Tropics in a Quid Pro Quo with Sub-Tropics Next 5 Days

Sunrise Thursday Morning Along the 700mb Trough Axis Which Now Lies across South Central Florida this Friday morning.  This means zero rain chances for North Central/NE Florida Through At least  Saturday

Change of Pace Post in Lieu of the Norm. Reason? Negotiations between the System in the Gulf (Depression vs. Sub-Tropical Depression vs Storm vs. Sub-Tropical Storm "Lee")...at hand. Until there is a hand shake or a victor in the arm wrestling match (big difference), if ever, the forecast for all of North Central and most of South Central Florida remains up in the air at best. Only in the next 36-48 can it be deemed feasible to project into the future, especially with even short term model disagreement.


GULF: Based on latest surface observations, winds well removed the surface low circulation of the depression are approaching Tropical Storm Strength. Whether or not the Hurricane Center will thus name the system today (if ever) is unknown. However, I do not see the system ever being anything beyond sub-tropical at this point. Namely because the system developed off of a combination of the persistent thunderstorm activity that had been off SW Florida, combined with a tropical wave in the SW Caribbean, and then enhanced by upper level jet stream wind divergence and mid-level vorticity (the later two are subtropical features). Now, if the jet stream winds that are currently in place (and are by the way what is causing the rain fall now)...were to breakaway..and the system gains a tighter surface circulation and banding around the core...that's a whole new ball game. However, not one model has shown that process to come to fruition. 


Either way, the system is causing high alert along the Louisiana Gulf Coast since some factors are in play either way for POTENTIAL high rainfall totals accumulating..sometimes in a short period of time...mainly anywhere along the immediate coast (and I -10) but also for all of the 'lower-boot' portion of the state.  


Note that there is a difference between the words 'potential' and 'will'.  Because the system is in a  'quid pro quo', which models does one lean toward? The tropical ones or the standard North America Models? How are those models treating this system?  In the short term, most rainfall in Louisiana today appears will be limited to I-10 in direct relation to this system, but other rainfall..maybe heavier, could fall as a result of more non-tropical dynamics associated with what one looks for in thunderstorm activity...a moisture gradient, a mid-level trough,and an unstable atmosphere...non of which are tropical factors (at least, not as far as Tropical Storms are concerned).  

Surface low is in red. Strongest wind is well removed from center (sub-tropical). Red is the mid-level trough axis. This axis extends SE ward toward Lake Okeechobee today. Dry air is north of that trough with high pressure as shown by the blue zig zag//high pressure also exits into the NE Quadrant of Florida today through tomorrow. This analysis is showing 40 kts but latest observations I've seen show only measured just below that. Either way, it could become a named system. The main point is, do not focus on the CENTER of circulation...it holds no bearing as to where the brunt of the system's impacts will be focused. 

    


TODAY/TOMORROW: For Florida, rain chances are limited to South Florida, and even there they could decrease with time. Thus, Florida's weather is also being impacted by this system..for better or for worse..  With time, extended outlooks are calling for worse by Monday...but even that cannot be stated with 100% guarantee (although based on the NAM and GFS it could). Must see what  this system does first...


TROPICS: Outside of the Gulf, there is still Katia.Not writing this system off as one of those "fish storms". There is another hand shake going on further from home...and no one there is eager to agree either...looks more like a stare down for now though.  A trough is developing  east of the U.S..that being, the 700mb trough extending across South Florida this morning extends back to the NE into this area which is being watched for further tropical development, although at this point it looks unlikely...this morning that is.  The same trough is what runs across or near I-10.  It appears Katia will by pass this trough..which leaves the next one to curve the storm away from the U.S.  BUT, that trough might get hung up at its southern end in the Southeast States. Why? Because of what is going on in the Gulf...back to square one. It sounds confusing if one doesn't have the mental  picture and the process envisioned:

This is a  GFS forecast for early Monday. Note how broad the gulf system is..and is never 'cut off' and on its own. Most impacts will be to the east of the center of this mid-level low . If this goes on Katia will be steered away as mid next week approaches

From  the looks of future development of Katia,  it is now in a shearing environment, but that looks to end in the next day after which point the storm could form into a monster. From that point, it could take on a life of its own and all models are out the window.


Thus, a lot of what happens in the next 1-4 days could have long lasting and major impacts to the weather anywhere east of the Mississippi 7-10 days down the line in regard to the depression or eventual storm. For now, watch out if it begins to fade off toward the SSW..this could have a big impact on the steering of Katia way down the line later next week.


Big surf looks like a given for the SE U.S. Coast come this time next week though...


Here's a case in point. The GFS has been trending for Katia to become a major hurricane poised toward Florida, but then being caught up in yet the next trough . So far, though, the system is forecast by the main models to eventually steer clear of the U.S.  I'm seeing only two scenarios..either it stays further south and runs toward the South Half Of Florida (if something toward the Navy model occurs, which so far does not quite seem to be the case) or the straits, or it curves and does not impact anyone directly. (which has been the preferred option by the pros including the NHC I believe).


One other note: Not to be short-changed, watch out anywhere up and down the Appalachians into Tennessee and North Carolina. The day too may come for flooding rains toward the second week of September if the GFS and ECMWF verify.