Forecast Discussion 9/17

NOTE: Written in the morning, a short update may be added to end this afternoon

All imediate potential Atlantic systems appear to be fizziling out at this time.  The NHC outlook lists no systems with even a low probability of development within the next 48 hours.  Primary targets for investigation over the next couple days continue to be ex-Fred and PG-26, however both systems have weakened substantially since yesterday.  Ex-Fred no longer associated with any kind of low-level circulation whatsoever, and convection has died down as well.  An upper-level low was superimposed over Fred yesterday, and likely still is today, and vorticity through the entire column over whatever remains of Fred is still fairly high.  However this upper level low is likely inhibiting any development and leading to weakening.  Shear over Fred is actually fairly minimal, and SST is high, so it warrants at least watching, but Fred is likely gone for good at this point.

PG-26 also looks much less organized today.  Convection has died considerably, and the circulation is much less organized on Quickscat imagery.  In fact, is is difficult to actually determine a center of circulation based on the winds.  Satellite imagery does appear to show a circulation, so this system appears slightly healthier than ex-Fred.  SSTof around 29 C and Shear < 15kts indicate the environment is condusive towards development, and several global models (NGP, CMC, MM5 (all 00Z)) at least maintain the system through 72 hours.  The MM5 is the only model that shows substantial strengthening.  The 6Z GFS maintains the system through 42 hours before it becomes impossible to track.

The area around PG-24 was identified yesterday as an area of potential development in the 3-5 day range.  The MM5 in particular showed the development of a tropical cyclone in the western Caribbean, with the NGP and potentially UKMET agreeing.  Today, the models are less agressive with the strength of this system, which is saying something because only one model, the MM5 really showed an intense system there yesterday.  That said, a number of models (all FSU MOE models including the GFS) still develop at least a closed low in SLP analysis in the 72-120 hour range.  The exact location of development varries from near the Yukatan pennisula to just off of S America.  Where it forms in relation to the TUTT low could be important, as Shear will be lower farther from the low.

Airport forecasts:

Ft Lauderdale
Thursday: No Flight
Friday Takeoff 10Z: <10kt winds out of the east, POPs < 20%, but can not rule out a stray thunderstorm
Friday Landing 18Z:  Env winds still <10kt out of east, T-storm influences could change dir/spd.  T-storms more likely as ridge moves west and diurnal T-storm cycle kicks in.  Biggest impact from T-storms likely to be outflow b/c coverage will remain fairly small  POP ~ 40%

Dryden
Thursday 18Z Takeoff: Calm wind, NWS says S-E and I have no reason to doubt them, but models and MOS  suggest N-E wind.  No POP
Saturday 00Z Landing: Winds ~ 10kts, out of the SW, No POP