeast portion of the vortmax.  Finally, the Gulf remains clear, and the convection and minimal vort max east of Puerto Rico from yesterday has diminished substantially.

Global models all show Ex-Fred weakening, which appears to finally be supported by observations.  That said, it is not expected to completely diminish before "landfall" and will likely still bring precip to portions of the east coast.  Model forecast tracks are in fairly good agreement and suggest a "landfall" along the Florida-Georgia border.  The speed varies more between the models, but a "landfall" overnight tonight appears likely, which should finally kill off Fred for good.

Ex-98L is actually kept around by all Global models for at least 72 hours, at which point the GFS looses it.  THe consensus seems to be that it wil continue to weaken over the  next 24-48 hours, but several models suggest slight strengthening after this.  CMC and MM5 are again on the extreme in terms of prediction of the development of this system, as both show fairly substantial deepening after 72 hours.  NGP also at least develops a closed low around the same time.  The predicted track continues to be a gradual turn to the northwest and eventually north, however the models have predicted this for days now, and the system has conitnued to remain almost stationary, drifting slowly west.  If more convection does develop around the center, it will likely begin to turn north, however low level winds are so light that without the development of convection, it will likely continue it's fairly stationary motion.  Model consensus track is 53W, 18N @ ooZ tonight, and 55W 23N by 00Z tomorrow, but as stated before, It would not be suprising to see a track further west if the system remains unorganized.  Phase Analysis shows that the models which are developing systems may be warm core to start, but quickly transition to cold core as the system accelerates northward.  However such a system composition would depend on the path, which in turn relies on intensity, so not much faith can be put in such forecasts at this point. 

In the Pacific, a high probability of TC development has been issued for 98E.  Model consensus shows a strengthening into a tropical storm within 48 hours, and this system will be monitored for a potential Global Hawk Desperation mission.  Model consensus for track has the system around 118W, 18N in 48 hours, with a fairly straight NW track to that point from its current location.

Airport Forecasts:
No Ft. Lauderdale/Dryden flights for the next 48 hours.